atoh1.2 and beta3.1 are two new bHLH-encoding genes expressed in selective precursor cells of the zebrafish anterior hindbrain.

Transcription factors of the bHLH class play crucial roles in neurogenesis by controlling the location and timing of neuronal commitment and differentiation, as well as influencing neuronal identity. Proneural bHLH factors belong to the Olig, Neurogenin, NeuroD, Achaete-scute and Atonal subfamilies, and are expressed in partially overlapping or complementary patterns within the vertebrate embryonic neural tube. The combinatorial expression of these factors likely drives the generic and cell type-specific properties of neurogenesis throughout the nervous system. As an approach towards identifying a complete set of vertebrate proneural factors, we report here the isolation of two new zebrafish neural bHLH gene members, atoh1.2 and beta3.1. Among other sites, both are expressed in the late embryonic and early larval anterior hindbrain. In this territory we demonstrate that atoh1.2 and beta3.1 are transcribed in distinct precursors, further highlighting the subdivision of anterior zebrafish hindbrain into subdomains of bHLH expression.