Introduction: Oocytes must effectively grow, accumulate reserves, and mature prior to fertilization. Errors in any of these processes affecting nuclear, cytoplasmic, or molecular maturation of the oocyte will result in poor embryonic development.
Materials and methods: Immunofluorescence, direct fluorescent staining, and autoradiography were combined with confocal, epifluorescent, and electron microscopy to study the transzonal projections (TZPs) between the cumulus cells and the oocyte. Total RNA and de novo synthesized transcripts were detected in the TZPs by selective staining. Long transcripts present in the TZPs were identified by RNA-Seq. Functional analyses of potential RNA transfer from the cumulus cells to the gamete was done by RT-qPCR, polyribosomal extraction and exposure to diverse inhibitors.
Results: We have demonstrated that long poly(A) bearing RNA molecules are shuttled to the oocyte by the cumulus cells down their TZPs during in vitro maturation. Vesicles existing between the TZP and the oolemma present a means of large molecule transfer capable of carrying RNA to the oocyte. Inhibition of vesicle function and RNA synthesis negatively impacted oocyte maturation. We also observed a time dependant increase in TZPs RNA content post-slaughter suggesting induction from a change in follicular status. Maturing oocytes collected pre-induction experienced significantly diminished maturation rates.
Discussion: We present a new perspective of how the cumulus cells influence the acquisition of the oocytes maturation potential by delivering exogenous RNA. Hormonal control of the follicle including the responsive cumulus cells will relay transcriptional support and directly influence the quality of the oocyte.
02 - 04 Sep 2014
World Congress of Reproductive Biology