Meeting Abstract

P3-111   -   Assessing seasonal changes in steroidogenic gene expression in male garter snakes Lincoln, JM*; Barlowe, ML; Rucker, HR; Thomas, RL; Parker, MR; James Madison University; James Madison University; James Madison University, University of Arizona; James Madison University; James Madison University lincoljm@dukes.jmu.edu

Sex steroid hormones are crucial in vertebrate reproduction because they regulate gametogenesis and reproductive behavior and can vary significantly in seasonally breeding species. In many vertebrate species, steroid hormones fluctuate in sync with maximal mating activity. Conversely, some vertebrates, such as the red-sided garter snake (Thamnophis sirtalis parietalis), have evolved a dissociated pattern where maxima in circulating sex steroids are decoupled from peak reproductive behavior. The red-sided garter snake has a strongly seasonal reproductive pattern where sex steroids dictate multiple facets of the snake’s natural history in a preparatory or anticipatory capacity. In males, this is an increase in androgens to promote spermatogenesis prior to prolonged hibernation and eventual spring mating. Because the reproductive events of this species are highly seasonal, the purpose of our study is to determine whether mRNA expression of key steroidogenic enzymes (StAR, Cyp17α1, 17βHSD3, and Cyp19α1 [aromatase]) in the testes of male garter snakes show similar seasonal variation. We have extracted mRNA from testes collected during spring, summer, and fall in the same year and developed a set of working primers, including three control genes, for use in quantitative PCR. We will perform qPCR to assess differences in gene expression using the Δct method. We predict that gonadal StAR, Cyp17α1, and 17βHSD3 should peak in fall, coinciding with spermatogenesis, while aromatase remains at low levels throughout the year. The seasonal modulation of these steroidogenic enzymes should align with known patterns of gametogenesis observed in this population, though we may observe seasonal expression of only some target genes. By examining this dissociated reproductive pattern at the molecular level, we may better understand how extreme latitudes can act as an evolutionary driver of unique reproductive patterns.