Meeting Abstract
Sex determination mechanisms vary greatly across the teleost fishes. In fact the process of, and environmental influences on, sexual differentiation often show a striking degree of phenotypic plasticity within a species. In the African cichlid fish Pelvicachromis pulcher, sex determination is influenced by pH, with a male bias at lower pH and a female bias at more neutral pH. Furthermore, male phenotypic morph and reproductive tactic is also influenced by pH. This species thus provides the opportunity to examine the mechanisms of environmental sex determination and differentiation both between and within the sexes. To this end, we have fully sequenced the upstream enhancer region of both the A and the B copies of the aromatase gene, cyp19a1, which convert testosterone to estrogen primarily in the gonads (A) and brain (B) respectively. Methylation levels and patterns in the gonadal (A) form of the gene have been linked to environmental sex determination in other species. The highly repetitive sequence in the upstream enhancer region is likely responsible for much interspecies variation, including the 400bp deletion found in P. pulcher relative to other cichlid species, as well as for intraspecies variation detected between P. pulcher individuals. We identified conserved putative transcription factor binding sites and CpG sites that play a potential role in the regulation of gene expression through methylation. While cyp19a1A, expressed primarily in gonads, includes a canonical CpG island ~1200 bp upstream from the start site, cyp19a1B, expressed primarily in the brain lacks a canonical CpG island.
