Corresponding author

Kenth Gustafsson
Division of Cell & Molecular Biology
Institute of Child Health
University of London
30 Guilford St.
London WC1N 1EH, UK

Tel #: x44-171-242 9789, ext. 2231
Fax: x44-171-831 4366

E-mail: K.Gustafsson@ich.ucl.ac.uk