Project Summary/Abstract One of the major challenges in neuroscience research is to understand the function of the brain at the level of genes, gene regulatory networks, neurons, and circuit structure. This proposal seeks to understand Drosophila reproductive behaviors, a highly tractable model, given knowledge of the master regulatory transcription factors and neuroanatomical structures that underlie these behaviors. fruitless (fru) encodes a set of master regulatory transcription factors, which are necessary and largely sufficient for specifying the potential for innate male courtship behaviors. This proposal is built on our results that demonstrate that a family of cell adhesion molecules, called Dprs and DIPs, have important functions in specifying the potential for reproductive behavior downstream of fru. We will determine the roles for behavior of subsets of fru-expressing neurons that overlap with Dpr/DIP expression (fru P1∩Dpr/Dip), using genetic intersectional strategies. We will also determine how anatomical sexual dimorphism in fru P1 neurons arises by functionally examining the roles of Dpr/DIPs. This study will also elucidate the Dpr/DIP interactome within fru-expressing neurons. Using cell-type specific genomic tools, we will also molecularly classify fru P1∩Dpr/Dip-expressing subpopulations to elucidate the molecular underpinnings that give rise to different neuronal functions.