[Frontiers in Bioscience 16, 3252-3274, June 1, 2011]

The DFNB1 subtype of autosomal recessive non-syndromic hearing impairment

Francisco J. del Castillo1, 2, Ignacio del Castillo1, 2

1Unidad de Genetica Molecular, Hospital Universitario Ramon y Cajal, IRYCIS, Madrid, Spain, 2Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), Madrid, Spain

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. GJB2 gene and connexin-26
3.1. Gene and protein structures
3.2. Gene expression and protein localization
3.3. Function of connexin-26
4. Mutations in the coding region of GJB2
5. Mutations affecting non-coding parts of the gene or regulatory elements
5.1. Splice-site mutations
5.2. Promoter mutations
5.3. Large deletions
6. Genetic epidemiology of DFNB1 hearing impairment
7. Genotype-phenotype correlations
7.1. Age of onset and evolution of the hearing impairment
7.2. Severity of the hearing impairment
7.3. Modifier genes
7.4. Inner ear malformations
7.5. Temporal bone histopathology
7.6. Vestibular function
7.7. Audiologic phenotype of carriers
7.8. Outcome of cochlear implantation
8. Animal models
9. Acknowledgements
10. References

1. ABSTRACT

Inherited hearing impairment is a frequent and highly heterogeneous condition. Among the different subtypes of autosomal recessive non-syndromic hearing impairment, DFNB1 is remarkable for its high frequency in most populations. It is caused by mutations in the coding region or splice-sites of the GJB2 gene, or by mutations affecting regulatory sequences that are essential for the expression of this gene. GJB2 encodes connexin-26, a protein component of intercellular gap junctions, which play crucial physiological roles in the cochlea. Because of its high frequency, DFNB1 hearing impairment has received continued attention from researchers along the years, resulting in a wealth of data that is unparalleled among these disorders. Here we review our current knowledge on the genetic, molecular, and phenotypic aspects of this subtype of hearing impairment.

2. INTRODUCTION

Hearing impairment (HI), the most common sensory disorder, can be caused by environmental or genetic factors and can manifest at all ages (1). Its effects are more devastating when the onset takes place in infancy, before speech acquisition (prelingual HI). Reported incidences for bilateral hearing loss of at least 40 dB range between 1 and 2 per 1,000 newborns in different studies (2). In developed countries, genetic causes account for over 60% of the cases. In at least 70% of these, HI is not associated to clinical signs in other organs (non-syndromic HI), and the autosomal recessive inheritance pattern is preponderant (3).

Soon it was noticed that localizing genes for non-syndromic prelingual HI was a formidable task, because of a combination of factors, namely the extreme genetic heterogeneity of HI, which results in many different etiological subtypes, the paucity of knowledge that may help to distinguish these subtypes clinically, and the endogamy between affected subjects. These problems were circumvented through the genetic study of single families, either large enough for conventional linkage analysis or amenable to homozygosity mapping because of consanguinity. By using this approach, the first locus for autosomal recessive non-syndromic HI (ARNSHI) was mapped to 13q12 (4). It was named DFNB1 (MIM# 220290), DFN being the acronym for deafness, B for autosomal recessive (the A letter was assigned to the dominant loci), and 1 for being the first to be discovered. As HI can be classified etiologically according to the gene that is mutated in each case, loci names are being used also to designate the different subtypes of ARNSHI. After the pioneer report of DFNB1, the list of DFNB loci has not stopped growing (5).

A milestone in the research on inherited HI was the finding that mutations in the GJB2 gene, which codes for connexin-26, a protein component of intercellular gap junctions, are the molecular cause of the DFNB1 subtype of ARNSHI (6). Subsequent studies revealed the high frequency of GJB2 mutations in most populations. Since then, molecular testing for GJB2 mutations has become the gold standard for the genetic diagnosis of ARNSHI. Moreover, generation and study of murine models and functional analyses of normal and mutated proteins have resulted in remarkable advances in our understanding of the underlying pathogenetic mechanism. In this review we summarize the current knowledge on the genetic, molecular, and phenotypic aspects of the DFNB1 subtype of ARNSHI.

3. GJB2 GENE AND CONNEXIN-26

3.1. Gene and protein structures

The GJB2 gene (MIM#121011) lies within a cluster of connexin genes on 13q12, flanked on the centromeric side by GJA3 (encoding connexin-46) and on the telomeric side by GJB6 (encoding connexin-30). GJB2 spans 5,513 bp and consists of just two exons. The 678-bp GJB2 coding sequence is completely contained in the second exon. Transcription from the single known transcription start site results in the production of two mRNAs of different lengths (2.4 and 2.8 kb) due to the use of alternative polyadenylation signals (7).

The 226-amino acid-long connexin-26 (Cx26), also known as Gap junction beta-2 protein, belongs to the connexin protein family, which comprises 21 different members in humans (8). Connexins are integral membrane proteins that form hydrophilic channels spanning a lipid bilayer. The connexin channel unit is a hexamer (termed "connexon"). Two connexons lying in the plasma membranes of two adjoining cells are able to assemble head to head (a process called "docking") to form an intercellular hydrophilic channel that directly connects the cytoplasms of the two cells. Arrays of hundreds of closely packed connexin intercellular channels form the characteristic plaques identifiable as gap junctions in electron microscopy images (9).

The crystal structure of the human Cx26 intercellular channel was recently determined at 3.5 Å resolution (10). Each Cx26 monomer consists of four transmembrane helical segments termed TM1 (residues 21-41), TM2 (residues 73-109), TM3 (residues 125-158) and TM4 (residues 186-216), joined by one cytosolic loop (residues 110-124) and two extracellular loops (E1, residues 42-72; and E2, residues 159-185), with N- and C-termini (residues 1-20 and 217-226, respectively) exposed to the cytosol (Figure 1 A). Overall, the Cx26 monomer forms a compact four-helix bundle in which adjacent helices are arranged in antiparallel conformation. Helices TM3 and TM4 face the hydrophobic environment of the membrane, whereas TM1 and TM2 face the interior of the channel (Figure 1 B-C). The longer helices TM2 and TM3 protrude into the cytosol. The four-helix bundle is stabilized both by different intramolecular interactions (hydrogen bonds or salt bridges) between the side chains of residues in adjacent transmembrane segments and by dipole-dipole interactions of the antiparallel helices.

Extracellular loops E1 and E2 play two distinct structural roles. Both loops have 3 cysteine residues each, with a specific spacing conserved in nearly all connexins (CX6CX3C in E1 and CX4CX5C in E2) (8), which are essential for normal folding and channel function. These cysteines form three intramolecular disulfide bonds (Cys53-Cys180, Cys60-Cys174 and Cys64-Cys169) between the E1 and E2 loops during the conformational maturation process that Cx26 undergoes when trafficking along the endoplasmic reticulum and Golgi complex. In addition, the E1 and E2 loops mediate the interactions between docked connexons in adjoining cell membranes that underlie the intercellular channel. The E1 loops of opposite monomers face each other across the extracellular gap; this is also the case with the E2 loops (Figure 1 C). Hydrogen bonds and salt bridges between polar residues in opposite E1-E1 loops and E2-E2 loops create a two-layered wall that bridges the gap between both cell membranes and separates the interior of the channel from the extracellular medium.

The actual hydrophilic pore of each connexon consists of an intracellular entrance (formed by the cytosolic protrusions of helices TM2 and TM3, with a net positive charge), a funnel (lined by the TM1 helix and the N-terminus), and an extracellular cavity (formed by the residues in the amino-terminal half of the E1 loop). Opening and closure of the channel depend on intracellular voltage-dependent interactions between residues in a short helix of the N-terminus and residues in TM1.

The structures of the cytoplasmic loop and C-terminus could not be modelled as they are disordered in electron density maps. They may participate in chemical gating or complete pore closure (10).

3.2. Gene expression and protein localization

The basal promoter of the GJB2 gene is contained in a 128-bp region located immediately upstream of the single transcription start site (7,11). The basal promoter contains a TATA motif (TTAAAA, at -24) and two identical GC boxes (CCGCCC, at -81 and -93), which are the core recognition sequences for transcription factors of the Sp1 family. These motifs are conserved between the human and murine basal promoter sequences, which are 81% identical (7). Electrophoretic mobility shift and supershift assays as well as transactivation experiments demonstrated that the Sp1 and Sp3 transcription factors bind the GC boxes; moreover, in vitro engineered mutations that destroy the consensus sequence for the Sp1 family factors in either of the GC boxes drastically reduce transcription from the GJB2 basal promoter, indicating that these two transcription factors indeed regulate the basal expression of GJB2 (11). Intriguingly, expression of the Gjb2 gene in mouse cochlear supporting cells is directly co-regulated with that of the neighbouring Gjb6 gene by a mechanism dependent on the activation of NF-kB (12). However, the relevance of this finding for the expression of human GJB2 is uncertain, as the human basal promoter lacks the NF-kB consensus binding site present in the murine basal promoter (11).

Northern blotting, RT-PCR, quantitative RT-PCR and in situ hybridization experiments in rodents have shown that GJB2 expression follows a tissue-specific pattern, with transcripts being detected in the mammary gland, inner ear (cochlea and vestibular organs), brain and hair follicles (13-17). Similar experiments performed with human material detected either GJB2 transcripts or Cx26 protein in preimplantation embryos (18), myometrium (19), lactating mammary gland (13, 20), corneal epithelium (21), skin keratinocytes throughout wound healing (22), sweat glands from normal skin (23) and inner ear structures (24).

Most of the data concerning the localization of Cx26 within the cochlea have been obtained from immunohistochemical experiments performed on mice or rats, because of the scarcity of fresh human cochlear material. Cx26 is one of the two major cochlear connexins, the other being Cx30, both in rodents (14, 16, 17) and humans (24). Both connexins are expressed in the same cochlear structures and co-localize (14, 16). In the adult, Cx26-containing cochlear gap junctions define two independent networks of coupled cells (Figure 2). The epithelial network couples all supporting cells of the organ of Corti and adjacent epithelial cells (25-27). The connective tissue network comprises fibrocytes and mesenchymal cells, and also includes basal and intermediate cells of the stria vascularis (25, 26, 28).

3.3. Function of connexin-26

Experiments performed on cultured cells that synthesize exogenous Cx26 have shown that Cx26 channels may play two different functional roles in tissue homeostasis. Cx26 intercellular gap-junction channels participate in the transfer from cell to cell of most hydrophilic compounds with a molecular mass below 1 kDa (including ions, metabolites and second messengers), down their electrochemical gradient. This kind of intercellular communication allows cells that are coupled by means of Cx26-gap junctions to act as a single functional unit. In addition to this transport role common to nearly all connexins, Cx26 so-called "hemichannels" (i.e. Cx26 connexons located at the plasma membrane that are not docked and thus connect the cytosol and the extracellular medium) participate in paracrine and autocrine signalling through the release or uptake of specific second messengers.

Within the cochlea, auditory transduction critically depends on the maintenance of the composition of endolymph and perilymph, on preserving the functionality of hair cells and on the production of the endocochlear potential. These homeostatic processes require the existence of specialized ion and solute transport mechanisms, in which gap junction networks are believed to be major players. Indeed, nearly all cochlear cells (except hair cells and marginal cells of the stria vascularis) are extensively coupled to their neighbours by numerous gap junctions, whose plaques are among the largest in the body (16, 25). On the basis of data gleaned from the analysis of cochlear organotypic cultures and of mouse models, four different roles for Cx26 channels in cochlear homeostasis have been postulated, three of them in the organ of Corti (spatial buffering of excitotoxic substances, supply of glucose to hair and supporting cells, calcium and ATP signalling in supporting cells) and one in the stria vascularis (transport of potassium ions for secretion into the endolymph) (Figure 2).

(i) Spatial buffering in the organ of Corti. Hair cells become depolarized when K+ ions flow into them upon sound stimulation. Hair cell repolarization involves K+ ion efflux through potassium channels at the basolateral domain of the hair cell membrane. K+ ions are then actively taken up by the supporting cells, what avoids the toxic effects of high extracellular K+ concentrations. It is believed that gap junctions coupling all supporting cells provide a pathway to disperse the excess K+ ions and funnel them away from the hair cells (Figure 2). This hypothesis is supported by the fact that deletion of GJB2 in the epithelial gap junction network (29, 30) results in death of hair cells on the onset of hearing, leading to the degeneration of the organ of Corti. Cx26 gap junctions in supporting cells would also help disperse other excitotoxic substances released by the receptor activity of hair cells, such as the neurotransmitter glutamate (29).

(ii) Gap junction-dependent metabolite transport. Energy consumption in the cells of the organ of Corti increases dramatically during sound transduction because of all the active transport processes that it entails. However, the organ of Corti is an avascular epithelium and, in consequence, hair cells and supporting cells lack a direct access to energy metabolites supplied by blood vessels. It was shown that glucose from the blood reaches the supporting cells by gap junction-mediated diffusion (31) (Figure 2).

(iii) Cx26-mediated Ca2+ and ATP signaling in the organ of Corti. Study of inositol 1,4,5-trisphosphate (IP3) transport in the organ of Corti showed that cochlear Cx26 participated in paracrine signalling (32). IP3 is a second messenger that causes intracellular release of Ca2+ ions and the spreading of Ca2+ oscillations to coupled supporting cells via gap junctions; these signaling processes are probably involved in the coordination of the activity of supporting cells, for instance to accomplish effective spatial buffering of K+ ions. Further characterization of this signaling route led to the identification of Cx26 hemichannel activity in supporting cells. Such hemichannels mediate the release of ATP, modulated by Ca2+ ions, to organ of Corti fluids. Extracellular binding of ATP by the purinergic P2X receptors of supporting cells elicits intracellular IP3 release and the propagation of a Ca2+ oscillation among coupled cells (33). In addition, ATP signaling through P2X receptors on outer hair cells modulates their electromotility, which regulates auditory transduction (34).

(iv) Transport of K+ ions within the stria vascularis for their secretion into endolymph. The stria vascularis generates the endocochlear potential and actively secretes K+ ions from the perilymph into the endolymph. The stria vascularis consists of two distinct epithelial cell layers (basal and marginal) that surround an extracellular space termed intrastrial space. Intermediate cells and capillaries are located in the intrastrial space. K+ ions are believed to be transferred to basal cells and intermediate cells, with the help of Cx26-containing gap junctions coupling these two cell types to fibrocytes within the connective tissue network (Figure 2). Other specialized transport mechanisms subsequently secrete K+ ions to the intrastrial space (which generates the endocochlear potential) and transfer them through the marginal cell layer into the endolymph (35-38).

4. MUTATIONS IN THE CODING REGION OF GJB2

Since the identification of the first DFNB1 pathogenic mutations, p.Trp24X and p.Trp77X (6), more than 100 sequence variants in the coding region of GJB2 have been reported. Most of these variants are responsible for DFNB1 hearing impairment, but mutations causing DFNA3 autosomal dominant non-syndromic HI or various skin disorders with or without HI have also been described. The sequence variants include nucleotide substitutions (nonsense, missense or silent mutations), and short insertions, duplications or deletions (either in-frame or causing frameshifts that lead to premature stop codons). It is not the purpose of this review to provide an exhaustive list of GJB2 variants that can be found in electronic databases (39). Instead, we focus our attention on the effects that the different classes of mutations causing DFNB1 HI exert on Cx26 function.

Given that the complete coding sequence of GJB2 is contained within the last exon of the gene, mutations generating premature stop codons are expected to escape the nonsense-mediated mRNA decay pathway (40, 41) and so truncated Cx26 proteins should actually be synthesized. This has been demonstrated for the c.235delC (p.Leu79CysfsX3) mutation, i.e. the truncated polypeptide was visualized by immunocytochemical methods in HeLa cells transiently transfected with a GJB2-c.235delC expression plasmid (42). Nevertheless, most of these truncated proteins lack one or several of the transmembrane segments, what is expected to have deleterious effects on protein folding, oligomerization, trafficking and localisation, and ultimately result in a complete loss of function.

