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.

中文翻译：

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褪黑素通过改善DNA甲基化重编程来增强猪克隆胚的发育。

在克隆的胚胎中不完全的DNA甲基化重编程导致较差的克隆效率。褪黑激素已被证明可以改善克隆胚胎的发育，但是，褪黑激素在体细胞核转移过程中的作用尚不清楚。这项工作表明10 ^-7褪黑素显着增强了发育进程，降低了合子基因组激活前的停滞率，并上调了克隆胚胎的胚泡率。褪黑素还通过上调抗凋亡因子的表达而下调促凋亡基因的转录来促进假核形成，增加胚泡细胞数量并减少胚胎凋亡。进一步的研究表明，用褪黑激素处理后，克隆的胚胎中的DNA甲基化重编程相关基因得到了极大的改善。然后，褪黑素可有效促进基因组DNA脱甲基和DNA再甲基化，多能性相关基因Oct4的DNA脱甲基，印迹基因H19 / Igf2的DNA甲基化维持组织特异性基因的，和DNA再次甲基化Thy1系中克隆胚胎。因此，基因组合子激活相关基因柽柳eIF1A，多能性相关基因的Oct4，Nanog的，和Sox2的，印迹基因IGF2和H19，和囊胚质量相关基因Cdx2的和ATP1B1均明显上调，和组织特异性基因Thy1系和COL5A2被沉默了。总之，褪黑激素通过改善DNA甲基化重编程增强了克隆胚胎的发育。这项工作表明褪黑激素可以调节DNA甲基化重编程，并为提高克隆效率提供了新颖的见解。