Identification and analysis of homeotic regulatory genes in Drosophila. H. Green , J.A. Kennison. Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.

   Specification of segment identities in Drosophila is regulated by the homeotic genes of the antennapedia complex (ANTC) and the bithorax complex (BXC). The identity of the fifth abdominal segment is specified by the Abd-B gene of the bithorax complex. The temporal and spatial expression of Abd-B in the fifth abdominal segment requires the iab5 cis-regulatory region and multiple trans-acting factors, including brahma. To identify additional trans-acting factors, we are screening for mutations that interact with brahma to specify fifth segment identity. Among the brahma-interacting genes we have identified are Taf110, trithorax, ash1 and kohtalo. We have also recovered multiple alleles of Abd-B (including an iab5 mutation). A number of putative mutants have been isolated in this study, and their characterization is currently underway.