A Blueprint of Sex-Specific Neuronal Regulation in the C. elegans Nervous System at Single-Cell Resolution
Sex-specific behaviors within a species are often attributed to variances in neuronal wiring and molecular signatures. However, how the genetic sex shapes the molecular architecture of the nervous system at a single neuron level is still unknown. To address this gap, we used single-cell RNA-sequencing (scRNA-seq) to profile the transcriptome of the sex-shared nervous system of adult male and hermaphrodite Caenorhabditis elegans. By ranking neurons based on the degree of molecular dimorphism, we uncover novel sexually dimorphic neurons such as PLM neurons, where functional dimorphism was corroborated by diminished posterior touch responses in hermaphrodites. We identify sex-specific regulators of mechanosensory behavior and neuronal function by combining our dataset with reverse genetic screens. While most sex-shared neurons retain their neurotransmitter identity, the male neuropeptide connectome undergoes substantial remodeling, with most of the neuropeptides showing a male-bias expression. This reinforces the notion that neuropeptides are crucial for diversifying connectome outputs. Furthermore, by correlating gene expression with outgoing synaptic connectivity, we identified regulatory candidates for synaptic wiring, including both shared and sex-specific genes. This comprehensive resource provides foundational insights into the molecular drivers of sexual dimorphism, facilitating future exploration of regulatory mechanisms and their impact on sex-specific behaviors in higher organisms. Overall design: Single-cell RNA-sequencing profiles were generated from young adult C. elegans larvae of both sexes (hermaphrodites and males), utilizing strains with pan-neuronal labeling. Neurons were isolated using fluorescence-activated cell sorting (FACS).