Two new Drosophila genes related to human hematopoietic and neurogenic transcription factors.

We have identified two new basic domain helix-loop-helix (bHLH) genes in Drosophila melanogaster, DroSCL and DroNHLH. DroSCL was identified because of its homology to the mammalian hematopoietic transcription factor SCL. DroNHLH was similarly identified by homology to NHLH1 and NHLH2, two bHLH genes expressed in the developing mammalian nervous system. A partial DroSCL complementary DNA clone was obtained from an early pupal (5.5-7.5-day) Drosophila library. DroSCL is 73% identical to SCL within the 55-amino acid region of the bHLH domain. A DroNHLH complementary DNA clone was obtained from an early instar (I and II) Drosophila library. Its coding region consists of 162 amino acids and encodes a predicted protein of 18,312 daltons. DroNHLH is 87% identical to NHLH1 and NHLH2 within the bHLH domain. DroSCL and DroNHLH are located on the X chromosome. A 1.7-kilobase DroSCL transcript and a 1.5-kilobase DroNHLH transcript were detected by Northern analysis of total Drosophila RNA. Examination of Drosophila embryos by tissue in situ hybridization reveals restricted expression of both genes in a subset of cells in the developing central nervous system.