Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

S. Clay Isom


S. Clay Isom


Abby Benninghoff


Korry Hintze


Irina Polejaeva


Lee Rickords


Dirk Vanderwall


An estimated 1.6 million American couples struggle with infertility. Some causes for poor fertility can be clearly defined but in many instances, subfertility is unexplained. Poor oocyte quality is now considered to be a main contributing factor for many causes of infertility. Good oocyte quality is crucial for many processes including embryo development and maintaining pregnancy. There is a possibility that any alterations to the oocyte can have long lasting effects on embryo development and the health of the offspring. The oocyte is very sensitive to any perturbations to its surrounding environment. Transcripts for apoptosis inhibitors and epigenetic modifiers were found to be significantly more abundant in in vivo-matured oocytes compared to oocytes that were matured in vitro. RNA degradation and chromatin remodeling pathways may also be perturbed in in vitro-matured oocytes. While examining the effects of maternal age on the oocyte, there are age-related differences in gene expression in equine cumulus-oocyte complexes. Differences in gene expression may lead to a decrease in oocyte developmental competence. Age related alterations to gene expression in the equine cumulus-oocyte complexes might be caused by increased rates of oxidative stress and subsequent DNA damage. These alterations could directly impact many processes within the oocyte. Higher incidences of apoptosis may be possible in the cumulus cells from aged mares, which would directly impact the developmental competence of the oocyte. Lastly, oocyte quality may be impacted by western dietary consumption patterns, which could lead to many genes being differentially expressed in oocytes. Alterations to the abundance of these genes have been shown to lead to effects that are commonly seen with metabolic syndrome, such as glucose intolerance, insulin resistance, obesity and diabetes. The results of this work will ultimately provide insight into the effects environmental influences have on the oocyte at the molecular level.