Species: mouse -
type: null mutation
fertility: subfertile
Comment: Ablation of the Sam68 gene impairs female fertility and gonadotropin-dependent follicle development. Bianchi E et al. Sam68 is a multifunctional RNA binding protein highly expressed in the gonads, whose ablation causes male infertility. Herein, we have investigated Sam68 expression in the adult ovary and its function in female fertility. Immunohistochemistry showed that Sam68 was localized in the nucleus of oocytes and follicular cells at all stages of folliculogenesis. Sam68(-/-) females were severely subfertile, they showed a delay in the age of first pregnancy, increased breeding time for successful pregnancy and yielded smaller litters. Morphological analyses indicated a significant reduction in the number of secondary and pre-antral follicles in the ovary. These defects were associated with alteration of estrus cycles and reduced number of ovulated oocytes, which were only partially restored by administration of exogenous gonadotropins. Crosslink/immunoprecipitation experiments showed that Sam68 directly binds the mRNAs for the follicle stimulating hormone (FSH) and the luteinizing hormone (LH) receptors (Fshr and Lhcgr), which were downregulated in ovaries of adult knockout females. Stimulation of immature females with the FSH-like PMSG, or of follicular cells with the FSH second messenger analogue 8Br-cAMP, caused upregulation of Sam68. The increase in Sam68 levels paralleled that of the Fshr and Lhcgr mRNAs in the preovulatory follicle and was required to allow accumulation of these transcripts in follicular cells. These studies identify a new crucial function of Sam68 in the regulation of female fertility and indicate that this protein is required to insure proper expression of the gonadotropin receptor transcripts in preovulatory follicles in adult ovary.