Basic helix-loop-helix(bH LH)transcription factors regulate the differentiation of various tissues in a vast diversity of species.The b HLH protein Atonal was first identified as a proneural gene involved in the formation of mechanosensory cells and photoreceptor cells in Drosophila(Jarman et al.,1993,1994).Atonal is expressed in sensory organ precursors and is required Basic helix-loop-helix (bH LH) transcription factors regulate the differentiation of various tissues in a vast diversity of species. B HLH protein Atonal was first identified as a proneural gene involved in the formation of mechanosensory cells and photoreceptor cells in Drosophila Jarman et al., 1993, 1994). Atonal is expressed in sensory organ precursors and is required