Expression of Drosophila trithorax-group homologues in chick embryos.

Mll, Brg1 and Brm are vertebrate homologues of Drosophila trithorax group (trxG) genes. We isolated chicken Mll cDNA clones, and examined patterns of Mll, Brg1 and Brm expression in chick embryos. All three genes were expressed from embryonic stage 2 onwards. Mll transcripts were just detectable in all tissues by in situ hybridization, with highest level in dorsal neural tube and notochord. Brg1 transcripts were readily detectable in all tissues, with highest levels in dorsal neural tube, dorsal trunk epithelium and limb bud epithelium and mesenchyme. Brm transcripts were more restricted, being found in dermomyotome, notochord, dorsal limb bud epithelium, eye and the roof and floor plates of the neural tube.