Abstract：Delay in maternal transcript degradation of DNMT1 (DNA (cytosine-5)-methyltransferase 1cytosine-5)-methyltransferase 1) in porcine (Sus scrofa) somatic cell nuclear transfer embryos compared with in vitro fertilized counterparts was confirmed, thereafter anti-DNMT1 siRNA was injected into embryos at one-cell stage to evaluate the effect of DNMT1 knockdown on the developmental rate of embryos and the mRNA levels and DNA methylation levels of several developmentally important genes. Though a higher proportion of blastocysts was obtained in 50 μmol/L siRNA injected embryos (30.43%) compared with mock injected embryos (23.01%) and untreated controls (25.74%), while the difference was not statistically significant (P= 0.19). In the case of genes expression, inhibition of DNMT1 significantly increased the mRNA levels of POU5F1 at four-cell stage and of NANOG at the blastocyst stage (P＜0.05). In the aspect of DNA methylation, inhibition of DNMT1 reduced the DNA methylation level of POU5F1 at four-cell stage and decreased the general methylation to the level of in vivo produced embryos at the blastocyst stage, whereas over-depressed DNMT1 disrupted the imprinted methylation of a long noncoding RNA H19. This study suggests that mild inhibition of over-expressed DNMT1 facilitates pluripotent genes transcription and demethylation reprogramming of porcine cloned embryos, furthermore provides a scientific reference for further research on function mechanisms of DNMT1 during early embryogenesis.
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