268. Suppressors of cytokine signalling (SOCS): roles in ovarian follicle activation

Abstract

Oocytes are sequestered in primordial follicles before birth and remain quiescent in the ovary for decades, until recruited into the growing pool throughout the reproductive years. Therefore activation of follicle growth is a major biological checkpoint that controls female reproductive potential. However we are only just beginning to elucidate the cellular mechanisms required, for either maintenance of the quiescent primordial pool, or initiation of follicle growth. Analysis of microarray data derived from neonatal mouse ovaries indicated that members of the Suppressors of Cytokine Signalling SOCS family of proteins may play pivotal roles in folliculogenesis. We undertook a detailed analysis of gene and protein expression patterns of the eight members of the SOCS family, namely CIS and SOCS1–7, within adult and neonatal mouse ovaries. Quantitative real time PCR and immunohistochemistry was performed to determine mRNA levels and cellular localisation in the ovaries of cycling and new born animals. SOCS proteins were expressed largely within the oocytes of developing follicles and in the granulosa cells of the larger preovulatory follicles. Expression of SOCS4 in the granulosa cells and SOCS5 within the oocyte was coincident with the activation of oocyte growth and the differentiation of squamous pregranulosa to cuboidal granulosa cells. Our investigation has identified a role for the SOCS family proteins within the ovary and SOCS4 and SOCS5 as major regulators of cytokine signalling pathways in follicle activation and development.