Pheromone circuits and transcriptional cascades modulating transcriptional and chromatin states in the Drosophila central brain with social experience

Social experience significantly influences the behavioral and physiological responses of animals, including humans. In many animals, social isolation increases aggression, courtship, locomotion, and feeding while disrupting sleep. This occurs when peripheral neurons detect social signals, such as pheromones, which activate decision-making circuits in the brain. However, the molecular and circuit mechanisms of how chronic social isolation or enrichment alter gene expression and affect neuronal function and behavior remain unclear. In this study, we examined how transcription patterns and chromatin marks in male Drosophila brains change in response to social experience, and the impact of pheromone circuits and transcription factors involved in social circuit function. We focused on pheromone receptors Or47b and Or67d, as well as transcription factors FruM and DsxM. Our findings suggest that social experience impacts multiple genes in the central brain. Disrupting Or47b, Or67d, FruM, and DsxM function normalized the transcriptional responses through antagonistic interactions. Specifically, Or47b circuits predominantly mediated transcriptional responses to social isolation through DsxM function, while Or67d and FruM regulated responses to group housing. Notably, mutants of fruM and dsxM exhibited more extensive transcriptional changes in the brain than Or mutants, especially for FruM/DsxM target genes. While social experience did not lead to detectable alterations in the overall chromatin profile in the whole brain, mutants of the four genes resulted in significant changes in the enrichment of H3K4me3 and RNA polymerase II (RNAPolII) compared to wild type. Furthermore, mutants in fruM and dsxM generally eliminated social experience-dependent changes in sleep and locomotion behaviors, whereas Or mutants exhibited more modest disruptions. Overall, our results uncover the pheromone circuits and transcriptional cascades in regulating molecular and behavioral responses to social experience.