Meeting Abstract
Maternally-generated variation in the embryonic endocrine milieu affects many physiological functions in offspring. Whereas effects of elevated in ovo testosterone exposure on growth, behavior, immune function and endocrine function have been explored in many avian species, very little is known about potential molecular bases for changes in these suites of traits. We tested the hypothesis that changes in hypothalamo-pituitary-gonadal (HPG) axis function induced by exposure to elevated yolk testosterone are regulated in part by changes in gene expression in the gonads, and that these changes are apparent early in post-natal development. We injected eggs with 10 ng of testosterone in oil (“T-treated”), or an oil vehicle alone (“control”), and then used quantitative real-time PCR to measure expression of a suite of genes relevant to HPG axis function in the testes and ovaries when chicks were 3 days old. T treatment had no effect on average plasma testosterone levels, but a significantly larger proportion of chicks from T-treated eggs had undetectable levels of plasma testosterone. Although T treatment did not affect gonadal gene expression, male and female chicks exhibited marked sex differences in expression, indicating sex-specific variation in HPG axis activity at this age. Our results suggest that organizational effects of maternal androgens on the HPG axis, at least at the level of the gonads, may not manifest until reproductive maturity.