In contrast, it is difficult to establish the pathogenic potential of GJB2 sequence variants not producing truncated proteins. Diverse assays have been developed to probe their effects on different aspects of gene or protein functions, such as transcription, translation, membrane insertion, oligomerization, intracellular traffic and plasma membrane targeting, and connexin-dependent intercellular communication (43, 44). These assays are robust and provide very helpful insights into Cx26 function, but they have two crucial shortcomings. The first one is that most of the techniques used are performed on cultured cells transiently or stably transfected with plasmids encoding the mutant Cx26 of interest. Thus, the in vitro or ex vivo conditions of the assay may not completely mimic the situation in an affected subject. The second shortcoming is specific to the assays for Cx26-dependent intercellular communication. They only probe some of the transport processes of Cx26 (e.g. transfer of fluorescent dyes, ion conductance) and, as Cx26 channels are permeable to many different compounds, the effects of some mutations on the transfer of specific substrates that are critical for the mechanism of hearing may be overlooked.

Moreover, experience shows that it is essential to combine genetic data obtained from sufficient numbers of affected subjects and ethnically-matched normal-hearing controls with results from functional assays, in order to conclude about the pathogenic potential of a non-truncating sequence variant. The cases of mutations p.Met34Thr and p.Val84Leu are illustrative. Mutation p.Met34Thr was originally described as a dominant negative DFNA3 allele on the basis of genetic data obtained from very few patients combined with the results of a single type of permeability assay (6, 45). Thereafter, genetic data from analyses of normal-hearing controls and of larger series of patients (46) established that p.Met34Thr was a hypomorphic recessive allele, as it was finally confirmed by more extensive testing with different types of functional assays (47-50). Conversely, results of assaying the wild-type Cx26 and the p.Val84Leu mutant protein in several model systems were indistinguishable (51), though genetic data supported that p.Val84Leu was a loss-of-function mutation (52). Eventually, experiments performed on cochlear organotypic cultures showed that the p.Val84Leu mutation impaired Cx26-dependent transfer of the second messenger IP3 between supporting cells of the organ of Corti, providing an explanation for its pathogenic effect (32).

Non-truncating sequence variants have been described in nearly all the structural elements of Cx26, with the exception of the very short C-terminus. Many of those that are pathogenic affect residues that are involved in connexon stabilization (through intra- and inter-monomer interactions) or that line the channel pore (Table 1).

There are four groups of residues that participate in intra-monomer interactions to stabilize the Cx26 four-helix bundle (10). Two of these groups are hydrophobic cores clustered around residues Trp-44 (with Ala-39, Ala-40, Val-43 and Ile-74) and Trp-77 (with Phe-154 and Met-195). Known variants affecting these residues are pathogenic (Table 1). The two other groups are clustered around arginine residues Arg-32 (which forms bonds with Gln-80, Glu-147 and Ser-199) and Arg-143 (which forms bonds with Ser-139 and Asn-206). Pathogenic mutations affecting every residue in these two groups have already been reported (Table 1). It is considered that mutations affecting residues in any of these four groups disrupt intra-monomer stabilizing interactions, which may result in impaired folding and/or oligomerization, in turn leading to the intracellular retention of the mutant proteins. This has been demonstrated by functional assays of the p.Trp77Arg mutation (47, 51, 53).

Residues involved in inter-monomer contacts are located in extracellular loops E1 (Asp-46, Glu-47, Gln-48, Asp-50, Asn-62, Tyr-65, Asp-66, Ser-72) or E2 (Arg-184), with the exceptions of Arg-75 (in TM2), Thr-186 and Glu-187 (both in TM4). Most of the GJB2 mutations causing dominantly inherited nonsyndromic deafness and/or skin disorders affect such residues (54), as could be expected because of their role in interactions between monomers. However, some mutations causing ARNSHI also affect residues in this category, such as p.Glu47Lys (55), p.Arg184Trp (56) and p.Arg184Pro (57). It is considered that these mutations would also impair folding and/or oligomerization. Indeed, p.Arg184Pro-Cx26 is unable to oligomerize (49) and it is never detected by immunochemical methods when expressed in HeLa cells (48, 49), suggesting that it is quickly degraded, perhaps due to misfolding.

Mutations in pore-lining residues at TM1 helix or E1 loop affect the permeability properties of the channel, altering its electrical conductance, charge selectivity or gating properties (Table 1). Two hypomorphic recessive mutations affect pore-lining residues in TM1: p.Met34Thr and p.Val37Ile (52). Both of them cause the loss of electrical conductance of the Cx26 gap junction channel when assayed in Xenopus oocytes (45, 51). In addition, p.Met34Thr blocks (47, 48) or significantly reduces (49) the ability of the Cx26 gap junction channel to transfer dyes. Cx26 channel permeability should also be altered by mutations targeting pore-lining residues in the N-terminus, such as p.Gly12Val (58). This does not happen, however, because p.Gly12Val-Cx26 is retained intracellularly (48), probably due to a membrane insertion defect that is also apparent in other mutations that affect N-terminal residues, like p.Ser19Thr (48, 58).

Some residues not participating in the interactions described above are also affected by pathogenic changes. Three mutations that substitute proline for different residues in TM2, p.Leu79Pro (59), p.Ser85Pro (60) and p. Leu90Pro (61), kink the helix and presumably evoke structural changes in the cytoplasmic domains of the Cx26 monomer (10), which may interfere with oligomerization or with the permeability properties of the channel. This has been confirmed in the case of p.Leu90Pro, which slightly impairs oligomerization, causes total loss of electrical conductance and blocks transfer of dyes when tested in functional assays (48, 49, 51). Also, several non-truncating variants affect residues in the cytoplasmic loop. Since the structure of this domain could not be determined, it is difficult to identify residues that are critical for the function of Cx26, and thus classify the sequence variants that are found in this region. However, at least two of them, p.Ser113Arg (52) and p.Glu120del (62), cause total loss of electrical conductance of the Cx26 channel (51) and they are clearly pathogenic.

In contrast, other missense variants do not affect residues critical for the structure of Cx26, and the currently available genetic data indicate that they are harmless polymorphisms. This group includes p.Val27Ile (52), p.Phe83Leu (63), p.Glu114Gly (64), p.Arg127His (65), p.Val153Ile (66), p.Gly160Ser (63) and p.Ile203Thr (67). Some of these sequence variants are very common in specific populations.

5. MUTATIONS AFFECTING NON-CODING PARTS OF THE GENE OR REGULATORY ELEMENTS

As mutation screening of the GJB2 gene in subjects with ARNSHI became a general practice, it was noticed that in a significant fraction (10-42 %) of affected subjects with mutations in the GJB2 coding region, only one mutant allele could be found, the expected accompanying mutation remaining unidentified. Part of these unexplained cases may be attributable to intrinsic drawbacks of the techniques for mutation detection, or they could represent just coincidental carriers of the most frequent GJB2 mutations, their HI having a different cause. However, it was long suspected that the missing mutations might be located in the non-coding parts of the gene, in regulatory elements acting at a distance, or in other genes.

5.1. Splice-site mutations

Only one splice-site mutation has been reported to date in GJB2 (61, 68). It affects the donor splice site of intron 1 (c.-23+1G>A or IVS1+1G>A, sometimes incorrectly referred to as -3170G>A). Since the coding region of GJB2 is fully contained in exon 2, this splice-site mutation has no effect on protein coding. On the contrary, sequencing of cDNA from a lymphoblastoid cell line that was generated from a heterozygous subject detected no transcript from the c.-23+1G>A allele, suggesting that it was not transcribed or that the transcript was extremely unstable (69). This mutation is the most frequent GJB2 pathogenic sequence variant in Mongolia (it accounts for about 50% of the pathogenic changes) (117), and it is relatively frequent in the Czech, Polish, Turkish, Kurdish and Chinese populations, being found in a significant fraction of cases with a single mutation in the coding region, and accounting for about 2-9.4 % of all DFNB1 alleles (70-73, 191).

5.2. Promoter mutations

A mutation affecting the GJB2 basal promoter was reported in a Portuguese subject with non-syndromic HI, who was a compound heterozygote, the accompanying mutation being p.Val84Met (74). The mutation was originally named -3438C>T, although according to the standard rules it should be renamed as g.-77C>T. It alters the fifth nucleotide of the GC box located at position -81 (CCGCCC > CCGCTC) (11), and so it is expected to impair the binding of the Sp1 and Sp3 transcription factors. Reporter-gene analysis performed in different cell lines demonstrated that the activity of the mutant promoter activity decreased dramatically or was abolished (74).

No further subjects with the g.-77C>T mutation have been reported to date, but data from extensive screenings are still scarce (75).

5.3. Large deletions

Four different large deletions have been reported to date in the DFNB1 locus (Table 2, Figure 3). They can be classified into three classes according to the genes that are involved.

The first class is constituted by large deletions encompassing the GJB2 gene. Only one deletion belonging to this class has been reported to date (76). It was found in the compound heterozygous state with a p.V84M mutant alelle of GJB2, in a French subject with non-syndromic, prelingual profound HI. The proximal limit of the deletion was not established, but the deleted segment spans at least 920 kb and removes many genes of the 13q11-q12 chromosomal region, including GJB2 and GJB6 (encoding connexin-30). The distal breakpoint is located in intron 2 of the CRYL1 gene, which codes for lambda-crystallin (76) (Figure 3). This deletion seems to be a private mutation, as it has not been reported in any other unrelated subject. Detection of this class of deletions is facilitated by the fact that they result in false homozygosity for the accompanying GJB2 point mutation in the affected subject, what can be noticed by studying its segregation in the pedigree.

The second class of deletions is constituted by those truncating GJB6, but not encompassing the GJB2 gene. The GJB6 gene has six exons (77), the coding region being fully contained in the last one. Several research groups reported large deletions affecting the GJB6 coding region in deaf subjects carrying only one mutant GJB2 allele (78-80). In one of these studies (79), the deletion breakpoint junction was isolated and sequenced. The proximal breakpoint lies within the coding region in GJB6 exon 6 and the distal breakpoint lies within the intergenic region between CRYL1 and IFT88 (intraflagellar transport 88 homolog), so truncating the GJB6 gene (the first five exons are eliminated) and removing the whole CRYL1 gene (Table 2, Figure 3). The analysis of the breakpoint junction suggested that this deletion most likely arose through a mechanism of illegitimate recombination. The size of the deletion interval was initially estimated to be 342 kb, according to the contemporary human sequence draft (79). Further investigation revealed that the deletions found by the three research groups (78-80) were the same one (81), which was named del(GJB6-D13S1830). Subsequent corrections of the human sequence draft established definitely its size in 309 kb (Table 2). The del(GJB6-D13S1830) mutation is a common allele in many European countries, its frequency peaking in Western Europe (Spain, France, United Kingdom) and decreasing towards the east. It has been reported in populations of European descent in America (United States, Brazil) and in Australia, and also in Ashkenazi Jews. On the contrary, it has not been reported to date in Asian or African populations. Although the finding of the del(GJB6-D13S1830) mutation provided an explanation for the hearing impairment in as many as 30%-70% of unelucidated GJB2 heterozygotes in some populations, it became evident that other DFNB1 mutations remained to be identified. Few years later, another deletion of the same class, del(GJB6-D13S1854), was detected, and its breakpoint junction was isolated and characterized (82). This deletion spans 232 kb and it was originated by homologous recombination between two Alu sequences, the proximal repeat being located in GJB6 intron 5 (so removing the first five exons), and the distal repeat in CRYL1 intron 4 (Table 2, Figure 3). It is a relatively common DFNB1 allele in some populations (Spain, United Kingdom, Brazil), but rare or absent in most populations. The detection of the del(GJB6-D13S1830) and del(GJB6-D13S1854) mutations for diagnostic purposes is facilitated by a multiplex PCR assay that amplifies the DNA segments containing the breakpoint junctions (82).

These findings could be interpreted on the basis of a digenic pattern of inheritance of mutations in GJB2 and GJB6. This hypothesis was supported by several facts: i) Both Cx26 and Cx30 are expressed in the same cochlear structures and co-localize (14, 16); ii) Connexons composed of Cx26 can bind connexons composed of Cx30 to form heterotypic gap-junction channels (83); iii) A mutation in GJB6 was reported in a case of autosomal dominant hearing impairment (84); iv) Cx30-deficient mice lack the endocochlear potential and exhibit a severe constitutive hearing impairment (85). However, the fact that point mutations in GJB6 have not been found to date in cases of ARNSHI in humans, argues against this hypothesis. In addition, Cx26+/-/Cx30+/- double heterozygous mice have only a moderate hearing impairment (86), in contrast with the phenotype observed in humans, where a majority of double heterozygotes for del(GJB6-D13S1830) and a GJB2 mutation have severe or profound hearing impairment (87). An alternative hypothesis postulated the existence of a cis-acting regulatory element that would activate the expression of GJB2 in the inner ear. This regulatory element would have been removed by the deletions, and its absence would have dramatic effects on the expression of GJB2, to the point that an otherwise normal allele would behave as a null allele. In fact, immunohistochemical analysis of a skin biopsy from a subject who was double heterozygous for c.35delG in GJB2 and del(GJB6-D13S1830) revealed that the expression of Cx26 was dramatically reduced in the ductal epithelium of sweat glands (23). Another study, using qualitative allele-specific RT-PCR to assess the relative abundance of the GJB2 transcript in buccal epithelium cells from three double heterozygous subjects (del(GJB6-D13S1830)/GJB2 mutation), demonstrated no detectable expression from the wild-type GJB2 allele that was in cis with the deletion (88).

Definitive evidence supporting the hypothesis of the cis-acting regulatory element has recently been provided by the detection and characterization of the first member of the third class of DFNB1 deletions, i.e. those encompassing neither GJB2 nor GJB6 (89, 90). The size of the deletion interval was estimated to be 131 kb, with the proximal breakpoint in the intergenic region between GJB6 and CRYL1, more than 100 kb upstream of the transcriptional start sites of GJB2 and GJB6 (90) (Table 2, Figure 3). It was found in several affected subjects of the same family, who were double heterozygous for the deletion and the c.35delG GJB2 mutation. In buccal epithelium cells from these subjects, qualitative allele-specific RT-PCR revealed that the expression from the wild-type GJB2 and GJB6 alleles in cis with the deletion was dramatically reduced. These results not only support the existence of the cis-acting regulatory element, but they also suggest that it could be involved in GJB2 and GJB6 co-regulation. If this were the case, the removal of GJB6 by the deletions of the second class could contribute to worsen the phenotype of HI of affected subjects, as it has been shown for del(GJB6-D13S1830) (see below, section 7.2). Overlapping of all deletion intervals that have been characterized to date defines a 95.4 kb interval that must contain the regulatory element, whose localization could be refined by molecular characterization of other novel DNA rearrangements in the DFNB1 locus leading to hearing impairment.

6. GENETIC EPIDEMIOLOGY OF DFNB1 HEARING IMPAIRMENT

Progress in the genetic epidemiology of ARNSHI is complicated by the large heterogeneity of these disorders and by the variability among different populations as regards the prevalence of each genetic subtype and the diversity and relative frequency of mutations in the different genes. A large part of this variability is due to diverse founder effects for specific mutations and to the abundance of private mutations. Among the many different subtypes of ARNSHI, DFNB1 is remarkable for being highly prevalent in most of the populations that have been tested. Consequently, a plethora of studies have provided epidemiological data for populations all over the world.

