Effect of oocyte vitrification on deoxyribonucleic acid methylation of H19, Peg3, and Snrpn differentially methylated regions in mouse blastocysts

Abstract

To examine whether mouse oocytes vitrification could alter the deoxyribonucleic acid (DNA) methylation of differentially methylated regions (DMRs) of three imprinted genes in invitro fertilized blastocysts. Invitro experiments using murine model. State key laboratory and university research laboratory. Kunming white mice. The mouse metaphase II oocytes were vitrified. After thawing, the surviving oocytes were fertilized invitro to produce blastocysts. The blastocysts derived invitro from fresh oocytes were used as a control. The DNA methylation patterns of the DMRs of imprinted genes in oocytes and blastocysts and the relative expression of DNMTs (Dnmt1, Dnmt3a, Dnmt3b, and Dnmt3l) in oocytes and blastocysts were detected. Methylation patterns of DMRs of H19, Peg3, and Snrpn analyzed by bisulfite mutagenesis and sequencing. Expression levels of messenger ribonucleic acid as measured by real-time reverse-transcriptase polymerase chain reaction. After oocytes vitrification, the methylation levels at H19, Peg3, and Snrpn DMRs in blastocysts were decreased. However, there was no significant difference in the percentage of hypermethylated strands at Peg3 DMRs between the vitrified and control groups. DNMTs expression in vitrified oocytes and the expression of Dnmt3b in blastocysts derived from vitrified oocytes were significantly reduced. Oocytes vitrification could lead to the loss of DNA methylation of imprinted genes (H19, Peg3, and Snrpn) in mouse blastocysts, which is mainly caused by the reductions of DNMTs after vitrification of oocytes.