DEFORMED EXPRESSION IN THE DROSOPHILA CENTRAL-NERVOUS-SYSTEM IS CONTROLLED BY AN AUTOACTIVATED INTRONIC ENHANCER

Deformed (Dfd) is a Drosophila homeotic selector gene required for nor mal development of maxillary segment morphology in the larval and adul t head. Consistent with this function, Dfd transcripts are restricted to epidermal, mesodermal and neural cells in the embyonic mandibular a nd maxillary primordia, Previous studies have identified a far upstrea m element in Dfd sequences which functions as an epidermal-specific au toregulatory enhancer, In a search through 35 kb of Dfd sequences for additional transcriptional control elements, we have identified a 3.2 kb DNA fragment containing an enhancer that mimics the expression of D fd in the subesophageal ganglion of the embryonic central nervous syst em, This Neural autoregulatory enhancer (NAE) maps in the large Dfd in tron just upstream of the homeobox exon and requires Dfd protein funct ion for its full activity, A 608 bp NAE subfragment retains regulatory function that is principally localized in the subesophageal ganglion, This small region of the Drosophila melanogaster genome contains nume rous blocks of sequence conservation with a comparable region from the Dfd locus of D,hydei, A pair of conserved blocks of NAE sequence matc h a Dfd protein binding site in the epidermal autoregulatory element, while another conserved sequence motif is repeated multiple times with in the 608 bp subelement.