Social and Gonadal Control of Neural Gene Expression

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Sexual differentiation of the brain and behavior results from internal and environmental cues influencing the expression of genes. Through studies in a variety of systems, it is becoming clear that different mechanisms can affect this differentiation and often lead to similar patterns of behavioral expression. The mechanisms by which reproductive hormones influence the sexual differentiation of brain and behavior are well researched, but those by which environmental cues exert their influence are less well understood. Bluehead wrasses, found in coral reefs, change their sex from females to males on becoming the dominant members of their social groups. Male behavior develops immediately, and functional testes develop within ten days. Importantly, the behavioral parts of this sex change can even occur in females whose ovaries have been removed. The goal of this project is to better characterize behavioral and gene expression changes induced by social interactions and steroid hormones during sex change. The first study will compare the expression of estrogen receptors and a key estrogen-producing enzyme across the sexes and sex change. The second study will contrast patterns of gene expression in the brain across the sexes and sex change using genomic tools (microarrays). Finally, gonadal and social influences on gene expression will be experimentally separated during sex change to assess their separate and combined effects. This project should identify key gene expression influences of social interactions on the nervous system and mechanisms underlying sexual and aggressive behavior. Aggressive behavior has enormous societal costs and a better understanding of social influences on the neural substrates of aggression is needed. Also, the increasing importance of aquaculture in the United States makes a better understanding of the control of sexual behavior and reproduction in fishes critical. Finally, this project will provide valuable training for graduate and undergraduate students in the integrated study of behavior, neuroendocrinology, and genomic biology.