Steroidogenesis in the Green Anole Lizard Brain and Gonad

摘要

Seasonally breeding animals reproduce during certain times of the year and, subsequently, behaviors, steroid hormone levels, and brain morphology change. The green anole lizard (Anolis carolinensis) is an excellent model to study the regulation of steroid hormone production because they have distinct hormonal and behavioral differences between sexes and seasons. As in other vertebrates, steroidogenesis in anoles is under the control of the hypothalamus-pituitary-gonadal (HPG) axis. We tested the hypothesis that natural variations in steroid hormone levels between sexes and seasons are mediated within the brain and gonad by examining four genes involved in steroidogenesis: StAR, Cyp17alpha1, HSD17?3, and Cyp19beta1. Adult male and female lizards were wild-caught during both the breeding (BS) and non-breeding (NBS) seasons. Gonads, brains, and blood were collected and stored at -80 °C. RNA from brain and gonad was extracted, reverse transcribed into cDNA and then gene expression was measured by qPCR (normalized to beta actin). We found that whole brain mRNA expression of StAR, Cyp17alpha1, and HSD17alpha3 have no differences between sex or season. Cyp19alpha1 mRNA expression in the brain was increased during the NBS in females, potentially revealing the presence of regulatory signaling for aromatase expression in the brain. In the anole gonad, StAR mRNA expression levels were increased in both males and females during the BS, while the expression levels of many of the other steroidogenic enzymes are increased when StAR expression is decreased, suggesting that the enzymes in the steroidogenic pathway are, in fact, potentially regulated independently of StAR. This work expands knowledge on the seasonal regulation of steroidogenesis in both the brain and gonad of a reptilian species but more work is necessary to further determine the regulatory mechanisms.