The forkhead domain gene unc-130 generates chemosensory neuron diversity in C-elegans

Coenorhabditis elegans responds to its complex chemical environment using a small number of chemosensory neurons. Each of these neurons exhibits a uni que sensory response repertoire. The developmental mechanisms that generate this diversity of function are largely unknown. Many C. elegans chemosenso ry neurons, including the AWA and ASG neurons, arise as lineal sisters of a n asymmetric division. Here we describe the gene unc-130, which plays a rol e in the generation of the AWA and ASG neurons. In unc-130 mutants, the ASG neurons adopt the fate of the AWA neurons, unc-130 encodes a member of the forkhead domain family of transcription factors, and is expressed in the p recursors to AWA and ASG neurons. Misexpression of unc-130 in the AWA neuro ns is partly sufficient to repress the AWA fate, but not to promote ASG fat e, unc-130 also plays a role in the development of additional chemosensory neurons. Our experiments show that the ASG neurons share a developmental de fault state in common with three types of olfactory neurons. We propose tha t distinct cell fates and hence diversity of function in the chemosensory n eurons of C. elegans are generated in a hierarchical manner, utilizing both lineage-dependent and independent mechanisms.