In this issue of Fertility and Sterility, Zhao et al. (1) have found that H19 putative imprinted control region (ICR) level of methylation significantly increased in vitrified two-cell bovine embryos and the generated blastocysts. They have also observed that incubation of vitrified-thawed 2-cell embryos with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) significantly reduced H19 ICR methylation and increased H19 expression by reverse transcription-polymerase chain reaction in the blastocysts derived from the vitrified embryos compared with those in fresh embryos.
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