Structure/function analyses of neural circuitry controlling courtship behaviours in Drosophila melanogaster

There has been a continuous production of high quality reports focussing on fruitless as the genetic switch for male sexual behaviour in Drosophila melanogaster, and on fruitless’s contributions to creating a male-specific neural circuit within the CNS. However it has become increasingly clear that fruitless is not sufficient in itself to specify the full complement of male-specific behavioural repertoires. One obvious genetic candidate that contributes to the male neural circuit is doublesex. doublesex has long been known to be pivotal to the specification of the sexually dimorphic adult soma but it’s function in specifying sex-specific neural substrates has, up till now, been largely unexplored. While fruitless has so far shown to be found only in insects, doublesex is a more ancient gene and, as member of the Dmrt family of genes, is both structurally and functionally conserved throughout the animal kingdom. Thus the study of doublesex offers great potential for understanding the neuronal, developmental and physiological logic underlying innate and species-specific behaviours, in not one but both sexes, in organisms throughout the animal kingdom. Using the novel dsxGAL4 transgenic tool, generated by ends-in homologous recombination at the doublesex locus, I have been able to perform a systematic temporal and spatial survey of doublesex expression both within, and outwith, the nervous system. Excitingly, as doublesex is endogenously expressed in both males and females, this has uncovered profound dimorphic differences in male and female neural substrates. In the male this circuit is shared with fruitless (whose expression is restricted to adult males) and has allowed myself, and my colleagues in the Goodwin lab, through functional behavioural analyses, to gain greater understanding into how male-specific behavioural outputs may be generated. Further though, functional analyses impinging on the novel doublesex female circuitry has allowed us to gain new insight into the (largely unstudied) role that females play in the courtship ritual. The dsx GAL4 transgenic tool, and the insights gained in this study, are also of import in relation to dissecting out mechanisms involved in the post-mating physiological and behavioural changes the female undergoes after successful copulation with a male. As well as this, as doublesex is known to play a pivotal role in establishing the dimorphic morphology of the fly, this tool has begun to allow us an understanding of how the assembly of these dimorphic neural circuits is coordinated with the development, and maintenance, of a sex-specific anatomy and physiology to produce the complete male or female ‘state’; Integrating both mind (fly brain) and body (fly soma).