Role of LH-induced cell migration and cofilin dephosphorylation in ovulation

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Project Abstract: In the ovary, luteinizing hormone (LH) signals through the luteinizing hormone receptor (LHR) to initiate the transition from preovulatory follicle to corpus luteum. Essential to this transition are the movement of the oocyte to the site of ovulation, basal lamina breakdown, and reorganization of the granulosa cells to form the corpus luteum. LHR-expressing cells migrate inwards in response to LH and at later time points after LH stimulation, the basal lamina is pulled inwards in regions of high HA-LHR expression. These results have led to the hypothesis that LH-induced granulosa cell migration aids in regulating the transition from preovulatory follicle to corpus luteum. Previous studies in isolated granulosa cells have indicated that LH signaling disrupts actin to allow cytoskeletal rearrangement and induces granulosa cell motility. One potential mediator of these actions is cofilin, an actin-depolymerizing protein. Cofilin activity is required for directional cell motility in multiple cell types, and expression of a dominant-negative form of the protein in granulosa cell inhibits LH-induced actin reorganization. However, the role of cofilin dephosphorylation in vivo has yet to be investigated. This project investigates the hypothesis that LH induces cell migration through dephosphorylation of cofilin, and that the migration pulls the basal lamina inward to aid in rupture during ovulation and reorganizes the cells to begin corpus luteum formation. In aim 1, live-tissue confocal and two-photon microscopy will be used to analyze granulosa cell migration in intact follicles and determine how granulosa cell migration contributes to basal lamina invaginations and ovulation. In aim two, a novel mouse line that expresses a dominant-negative form of cofilin will be used to explore the hypothesis that cofilin dephosphorylation regulates granulosa cell migration. These studies will provide novel information about the regulation of ovulation and could lead to clinical treatments for anovulatory diseases.