Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK,
We have cloned a Sox box gene, Dichaete, from Drosophila melanogaster. The gene contains a DNA binding domain closely related to the product of the mammalian testis determining gene, SRY. Dichaete maps cytologically to 70D1-2 on the left arm of chromosome 3 and encodes a single transcription unit of 1800 nucleotides . The distribution of Dichaete transcript in the embryo shows a dynamic pattern initiated late in stage 4 as a broad domain reminiscent of gap gene expression and develops into 7 stripes resembling pair rule gene expression. Later on Dichaete is expressed in the ventral neuroectoderm, in the midline and in a subset of neuroblasts and their daughter cells. Analyses of the phenoptypes caused by recessive lethal Dichaete alleles show that Dichaete is involved in segmentation and neurogenesis. Dichaete11 mutant embryos show defects in midline derivaties and an increase in the number of specific neurons, but only minor segmentation defects. Ectopic expression of Dichaete between 4-6h of development leads to opposit defects in the nervous system but segmentation is not affected. Thus, Dichaete appears to play a direct role in neurogenesis. We are currently investigating the mechanisms by which Dichaete regulates aspects of neural development.