509. REGULATING MURINE FOLLICLE DEVELOPMENT BY STIMULATION OF THE JAK2/STAT3 SIGNAL TRANSDUCTION PATHWAY

Abstract

Follicular development requires the recruitment of primordial follicles into the growing follicle pool following initiation of multiple cytokine signalling pathways.  Suppression of follicular development is thought to be key to maintaining the population of primordial follicles and allowing for controlled release of these follicles throughout the reproductive lifespan of the female.  However, little is known of the processes and signalling molecules that suppress primordial follicle activation and early follicle growth.  Our group has identified significant upregulation of the Janus Kinase 2 (JAK2)/ Signal Transducer and Activator of Transcription 3 (STAT3) signalling pathway inhibitor the Suppressor of Cytokine Signalling 4 (SOCS4) that coincides with the initial wave of follicular activation in the neonatal mouse ovary.  Further studies by our group have localised the SOCS4 protein to the granulosa cells of activating and growing follicles, suggesting SOCS4 expression may be linked to follicular activation.  We have focused on examining protein localisation and gene expression patterns of the eight SOCS family members CIS and SOCS1-7.  We have recently demonstrated that co-culture of neonatal ovaries with Kit Ligand (KL) for 2 days increases the mRNA levels of all SOCS genes.  We also demonstrated the co-localisation of SOCS2 proteins with the KL receptor c-kit in the mural granulosa cells of antral, and large pre-antral follicles suggesting a significant role for SOCS2 in the later stages of follicular development.  We have also shown that culturing ovaries with the potent JAK2 inhibitor AG490 substantially reduces mRNA levels of all SOCS and STAT genes that we have so far measured.  We hypothesise a significant role for JAK2/STAT3 signalling in promoting the activation and early growth of ovarian follicles.  Our investigations have identified significant roles for JAK2/STAT3 and the SOCS family in the regulation of ovarian follicle development.