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5 February 2014 Functional Role of the Bovine Oocyte-Specific Protein JY-1 in Meiotic Maturation, Cumulus Expansion, and Subsequent Embryonic Development
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Oocyte-expressed genes regulate key aspects of ovarian follicular development and early embryogenesis. We previously demonstrated a requirement of the oocyte-specific protein JY-1 for bovine early embryogenesis. Given that JY-1 is present in oocytes throughout folliculogenesis, and oocyte-derived JY-1 mRNA is temporally regulated postfertilization, we hypothesized that JY-1 levels in oocytes impact nuclear maturation and subsequent early embryogenesis. A novel model system, whereby JY-1 small interfering RNA was microinjected into cumulus-enclosed germinal vesicle-stage oocytes and meiotic arrest maintained for 48 h prior to in vitro maturation (IVM), was validated and used to determine the effect of reduced oocyte JY-1 expression on nuclear maturation, cumulus expansion, and embryonic development after in vitro fertilization. Depletion of JY-1 protein during IVM effectively reduced cumulus expansion, percentage of oocytes progressing to metaphase II, proportion of embryos that cleaved early, total cleavage rates and development to 8- to 16-cell stage, and totally blocked development to the blastocyst stage relative to controls. Supplementation with JY-1 protein during oocyte culture rescued effects of JY-1 depletion on meiotic maturation, cumulus expansion, and early cleavage, but did not rescue development to 8- to 16-cell and blastocyst stages. However, effects of JY-1 depletion postfertilization on development to 8- to 16-cell and blastocyst stages were rescued by JY-1 supplementation during embryo culture. In conclusion, these results support an important functional role for oocyte-derived JY-1 protein during meiotic maturation in promoting progression to metaphase II, cumulus expansion, and subsequent embryonic development.

Kyung-Bon Lee, Gabbine Wee, Kun Zhang, Joseph K. Folger, Jason G. Knott, and George W. Smith "Functional Role of the Bovine Oocyte-Specific Protein JY-1 in Meiotic Maturation, Cumulus Expansion, and Subsequent Embryonic Development," Biology of Reproduction 90(3), (5 February 2014).
Received: 17 October 2013; Accepted: 1 January 2014; Published: 5 February 2014

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