It is important to note that there are many differences between the diverse studies as regards issues that are critical for a proper comparison. These include: i) Differences in the clinical criteria for inclusion/exclusion of affected subjects in the cohorts under study. Special attention should be paid to whether results of a given study refer to prelingual non-syndromic HI, childhood non-syndromic HI (including prelingual and postlingual forms), or just ARNSHI. Although it is true that most ARNSHI corresponds to prelingual HI, these are not equivalent categories. Attention should also be paid to possible biases in selection as regards the severity of the HI; ii) Differences in the proportion of multiplex (familial) or simplex (sporadic) cases in the cohorts under study. Given that the frequencies of DFNB1 HI that are observed in multiplex cases are usually significantly higher than those observed in sporadic cases, it is advisable to present these data separately, not combining them in a single value, to facilitate accurate comparison between populations; iii) Differences in the criteria for classifying a case as DFNB1. Only cases with two DFNB1 mutant alleles (the so-called biallelic cases, i.e. confirmed DFNB1 cases) should be counted up. Cases heterozygous for a single pathogenic mutation (so-called monoallelic), who could be just coincidental carriers, their HI being caused by mutations in other genes, should not be added up to the confirmed DFNB1 cases. Since this information is also valuable, it should be provided as a separate number; iv) Differences in the genotyping methods (direct sequencing or previous screening by mutation detection techniques with different detection rates) and in how comprehensive was the screening, i.e. whether only the GJB2 coding region was examined or whether mutations affecting non-coding parts of the gene and large deletions were also investigated. It should be noted that these differences might have a strong impact on the number of cases with a single pathogenic mutation, being a source of error when estimating the contribution of DFNB1 to ARNSHI; v) Differences in the consideration of specific alleles as pathogenic or harmless. Relative frequencies of DFNB1 pathogenic alleles are consequently biased; vi) Differences in the ethnic composition of the cohorts from a same country; and vii) Differences in the size of the cohorts under study. In spite of all these issues, which make that most of the studies are not strictly comparable, several conclusions have emerged.

The high prevalence of DFNB1 among ARNSHI was early observed (56, 91). Subsequent studies indicated that it is a major cause of ARNSHI in many populations. DFNB1 HI is highly frequent (20-40% of all cases with ARNSHI) in Europe (58, 61, 92-99), in the Middle East (69, 100-102), and in Argentina (103). It is less frequent (12-22%), but still a major cause of ARNSHI, in USA (104-107), Brazil (108, 109), East Asia (110, 111), and Australia (57, 112). In Central Asia, moderate frequencies (about 15%) are observed in Iran and India (113-115), whereas low frequencies are reported in Pakistan (6%) (116) and Mongolia (4.5 %) (117). It seems to be rare in Indonesia (118) and it was not found in the Omani population (data from a small cohort of affected subjects) (119).

The spectra of DFNB1 mutations also vary across the different populations, as regards the list of the sequence variants and their relative frequencies. Many different mutations in the DFNB1 locus have been found repeatedly in diverse populations (39), but few of them predominate, as indicated below.

The c.35delG mutation was early shown to be highly frequent in Caucasians (56, 91). It accounts for 42-88% of mutant GJB2 alleles found in subjects with DFNB1 HI in Caucasian populations from Europe, America, and Australia (57, 58, 61, 92-99, 103-109, 112). Its carrier frequency in the general population ranges from about 1% in Northern and Central Europe to 2-3% in the European Mediterranean countries (120). It was initially hypothesized that the stretch of six guanosine nucleotides that is affected by c.35delG might represent a hot spot for mutation, what would imply recurrency and multiple origins (52, 121). However, further studies revealed a common founder (122-126). The mutation seems to trace its origins to the Eastern Mediterranean region or to the Middle East. A Greek origin has been postulated (127, 128).

The c.235delC mutation was first identified in a cohort of Japanese affected subjects (64). Later on it was shown to be frequent in East Asian populations, accounting for 34-70 % of mutant GJB2 alleles found in subjects with DFNB1 HI (60, 110, 111, 129, 130), carrier frequencies in the general population being 1-2% (60, 129-131). A common founder is responsible for this high frequency (130, 132).

The p.Arg143Trp mutation was first reported in families from a small village in Ghana, West Africa (133), and later on it was shown to be highly frequent (91% of GJB2 pathogenic alleles) in a cohort of affected subjects from all the country (59). This high frequency might be related to a putative selective advantage provided by the mutation. A study on skin biopsies from homozygotes, heterozygotes and wild-type subjects from the same family, showed that the epidermis was significantly thicker in homozygotes and heterozygotes for p.Arg143Trp. Moreover, sodium and chloride concentrations in sweat were higher in homozygotes (134). These findings were postulated to provide a more robust mechanical skin barrier to trauma and insect bites, and an unfavourable osmotic milieu for microbial colonization, as demonstrated for the enteric pathogen Shigella flexneri (134, 135). However, this high frequency is likely not to be extrapolatable to all Subsaharan Africa, since the mutation was not found in a combined cohort of subjects from Kenya and Sudan (136).

The c.167delT mutation was early identified (91), and subsequently it was shown to be highly frequent in Ashkenazi Jews because of sharing a common founder (121, 137). It accounts for 76% of GJB2 pathogenic alleles (138), and its carrier rate in the general population has been estimated to be 2.8-7.5% (121, 137-139).

The p.Trp24X mutation was first described in a Pakistani family (6). Subsequent studies demonstrated that it is the predominating GJB2 allele in India (83-91% of the pathogenic DFNB1 alleles) (114, 115) and also in the European Romani (Gypsy) populations (64-93% of the pathogenic DFNB1 alleles) (96, 140, 141). Its carrier rate in India was estimated to be 2.4% (115), and it is consistently found in the 4%-5% range in the Romani populations, although it is highly variable among cohorts (140-142). These results place p.Trp24X among the three most common founder mutations in the Gypsies, and classify them as one of the high-risk populations for prelingual deafness (142). Common founders have been demonstrated separately for the Indian and Romani populations (115, 141), but it is very likely that the origin of the mutation took place in the Indian subcontinent, where the Romani people was originally settled before moving in successive migrations towards the European countries.

7. GENOTYPE-PHENOTYPE CORRELATIONS

Early studies on genotype-phenotype correlations in the DFNB1 subtype of ARNSHI concluded that it was prelingual, with a great variability in severity, which ranged from mild to profound even for equal mutant genotypes (61, 143). Audiogram shapes were generally flat or sloping, but they were not pathognomonic (61). The HI was stable or slightly progressive, and no radiologically detectable inner ear malformations were observed (61, 143). Further studies have essentially confirmed these conclusions (87, 97-99, 105, 107, 144-151), but they have also provided insight into some specific issues.

7.1. Age of onset and evolution of the hearing impairment

DFNB1 HI is mostly prelingual (only a few specific mutations may result in later onset; see below), but evidence is accumulating against being mostly congenital. A study reported nine children with two DFNB1 mutant alleles who passed the newborn audiologic hearing screening and were diagnosed with HI later on (152). In another study on 47 children with profound HI and two GJB2 mutations, 55% of them had good auditory capacity at 3 months of age, which worsened suddenly later on (153). In fact, it has been postulated that the onset of DFNB1 prelingual non-congenital HI could be followed by a rapidly progressive hearing loss (154). A sudden late onset followed by rapid progression of HI was also documented in an 8-year-old boy with a c.35delG/c.299-300delAT genotype (151). Furthermore, another boy who was homozygous for c.35delG and had postlingual HI (onset at age 8 years), experienced a sudden worsening of his HI at age 23 years (155). Given the high prevalence of DFNB1 HI, these issues are of concern to the protocols that try to anticipate the clinical diagnosis of HI.

7.2. Severity of the hearing impairment

In a cross-sectional analysis of DFNB1 genotype and audiometric data from over 1,500 affected subjects from 16 countries, mutations were classified as truncating (those resulting in premature stop codons, and also del(GJB6-D13S1830) and c.-23+1G>A) or non-truncating (missense mutations and in-frame deletions). As expected, variability in the severity of the HI was observed even for the same genotype (e.g. homozygous c.35delG). But interestingly, the degree of HI associated with the presence of two truncating mutations was shown to be significantly more severe than that of the HI associated with two non-truncating mutations (87). The severity of HI associated with truncating/non-truncating genotypes was intermediate between those two groups. Furthermore, some genotypes were consistently associated with specific degrees of severity. Genotypes c.35delG/p.Arg143Trp and c.35delG/del(GJB6-D13S1830) usually resulted in profound HI (87). In contrast, genotypes including p.Leu90Pro, p.Met34Thr, or p.Val37Ile with a truncating mutation in trans were associated with mild or moderate HI (86, 144). Further studies in smaller cohorts have confirmed these conclusions (97, 99, 107, 145, 150, 151).

The pathogenic potential of p.Met34Thr and p.Val37Ile has been a controversial issue for years (46, 52, 67, 156, 157). Both affect pore-lining residues in TM1, both have high carrier rates in specific populations, and both have been reported in subjects with HI and in subjects with normal hearing, either in the homozygous state or in the compound heterozygous state with clearly pathogenic mutations. Taking all available data together, these two alleles must be classified as hypomorphic, i.e. with low penetrance and weak pathogenic potential. The associated phenotype is expected to range from normal hearing to late onset, progressive, mild to moderate hearing loss (71, 111, 158-162).

7.3. Modifier genes

The wide range in the degree of severity that is observed in DFNB1 HI has been attributed at least partly to the influence of modifier genes. To investigate this issue, a whole-genome association study was performed on c.35delG homozygotes, by comparing the genotypes of mild/moderate cases and profound cases. The first analysis consisted in a pooling-based whole-genome association study of 255 samples. The top 250 most significantly associated SNPs were genotyped individually in the same sample set. A total of 192 SNPs still had significant P-values. These were then genotyped in a second independent set of 297 samples for replication. Significant P-values were replicated in nine SNPs. These results suggest that the variability in the degree of severity observed in c.35delG homozygotes cannot be explained by the effect of one major modifier gene. Each one of those nine SNPs might contribute with just a small modifying effect on the phenotype (163).

7.4. Inner ear malformations

The existence of putative inner ear malformations associated with DFNB1 HI has been investigated by means of high-resolution computed tomography (CT) scans of temporal bones of affected subjects. In an early study, no temporal bone anomalies were found in a series of 23 subjects with biallelic GJB2 mutations (61). Most of the subsequent studies coincide in establishing that the prevalence of temporal bone malformations in DFNB1 HI subjects would be typically lower than 10% (104, 164-166). Only one study contradicts this view, by reporting a prevalence of temporal bone anomalies of 72% in a cohort of subjects with DFNB1 HI. These anomalies included dilated endolymphatic fossa, hypoplastic modiolus, enlarged vestibular aqueduct, or hypoplastic cochlea (167). This discrepancy might be due to differences in methodology (thickness of the CT slices, measurement techniques) and in the composition of the cohorts of subjects as regards the severity of the HI (168). Further research is needed to determine whether subtle anomalies are being missed by conventional methods or whether a too high rate of detection is attributable to a technical artifact.

7.5. Temporal bone histopathology

In contrast to the wealth of audiological data obtained from subjects with GJB2 mutations, very little is known on the histopathological processes that occur in DFNB1 HI. In the single report published to date (169), the archives of a repository of temporal bones were examined in search of samples obtained from subjects with congenital, severe-to-profound or profound HI. Five temporal bones of subjects meeting those characteristics were screened for GJB2 mutations and subjected to histological analysis. Only one of the subjects, a compound heterozygote for c.35delG and p.Glu101Gly, had DFNB1 HI. Microscopic analysis of cochlear sections from this subject showed almost total degeneration of hair cells in the organ of Corti, a detached tectorial membrane, and agenesis of the stria vascularis with formation of a large cyst in the region where the stria should have been. Notably, neural degeneration was not observed, as both the spiral ganglion cell population and the eighth cranial nerve were normal. These alterations are in good agreement with the known sites of GJB2 expression within the cochlea, but the subject had suffered from other pathologies (diabetes mellitus, hypertension, chronic renal failure and coronary atherosclerosis) that might have influenced the degenerative process.

7.6. Vestibular function

Vestibular function of subjects with DFNB1 HI is not routinely explored, because they do not complain of vertigo or dizziness. However, a study performed on two subjects with two pathogenic GJB2 mutations revealed pathological recordings of vestibular-evoked myogenic potentials, which would suggest a saccular dysfunction. No abnormalities in the function of utricle and semicircular canals were observed. These subjects did not complain of vertigo or dizziness, possibly because of central compensation (170). In another study performed on seven subjects with two pathogenic GJB2 mutations, vestibular-evoked myogenic potentials revealed unilaterally abnormal responses in three subjects, the four other showing normal responses (171). Investigation of larger series of affected subjects is clearly needed to reach conclusions on this issue.

7.7. Audiologic phenotype of carriers

As expected for a recessive trait, heterozygous carriers of DFNB1 mutations have apparently normal hearing. However, subtle audiological alterations might be present. In studies performed on heterozygous carriers for c.35delG, p.Trp77Arg or p.Val37Ile from the same Israeli Arab village in Galilee, audiograms and auditory brainstem responses were normal. However, when testing distortion-product oto-acoustic emissions, responses from carriers had significantly lower amplitudes than those of non-carrier controls, a result that would suggest that GJB2 mutations affect primarily the outer hair cells (172, 173). In another study, audiograms from c.35delG heterozygous carriers showed mild hearing losses at the high frequencies (6 and 8 kHz) (174). Confirmation of these conclusions requires further research of larger series of carriers and more mutations.

7.8. Outcome of cochlear implantation

The outcome of cochlear implantation has been examined in subjects with DFNB1 HI in comparison with subjects having non-DFNB1 HI. Several studies showed a clear improvement in speech perception skills after implantation for the two groups, without significant differences between them (175-178). On the contrary, reading performance of subjects with DFNB1 HI was consistently better (175, 176).

8. ANIMAL MODELS

To fill the gap in our understanding of the histopathological processes that occur in DFNB1 HI, researchers resorted to the generation of a mouse model of the disease. Unfortunately, mice homozygous for a targeted inactivation of Gjb2 die in mid-gestation due to a defect in placental transport of nutrients, what precluded any analysis of cochlear structure or auditory function (179). Conditional knockouts have been thus used in an attempt to replicate the consequences of Cx26 deficiency on the inner ear. However, it has been technically difficult so far to obtain a conditional model in which Cx26 is homogeneously ablated in all the cochlear structures that express GJB2.

The available models use Cre-loxP conditional technology to achieve deletion by homologous recombination of the complete coding region of Gjb2 in the Gjb2loxP/loxP mouse line (29). This line has been used in studies that followed different approaches to achieve Gjb2 deletion: either cell-type specific (Otog-Cre, Foxg1-Cre, Pax2-Cre) (29, 180) or time-specific (R26Cre-ERT; deletion is activated by a dose of tamoxifen) (30). In Otog-Cre Gjb2loxP/loxP mice, Gjb2 deletion was restricted to the organ of Corti (the epithelial gap-junction network) (29). In those mice, the organ of Corti developed normally, but it suddenly degenerated just after the onset of hearing (which takes place on postnatal day 14 in mice), starting with death of the supporting cells that eventually extended to encompass the hair cells. The resulting loss of integrity of the endolymph-perilymph barrier at the organ of Corti caused significant decreases of the endocochlear potential and of the endolymphatic potassium concentration, leading to hearing impairment across all frequencies.

In R26Cre-ERT Gjb2loxP/loxP, Foxg1-Cre Gjb2loxP/loxP, and Pax2-Cre Gjb2loxP/loxP mice, complete deletion of Gjb2 was only achieved in the organ of Corti, while deletion was just partial in other cochlear structures, including the stria vascularis (30, 180). The organ of Corti of these three murine lines developed normally at first, although the spaces of Nuel and the tunnel of Corti failed to open at postnatal day 9, suggesting a role for Cx26 in the final development of the organ of Corti (180). Hair cell degeneration started just after the onset of hearing, although cell death occurred more gradually than in Otog-Cre Gjb2loxP/loxP mice. Many spiral ganglion neurons subsequently disappeared. Notably, the most severe degeneration occurred in the middle turn of the cochlea, i.e. the region most sensitive to sound, although hearing impairment extended across all frequencies (30, 180).

