Control of sexual differentiation and behavior by the doublesex gene in Drosophila melanogaster

Doublesex proteins, part of the structurally and functionally conserved Dmrt gene family, play essential roles in sex determination throughout the animal kingdom. We targeted the insertion of GAL4 into the doublesex (dsx) locus of Drosophila melanogaster, allowing visualization and manipulation of dsx cells in various tissues. In the nervous system, significant differences between the sexes were detected in dsx neuronal numbers, axonal projections, and synaptic density. We show that dsx is required for the development of male-specific neurons that co-express fruitless (fru), a key regulator of male sexual behavior. We propose that both dsx and fru act together to form the neuronal framework necessary for male sexual behavior. Significantly, we show that disrupting dsx neuronal function has profound effects on male sexual behavior. Furthermore, we demonstrate a role for dsx neurons in pre- through to post-copulatory female reproductive behaviors. Significant insights into the genetic and developmental logic supporting sex-specific behaviors have come from the genetically and behaviorally tractable model organism, Drosophila melanogaster1. In Drosophila, genes of the sex-determination hierarch