2 ENHANCER DOMAINS CONTROL EARLY ASPECTS OF THE COMPLEX EXPRESSION PATTERN OF MSX1

To understand how the complex embryonic expression pattern of the Msx1 gene is produced a transgenic analysis of 13 kb of DNA around the Msx 1 locus was carried out. Most of the extensive expression pattern of t he Msx1 gene was reproduced in transgenics using the LacZ gene fused t o 5 kb of Msx1 5' flanking DNA. Two enhancer domains were identified w hich produced this pattern. The distal element produced expression in the first arch and the nasal epithelium and was restricted to 240 bp. However, the proximal element which produced expression in superficial nasal epithelium, dorsal and ventral myotome, limb mesenchyme, eye, e ar, roof plate, second arch, genital ridge and epiphysis, was containe d in only 78 bp. (C) 1997 Elsevier Science Ireland Ltd.