The PVD neuron has male-specific structure and mating function inC. elegans

Abstract

Neurons display unique shapes and establish intricate networks, which may differ between sexes. In complex organisms, studying sex differences in structure and function of individual neurons is difficult. The nematode Caenorhabditis elegans hermaphrodites and males present an exceptional model for studying neuronal morphogenesis in a simple, sexually-dimorphic system. We focus on the polymodal sensory bilateral neuron pair PVD, which forms a complex but stereotypic dendritic tree composed of multiple subunits that resemble candelabra. PVD was previously studied in hermaphrodites, but not in males. We find here that during larval development, male PVDs extend a similar architecture to the hermaphrodite utilizing a sexually-shared patterning mechanism. In early adulthood, however, male PVD develops a unique extension into the copulatory tail structure. This sexually-dimorphic arborization is absent in mutant backgrounds which perturb the sex-shared PVD guidance complex. SAX-7/L1CAM, a hypodermal component of this complex, shows a male-specific expression pattern which precedes PVD extension. Further, our results reveal that genetically altered arborization or ablation of the PVD result in male mating behavioral defects, particularly as males turn around the hermaphrodite. These results uncover an adult-stage sexual dimorphism of dendritic branching and uncover a new function for PVD in male sexual behavior.