New members of the Drosophila Myc transcription factor subfamily revealed by a genome-wide examination for basic helix-loop-helix genes

The basic helix-loop-helix (bHLH) proteins represent an evolutionary conser ved class of transcription factors that are known to play important roles i n cell determination and differentiation during animal embryonic developmen t. Following an exhaustive search of the complete Drosophila genome sequenc e using a PSI-BLAST strategy, we identified 19 new genes, bringing the tota l number of bHLH-encoding genes in the Drosophila genome to 56. These new g enes belong to various subfamilies of bHLH transcription factors, such as t he Daughterless, Hairy-Enhancer of split, bHLH-PAS or bHLHZip subfamilies. The embryonic expression pattern of each of these new genes has been analyz ed by in situ hybridization. By looking for closely structurally related mo tifs, we found two genes that represent likely orthologues of vertebrate Mn t and Mix. Together with previous reports, our data suggest that, similar t o networks involved in neurogenesis and myogenesis, the network of Myc-rela ted genes has been globally conserved throughout evolution. (C) 2001 Elsevi er Science Ireland Ltd. All rights reserved.