Melatonin Enhances the Development of Porcine Cloned Embryos by Improving DNA Methylation Reprogramming

Incomplete DNA methylation reprogramming in cloned embryos leads to poor cloning efficiency. Melatonin has been proven to improve the development of cloned embryos, however, the role of melatonin during somatic cell nuclear transfer remains unclear. This work demonstrated that 10(-7) M melatonin significantly enhanced the developmental progress, reduced the arrested rate before zygotic genome activation, and upregulated the blastocyst rate of cloned embryos. Melatonin also promoted the pseudo-pronucleus formation, increased blastocyst cell number, and reduced embryo apoptosis through upregulating the expression of antiapoptosis factors while downregulating the transcription of proapoptosis genes. Further study displayed that DNA methylation reprogramming related genes were greatly improved in cloned embryos when treated with melatonin; then, melatonin effectively promoted genomic DNA demethylation and DNA remethylation, DNA demethylation of pluripotency related gene Oct4, DNA methylation maintenance of imprinted gene H19/Igf2, and DNA remethylation of tissue-specific gene Thy1 in cloned embryos. Thus, zygotic genome activation related gene Eif1a, pluripotency related genes Oct4, Nanog, and Sox2, imprinted genes Igf2 and H19, and blastocyst quality related genes Cdx2 and ATP1b1 were remarkably upregulated, and tissue-specific genes Thy1 and Col5a2 were considerably silenced. In conclusion, melatonin enhanced the development of cloned embryos by ameliorating DNA methylation reprogramming. This work reveals that melatonin can regulate DNA methylation reprogramming and provides a novel insight to improve cloning efficiency.