Ashton Sydney E, Vernasco Ben J, Moore Ignacio T, Parker M Rockwell
Department of Biology, James Madison University, Harrisonburg, VA 22807, United States; Graduate Program in Neuroscience, School of Medicine, University of Maryland, Baltimore, MD 21201, United States.
Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States.
Gen Comp Endocrinol. 2018 Oct 1;267:59-65. doi: 10.1016/j.ygcen.2018.05.026. Epub 2018 May 25.
Estrogens are important regulators of reproductive physiology including sexual signal expression and vitellogenesis. For the regulation to occur, the hormone must bind and activate receptors in target tissues, and expression of the receptors can vary by sex and/or season. By simultaneously comparing circulating hormone levels with receptor expression, a more complete understanding of hormone action can be gained. Our study species, the red-sided garter snake (Thamnophis sirtalis parietalis), provides an excellent opportunity to study the interaction between sex steroid hormones and receptor expression in addition to sexual dimorphism and seasonality. During the spring mating season, male garter snakes rely exclusively on the female's skin-based, estrogen-dependent sex pheromone to direct courtship. Males can be stimulated to produce this sexual attractiveness pheromone by treatment with estradiol (E), which also induces male vitellogenesis. Estrogen receptors (ESRs) are required to transduce the effects of estrogens, thus we used quantitative RT-PCR to analyze expression of ESR alpha (ERα; gene ESR1) mRNA in the skin and liver of wild caught male and female garter snakes across simulated spring and fall conditions in the laboratory. While ESR1 was present in the skin of both sexes, there were no sex or seasonal differences in expression levels. Liver expression of ESR1, however, was sexually dimorphic, with females showing greatest expression in fall when circulating E concentrations were lowest. There were no statistically significant correlations between E and ESR1 expression. Our data suggest that the skin of both sexes is sensitive to estrogen signaling and thus the production of sex pheromone is dependent on bioavailable levels of E. Female expression of ESR1 in the liver may increase in the fall to prime energy storage mechanisms required for vitellogenesis the following year.
雌激素是生殖生理学的重要调节因子，包括性信号表达和卵黄生成。为了实现这种调节，激素必须与靶组织中的受体结合并激活受体，而受体的表达会因性别和/或季节而有所不同。通过同时比较循环激素水平和受体表达，可以更全面地了解激素的作用。我们的研究物种——红边束带蛇（Thamnophis sirtalis parietalis），除了性别二态性和季节性外，还为研究性类固醇激素与受体表达之间的相互作用提供了绝佳机会。在春季交配季节，雄性束带蛇完全依靠雌性基于皮肤的、雌激素依赖性性信息素来引导求偶行为。用雌二醇（E）处理可刺激雄性产生这种性吸引力信息素，同时也会诱导雄性卵黄生成。雌激素受体（ESRs）是转导雌激素作用所必需的，因此我们使用定量RT-PCR分析了在实验室模拟的春季和秋季条件下，野生捕获的雄性和雌性束带蛇皮肤和肝脏中雌激素受体α（ERα；基因ESR1）mRNA的表达。虽然ESR1在两性皮肤中均有表达，但表达水平没有性别或季节差异。然而，ESR1在肝脏中的表达存在性别二态性，雌性在秋季循环E浓度最低时表达最高。E与ESR1表达之间没有统计学上的显著相关性。我们的数据表明，两性皮肤对雌激素信号敏感，因此性信息素的产生取决于E的生物可利用水平。雌性肝脏中ESR1的表达可能在秋季增加，为次年卵黄生成所需的能量储存机制做好准备。
