/NeuroD1 Functions with the Homeobox Gene /Vax2 and Hox Gene /labial To Specify Aspects of RME and DD Neuron Fate in .

Identifying the mechanisms behind neuronal fate specification are key to understanding normal neural development in addition to neurodevelopmental disorders such as autism and schizophrenia. cell fate specification is difficult to study in vertebrates. However, the nematode , with its invariant cell lineage and simple nervous system of 302 neurons, is an ideal organism to explore the earliest stages of neural development. We used a comparative transcriptome approach to examine the role of /NeuroD1 in nervous system development and function. This basic helix-loop-helix transcription factor is deeply conserved across phyla and plays a crucial role in cell fate specification in both the vertebrate nervous system and pancreas. We find that controls expression of , a Vax2-like homeobox class transcription factor, in the RME head motorneurons and PVQ tail interneurons. We also show that functions redundantly with the Hox gene /labial in defining the fate of DD1 and DD2 embryonic ventral nerve cord motorneurons. These data highlight the utility of comparative transcriptomes for identifying transcription factor targets and understanding gene regulatory networks.