Probable transcription factor involved in the development of the adult pattern of macrochaetae. Required for accumulation of achaete (ac) and scute (sc) in proneural clusters. Probably acts by binding to the proneural cluster-specific enhancers of the ac/sc complex and increasing enhancer efficiency, thereby acting as a stimulator of ac/sc expression in proneural clusters. Also required for correct development of the embryonic/larval peripheral nervous system (PNS). Expressed in the PNS and CNS. In early blastoderm stages, it is ubiquitously expressed, then, before stage 5, it disappears from the poles of the embryo and faint stripes are visible. At stage 5, it also accumulates in the dorsal region, cephalic furrow ectodermal patches between the tracheal pits, where neurons of the PNS appear. In older embryos (stage 15) a strong expression is mostly restricted to the central nervous system (CNS) and PNS. In PNS, the pattern suggests that expression occur in many of the neurons of the ventral, lateral and dorsal clusters of neurons. In third instar wing disks, it is expressed in rows of cells on either side of the prospective anterior wing margin and in groups of cells that coincide with proneural clusters of ac/sc expression. Also expressed independently of ac/sc in certain areas of the disk, such as the postnotum and posterior dorsal proximal wing. Expressed in the proneural clusters of the leg disks and in the eye/antenna disk. Up-regulated by ac/sc in proneural clusters of the wing disk.