Horan GS, Wu K, Wolgemuth DJ, Behringer RR:
Homeotic transformation of cervical vertebrae in Hoxa-4 mutant mice.
Proceedings of the National Academy of Sciences of the United States of
America 1994 Dec 20;91(26):12644-8
ABSTRACT
Hoxa-4 (previously known as Hox-1.4) is a mouse homeobox-containing
gene that is expressed in the presumptive hindbrain and spinal cord,
prevertebrae, and other tissues during embryogenesis. To understand
the role of Hoxa-4 during development, we generated Hoxa-4 mutant
mice. Homozygous mutants were viable and fertile. Analysis of
neonatal skeletons revealed the development of ribs on the seventh
cervical vertebra at variable penetrance and expressivity. A low
frequency of alterations in sternal morphogenesis was also observed.
In addition, we analyzed the skeletons of transgenic mice that
overexpress Hoxa-4 and found that the formation of the small rib
anlagen that often develop on the seventh cervical vertebra was
suppressed. Analysis of adult homozygous mutant skeletons revealed
that the dorsal process normally associated with the second cervical
vertebra was also found on the third cervical vertebra. These
results demonstrate that Hoxa-4 plays a role in conferring
positional information along the anteroposterior axis to specify the
identity of the third and the seventh cervical vertebrae.