Altogether, the results obtained with the various Gjb2 conditional inactivation approaches supports the concept that hair cell death due to lack of Cx26 is triggered by sound-driven activities, whether because of a loss of spatial buffering of excitotoxic substances (29) or because of impaired transport of energy metabolites that are actively being consumed (30). Unfortunately, all these conditional mice, while very valuable, do not mimic the situation in most human DFNB1 patients, who completely lack Cx26. Thus, a model with complete inactivation of Cx26 in the cochlea is necessary to fully understand the pathogenesis of DFNB1 and, eventually, to test prospective therapies.

9. ACKNOWLEDGEMENTS

Research on the genetics of DFNB1 hearing impairment in the laboratory of the authors has received funding from Instituto de Salud Carlos III (grants FIS08/0818 and CP06/00050), Ministerio de Ciencia e Innovacion (grant SAF2008-03216), Fundacion Mutua Madrilena and Fundacion Ramon Areces.

10. REFERENCES

1. Joseph B. Nadol: Hearing loss. N Engl J Med 329, 1092-1102 (1993)
doi:10.1056/NEJM199310073291507

2. Cynthia C. Morton and Walter E. Nance: Newborn hearing screening - a silent revolution. N Engl J Med 354, 2151-2164 (2006)
doi:10.1056/NEJMra050700

3. Christine Petit: Genes responsible for human hereditary deafness: symphony of a thousand. Nat Genet 14, 385-391 (1996)
doi:10.1038/ng1296-385

4. Parry Guilford, Saida Ben Arab, Stéphane Blanchard, Jacqueline Levilliers, Jean Weissenbach, Ali Belkahia, Christine Petit: A non-syndromic form of neurosensory, recessive deafness maps to the pericentromeric region of chromosome 13q. Nat Genet 6, 24-28 (1994)
doi:10.1038/ng0194-24

5. Guy Van Camp, Richard J.H. Smith: Hereditary Hearing Loss Homepage. URL: http://hereditaryhearingloss.org

6. David P. Kelsell, John Dunlop, Howard P. Stevens, Nicholas J. Lench, Jianning Liang, Gareth Parry, Robert F. Mueller, Irene M. Leigh: Connexin 26 mutations in hereditary non-syndromic sensorineural deafness. Nature 387, 80-83 (1997)
doi:10.1038/387080a0

7. David T. Kiang, Ni Jin, Zheng Jin Tu, Her H. Lin: Upstream genomic sequence of the human connexin26 gene. Gene 199, 165-171 (1997)
doi:10.1016/S0378-1119(97)00365-X

8. Véronique O. Cruciani, Svein-Ole Mikalsen: The vertebrate connexin family. Cell Mol Life Sci 63, 1125-1140 (2006)
doi:10.1007/s00018-005-5571-8

9. Nalin M. Kumar, Norton B. Gilula: The gap junction communication channel. Cell 84, 381-388 (1996)
doi:10.1016/S0092-8674(00)81282-9

10. Shoji Maeda, So Nakagawa, Michihiro Suga, Eiki Yamashita, Atsunori Oshima, Yoshinori Fujiyoshi, Tomitake Tsukihara: Structure of the connexin 26 gap junction channel at 3.5 Ǻ resolution. Nature 458, 597-604 (2009)
doi:10.1038/nature07869

11. Zheng J. Tu, David T. Kiang: Mapping and characterization of the basal promoter of the human connexin26 gene. Biochim Biophys Acta 1443, 169-181 (1998)

doi:10.1016/S0167-4781(98)00212-7

12. Saida Ortolano, Giovanni Di Pasquale, Giulia Crispino, Fabio Anselmi, Fabio Mammano, John A. Chiorini: Coordinated control of connexin 26 and connexin 30 at the regulatory and functional level in the inner ear. Proc Natl Acad Sci USA 105, 18776-18781 (2008)
doi:10.1073/pnas.0800831105

13. Ambra Pozzi, Boris Risek, David T. Kiang, Norton B. Gilula, Nalim M. Kumar: Analysis of multiple gap junction gene products in the rodent and human mammary gland. Exp Cell Res 220, 212-219 (1995)
doi:10.1006/excr.1995.1308

14. Jürgen Lautermann, Wouter-Jan F. ten Cate, Petra Altenhoff, Ruth Grümmer, Otto Traub, H.-G. Frank, Klaus Jahnke, Elke Winterhager: Expression of the gap-junction connexins 26 and 30 in the rat cochlea. Cell Tissue Res 294, 415-420 (1998)
doi:10.1007/s004410051192

15. Kevin Bittman, David L. Becker, Federico Cicirata, John G. Parnavelas: Connexin expression in homotypic and heterotypic cell coupling in the developing cerebral cortex. J Comp Neurol 443, 201-212 (2002)
doi:10.1002/cne.2121

16. Andrew Forge, David Becker, Stefano Casalotti, Jill Edwards, Nerissa Marziano, Graham Nevill: Gap junctions in the inner ear: Comparison of distribution patterns in different vertebrates and assessment of connexin composition in mammals. J Comp Neurol 467, 207-231 (2003)
doi:10.1002/cne.10916

17. Annalisa Buniello, Donatella Montanaro, Stefano Volinia, Paolo Gasparini, Valeria Marigo: An expression atlas of connexin genes in the mouse. Genomics 83, 812-820 (2004)
doi:10.1016/j.ygeno.2003.10.011

18. Debra J. Bloor, Yvonne Wilson, Mark Kibschull, Otto Traub, Henry J Leese, Elke Winterhager, Susan J Kimber: Expression of connexins in human preimplantation embryos in vitro. Reprod Biol Endocrinol 2, 25 (2004)
doi:10.1186/1477-7827-2-25

19. H. Nadir Çiray, Xin Fu, Matts Olovsson, Göran Ahlsen, Cynthia Shuman, Bo Lindblom, Ulf Ulmsten: Presence and localization of connexins 43 and 26 in cell cultures derived from myometrial tissues from nonpregnant and pregnant women and from leiomyomas. Am J Obstet Gynecol 182, 926-930 (2000)
doi:10.1016/S0002-9378(00)70348-6

20. Susan Jamieson, James J. Going, Roy D'Arcy, W. David George: Expression of gap junction proteins connexin 26 and connexin 43 in normal human breast and in breast tumours. J Pathol 184, 37-43 (1998)
doi:10.1002/(SICI)1096-9896(199801)184:1<37::AID-PATH966>3.0.CO;2-D

21. Daniel L. Shurman, Lisa Glazewski, Anna Gumpert, James D. Zieske, Gabriele Richard: In vivo and in vitro expression of connexins in the human corneal epithelium. Inves Ophthalm Vis Sci 46, 1957-1965 (2005)
doi:10.1167/iovs.04-1364

22. Johanna M Brandner, Pia Houdek, Birgit Hüsing, Colette Kaiser, Ingrid Moll: Connexins 26, 30, and 43: differences among spontaneous, chronic, and accelerated human wound healing. J Invest Dermatol 122, 1310-1320 (2004)
doi:10.1111/j.0022-202X.2004.22529.x

23. John E.A. Common, Maria Bitner-Glindzicz, Edel A. O'Toole, Michael R. Barnes, Lucy Jenkins, Andrew Forge, David P. Kelsell: Specific loss of connexin 26 expression in ductal sweat gland epithelium associated with the deletion mutation del(GJB6-D13S1830). Clin Exp Dermatol 30, 688-693 (2005)
doi:10.1111/j.1365-2230.2005.01878.x

24. Wei Liu, Marja Boström, Anders Kinnefors, Helge Rask-Andersen: Unique expression of connexins in the human cochlea. Hear Res 250, 55-62 (2009)
doi:10.1016/j.heares.2009.01.010

25. Toshihiko Kikuchi, Joe C. Adams, David L. Paul, Robert S. Kimura: Gap junction systems in the rat vestibular labyrinth: Immunohistochemical and ultrastructural analysis. Acta Otolaryngol 114, 520-528 (1994)
doi:10.3109/00016489409126097

26. Toshihiko Kikuchi, Robert S. Kimura, David L. Paul, Joe C. Adams: Gap junctions in the rat cochlea: immunohistochemical and ultrastructural analysis. Anat Embryol 191, 101-118 (1995)
doi:10.1007/BF00186783

27. Christopher M. Frenz, Thomas R. Van De Water: Immunolocalization of connexin26 in the developing mouse cochlea. Brain Res Rev 32, 172-180 (2000)
doi:10.1016/S0165-0173(99)00078-8

28. An-Ping Xia, Toshihiko Kikuchi, Koji Hozawa, Yukio Katori, Tomonori Takasaka: Expression of connexin26 and Na,K-ATPase in the developing mouse cochlear lateral wall: functional implications. Brain Res 846, 106-111 (1999)
doi:10.1016/S0006-8993(99)01996-4

29. Martine Cohen-Salmon, Thomas Ott, Vincent Michel, Jean-Pierre Hardelin, Isabelle Perfettini, Michel Eybalin, Tao Wu, Daniel C. Marcus, Philine Wangemann, Klaus Willecke, Christine Petit: Targeted ablation of connexin26 in the inner ear epithelial gap junction network causes hearing impairment and cell death. Curr Biol 12, 1106-1111 (2002)
doi:10.1016/S0960-9822(02)00904-1

30. Yu Sun, Wenxue Tang, Qing Chang, Yunfeng Wang, Weijia Kong, Xi Lin: Connexin30 null and conditional connexin26 null mice display distinct pattern and time course of cellular degeneration in the cochlea. J Comp Neurol 516, 569-579 (2009)
doi:10.1002/cne.22117

31. Qing Chang, Wenxue Tang, Shoeb Ahmad, Binfei Zhou, Xi Lin: Gap junction mediated intercellular metabolite transfer in the cochlea is compromised in connexin30 null mice. PLoS ONE 3, e4088 (2008)
doi:10.1371/journal.pone.0004088

32. Martina Beltramello, Valeria Piazza, Feliksas F. Bukauskas, Tullio Pozzan, Fabio Mammano: Impaired permeability to IP3 in a mutant connexin underlies recessive hereditary deafness. Nat Cell Biol 7, 63-69 (2005)
doi:10.1038/ncb1205

33. Fabio Anselmi, Victor H. Hernandez, Giulia Crispino, Anke Seydel, Saida Ortolano, Stephen D. Roper, Nicoletta Kessaris, William Richardson, Gesa Rickheit, Mikhail A. Filippov, Hannah Monyer, Fabio Mammano: ATP release through connexin hemichannels and gap junction transfer of second messengers propagate Ca2+ signals across the inner ear. Proc Natl Acad Sci USA 105, 18770-18775 (2008)
doi:10.1073/pnas.0800793105

34. Hong-Bo Zhao, Ning Yu, Carrie R. Fleming: Gap junctional hemichannel-mediated ATP release and hearing controls in the inner ear. Proc Natl Acad Sci USA 102, 18724-18729 (2005)
doi:10.1073/pnas.0506481102

35. Philine Wangemann, Jianzhong Liu, Daniel C. Marcus: Ion transport mechanisms responsible for K+ secretion and the transepithelial voltage across marginal cells of stria vascularis in vitro. Hear Res 84, 19-29 (1995)
doi:10.1016/0378-5955(95)00009-S

36. Shunji Takeuchi, Motonori Ando, Akinobu Kakigi: Mechanism generating endocochlear potential: role played by intermediate cells in stria vascularis. Biophys J 79, 2572-2582 (2000)
doi:10.1016/S0006-3495(00)76497-6

37. Daniel C. Marcus, Tao Wu, Philine Wangemann, Paulo Kofuji: KCNJ10 (Kir4.1) potassium channel knockout abolishes endocochlear potential. Am J Physiol Cell Physiol 282, C403-407 (2002)
doi:10.1152/ajpcell.00312.2001

38. Florian Lang, Volker Vallon, Marlies Knipper, Philine Wangemann: Functional significance of channels and transporters expressed in the inner ear and kidney. Am J Physiol Cell Physiol 293, C1187-C1208 (2007)
doi:10.1152/ajpcell.00024.2007

39. Ester Ballana, Marina Ventayol, Xavier Estivill: Connexins and deafness Homepage. URL: http://www.crg.es/deafness

40. Lynne E. Maquat: Nonsense-mediated mRNA decay: splicing, translation and mRNP dynamics. Nat Rev Mol Cell Biol 5, 89-99 (2004)
doi:10.1038/nrm1310

41. Holly A. Kuzmiak, Lynne E. Maquat: Applying nonsense-mediated mRNA decay research to the clinic: progress and challenges. Trends Mol Med 12, 306-316 (2006)
doi:10.1016/j.molmed.2006.05.005

42. Yun Hoon Choung, Sung-Kyun Moon, Hong-Joon Park: Functional Study of GJB2 in Hereditary Hearing Loss. Laryngoscope 112, 1667-1671 (2002)
doi:10.1097/00005537-200209000-00026

43. Judy K. VanSlyke, Linda S. Musil: Analysis of connexin intracellular transport and assembly. Methods 20, 156-164 (2000)
doi:10.1006/meth.1999.0933

44. Muriel Abbaci, Muriel Barberi-Heyob, Walter Blondel, François Guillemin, Jacques Didelon: Advantages and limitations of commonly used methods to assay the molecular permeability of gap junctional intercellular communication. BioTechniques 45, 33-62 (2008)
doi:10.2144/000112810

45. Thomas W White, Michael R. Deans, David P. Kelsell, David L. Paul: Connexin mutations in deafness. Nature 394, 630-631 (1998)
doi:10.1038/29202

46. Andrew J. Griffith, Aqeel A. Chowdhry, Kiyoto Kurima, Linda J. Hood, Bronya Keats, Charles I. Berlin, Robert J. Morell, Thomas B. Friedman: Autosomal recessive nonsyndromic neurosensory deafness at DFNB1 not associated with the compound-heterozygous GJB2 (connexin 26) genotype M34T/167delT. Am J Hum Genet 67, 745-749 (2000)
doi:10.1086/303045

47. Patricia E.M. Martin, Sharon L. Coleman, Stefano O. Casalotti, Andrew Forge, W. Howard Evans: Properties of connexin26 gap junctional proteins derived from mutations associated with non-syndromal hereditary deafness. Hum Mol Genet 8, 2369-2376 (1999)
doi:10.1093/hmg/8.13.2369

48. Paola D'Andrea, Valentina Veronesi, Massimiliano Bicego, Salvatore Melchionda, Leopoldo Zelante, Enzo Di Iorio, Roberto Bruzzone, Paolo Gasparini: Hearing loss: frequency and functional studies of the most common connexin26 alleles. Biochem Biophys Res Com 296, 685-691 (2002)
doi:10.1016/S0006-291X(02)00891-4

49. Eva Thönnissen, Raquel Rabionet, Maria Lourdes Arbonès, Xavier Estivill, Klaus Willecke, Thomas Ott: Human connexin26 (GJB2) deafness mutations affect the function of gap junction channels at different levels of protein expression. Hum Genet 111, 190-197 (2002)
doi:10.1007/s00439-002-0750-2

50. Ingrid M. Skerrett, Wei-Li Di, Eileen M. Kasperek, David P. Kelsell, Bruce J. Nicholson: Aberrant gating, but a normal expression pattern, underlies the recessive phenotype of the deafness mutant Connexin26 M34T. FASEB J 18, 860-862 (2004)
doi:10.1096/fj.03-0763fje

