This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. To develop strategies for using cytoplasm transfer to improve the developmental competence of in vitro matured (IVM) oocytes. Understanding the causes of developmental failure of embryos derived from IVM oocytes will lead to improvements in protocols for in vitro maturation of oocytes that would be extremely valuable for treatment of infertility, especially for women with polycystic ovarian syndrome and cancer patients undergoing radio- or chemo-therapy. We have focused on developing strategies for transfer of cytoplasm from in vivo to in vitro matured oocytes. Bovine oocytes were used to assess the developmental competence of oocytes from which 0%, 25%, or 50% of the cytoplasm was removed. Blastocyst development was negatively correlated with the amount of cytoplasm removed. Therefore, in a second series of experiments, mature zona-free oocytes were fused to enucleated cytoplasts to form 'giant eggs'. Fusion rates were approximately 75% for both bovine and rhesus. Zona-free rhesus monkey zygotes were cultured in microdrops and developed into blastocysts at an equivalent rate to zona- intact control embryos. Recent goals have been to fuse in vivo matured rhesus cytoplasts to in vitro matured rhesus oocytes approximately 3 hours after insemination and evaluate their developmental competence compared to that of nonmanipulated in vivo and in vitro matured rhesus oocytes. Parallel studies were conducted to determine whether developmental failure of IVM oocytes is associated with impairments in the initiation of mRNA synthesis, rRNA synthesis, or both, among individual blastomeres of 8-cell stage embryos. The project ended during this report period. This research used WNPRC Animal Services.
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