Zebrafish exhibit unique sex determination and differentiation mechanisms. Laboratory strains lack a sex chromosome, and no sex-determining gene has been identified. All juvenile zebrafish contain a bipotential gonad that appears histologically as an immature ovary. In female zebrafish this bipotential gonad matures into a functional ovary, whereas in males the bipotential gonad regresses and is replaced by a testis. The signals that determine whether a juvenile, bipotential gonad develops into testes or ovaries are not well understood.

Multiple genes may be interacting as a network to establish sex. We are trying to understand how sex hormone genes, such as estrogen and androgen receptors, influence sex determination and gonad development in zebrafish. We found that the nuclear androgen receptor is critical for proper organization of the testes and for oocyte development in ovaries. Androgen receptor mutants exhibit a female sex bias with altered secondary sex characteristics. In contrast, the non-canonical G protein-coupled estrogen receptor appears to be dispensable for proper ovary differentiation and function. Current work in the lab is focused on investigating the signaling pathways by which androgens & estrogens influence testes organization and oocyte development.

Publications

Crowder CM, Romano SN, Gorelick DA. G protein-coupled estrogen receptor is not required for sex determination or ovary function in zebrafish. Endocrinology (2018)

Crowder CM, Lassiter CS, Gorelick DA. Nuclear androgen receptor regulates testes organization and oocyte maturation in zebrafish. Endocrinology (2018)