Cellular Determinants of Granulosa Cell Differentiation in Avian Ovarian Follicles

在每个排卵周期只排出有限数量的卵的雌性脊椎动物（如哺乳动物、鸟类和某些爬行动物）中，卵泡选择的过程代表了繁殖能力的限速步骤。卵泡选择是指在排卵前将一个（或多个）未分化的卵泡选择性招募到成熟的最后阶段，但这一过程的潜在机制目前在任何脊椎动物物种中都不明确。最终，选择机制决定了在任何给定的繁殖周期内可以产生的最大数量的后代。目前的研究将验证一个假设，即未分化的卵泡无法自发进行卵泡选择通常是由于卵泡颗粒细胞层分化所需的一个或多个基因（如促卵泡激素受体；FSHR）的主动抑制。重要的是，正是颗粒细胞层在卵泡发育过程中滋养卵母细胞。第二个有待检验的假设是，在卵泡选择的时候，FSHR基因表达的负调控会转变为表达的上调。这一事件被广泛认为是卵巢卵泡成熟到排卵前阶段的先决条件。实验设计结合了细胞和分子技术，旨在确定基因组机制，通过该机制，鸡中对这一选择过程至关重要的基因表达被抑制或增强。预计这些研究结果将影响我们提高濒危物种和家养食用动物雌性生育能力的能力，并更好地了解女性不孕的某些原因。更广泛地说，拟议的研究将有助于为职业目标包括教学和/或研究的本科生和研究生（包括那些来自代表性不足的群体的学生）提供相关和前沿的培训。

In female vertebrate animals that ovulate a limited number of oocytes (eggs) per ovulation cycle (e.g., mammals, birds, some reptiles), it is the process of ovarian follicle selection that represents the rate-limiting step to fecundity. Follicle selection entails the selective recruitment of one (or more) undifferentiated follicle(s) into the final stages of maturation prior to ovulation, yet the underlying mechanisms of this process are currently undefined in any vertebrate species. Ultimately, the selection mechanism determines the maximum number of offspring that can be produced within any given reproductive cycle. The present studies will test the hypothesis that the inability of undifferentiated follicles to spontaneously undergo follicle selection is normally due to the active suppression of one or more genes (e.g., the Follicle Stimulating Hormone receptor; FSHR) that are required for the differentiation of the follicle's granulosa cell layer. Importantly, it is the granulosa cell layer that nurtures the oocyte throughout follicle development. A second hypothesis to be tested is that at the time of follicle selection there is a switch from a negative regulation of FSHR gene expression to an upregulation of expression. This event is widely assumed to be prerequisite for the maturation of ovarian follicles to the preovulatory stage. The experimental design incorporates cellular and molecular techniques directed at identifying genomic mechanisms by which the expression of genes critical to this selection process in chickens is repressed or enhanced. Results from these studies are predicted to impact our ability to enhance female fertility in endangered species and domesticated food animals, and to better understand select causes of infertility in women. More broadly, the proposed research will serve to provide relevant and cutting-edge training to undergraduate and graduate students (including those from underrepresented populations) whose career goals include teaching and/or research.