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Genomic studies of oocyte physiology reveal mechanisms critical to oocyte competence

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Title: Genomic studies of oocyte physiology reveal mechanisms critical to oocyte competence
Author(s): Yuan, Ye
Director of Research: Wheeler, Matthew B.
Doctoral Committee Chair(s): Nowak, Romana A.
Doctoral Committee Member(s): Krisher, Rebecca L.; Tanaka, Tetsuya S.; Herrick, Jason R.; Wheeler, Matthew B.
Department / Program: Animal Sciences
Discipline: Animal Sciences
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Oocyte Porcine Gene expression in vitro maturation
Abstract: In vitro maturation of porcine oocytes has been intensively studied for many years. However, the in vitro maturation system is still inefficient to produce competent oocytes that can develop to viable embryos. The studies discussed in this dissertation attempt to use different techniques and methods to characterize and improve the developmental competence of in vitro matured porcine oocytes. Medium environment impacts the metabolism and physiology of oocytes. Using chemically defined medium, we demonstrated the detrimental effects of ammonium on porcine oocyte maturation and developmental potential. This result suggested that using a more stable dipeptide, alanyl-glutamine, to replace the highly volatile glutamine can optimize the maturation medium. The microfluidic well system provides an easy-to-use physical platform that can successfully mature porcine oocytes and culture embryos individually without compromising their competence. Further optimization of the current system may result in a novel system that can also increase the development of oocytes and embryos. The main focus of this dissertation is to identify the specific genes whose function is related to oocyte competence. Functional studies were also conducted to further validate the relationship of selected genes with oocyte competence. In one experiment, we found genes related to cholesterol synthesis, fatty acid oxidation, glycolysis, and 4 other genes, TNF, PERV, TL10 and SRSF1, were differentially expressed between adult (more competent) and prepubertal (less competent) porcine in vitro matured oocytes. These genes were further analyzed by comparing transcript abundance in in vitro and in vivo matured prepubertal and adult oocytes. The different gene expression patterns between competent and less competent models suggested these pathways and genes may be functionally relevant to oocyte competence. The functional study of TNF demonstrated that TNF in the medium regulates TNFAIP6 expression in cumulus cells, and thus influence oocyte development. The other experiment focused on the genes that are related to redox homeostasis. Using same oocyte competence models (prepubertal versus adult, in vivo versus in vitro) we found that GLRX2, PDIA4, PDIA6 and TRXR1 may be functionally relevant to oocyte competence. By maturing oocytes in different redox environments, we found that a balanced redox environment is critical for oocyte development. Elevated glutathione in prepubertal oocytes suggested the disrupted redox homeostasis exists in these cells. By further comparing redox gene expression patterns, we found aberrant expression patterns in prepubertal oocytes when extra antioxidant was supplemented to the medium. These results suggested that prepubertal oocytes are less competent in regulating redox balance compared to adult oocytes. The aberrant expression patterns of GLRX2, PDIA4, PDIA6 and TRXR1 may contribute to the decreased developmental competence in prepubertal porcine oocytes. In conclusion, the studies in this dissertation provide a molecular sketch of genes and metabolic pathways that may be important regulators of oocyte quality in pigs. Further studies of these genes and pathways may result in a better understanding of oocyte competence and how better to support optimal competence during in vitro maturation.
Issue Date: 2012-02-06
URI: http://hdl.handle.net/2142/29758
Rights Information: Copyright 2011 Ye Yuan
Date Available in IDEALS: 2012-02-06
Date Deposited: 2011-12
 

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