2 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 f actor SCL. DroNHLH was similarly identified by homology to NHLH1 and N HLH2, two bHLH genes expressed in the developing mammalian nervous sys tem. A partial DroSCL complementary DNA clone was obtained from an ear ly 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 comp lementary DNA clone was obtained from an early instar (I and II) Droso phila library. Its coding region consists of 162 amino acids and encod es 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-kilob ase DroNHLH transcript were detected by Northern analysis of total Dro sophila RNA. Examination of Drosophila embryos by tissue in situ hybri dization reveals restricted expression of both genes in a subset of ce lls in the developing central nervous system.