51. Roberto Bruzzone, Valentina Veronesi, Danielle Gomès, Massimiliano Bicego, Nathalie Duval, Sandrine Marlin, Christine Petit, Paola D'Andrea, Thomas W. White: Loss-of-function and residual channel activity of connexin26 mutations associated with non-syndromic deafness. FEBS Lett 533, 79-88 (2003)
doi:10.1016/S0014-5793(02)03755-9

52. Philip M. Kelley, Djuana J. Harris, Brett C. Comer, James W. Askew, Thomas W. Fowler, Shelley D. Smith, William J. Kimberling: Novel mutations in the connexin 26 Gene (GJB2) that cause autosomal recessive (DFNB1) hearing loss. Am J Hum Genet 62, 792-799 (1998)
doi:10.1086/301807

53. Minerva M. Carrasquillo, Joel Zlotogora, Saleh Barges, Aravinda Chakravarti: Two different connexin 26 mutations in an inbred kindred segregating non-syndromic recessive deafness: implications for genetic studies in isolated populations. Hum Mol Genet 6, 2163-2172 (1997)
doi:10.1093/hmg/6.12.2163

54. Jack R. Lee, Thomas W. White: Connexin-26 mutations in deafness and skin disease. Expert Rev Mol Med 11, e35 (2009)
doi:10.1017/S1462399409001276

55. Sai Prasad, Robert A. Cucci, Glenn E. Green, Richard J.H. Smith: Genetic Testing for Hereditary Hearing Loss: Connexin 26 (GJB2) Allele Variants and Two Novel Deafness-Causing Mutations (R32C and 645-648delTAGA). Hum Mutat 16, 502-508 (2000)
doi:10.1002/1098-1004(200012)16:6<502::AID-HUMU7>3.3.CO;2-W


doi:10.1002/1098-1004(200012)16:6<502::AID-HUMU7>3.0.CO;2-4

56. Françoise Denoyelle, Dominique Weil, Marion A. Maw, Stephen A. Wilcox, Nicholas J. Lench, Denise R. Allen-Powell, Amelia H. Osborn, Hans-Henrik M. Dahl, Anna Middleton, Mark J. Houseman, Catherine Dode, Sandrine Marlin, Amel Boulila-ElGaied, Mohammed Grati, Hammadi Ayadi, Saida BenArab, Pierre Bitoun, Genevieve Lina-Granade, Jacqueline Godet, Mirna Mustapha, Jacques Loiselet, Élie El-Zir, Anne Aubois, Alain Joannard, Jacqueline Levilliers, Érea-Noel Garabedian, Robert F. Mueller, R. J. McKinlay Gardner, Christine Petit: Prelingual deafness: high prevalence of a 30delG mutation in the connexin 26 gene. Hum Mol Genet 6, 2173-2177 (1997)
doi:10.1093/hmg/6.12.2173

57. Stephen A. Wilcox, Kerryn Saunders, Amelia H. Osborn, Angela Arnold, Julia Wunderlich, Therese Kelly, Veronica Collins, Leah J. Wilcox, R.J. McKinlay Gardner, Maria Kamarinos, Barbara Cone-Wesson, Robert Williamson, Hans-Henrik M. Dahl: High frequency hearing loss correlated with mutations in the GJB2 gene. Hum Genet 106, 399-405 (2000)
doi:10.1007/s004390000273

58. Raquel Rabionet, Leopoldo Zelante, Núria López-Bigas, Leonardo D'Agruma, Salvatore Melchionda, Gabriella Restagno, Maria Lourdes Arbonés, Paolo Gasparini, Xavier Estivill: Molecular basis of childhood deafness resulting from mutations in the GJB2 (connexin 26) gene. Hum Genet 106, 40-44 (2000)
doi:10.1007/s004390051007

59. Christoph Hamelmann, Geoffrey K. Amedofu, Katrin Albrecht, Birgit Muntau, Annette Gelhaus, George W. Brobby, and Rolf D. Horstmann: Pattern of connexin 26 (GJB2) mutations causing sensorineural hearing impairment in Ghana. Hum Mutat 18, 84-85 (2001)
doi:10.1002/humu.1156

60. Hong-Joon Park, Si Houn Hahn, Young-Myoung Chun, Keehyun Park, Hee-Nam Kim: Connexin26 mutations associated with nonsyndromic hearing loss. Laryngoscope 110: 1535-1538 (2000)
doi:10.1097/00005537-200009000-00023

61. Françoise Denoyelle, Sandrine Marlin, Dominique Weil, Lucien Moatti, Pierre Chauvin, Éréa-Noël Garabédian, Christine Petit: Clinical features of the prevalent form of childhood deafness, DFNB1, due to a connexin-26 gene defect: implications for genetic counselling. Lancet 353, 1298-1303 (1999)
doi:10.1016/S0140-6736(98)11071-1

62. Alessandra Murgia, Eva Orzan, Roberta Polli, Maddalena Martella, Cinzia Vinanzi, Emanuela Leonardi, Edoardo Arslan, Franco Zacchello: Cx26 deafness: mutation analysis and clinical variability. J Med Genet 36, 829-832 (1999)

63. Daryl A. Scott, Michelle L. Kraft, Rivka Carmi, Arabandi Ramesh, Khalil Elbedour, Yael Yairi, C.R. Srikumari Srisailapathy, Sally S. Rosengren, Alexander F. Markham, Robert F. Mueller, Nicholas J. Lench, Guy Van Camp, Richard J.H. Smith, Val C. Sheffield: Identification of mutations in the connexin 26 gene that cause autosomal recessive nonsyndromic hearing loss. Hum Mutat 11, 387-394 (1998)
doi:10.1002/(SICI)1098-1004(1998)11:5<387::AID-HUMU6>3.3.CO;2-#

64. Yuka Fuse, Katsumi Doi, Taro Hasegawa, Ayako Sugii, Hiroshi Hibino and Takeshi Kubo: Three novel connexin26 gene mutations in autosomal recessive nonsyndromic deafness. NeuroReport 10, 1853-1857 (1999)
doi:10.1097/00001756-199906230-00010

65. Xavier Estivill, Paolo Fortina, Saul Surrey, Raquel Rabionet, Salvatore Melchionda, Leonardo D'Agruma, Elaine Mansfield, Eric Rappaport, Nancy Govea, Montse Milà, Leopoldo Zelante, Paolo Gasparini: Connexin-26 mutations in sporadic and inherited sensorineural deafness. Lancet 351, 394-398 (1998)
doi:10.1016/S0140-6736(97)11124-2

66. Sarah Rickard, David P. Kelsell, Tony Sirimana, Kaukab Rajput, Breege MacArdle, Maria Bitner-Glindzicz: Recurrent mutations in the deafness gene GJB2 (connexin 26) in British Asian families. J Med Genet 38, 530-533 (2001)
doi:10.1136/jmg.38.8.530

67. Takayuki Kudo, Katsuhisa Ikeda, Shigeo Kure, Yoichi Matsubara, Takeshi Oshima, Ken-ichi Watanabe, Tetsuaki Kawase, Kuniaki Narisawa, Tomonori Takasaka: Novel Mutations in the Connexin 26 Gene (GJB2) Responsible for Childhood Deafness in the Japanese Population. Am J Med Genet 90, 141-145 (2000)
doi:10.1002/(SICI)1096-8628(20000117)90:2<141::AID-AJMG10>3.0.CO;2-G

68. Glenn E. Green, Daryl A. Scott, Joshua M. McDonald, George G. Woodworth, Val C. Sheffield, Richard J.H. Smith: Carrier rates in the midwestern United States for GJB2 mutations causing inherited deafness. JAMA 281, 2211-2216 (1999)
doi:10.1001/jama.281.23.2211

69. Hashem Shahin, Tom Walsh, Tama Sobe, Eric Lynch, Mary-Claire King, Karen B. Avraham, Moien Kanaan: Genetics of congenital deafness in the Palestinian population: multiple connexin 26 alleles with shared origins in the Middle East. Hum Genet 110, 284-289 (2002)
doi:10.1007/s00439-001-0674-2

70. Pavel Seeman, Iva Sakmaryová: High prevalence of the IVS 1 + 1 G to A/GJB2 mutation among Czech hearing impaired patients with monoallelic mutation in the coding region of GJB2. Clin Genet 69, 410-413 (2006)
doi:10.1111/j.1399-0004.2006.00602.x

71. Agnieszka Pollak, Agata Skórka, Malgorzata Mueller-Malesinska, Grazyna Kostrzewa, Bartlomiej Kisiel, Jaroslaw Waligóra, Pawel Krajewski, Monika Oldak, Lech Korniszewski, Henryk Skarzynski, Rafal Ploski: M34T and V37I mutations in GJB2 associated hearing impairment: evidence for pathogenicity and reduced penetrance. Am J Med Genet 143A, 2534-2543 (2007)
doi:10.1002/ajmg.a.31982

72. Asli Sirmaci, Duygu Akcayoz-Duman, Mustafa Tekin: The c.IVS1+1G>A mutation in the GJB2 gene is prevalent and large deletions involving the GJB6 gene are not present in the Turkish population. J Genet 85, 213-216 (2006)
doi:10.1007/BF02935334

73. Nejat Mahdieh, Carla Nishimura, K Ali-Madadi, Yasser Riazalhosseini, H. Yazdan, Sanaz Arzhangi, Khadijeh Jalalvand, Ahmad Ebrahimi, S. Kazemi, Richard J.H. Smith, Hossein Najmabadi: The frequency of GJB2 mutations and the del(GJB6-D13S1830) deletion as a cause of autosomal recessive non-syndromic deafness in the Kurdish population. Clin Genet 65, 506-508 (2004)
doi:10.1111/j.1399-0004.2004.00262.x

74. Tiago D. Matos, Helena Caria, Helena Simões-Teixeira, Trond Aasen, Regina Nickel, Daniel J. Jagger, Assunçao O'Neill, David P. Kelsell, Graça Fialho: A novel hearing-loss-related mutation occurring in the GJB2 basal promoter. J Med Genet 44, 721-725 (2007)
doi:10.1136/jmg.2007.050682

75. Agnieszka Pollak, Malgorzata Mueller-Malesinska, Agata Skórka, Grazyna Kostrzewa, Monika Oldak, Lech Korniszewski, Henryk Skarzynski, Rafal Ploski: GJB2 and hearing impairment: promoter defects do not explain the excess of monoallelic mutations. J Med Genet 45, 607-608 (2008)
doi:10.1136/jmg.2008.059873

76. Delphine Feldmann, Cedric Le Marechal, Laurence Jonard, Patrick Thierry, Cecile Czajka, Remy Couderc, Claude Ferec, Françoise Denoyelle, Sandrine Marlin, Florence Fellmann: A new large deletion in the DFNB1 locus causes nonsyndromic hearing loss. Eur J Med Genet 52, 195-200 (2009)
doi:10.1016/j.ejmg.2008.11.006

77. Guilherme M. Essenfelder, Gaelle Larderet, Gilles Waksman, Jerome Lamartine: Gene structure and promoter analysis of the human GJB6 gene encoding connexin30. Gene 350, 33-40 (2005)
doi:10.1016/j.gene.2004.12.048

78. Israela Lerer, Michal Sagi, Ziva Ben-Neriah, Tieling Wang, Haya Levi, Dvorah Abeliovich: A deletion mutation in GJB6 cooperating with a GJB2 mutation in trans in non-syndromic deafness: a novel founder mutation in Ashkenazi jews. Hum Mutat 18, 460 (2001)
doi:10.1002/humu.1222

79. Ignacio del Castillo, Manuela Villamar, Miguel A. Moreno-Pelayo, Francisco J. del Castillo, Araceli Alvarez, Dolores Telleria, Ibis Menendez, Felipe Moreno: A deletion involving the connexin 30 gene in nonsyndromic hearing impairment. N Engl J Med 346, 243-249 (2002)
doi:10.1056/NEJMoa012052

80. Nathalie Pallares-Ruiz, Patricia Blanchet, Michel Mondain, Mireille Claustres, Anne-Françoise Roux: A large deletion including most of GJB6 in recessive non syndromic deafness: a digenic effect? Eur J Hum Genet 10, 72-76 (2002)
doi:10.1038/sj.ejhg.5200762

81. Ignacio del Castillo, Miguel A. Moreno-Pelayo, Francisco J. del Castillo, Zippora Brownstein, Sandrine Marlin, Quint Adina, David J. Cockburn, Arti Pandya, Kirby R. Siemering, G. Parker Chamberlin, Ester Ballana, Wim Wuyts, Andrea T. Maciel-Guerra, Araceli Alvarez, Manuela Villamar, Mordechai Shohat, Dvorah Abeliovich, Hans-Henrik M. Dahl, Xavier Estivill, Paolo Gasparini, Tim Hutchin, Walter E. Nance, Edi L. Sartorato, Richard J.H. Smith, Guy Van Camp, Karen B. Avraham, Christine Petit, Felipe Moreno: Prevalence and evolutionary origins of the del(GJB6-D13S1830) mutation in the DFNB1 locus in hearing impaired subjects: a multicenter study. Am J Hum Genet 73, 1452-1458 (2003)
doi:10.1086/380205

82. Francisco J. del Castillo, Montserrat Rodriguez-Ballesteros, Araceli Alvarez, Tim Hutchin, Leonardi E, Camila A. de Oliveira, Hela Azaiez, Zippora Brownstein, Mathew R. Avenarius, Sandrine Marlin, Arti Pandya, Hashem Shahin, Kirby R. Siemering, Dominique Weil, Wim Wuyts, Luis A. Aguirre, Yolanda Martin, Miguel A. Moreno-Pelayo, Manuela Villamar, Karen B. Avraham, Hans-Henrik M. Dahl, Moien Kanaan, Walter E. Nance, Christine Petit, Richard J.H. Smith, Guy Van Camp, Edi L. Sartorato, Alessandra Murgia, Felipe Moreno, Ignacio del Castillo: A novel deletion involving the connexin-30 gene, del(GJB6-D13S1854), found in trans with mutations in the GJB2 gene (connexin-26) in subjects with DFNB1 non-syndromic hearing impairment. J Med Genet 42, 588-594 (2005)
doi:10.1136/jmg.2004.028324

83. Edgar Dahl, Dieter Manthey, Ye Chen, Hans-Jürgen Schwarz, Young Sook Chang, Peter A. Lalley, Bruce J. Nicholson, Klaus Willecke: Molecular cloning and functional expression of mouse connexin-30, a gap junction gene highly expressed in adult brain and skin. J Biol Chem 271, 17903-17910 (1996)
doi:10.1074/jbc.271.30.17903

84. Anna Grifa, Carsten A. Wagner, Lucrezia D'Ambrosio, Salvatore Melchionda, Francesco Bernardi, Nuria Lopez-Bigas, Raquel Rabionet, Mariona Arbones, Matteo Della Monica, Xavier Estivill, Leopoldo Zelante, Florian Lang, Paolo Gasparini: Mutations in GJB6 cause nonsyndromic autosomal dominant deafness at DFNA3 locus. Nat Genet 23, 16-18 (1999)
doi:10.1038/12612

85. Barbara Teubner, Vincent Michel, Jörg Pesch, Jürgen Lautermann, Martine Cohen-Salmon, Goran Söhl, Klaus Jahnke, Elke Winterhager, Claus Herberhold, Jean-Pierre Hardelin, Christine Petit, Klaus Willecke: Connexin30 (Gjb6)-deficiency causes severe hearing impairment and lack of endocochlear potential. Hum Mol Genet 12, 13-21 (2003)
doi:10.1093/hmg/ddg001

86. Vincent Michel, Jean-Pierre Hardelin, Christine Petit. Molecular mechanism of a frequent genetic form of deafness. N Engl J Med 349, 716-717 (2003)
doi:10.1056/NEJMc030327

