The present study was designed to determine the effects of vitrification on promoter methylation and the expression levels of pluripotency and differentiation genes in mouse blastocysts. Promoter region CpG methylation patterns and the expression levels of octamer-binding transcription factor (Oct4), Nanog homeobox (Nanog), caudal-type homeobox 2 (Cdx2), and heart and neural crest derivatives-expressed transcript 1 (Hand1) were analyzed in fresh and vitrified mouse blastocysts. Methylation was measured by bisulphate mutagenesis and sequencing; gene expression was determined by real-time reverse transcription-PCR. The results showed that vitrification significantly reduced the methylation levels of the Oct4 (85% vs. 62.5%), Nanog (77.5% vs. 55%), and Cdx2 promoters (4.6% vs. 1.4%; P < 0.05) in mouse blastocysts, which correlated with increased expression of Oct4 and Nanog in vitrified blastocysts. Hand1 promoter methylation was not significantly different in the fresh (17.9%) versus vitrification group (21.4%; P > 0.05). The expression levels of Cdx2 and Hand1 were not significantly different in fresh and vitrified blastocysts. In conclusion, vitrification significantly decreased Oct4, Nanog, and Cdx2 promoter methylation in mouse blastocysts, which correlated with increased expression of Oct4 and Nanog.
Animals Basic Helix-Loop-Helix Transcription Factors