Mechanisms of KIT signaling in the regulation of primordial follicle formation

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PROJECT SUMMARY/ABSTRACT Despite its importance to the continuation of species, the differentiation of primordial germ cells into functional oocytes is poorly understood. Primordial germ cells begin to differentiate into oocytes during embryonic development in the mouse. The oocytes develop in clusters called germline cysts, a conserved phase of oocyte development in both vertebrates and invertebrates. Oocytes progress through prophase I of meiosis and arrest at the diplotene stage. They then undergo primordial follicle formation during which germ cell cysts break apart into single oocytes (cyst breakdown) and granulosa cells migrate around individual oocytes to form primordial follicles. During the process of cyst breakdown, a subset of cells in each cyst die with only a third of the initial number of oocytes surviving to form primordial follicles. The mechanisms that control meiotic progression, cyst breakdown, granulosa cell recruitment and oocyte survival are not well understood. Our long-term goal is to understand molecular and cellular mechanisms used to establish the primordial follicle pool in the mouse ovary. The objective of this proposal is to understand the role of the KIT signaling pathway in regulating meiotic prophase I and primordial follicle formation. The central hypothesis of the proposed research is that signaling from the receptor tyrosine kinase, KIT, promotes primordial follicle formation and oocyte progression to the diplotene stage of prophase I through the regulation of downstream targets. Recent work from our laboratory suggests KIT signaling may play an important role. This proposal explores the molecular and cellular aspects of KIT signaling in establishing the pool of primordial follicles. The specific aims of this research are to: 1) elucidate the role of KIT signal transduction in primordial follicle formation and oocyte progression through meiotic prophase I; and 2) identify targets downstream of KIT that are important during oocyte development. These goals will be achieved through techniques including immunohistochemistry, confocal microscopy, ovary organ culture, real time PCR and single cell RNA sequencing analysis. Research proposed in the current application is significant because it will enhance our current knowledge by elucidating the mechanisms important to establish the primordial follicle pool. Results obtained in this grant will help improve research efforts in ovarian biology and in treatment of conditions causing female infertility such as primary ovarian insufficiency.