87. Rikkert L. Snoeckx, Patrick L.M. Huygen, Delphine Feldmann, Sandrine Marlin, Françoise Denoyelle, Jaroslaw Waligora, Malgorzata Mueller-Malesinska, Agneszka Pollak, Rafal Ploski, Alessandra Murgia, Eva Orzan, Pierangela Castorina, Umberto Ambrosetti, Ewa Nowakowska-Szyrwinska, Jerzy Bal, Wojciech Wiszniewski, Andreas R. Janecke, Doris Nekahm-Heis, Pavel Seeman, Olga Bendova, Margaret A. Kenna, Anna Frangulov, Heidi L. Rehm, Mustafa Tekin, Armagan Incesulu, Hans-Henrik M. Dahl, Desirée du Sart, Lucy Jenkins, Deirdre Lucas, Maria Bitner-Glindzicz, Karen B. Avraham, Zippora Brownstein, Ignacio del Castillo, Felipe Moreno, Nikolaus Blin, Markus Pfister, Istvan Sziklai, Timea Toth, Philip M Kelley, Edward S. Cohn, Lionel Van Maldergem, Pascale Hilbert, Anne-Françoise Roux, Michel Mondain, Lies H. Hoefsloot, Cor WRJ Cremers, Tuija Löppönen, Heikki Löppönen, Agnete Parving, Karen Gronskov, Iris Schrijver, Joseph Roberson, Francesca Gualandi, Alessandro Martini, Geneviève Lina-Granade, Nathalie Pallares-Ruiz, Céu Correia, Graça Fialho, Kim Cryns, Nele Hilgert, Paul Van de Heyning, Carla J Nishimura, Richard J.H. Smith, Guy Van Camp: GJB2 mutations and degree of hearing loss: a multi-center study. Am J Hum Genet 77, 945-957 (2005)
doi:10.1086/497996

88. Juan Rodriguez-Paris, Iris Schrijver: The digenic hypothesis unraveled: the GJB6 del(GJB6-D13S1830) mutation causes allele-specific loss of GJB2 expression in cis. Biochem Biophys Res Commun 389, 354-359 (2009)
doi:10.1016/j.bbrc.2009.08.152

89. Ellen Wilch, Mei Zhu, Kirk B. Burkhart, Martha Regier, Jill L. Elfenbein, Rachel A. Fisher, Karen H. Friderici: Expression of GJB2 and GJB6 is reduced in a novel DFNB1 allele. Am J Hum Genet 79, 174-179 (2006)
doi:10.1086/505333

90. Ellen Wilch, Hela Azaiez, Rachel A. Fisher, Jill Elfenbein, Alessandra Murgia, Ralf Birkenhäger, Hanno Bolz, Sueli M. Da Silva-Costa, Ignacio del Castillo, Thomas Haaf, Lies Hoefsloot, Hannie Kremer, Christian Kubisch, Cédric Le Maréchal, Arti Pandya, Edi L. Sartorato, Eberhard Schneider, Guy Van Camp, Wim Wuyts, Richard J.H. Smith, Karen H. Friderici: A novel DFNB1 deletion allele supports the existence of a distant cis-regulatory region that controls GJB2 and GJB6 expression. Clin Genet 78, 267-274 (2010)
doi:10.1111/j.1399-0004.2010.01387.x

91. Leopoldo Zelante, Paolo Gasparini, Xavier Estivill, Salvatore Melchionda, Leonardo D'Agruma, Nancy Govea, Monserrat Milá, Matteo Della Monica, Jaber Lutfi, Mordechai Shohat, Elaine Mansfield, Kathleen Delgrosso, Eric Rappaport, Saul Surrey, Paolo Fortina: Connexin26 mutations associated with the most common form of non-syndromic neurosensory autosomal recessive deafness (DFNB1) in Mediterraneans. Hum Mol Genet 6, 1605-1609 (1997)
doi:10.1093/hmg/6.9.1605

92. Eva Orzan, Alessandra Murgia, Roberta Polli, Maddalena Martella, Alberto Mazza, Franco Zacchello, Gregorio Babighian: Connexin 26 preverbal hearing impairment: mutation prevalence and heterozygosity in a selected population. Int J Audiol 41, 120-124 (2002)
doi:10.3109/14992020209090402

93. Klemens Frei, Karoly Szuhai, Trevor Lucas, Klara Weipoltshammer, Christian Schofer, Reinhard Ramsebner, Wolf-Dieter Baumgartner, Anton K Raap, Reginald Bittner, Franz J. Wachtler, Karin Kirschhofer: Connexin 26 mutations in cases of sensorineural deafness in eastern Austria. Eur J Hum Genet 10, 427-432 (2002)
doi:10.1038/sj.ejhg.5200826

94. Andreas Pampanos, John Economides, Vassiliki Iliadou, Polyxeni Neou, Paulos Leotsakos, Nikolaos Voyiatzis, Nikolaos Eleftheriades, Michael Tsakanikos, Thalia Antoniadi, Angeliki Hatzaki, Irene Konstantopoulou, Drakoulis Yannoukakos, Karen Gronskov, Karen Brondum-Nielsen, Maria Grigoriadou, Jolanda Gyftodimou, Theophilos Iliades, Antonios Skevas, Michael B. Petersen: Prevalence of GJB2 mutations in prelingual deafness in the Greek population. Int J Pediatr Otorhinolaryngol 65, 101-108 (2002)
doi:10.1016/S0165-5876(02)00177-5

95. Anne-Françoise Roux, Nathalie Pallares-Ruiz, Anne Vielle, Valerie Faugere, Carine Templin, Dorothee Leprevost, Françoise Artieres, Genevieve Lina, Nicolas Molinari, Patricia Blanchet, Michel Mondain, Mireille Claustres: Molecular epidemiology of DFNB1 deafness in France. BMC Med Genet 5, 5 (2004)
doi:10.1186/1471-2350-5-5


doi:10.1186/1471-2156-5-5

96. Pavel Seeman, M Malikova, D Raskova, O Bendova, D Groh, M Kubalkova, I Sakmaryova, E Seemanova, Z Kabelka: Spectrum and frequencies of mutations in the GJB2 (Cx26) gene among 156 Czech patients with pre-lingual deafness. Clin Genet 66, 152-157 (2004)
doi:10.1111/j.1399-0004.2004.00283.x

97. Sandrine Marlin, Delphine Feldmann, Helene Blons, Natalie Loundon, Isabelle Rouillon, Sebastien Albert, Pierre Chauvin, Erea-Noel Garabedian, Remy Couderc, Sylvie Odent, Alain Joannard, Sebastien Schmerber, Bruno Delobel, Jacques Leman, Hubert Journel, Helene Catros, Cedric Lemarechal, Helene Dollfus, Marie-Madeleine Eliot, Jean-Louis Delaunoy, Albert David, Catherine Calais, Valerie Drouin-Garraud, Marie-Françoise Obstoy, Cyril Goizet, Françoise Duriez, Florence Fellmann, Jocelyne Helias, Jacqueline Vigneron, Bettina Montaut, Dominique Matin-Coignard, Laurence Faivre, Clarisse Baumann, Patricia Lewin, Christine Petit, Françoise Denoyelle: GJB2 and GJB6 mutations: Genotypic and phenotypic correlations in a large cohort of hearing-impaired patients. Arch Otolaryngol Head Neck Surg 131, 481-487 (2005)
doi:10.1001/archotol.131.6.481

98. Elona Cama, Salvatore Melchionda, Teresa Palladino, Massimo Carella, Rosamaria Santarelli, Elisabetta Genovese, Filippo Benettazzo, Leopoldo Zelante, Edoardo Arslan: Hearing loss features in GJB2 biallelic mutations and GJB2/GJB6 digenic inheritance in a large Italian cohort. Int J Audiol 48, 12-17 (2009)
doi:10.1080/14992020802400654

99. Oliver Bartsch, A. Vatter, Ulrich Zechner, Nicolai Kohlschmidt, C. Wetzig, A. Baumgart, S. Nospes, Thomas Haaf, Annerose Keilmann: GJB2 mutations and genotype-phenotype correlation in 335 patients from Germany with nonsyndromic sensorineural hearing loss: evidence for additional recessive mutations not detected by current methods. Audiol Neurotol 15:375-382 (2010)
doi:10.1159/000297216

100. Tama Sobe, Sarah Vreugde, Hashem Shahin, Mira Berlin, Noa Davis, Moien Kanaan, Yuval Yaron, Avi Orr-Urtreger, Moshe Frydman, Mordechai Shohat, Karen B. Avraham: The prevalence and expression of inherited connexin 26 mutations associated with nonsyndromic hearing loss in the Israeli population. Hum Genet 106, 50-57 (2000)
doi:10.1007/s004390051009

101. Oya Uyguner, Melike Emiroglu, Abdullah Üzümcü, Gunter Hafiz, A. Ghanbari, Nermin Baserer, Memnune Yuksel-Apak, Bernd Wollnik: Frequencies of gap- and tight-junction mutations in Turkish families with autosomal-recessive non-syndromic hearing loss. Clin Genet 64, 65-69 (2003)
doi:10.1034/j.1399-0004.2003.00101.x

102. Myrna Mustapha, Nabiha Salem, Valerie Delague, Eliane Chouery, Michella Ghassibeh, Myriam Rai, Jacques Loiselet, Christine Petit, André Mégarbané: Autosomal recessive non-syndromic hearing loss in the Lebanese population: prevalence of the 30delG mutation and report of two novel mutations in the connexin 26 (GJB2) gene. J Med Genet 38, e36 (2001)
doi:10.1136/jmg.38.10.e36

103. Viviana Dalamon, Vanesa Lotersztein, Agustina Beheran, Marcela Lipovsek, Fernando Diamante, Norma Pallares, Liliana Francipane, Gustavo Frechtel, Bibiana Paoli, Enrique Mansilla, Vicente Diamante, Ana B. Elgoyhen: GJB2 and GJB6 genes: molecular study and identification of novel GJB2 mutations in the hearing-impaired Argentinean population. Audiol Neurotol 15, 194-202 (2010)
doi:10.1159/000254487

104. Margaret A. Kenna, Bai-Lin Wu, Douglas A. Cotanche, Bruce R. Korf, Heidi L. Rehm: Connexin 26 studies in patients with sensorineural hearing loss. Arch Otolaryngol Head Neck Surg 127, 1037-1042 (2001)

105. Lynne H.Y. Lim, John K. Bradshaw, Yingshi Guo, Valentina Pilipenko, Colm Madden, David Ingala, Mehdi Keddache, Daniel I. Choo, Richard Wenstrup, John H. Greinwald: Genotypic and phenotypic correlations of DFNB1-related hearing impairment in the Midwestern United States. Arch Otolaryngol Head Neck Surg 129, 836-840 (2003)
doi:10.1001/archotol.129.8.836

106. Arti Pandya, Kathleen S. Arnos, Xia J. Xia, Katherine O. Welch, Susan H. Blanton, Thomas B. Friedman, Guillermina Garcia-Sanchez, Xiu Z. Liu, Robert Morell, Walter E. Nance: Frequency and distribution of GJB2 (connexin 26) and GJB6 (connexin 30) mutations in a large North American repository of deaf probands. Genet Med 5, 295-303 (2003)
doi:10.1097/01.GIM.0000078026.01140.68

107. Hela Azaiez, G. Parker Chamberlin, Stephanie M. Fischer, Chelsea L. Welp, Sai D. Prasad, R. Thomas Taggart, Ignacio del Castillo, Guy Van Camp, Richard J. H. Smith: GJB2: The spectrum of deafness-causing allele variants and their phenotype. Hum Mutat 24, 305-311 (2004)
doi:10.1002/humu.20084

108. Camila A. Oliveira, Andrea T. Maciel-Guerra, Edi L. Sartorato. Deafness resulting from mutations in the GJB2 (connexin 26) gene in Brazilian patients. Clin Genet 61, 354-358 (2002)
doi:10.1034/j.1399-0004.2002.610506.x

109. Ana C. Batissoco, Ronaldo S. Abreu-Silva, Maria Cristina C. Braga, Karina Lezirovitz, Valter Della-Rosa, Tabith Alfredo, Paulo A. Otto, Regina C. Mingroni-Netto: Prevalence of GJB2 (Connexin-26) and GJB6 (Connexin-30) mutations in a cohort of 300 Brazilian hearing-impaired individuals: implications for diagnosis and genetic counseling. Ear Hear 30, 1-7 (2009)
doi:10.1097/AUD.0b013e31819144ad

110. Pu Dai, Fei Yu, Bing Han, Xuezhong Liu, Guojian Wang, Qi Li, Yongyi Yuan, Xin Liu, Deliang Huang, Dongyang Kang, Xin Zhang, Huijun Yuan, Kun Yao, Jinsheng Hao, Jia He, Yong He, Youqin Wang, Qing Ye, Youjun Yu, Hongyan Lin, Lijia Liu, Wei Deng, Xiuhui Zhu, Yiwen You, Jinghong Cui, Nongsheng Hou, Xuehai Xu, Jin Zhang, Liang Tang, Rendong Song, Yongjun Lin, Shuanzhu Sun, Ruining Zhang, Hao Wu, Yuebing Ma, Shanxiang Zhu, Bai-lin Wu, Dongyi Han, Lee-Jun C Wong: GJB2 mutation spectrum in 2063 Chinese patients with nonsyndromic hearing impairment. J Translat Med 7, 26 (2009)
doi:10.1186/1479-5876-7-26

111. Keita Tsukada, Shinya Nishio, Shin-ichi Usami and the Deafness Gene Study Consortium: A large cohort study of GJB2 mutations in Japanese hearing loss patients. Clin Genet 78, 464-470 (2010)
doi:10.1111/j.1399-0004.2010.01407.x

112. Hans-Henrik M. Dahl, Kerryn Saunders, Therese M. Kelly, Amelia H. Osborn, Stephen Wilcox, Barbara Cone-Wesson, Julia L. Wunderlich, Desiree Du Sart, Maria Kamarinos, R.J. McKinlay Gardner, Shirley Dennehy, Robert Williamson, Neil Vallance, Patricia Mutton: Prevalence and nature of connexin 26 mutations in children with non-syndromic deafness. Med J Australia 175, 191-194 (2001)

113. Hossein Najmabadi, Carla Nishimura, Kimia Kahrizi, Yasser Riazalhosseini, Mahdi Malekpour, Ahmad Daneshi, Mohammad Farhadi, Marzieh Mohseni, Nejat Mahdieh, Ahmad Ebrahimi, Niloofar Bazazzadegan, Anoosh Naghavi, Matthew Avenarius, Sanaz Arzhangi, Richard J.H. Smith: GJB2 mutations: passage through Iran. Am J Med Genet 133A, 132-137 (2005)
doi:10.1002/ajmg.a.30576

114. Manjula Maheshwari, R. Vijaya, Manju Ghosh, Shivaram Shastri, Madhulika Kabra, P.S.N. Menon: Screening of families with autosomal recessive non-syndromic hearing impairment (ARNSHI) for mutations in GJB2 gene: Indian scenario. Am J Med Genet 120A, 180-184 (2003)
doi:10.1002/ajmg.a.20014

115. M. RamShankar, S. Girirajan, O. Dagan, H.M. Ravi Shankar, Rajeev Jalvi, Raghunath Rao Rangasayee, Karen B. Avraham, Anuranjan Anand: Contribution of connexin26 (GJB2) mutations and founder effect to non-syndromic hearing loss in India. J Med Genet 40, e68 (2003)
doi:10.1136/jmg.40.5.e68

116. Regie Lyn P. Santos, Muhammad Wajid, Thanh L. Pham, J. Hussan, Ghazanfar Ali, Wasim Ahmad, Suzanne M. Leal: Low prevalence of connexin 26 (GJB2) variants in Pakistani families with autosomal recessive non-syndromic hearing impairment. Clin Genet 67, 61-68 (2005)
doi:10.1111/j.1399-0004.2005.00379.x

