One fundamental question in cell biology is how complex neuronal structures are sculpted and maintained. The unique property of neuronal plasticity means sensory experience can affect the structure and function of the nervous system. I will show that such plasticity can be demonstrated at the single neuron level, where arborized dendritic trees of the polymodal PVD neuron in C. elegans undergo modifications related to sensory experience and sex.

In hermaphrodites, mechanosensory signals received by conspecific worms in the plate induce structural changes. We found that both mechanosensory experience and Degenerins/ Epithelial sodium channels affect PVD architecture. The dendritic tree changes its number of branches, their geometry and the self-avoidance between its repetitive candelabra-like units. Furthermore, we show that differential mechanosensory deprivation, mediated via degenerins, induces behavioral changes in nociceptive avoidance.

In males, analyses of the PVD larval morphogenesis revealed that the dendritic structure maintains a stereotyped branching tree similar to hermaphrodites.

However, during adult sexual maturation, male PVD uniquely extends dendritic branches into its distinct tail fan rays within the male copulatory organ. This unique arborization pattern follows a male-specific expression of the sexually-shared epidermal guidance complex component SAX-7/L1CAM. Altered arborization by defective PVD morphogenesis, or genetic ablation of the PVD, result in male mating behavioral defects. These results reveal that the most arborized neuron in C.elegans has a novel sexually dimorphic structure and mating function