| Summary: | The precise mechanisms that regulate the ovulation rate of species are not entirely understood. The C1galt1 Mutant mouse, in which oocytes lack core 1-derived O-glycans, is characterised by (i) increased fertility, evident from ~40-50% larger litters as a result of increased number of growing follicles and (ii) modified cumulus expansion. Work carried out in this thesis investigated both of these phenotypes and led to the understanding of possible mechanisms involved in increased fertility. Through detailed analysis of the cumulus complex both prior- and post-ovulation in Control mice, novel characteristics regarding the physiology of cumulus expansion have been found. In addition, the analysis of C1galt1 Mutants has revealed that a functional cumulus-oocyte-complex requires the essential components to be present above a minimum threshold level, and thus some variation in ECM composition does not adversely affect oocyte development, ovulation or fertilisation. These data have important implications for IVF and the use of cumulus expansion as a criterion for oocyte assessment. C1galt1 Mutants have (i) altered follicle growth characteristics, (ii) reduction in apoptosis levels and (iii) reduction in AMH levels, all of which could be directly or indirectly contributing to the increased fertility phenotype. These data reveal new and important roles for the oocyte in follicle development and female fertility, providing perspectives for future work in female reproduction.
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