HLH-3 Is Required for the Maturation of Neurons Necessary for Male Specific Exploration Behavior

Sexually dimorphic gene expression within the nervous system of many organisms gives rise to features that underline sexually dimorphic behaviors. In C. elegans , terminal differentiation of neurons with sexually dimorphic features often occur not at the time of neuronal birth, but rather during the juvenile to adult stage transition, when sexual maturation occurs. Previous works have shown that the bHLH transcription factor, HLH-3, is necessary for the differentiation of sex-specific neurons in hermaphrodites. Expression of the bHLH transcription factor, hlh-3 , is dynamic and widespread throughout the embryo. Post-embryonic expression in the hermaphrodite is restricted to the HSNs, and the P cells and their descendants, including the VCs. In this work, we characterize the post-embryonic expression pattern of hlh-3 in the male. Our findings show that the pattern of expression observed in males varies dramatically from that observed in hermaphrodites. Males show expanded expression in the head at the L1 and late L3/early L4 stage, as well as broader expression in the tail at the early L3/Late L4 stage. This leads us to the conclusion that the post-embryonic expression pattern of hlh-3 is sexually dimorphic. We also describe the role of hlh-3 in the maturation of a subset of neurons required for male specific exploration behavior. Our findings show that in the absence of hlh-3 function, the AWA, ASJ, and AIM neurons fail to acquire terminally differentiated features and therefore contribute to the failure of males to perform behaviors mediated by these cells.