How does sexual identity lead to sexual dimorphism? A genomic analysis of sex determination

Sex determination pathways are diverse throughout the animal kingdom, but converge upon conserved genes that encode products that regulate sex specific gene expression. In Drosophila, nearly all manifestations of sexual dimorphism, outside the nervous system, are regulated by doublesex. The role of doublesex is highly conserved in different insects, and dsx homologs (dsx, mab-3 related transcription factors, DMRTs) play roles in sexual differentiation in a diverse array of animals such as, frogs, fish, birds, reptiles, mice, and man.                                                            

In Drosophila, there are only three known direct targets of DSX, which are unlikely to account for all the differences in sexually dimorphic tissues. Males and females express different isoforms of DSX (DSX^M and DSX^F, respectively), and this change in isoform is sufficient to transform from male to female morphology. To gain a comprehensive understanding of biologically significant targets of DSX, we performed RNA-seq on animals that have undergone an acute switch in DSX isoform, from DSX^M to DSX^F, and vice versa. We are comparing the results of these experiments to additional experiments that determine where the DSX protein is bound in the genome, and genetic analysis that identifies new dsx-interacting genes. Knowledge of the genes controlled by DSX will elucidate how sexual dimorphism is created and provide insight into the mechanism of DSX function in sexually dimorphic tissues.