117. Mustafa Tekin, Xia-Juan Xia, Radnaabazar Erdenetungalag, Filiz B. Cengiz, Thomas W. White, Janchiv Radnaabazar, Begzsuren Dangaasuren, Hakki Tastan, Walter E. Nance, Arti Pandya: GJB2 Mutations in Mongolia: complex alleles, low frequency, and reduced fitness of the deaf. Ann Hum Genet 74, 155-164 (2010)
doi:10.1111/j.1469-1809.2010.00564.x

118. Rikkert L. Snoeckx, Bulantrisna Djelantik, Lut Van Laer, Paul Van de Heyning, Guy Van Camp: GJB2 (connexin 26) mutations are not a major cause of hearing loss in the Indonesian population. Am J Med Genet 135A, 126-129 (2005)
doi:10.1002/ajmg.a.30726

119. Mehmet Simsek, Nadia Al-Wardy, Aisha Al-Khayat, Muralitharan Shanmugakonar, Talal Al-Bulushi, Mazin Al-Khabory, Sheikha Al-Mujeni, Samia Al-Harthi: Absence of deafness-associated connexin-26 (GJB2) gene mutations in the Omani population. Hum Mutat 18, 545-546 (2001)
doi:10.1002/humu.1233

120. Paolo Gasparini, Raquel Rabionet, Guido Barbujani, Salvatore Melchionda, Michael Petersen, Karen Brondum-Nielsen, Andres Metspalu, Eneli Oitmaa, Marina Pisano, Paolo Fortina, Leopoldo Zelante, Xavier Estivill and the Genetic Analysis Consortium of GJB2 35delG: High carrier frequency of the 35delG deafness mutation in European populations. Eur J Hum Genet 8, 19-23 (2000)
doi:10.1038/sj.ejhg.5200406

121. Robert J. Morell, Hung J. Kim, Linda J. Hood, Leah Goforth, Karen Friderici, Rachel Fisher, Guy Van Camp, Charles I. Berlin, Carole Oddoux, Harry Ostrer, Bronya Keats, Thomas B. Friedman: Mutations in the connexin 26 gene (GJB2) among Ashkenazi Jews with nonsyndromic recessive deafness. N Engl J Med 339, 1500-1505 (1998)
doi:10.1056/NEJM199811193392103

122. Lut Van Laer, Paul Coucke, Robert F. Mueller, Goele Caethoven, Kris Flothmann, Sai D. Prasad, G. Parker Chamberlin, Mark Houseman, Graham R. Taylor, C.M. Van de Heyning, Erik Fransen, J. Rowland, Robert A. Cucci, Richard J.H. Smith, Guy Van Camp: A common founder for the 35delG GJB2 gene mutation in connexin 26 hearing impairment. J Med Genet 38, 515-518 (2001)
doi:10.1136/jmg.38.8.515

123. Caryn R. Rothrock, Alessandra Murgia, Edi L. Sartorato, Emanuela Leonardi, Sainan Wei, Sarah L. Lebeis, Laura E. Yu, Jill L. Elfenbein, Rachel A. Fisher, Karen H. Friderici: Connexin 26 35delG does not represent a mutational hotspot. Hum Genet 113, 18-23 (2003)
doi:10.1007/s00439-003-0944-2

124. Hanen Belguith, S. Hajji, N Salem, Ilhem Charfeddine, Imed Lahmar, Mohamed Ben Amor, K. Ouldim, Eliane Chouery, Nabil Driss, Mohammed Drira, André Mégarbané, Ahmed Rebai, A. Sefiani, Saber Masmoudi, Hammadi Ayadi: Analysis of GJB2 mutation: evidence for a Mediterranean ancestor for the 35delG mutation. Clin Genet 68, 188-189 (2005)
doi:10.1034/j.1399-0004.2000.570607.x

125. Haris Kokotas, Lut Van Laer, Maria Grigoriadou, Vassiliki Iliadou, John Economides, Stella Pomoni, Andreas Pampanos, Nikos Eleftheriades, Elisabeth Ferekidou, Stavros Korres, Aglaia Giannoulia-Karantana, Guy Van Camp, Michael B. Petersen: Strong linkage disequilibrium for the frequent GJB2 35delG mutation in the Greek population. Am J Med Genet 146A, 2879-2884 (2008)
doi:10.1002/ajmg.a.32546

126. Omar Abidi, Redouane Boulouiz, Halima Nahili, Laila Imken, Hassan Rouba, Abdelaziz Chafik, Abdelhamid Barakat: The analysis of three markers flanking GJB2 gene suggests a single origin of the most common 35delG mutation in the Moroccan population. Biochem Biophys Res Commun 377, 971-974 (2008)
doi:10.1016/j.bbrc.2008.10.086

127. Gerard Lucotte, Florent Dieterlen: The 35delG mutation in the connexin 26 gene (GJB2) associated with congenital deafness: European carrier frequencies and evidence for its origin in ancient Greece. Genet Test 9, 20-25 (2005)
doi:10.1089/gte.2005.9.20

128. Haris Kokotas, Maria Grigoriadou, Manuela Villamar, Aglaia Giannoulia-Karantana, Ignacio del Castillo, Michael B. Petersen. Hypothesizing an ancient Greek origin of the GJB2 35delG mutation: can science meet history? Genet Test Mol Biomarkers 14, 183-187 (2010)
doi:10.1089/gtmb.2009.0146

129. Satoko Abe, Shin-ichi Usami, Hideichi Shinkawa, Philip M Kelley, William J Kimberling: Prevalent connexin 26 gene (GJB2) mutations in Japanese. J Med Genet 37, 41-43 (2000)
doi:10.1136/jmg.37.1.41

130. Akihiro Ohtsuka, Isamu Yuge, Shinobu Kimura, Atsushi Namba, Satoko Abe, Lut Van Laer, Guy Van Camp, Shin-ichi Usami: GJB2 deafness gene shows a specific spectrum of mutations in Japan, including a frequent founder mutation. Hum Genet 112, 329-333 (2003)
doi:10.1007/s00439-002-0889-x

131. Xue Z. Liu, Xia J. Xia, Xiao M. Ke, Xiao M. Ouyang, Li L. Du, Yu H. Liu, Simon Angeli, Fred F. Telischi, Walter E. Nance, Thomas Balkany, Li R. Xu: The prevalence of connexin 26 (GJB2) mutations in the Chinese population. Hum Genet 111, 394-397 (2002)
doi:10.1007/s00439-002-0811-6

132. Denise Yan, Hong-Joon Park, Xiao M. Ouyang, Arti Pandya, Katsumi Doi, Raadnabazar Erdenetungalag, Li L. Du, Naoki Matsushiro, Walter E. Nance, Andrew J. Griffith, Xue Z. Liu: Evidence of a founder effect for the 235delC mutation of GJB2 (connexin 26) in east Asians. Hum Genet 114, 44-50 (2003)
doi:10.1007/s00439-003-1018-1

133. George W. Brobby, Bertram Muller-Myhsok, Rolf D. Horstmann: Connexin 26 R143W mutation associated with recessive nonsyndromic sensorineural deafness in Africa. N Engl J Med 338, 548-550 (1998)
doi:10.1056/NEJM199802193380813

134. Christian G. Meyer, Geoffrey K. Amedofu, Johanna M. Brandner, Dieter Pohland, Christian Timmann, Rolf D. Horstmann: Selection for deafness? Nat Med 8, 1332-1333 (2002)
doi:10.1038/nm1202-1332

135. Y.K. Stella Man, Caroline Trolove, Daniel Tattersall, Anna C. Thomas, Annie Papakonstantinopoulou, Drashnika Patel, Claire Scott, Jiehan Chong, Daniel J. Jagger, Edel A. O'Toole, Harshad Navsaria, Michael A. Curtis, David P. Kelsell: A deafness associated mutant human connexin 26 improves the epithelial barrier in vitro. J Membr Biol 218, 29-37 (2007)
doi:10.1007/s00232-007-9025-0

136. Nagla M.A. Gasmelseed, Martin Schmidt, Mubarak M.A. Magzoub, Muthure Macharia, Osman M. Elmustafa, Benson Ototo, Enno Winkler, Gerd Ruge, Rolf D. Horstmann, Christian G. Meyer: Low frequency of deafness-associated GJB2 variants in Kenya and Sudan and novel GJB2 variants. Hum Mutat 23, 206-207 (2004)
doi:10.1002/humu.9216

137. Tama Sobe, Porat Erlich, Asher Berry, Michael Korostichevsky, Sarah Vreugde, Karen B. Avraham, Batsheva Bonne-Tamir, Mordechai Shohat: High frequency of the deafness-associated 167delT mutation in the connexin 26 (GJB2) gene in Israeli Ashkenazim. Am J Med Genet 86, 499-500 (1999)
doi:10.1002/(SICI)1096-8628(19991029)86:5<499::AID-AJMG19>3.0.CO;2-O


doi:10.1002/(SICI)1096-8628(19991029)86:5<499::AID-AJMG19>3.3.CO;2-F

138. Israela Lerer, Michal Sagi, Esther Malamud, Haya Levi, Annick Raas-Rothschild, Dvorah Abeliovich: Contribution of connexin 26 mutations to nonsyndromic deafness in Ashkenazi patients and the variable phenotypic effect of the mutation 167delT. Am J Med Genet 95, 53-56 (2000)
doi:10.1002/1096-8628(20001106)95:1<53::AID-AJMG11>3.0.CO;2-2

139. Jianli Dong, David R. Katz, Christine M. Eng, Ruth Kornreich, Robert J. Desnick: Nonradioactive detection of the common connexin 26 167delT and 35delG mutations and frequencies among Ashkenazi Jews. Mol Genet Metab 73, 160-163 (2001)
doi:10.1006/mgme.2001.3182

140. Gabriel Minarik, Vladimir Ferak, Eva Ferakova, Andrej Ficek, Helena Polakova, Ludevit Kadasi: High frequency of GJB2 mutation W24X among Slovak Romany (Gypsy) patients with non-syndromic hearing loss (NSHL). Gen Physiol Biophys 22, 549-556 (2003)

141. Araceli Alvarez, Ignacio del Castillo, Manuela Villamar, Luis A. Aguirre, Anna Gonzalez-Neira, Alicia Lopez-Nevot, Miguel A. Moreno-Pelayo, Felipe Moreno: High prevalence of the W24X mutation in the gene encoding connexin-26 (GJB2) in Spanish Romani (Gypsies) with autosomal recessive non-syndromic hearing loss. Am J Med Genet 137A, 255-258 (2005)
doi:10.1002/ajmg.a.30884

142. Sonja Bouwer, Dora Angelicheva, David Chandler, Pavel Seeman, Ivailo Tournev, Luba Kalaydjieva: Carrier rates of the ancestral Indian W24X mutation in GJB2 in the general Gypsy population and individual subisolates. Genet Test 11, 455-458 (2007)
doi:10.1089/gte.2007.0048

143. Edward S. Cohn, Philip M. Kelley, Thomas W. Fowler, Michael P. Gorga, David M. Lefkowitz, Harold J. Kuehn, G. Bradley Schaefer, Lisa S. Gobar, Francis J. Hahn, Djuana J. Harris, William J. Kimberling: Clinical studies of families with hearing loss attributable to mutations in the connexin 26 gene (GJB2/DFNB1). Pediatrics 103, 546-550 (1999)
doi:10.1542/peds.103.3.546

144. Kim Cryns, Eva Orzan, Alessandra Murgia, Patrick L.M. Huygen, Felipe Moreno, Ignacio del Castillo, G. Parker Chamberlin, Hela Azaiez, Sai D. Prasad, Robert A. Cucci, Emanuela Leonardi, Rikkert L Snoeckx, Paul J Govaerts, Paul H. Van de Heyning, C.M. Van de Heyning, Richard J.H. Smith, Guy Van Camp: A genotype-phenotype correlation for GJB2 (connexin 26) deafness. J Med Genet 41, 147-154 (2004)
doi:10.1136/jmg.2003.013896

145. Xue Z. Liu, Arti Pandya, Simon Angeli, Fred F. Telischi, Kathleen S. Arnos, Walter E. Nance, Thomas Balkany: Audiological features of GJB2 (connexin 26) deafness. Ear Hear 26:361-369 (2005)
doi:10.1097/00003446-200506000-00011

146. Tomohiro Oguchi, Akihiro Ohtsuka, Shigenari Hashimoto, Aki Oshima, Satoko Abe, Yumiko Kobayashi, Kyoko Nagai, Tatsuo Matsunaga, Satoshi Iwasaki, Takashi Nakagawa, Shin-ichi Usami: Clinical features of patients with GJB2 (connexin 26) mutations: severity of hearing loss is correlated with genotypes and protein expression patterns. J Hum Genet 50:76-83 (2005)
doi:10.1007/s10038-004-0223-7

147. Regie Lyn P. Santos, Yurii S. Aulchenko, Patrick L.M. Huygen, Kim P. van der Donk, Ilse J. de Wijs, Martijn H. Kemperman, Ronald J.C. Admiraal, Hannie Kremer, Lies H. Hoefsloot, Cor W.R.J. Cremers: Hearing impairment in Dutch patients with connexin 26 (GJB2) and connexin 30 (GJB6) mutations. Int J Pediatr Otorhinolaryngol 69, 165-174 (2005)
doi:10.1016/j.ijporl.2004.08.015

148. Burcu O. Hismi, Suna T. Yilmaz, Armagan Incesulu, Mustafa Tekin: Effects of GJB2 genotypes on the audiological phenotype: variability is present for all genotypes. Int J Pediatr Otorhinolaryngol 70, 1687-1694 (2006)
doi:10.1016/j.ijporl.2006.03.015

149. Simon I. Angeli: Phenotype/genotype correlations in a DFNB1 cohort with ethnical diversity. Laryngoscope 118, 2014-2023 (2008)
doi:10.1097/MLG.0b013e31817fb7ad

150. Paola Primignani, Luca Trotta, Pierangela Castorina, Faustina Lalatta, Francesca Sironi, Chiara Radaelli, Dario Degiorgio, Cristina Curcio, Maurizio Travi, Umberto Ambrosetti, Antonio Cesarani, Livia Garavelli, Patrizia Formigoni, Donatella Milani, Alessandra Murri, Domenico Cuda, Domenico A. Coviello: Analysis of the GJB2 and GJB6 genes in Italian patients with nonsyndromic hearing loss: frequencies, novel mutations, genotypes, and degree of hearing loss. Genet Test Mol Biomarkers 13, 209-217 (2009)
doi:10.1089/gtmb.2008.0086

151. Margaret A. Kenna, Henry A. Feldman, Marilyn W. Neault, Anna Frangulov, Bai-Lin Wu, Brian Fligor, Heidi L. Rehm: Audiologic phenotype and progression in GJB2 (Connexin 26) hearing loss. Arch Otolaryngol Head Neck Surg 136, 81-87 (2010)
doi:10.1001/archoto.2009.202

152. Virginia W. Norris, Kathleen S. Arnos, Wendy D. Hanks, Xia Xia, Walter E. Nance, Arti Pandya: Does universal newborn hearing screening identify all children with GJB2 (Connexin 26) deafness? Penetrance of GJB2 deafness. Ear Hear 27, 732-741 (2006)
doi:10.1097/01.aud.0000240492.78561.d3

153. Eva Orzan, Alessandra Murgia: Connexin 26 deafness is not always congenital. Int J Pediatr Otorhinolaryngol 71, 501-507 (2007)
doi:10.1016/j.ijporl.2006.12.002

154. Deepika Gopalarao, William J. Kimberling, Walt Jesteadt, Philip M. Kelley, Kathryn L. Beauchaine, Edward S. Cohn: Is hearing loss due to mutations in the Connexin 26 gene progressive? Int J Audiol 47, 11-20 (2008)
doi:10.1080/14992020701602087

