VND, A GENE REQUIRED FOR EARLY NEUROGENESIS OF DROSOPHILA, ENCODES A HOMEODOMAIN PROTEIN

The development of the central nervous system in Drosophila is initiat ed by the segregation of neuroblasts, the neural progenitors, from the embryonic neuroectoderm, This process is guided by at least two class es of genes: the achaete-scute complex (AS-C) proneural genes and the neurogenic genes. It has been known for some time that loss-of-functio n mutations in the AS-C result in neural hypoplasia and the first obse rved defect is failure of segregation of a fraction of neuroblasts. Lo ss-of-function mutations at the ventral nervous system defective (vnd) locus are known to lead to similar phenotypic defects in early neurog enesis. More recently, the vnd locus has been implicated in the regula tion of the proneural AS-C genes and the neurogenic genes of the Enhan cer of spilt complex. In this paper we report the identification of a transcript associated with the vnd locus, the transcript distribution in embryogenesis, which is compatible with the nervous system mutant p henotypes described for this gene, and that the protein product is a m ember of the NK-2 homeodomain family. We discuss these findings within the framework of early Drosophila neurogenesis and the known phenotyp es associated with the vnd locus.