Specificity of CNS and PNS regulatory subelements comprising pan-neural enhancers of the deadpan and scratch genes is achieved by repression.

The Drosophila pan-neural genes deadpan (dpn) and scratch (scrt) are expressed in most or all developing neural precursor cells of the central nervous system (CNS) and peripheral nervous system (PNS). We have identified a cis-acting enhancer element driving full pan-neural expression of the dpn gene which is composed of independent CNS- and PNS-specific subelements. We have also identified CNS- and PNS-specific subelements of the scrt enhancer. Deletion analysis of the dpn and scrt PNS-specific subelements reveals that PNS specificity of these two evolutionarily unrelated enhancers is achieved in part by repression of CNS expression. We discuss the implications of the striking organizational similarities of the dpn, scrt, and sna pan-neural enhancers.