A DROSOPHILA HOMOLOG OF HUMAN PROTOONCOGENE RET TRANSIENTLY EXPRESSEDIN EMBRYONIC NEURONAL PRECURSOR CELLS INCLUDING NEUROBLASTS AND CNS CELLS

We have identified a Drosophila gene encoding a putative receptor tyro sine kinase by screening a genomic DNA library with a DNA probe for a Drosophila homolog of fibroblast growth factor receptors. The newly is olated gene codes for a transmembrane protein most similar in sequence to a mammalian proto-oncogene ret; thus, the gene was termed Dret. Dr et mRNA is transcribed in very small amounts in the embryonic, larval, and pupal stages. Whole mount in situ hybridization experiments revea led that the mRNA is transiently expressed in neuroblasts in early emb ryos. In late embryos, Dret mRNA was detected in subpopulations of dif ferentiating CNS and PNS cells. In addition, Dret expression was affec ted in neurogenic mutants. These results suggest that Dret can be cons idered as a functional homolog of mammalian ret and should play import ant roles in neurogenesis.