PARENT SESSION
OVARIAN FOLLICLE
Laurel
7:30 AM-10:00 AM

(78) REGULATED EXPRESSION AND POTENTIAL ROLE OF PROHIBITIN GENE PRODUCT DURING FOLLICULAR DEVELOPMENT AND ATRESIA IN THE RAT OVARY.

Branch, Alicia¹, Asselin, Eric³, Stiles, Jonathan², Tsang, Benjamin³, Thompson, Winston¹, ¹ Department of Obstetrics & Gynecology and Cooperative Reproductive Science Research Center, Atlanta, GA³ Department of Obstetrics & Gynecology and Cellular & Molecular Medicine, Ottawa, CA² Department of Microbiology Biochemistry and Immunology, Atlanta, GA

ABSTRACT- We have previously demonstrated that prohibitin is associated with granulosa cell development and that its expression may, in part, be regulated by gonadotropin. Recently, we have shown that prohibitin content is inversely associated with cell proliferation, but increases during granulosa cell differentiation, and in earlier events of apoptosis in a temperature-sensitive granulosa cell line. In an attempt to extend these observations to examine the role and regulation of prohibitin in follicular cell fate determination in immature rat ovaries, we have used established in vivo models for the induction of follicular development and atresia to provide a comprehensive characterization of the temporal and spatial patterns for prohibitin. Western blot analyses of total protein in granulosa cells prepared from control, equine CG (eCG)-primed and anti-eCG treated ovaries revealed an increase in prohibitin protein level in gonadotropin treated cells when compared to control and gonadotropin withdrawal cells. Granulosa cell nuclear fragmentation, as assessed by Hoechst staining, showed a significant increase in the percentage of apoptotic cells of anti-eCG treated ovaries. Next, we compared the immunolocalization pattern of prohibitin to proliferating cell nuclear antigen (PCNA), cholesterol side-chain cleavage cytochrome P450 (P450scc), and in situ terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin end labeling (TUNEL) on paraffin embedded section. Prohibitin is expressed in granulosa cells, theca-interstitial cells and the oocyte. During follicular maturation there was an inverse relationship between prohibitin localization and PCNA expression. Prohibitin colocalizes with P450scc indicating a strong association with steroidogenic cells. Prohibitin immunostaining markedly decreased in TUNEL positive cells. Taken together, these results suggest that prohibitin may be involved in modulating the growth of granulosa cells, mediating the steroidogenic potential of these cells, and potentially suppressing apoptosis. Thus, it may be playing an important role in determining the fate of these cells and eventual follicular destiny (Supported by NIH-RR03034,GM08248,HD41749,NCI-SPORE, and the Canadian Institutes of Health Research).

KEY WORDS: Ovary, Prohibitin, Differentiation, Apoptosis