DNA Methylation Pattern in Pronuclear-Stage Mouse Embryos： Effect of Oocyte Vitrification

• Published in: 畜牧与生物技术杂志(英文版) Vol. 2; no. 4; pp. 192 - 198
• Main Author: Ying Liang Xiangwei Fu Junjie Li Dianshuai Yuan Shien Zhu
• Format: Journal Article
• Language: English
• Published: Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology,China Agricultural University, Beijing, 100193, China 2011
• Subjects: DNA甲基化; 免疫荧光检测; 原核; 小鼠卵母细胞; 异硫氰酸荧光素; 玻璃化冷冻保存; 胚胎; 试管婴儿; open-pulled straw vitrification; DNA methylation; mouse; pronucleus; oocyte
• ISSN: 1674-9782; 2049-1891
• DOI: 10.3969/j.issn.1674-9782.2011.04.192

This study was conducted to investi- gate the pattern of DNA methylation in pronuclearstage mouse embryos derived from vitrified-warmed oocytes. Mouse oocytes at metaphase II （MII） stage of meiosis were allocated randomly into three groups： 1） untreated （control）; 2 ） exposed to vitrification solution without being plunged into liquid nitrogen （toxicity）; and 3 ） vitrified by open-pulled straw （OPS） method （vitrification）. Oocytes were fertilized in vitro （IVF）. The level of DNA methylation was examined at 8 hpf （hours post-fertilization） by immunofluorescence using an anti-5-methylcytosine （5-MeC） monoclonal antibody and fluorescein isothiocyanate （FITC）-conjugated goat anti-mouse IgG. After IVF, rates of 2-cell embryos （ 51.39% ） and blastocysts （35.82%） for vitrified-warmed oocytes were lower （P〈0.01） than that for control （70.83%, 47.82% ） or vitrification solution treated （64.80%, 46.29% ） oocytes. At 8 hpf, there were more （P 〈 0.05） pronuclear-stage oocytes in which syngamy of pronuclei had not occurred in the vitrifica- tion group. In addition, 5-MeC fluorescent intensities for the female pronucleus and zygote were lower in the vitrification group （P 〈0.01 ） compared to pronuclear-stage embryos in the control and toxicity groups. In conclusion, oocyte vitrification causes a reduction in global genomic methylation in the female pronucleus and zygote, resulting in delayed fusion of pronuclei and compromising the developmental potential of mouse zygotes and embryos.