155. Haris Kokotas, Maria Theodosiou, George Korres, Maria Grigoriadou, Elisabeth Ferekidou, Aglaia Giannoulia-Karantana, Michael B. Petersen, Stavros Korres: Sudden hearing loss in a family with GJB2 related progressive deafness. Int J Pediatr Otorhinolaryngol 72, 1735-1740 (2008)
doi:10.1016/j.ijporl.2008.08.006

156. Sandrine Marlin, Éréa-Noël Garabédian, Gilles Roger, Lucien Moatti, Nicole Matha, Patricia Lewin, Christine Petit, Françoise Denoyelle: Connexin 26 gene mutations in congenitally deaf children. Arch Otolaryngol Head Neck Surg 127, 927-933 (2001)

157. Delphine Feldmann, Françoise Denoyelle, Natalie Loundon, Dominique Weil, Erea-Noel Garabedian, Remy Couderc, Alain Joannard, Sebastien Schmerber, Bruno Delobel, Jacques Leman, Hubert Journel, Helene Catros, Claude Ferrec, Valerie Drouin-Garraud, Marie-Françoise Obstoy, Lucien Moati, Christine Petit, Sandrine Marlin: Clinical evidence of the nonpathogenic nature of the M34T variant in the connexin 26 gene. Eur J Hum Genet 12, 279-284 (2004)
doi:10.1038/sj.ejhg.5201147

158. Robert A. Cucci, Sai Prasad, Philip M. Kelley, Glenn E. Green, Katrien Storm, Sandra Willocx, Edward S. Cohn, Guy Van Camp, Richard J.H. Smith: The M34T allele variant of connexin 26. Genet Test 4, 335-344 (2000)
doi:10.1089/109065700750065063

159. Mark J Houseman, Lucy A Ellis, Alistair Pagnamenta,Wei-Li Di, Sarah Rickard, Amelia H Osborn, Hans-Henrik M Dahl, Graham R Taylor, Maria Bitner-Glindzicz, William Reardon, Robert F Mueller, David P Kelsell: Genetic analysis of the connexin-26 M34T variant: identification of genotype M34T/M34T segregating with mild-moderate non-syndromic sensorineural hearing loss. J Med Genet 38, 20-25 (2001)
doi:10.1136/jmg.38.1.20

160. C. Huculak, Helene Bruyere, Tanya N. Nelson, Frederick K. Kozak, Sylvie Langlois: V37I connexin 26 allele in patients with sensorineural hearing loss: evidence of its pathogenicity. Am J Med Genet 140A, 2394-2400 (2006)
doi:10.1002/ajmg.a.31486

161. Iris Schrijver, Kay W. Chang: Two patients with the V37I/235delC genotype: Are radiographic cochlear anomalies part of the phenotype? Int J Pediatr Otorhinolaryngol 70, 2109-2113 (2006)
doi:10.1016/j.ijporl.2006.07.015

162. Hans-Henrik M. Dahl, Sherryn Tobin, Zeffie Poulakis, Field W. Rickards, X Xu, Lynn Gillam, Joanne Williams, Kerryn Saunders, Barbara Cone-Wesson, Melissa Wake: The contribution of GJB2 mutations to slight or mild hearing loss in Australian elementary school children. J Med Genet 43, 850-855 (2006)
doi:10.1136/jmg.2006.042051

163. Nele Hilgert, Matthew J. Huentelman, Ashley Q. Thorburn, Erik Fransen, Nele Dieltjens, Malgorzata Mueller-Malesinska, Agnieszka Pollak, Agata Skorka, Jaroslaw Waligora, Rafal Ploski, Pierangela Castorina, Paola Primignani, Umberto Ambrosetti, Alessandra Murgia, Eva Orzan, Arti Pandya, Kathleen Arnos, Virginia Norris, Pavel Seeman, Petr Janousek, Delphine Feldmann, Sandrine Marlin, Françoise Denoyelle, Carla J Nishimura, Andreas Janecke, Doris Nekahm-Heis, Alessandro Martini, Elena Mennucci, Timea Toth, Istvan Sziklai, Ignacio del Castillo, Felipe Moreno, Michael B. Petersen, Vasiliki Iliadou, Mustafa Tekin, Armagan Incesulu, Ewa Nowakowska, Jerzy Bal, Paul Van de Heyning, Anne-Françoise Roux, Catherine Blanchet, Cyril Goizet, Guenaelle Lancelot, Graça Fialho, Helena Caria, Xue Zhong Liu, Ouyang Xiaomei, Paul Govaerts, Karen Gronskov, Karianne Hostmark, Klemens Frei, Ingeborg Dhooge, Stephen Vlaeminck, Erdmute Kunstmann, Lut Van Laer, Richard J.H. Smith, Guy Van Camp: Phenotypic variability of patients homozygous for the GJB2 mutation 35delG cannot be explained by the influence of one major modifier gene. Eur J Hum Genet 17, 517 - 524 (2009)
doi:10.1038/ejhg.2008.201

164. Diego A. Preciado, Lynne H.Y. Lim, Aliza P. Cohen, Colm Madden, David Myer, Chris Ngo, John K. Bradshaw, Louise Lawson, Daniel I. Choo, John H. Greinwald: A diagnostic paradigm for childhood idiopathic sensorineural hearing loss. Otolaryngol Head Neck Surg 131, 804-809 (2004)
doi:10.1016/j.otohns.2004.06.707

165. Hela Azaiez, Richard J.H. Smith: In reference to temporal bone imaging in GJB2 deafness. Laryngoscope 117: 1127 (2007)
doi:10.1097/MLG.0b013e3180421718


doi:10.1097/MLG.0b013e3180421729

166. Kenneth H. Lee, Daniel A. Larson, Gordon Shott; Brian Rasmussen; Aliza P. Cohen, Corning Benton, Mark Halsted, Daniel Choo, Jareen Meinzen-Derr, John H. Greinwald: Audiologic and temporal bone imaging findings in patients with sensorineural hearing loss and GJB2 Mutations. Laryngoscope, 119, 554-558 (2009)
doi:10.1002/lary.20162

167. Evan J. Propst, Susan Blaser, Tracy L. Stockley, Robert V. Harrison, Karen A. Gordon, Blake C. Papsin: Temporal bone imaging in GJB2 deafness. Laryngoscope, 116, 2178-2186 (2006)
doi:10.1097/01.mlg.0000244389.68568.a7

168. Evan J. Propst, Robert V. Harrison, Karen A. Gordon, Blake C. Papsin, Susan Blaser, Tracy L. Stockley: In reply to "In reference to temporal bone imaging in GJB2 deafness". Laryngoscope 117: 1127-1129 (2007)
doi:10.1097/MLG.0b013e3180421729


doi:10.1097/MLG.0b013e3180421718

169. Andrew I. Jun, Wyman T. McGuirt, Raul Hinojosa, Glenn E. Green, Nathan Fischel-Ghodsian, Richard J.H. Smith: Temporal bone histopathology in connexin 26-related hearing loss. Laryngoscope 110, 269-275 (2000)
doi:10.1097/00005537-200002010-00016

170. Ingo Todt, Hans C. Hennies, Dietmar Basta, Arne Ernst: Vestibular dysfucntion of patients with mutations of connexin 26. NeuroReport 16, 1179-1181 (2005)
doi:10.1097/00001756-200508010-00009

171. Misato Kasai, Chieri Hayashi, Takashi Iizuka, Ayako Inoshita, Kazusaku Kamiya, Hiroko Okada, Yukinori Nakajima, Kimitaka Kaga, Katsuhisa Ikeda: Vestibular function of patients with profound deafness related to GJB2 mutation. Acta Oto-Laryngologica 130, 990-995 (2010)
doi:10.3109/00016481003596508

172. Batya Engel-Yeger, Suliman Zaaroura, Joel Zlotogora, Stavit Shalev, Yasir Hujeirat, Minerva Carrasquillo, Saleh Barges, Hillel Pratt: The effects of a connexin 26 mutation - 35delG - on oto-acoustic emissions and brainstem evoked potentials: homozygotes and carriers. Hear Res 163, 93-100 (2002)
doi:10.1016/S0378-5955(01)00386-0

173. Batya Engel-Yeger, Suliman Zaaroura, Joel Zlotogora, Stavit Shalev, Yasir Hujeirat, Minerva Carrasquillo, B. Saleh, Hillel Pratt: Otoacoustic emissions and brainstem evoked potentials in compound carriers of connexin 26 mutations. Hear Res 175, 140-151 (2003)
doi:10.1016/S0378-5955(02)00719-0

174. Annamaria Franze, Antonella Caravelli, Francesca Di Leva, Elio Marciano, Gennaro Auletta, Federica D'Aulos, Claudio Saulino, Laura Esposito, Massimo Carella, Paolo Gasparini: Audiometric evaluation of carriers of the connexin 26 mutation 35delG. Eur Arch Otorhinolaryngol 262, 921-924 (2005)
doi:10.1007/s00405-005-0918-1

175. Glenn E. Green, Daryl A. Scott, Joshua M. McDonald, Holly F.B. Teagle, Bruce J. Tomblin, Linda J. Spencer, George G. Woodworth, John F. Knutson, Bruce J. Gantz, Val C. Sheffield, Richard J.H. Smith: Performance of cochlear implant recipients with GJB2-related deafness. Am J Med Genet 109, 167-170 (2002)
doi:10.1002/ajmg.10330

176. Paul W. Bauer, Ann E. Geers, Christine Brenner, Jean S. Moog, Richard J. H. Smith: The effect of GJB2 allele variants on performance after cochlear implantation. Laryngoscope 113, 2135-2140 (2003)
doi:10.1097/00005537-200312000-00015

177. Robert D. Cullen, Craig A. Buchman, Carolyn J. Brown, Ben J. Copeland, Carlton Zdanski, Harold C. Pillsbury, Carol G. Shores: Cochlear implantation for children with GJB2-related deafness. Laryngoscope 114, 1415-1419 (2004)
doi:10.1097/00005537-200408000-00019

178. Riki Taitelbaum-Swead, Zippora Brownstein, Chava Muchnik, Liat Kishon-Rabin, Jona Kronenberg, Lela Megirov, Moshe Frydman, Minka Hildesheimer, Karen B. Avraham: Connexin-associated deafness and speech perception outcome of cochlear implantation. Arch Otolaryngol Head Neck Surg 132, 495-500 (2006)
doi:10.1001/archotol.132.5.495

179. Heinz-Dieter Gabriel, Dirk Jung, Christoph Bützler, Achim Temme, Otto Traub, Elke Winterhager, Klaus Willecke: Transplacental uptake of glucose is decreased in embryonic lethal connexin26-deficient mice. J Cell Biol 140, 1453-1461 (1998)
doi:10.1083/jcb.140.6.1453

180. Yunfeng Wang, Qing Chang, Wenxue Tang, Yu Sun, Binfei Zhou, Huawei Li, Xi Lin: Targeted connexin26 ablation arrests postnatal development of the organ of Corti. Biochem Biophys Res Comm 385, 33-37 (2009)
doi:10.1016/j.bbrc.2009.05.023

181. Hung-Li Wang, Wen-Teng Chang, Allen H. Li, Tu-Hsueh Yeh, Ching-Yi Wu, Mei-Shin Chen, Pei-Chen Huang: Functional analysis of connexin-26 mutants associated with hereditary recessive deafness. J Neurochem 84, 735-742 (2003)
doi:10.1046/j.1471-4159.2003.01555.x

182. Gülistan Mese, Eric Londin, Rickie Mui, Peter R. Brink, Thomas W. White: Altered gating properties of functional Cx26 mutants associated with recessive non-syndromic hearing loss. Hum Genet 115, 191-199 (2004)
doi:10.1007/s00439-004-1142-6

183. Klemens Frei, Trevor Lucas, Reinhard Ramsebner, Christian Schöfer, Wolf-Dieter Baumgartner, Klara Weipoltshammer, Nihan Erginel-Unaltuna, Franz J. Wachtler, Karin Kirschhofer: A novel connexin 26 mutation associated with autosomal recessive sensorineural deafness. Audiol Neurootol 9, 47-50 (2004)
doi:10.1159/000074186

184. Ram Shankar Mani, Aparna Ganapathy, Rajeev Jalvi, C.R. Srikumari Srisailapathy, Vikas Malhotra, Shelly Chadha, Arun Agarwal, Arabandi Ramesh, Raghunath Rao Rangasayee, Anuranjan Anand: Functional consequences of novel connexin 26 mutations associated with hereditary hearing loss. Eur J Hum Genet 17, 502-509 (2009)
doi:10.1038/ejhg.2008.179

185. Birgit Haack, Kathrin Schmalisch, Monica Palmada, Christoph Böhmer, Nicolai Kohlschmidt, Annerose Keilmann, Ulrich Zechner, Annette Limberger, Stefan Beckert, Hans-Peter Zenner, Florian Lang, Susan Kupka: Deficient membrane integration of the novel p.N14D GJB2 mutant associated with non-syndromic hearing impairment. Hum Mutat 27, 1158-1159 MIB #935 online (2006)
doi:10.1002/humu.9464

186. Andreas R. Janecke, Hans Christian Hennies, Barbara Günther, Gabriele Gansl, Josef Smolle, Elisabeth M. Messmer, Gerd Utermann, Olaf Rittinger: GJB2 mutations in Keratitis-Ichthyosis-Deafness syndrome including its fatal form. Am J Med Genet 133A, 128-131 (2005)
doi:10.1002/ajmg.a.30515

187. Andrew J. Griffith, Yandan Yang, Shannon P. Pryor, Hong-Joon Park, Ethylin Wang Jabs, Joseph B. Nadol, Laura J. Russell, Daniel I. Wasserman, Gabriela Richard, Joe C. Adams, Saumil N. Merchant: Cochleosaccular dysplasia associated with a connexin 26 mutation in Keratitis-Ichthyosis-Deafness Syndrome. Laryngoscope 116, 1404-1408 (2006)
doi:10.1097/01.mlg.0000224549.75161.ca

188. Benjamin C. Stong, Qing Chang, Shoeb Ahmad, Xi Lin: A novel mechanism for connexin 26 mutation linked deafness: cell death caused by leaky gap junction hemichannels. Laryngoscope 116, 2205-2210 (2006)
doi:10.1097/01.mlg.0000241944.77192.d2

189. Dwan A. Gerido, Adam M. DeRosa, Gabriela Richard, Thomas W. White: Aberrant hemichannel properties of Cx26 mutations causing skin disease and deafness. Am J Physiol Cell Physiol 293, C337-C345 (2007)
doi:10.1152/ajpcell.00626.2006

190. Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/

191. Yongyi Yuan, Fei Yu, Guojian Wang, Shasha Huang, Ruili Yu, Xin Zhang, Deliang Huang, Dongyi Han, Pu Dai: Prevalence of the GJB2 IVS1+1G>A mutation in Chinese hearing loss patients with monoallelic pathogenic mutation in the coding region of GJB2. J Transl Med 8, 127 (2010)
doi:10.1186/1479-5876-8-127

Abbreviations: ARNSHI: autosomal recessive non-syndromic hearing impairment; HI: hearing impairment; Hz, hertzs; RT-PCR: reverse transcriptase PCR.

Key Words Hearing impairment, DFNB1, GJB2, GJB6, Connexin-26, Connexin-30, Genetic epidemiology, Genotype-phenotype correlations, Animal models, Review

Send correspondence to: Ignacio del Castillo, Unidad de Genetica Molecular, Hospital Universitario Ramon y Cajal, Carretera de Colmenar km 9, 28034 Madrid, Spain, Tel: 34-913368542, Fax: 34-913368541, E-mail:idelcastillo.hrc@salud.madrid.org