The H4K16 histone acetyltransferase chameau is a putative target of Doublesex. Emily Clough¹, Cale Whitworth², Erin Jimenez², Hania Pavlou³, Megan Neville³, Stephen Goodwin³, Mark Van Doren², Brian Oliver¹. 1) Laboratory of Cellular and Developmental Biology, NIDDK/NIH, Bethesda , MD; 2) Department of Biology, Johns Hopkins University, Baltimore, MD; 3) Department of Physiology, Anatomy and Genetics,University of Oxford, Oxford, UK.

   Doublesex (DSX) is a sex-specifically spliced DMRT family member transcription factor that regulates somatic sex determination in Drosophila. Although dsx is an essential regulator of sexual differentiation, few direct targets have been characterized. We have used multiple genome-wide approaches to assay DSX occupancy across diverse developmental and chromatin contexts including chromatin immunoprecipitation-sequencing (ChIP-seq) and DNA Adenine Methylation-Identification (DamID). These studies have yielded thousands of sites that are concentrated near transcriptional start sites. Furthermore, the DNA captured beneath the peaks is enriched for previously identified DSX binding sequences. In order to make connections between putative target genes associated with DSX occupancy and dsx phenotype, we are knocking down these genes specifically in dsx-expressing cells to evaluate their role in sexual differentiation. Our DSX occupancy experiments reveal that DSX protein is associated with the gene chameau (chm) at a site within one of it's large introns that also contains a DSX-binding sequence. chm is characterized as an H4K16 acetyltransferase with no known role in sexual differentiation. Knockdown of chm in dsx-expressing cells produces several dsx-like phenotypes including defective rotation of male genitalia, sterility and male sex comb bristles that are reduced in number with thin, pointed ends. Further evidence of a role for chm in somatic sex determination is provided by the observation that chm genetically interacts with dsx to promote terminal filament formation, a feature of the female gonad. Collectively, these data suggest that chm is a direct target of DSX and may impact sexual differentiation of many tissues.