Imprinting disorder in donor cells is detrimental to the development of cloned embryos in pigs
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Xuexiong Song1,*, Fangzheng Li1,*, Zhongling Jiang1,*, Yueping Sun1, Huatao Li1, Shansong Gao1, Liping Zhang1, Binghua Xue2, Guimin Zhao3, Jingyu Li2, Zhonghua Liu2, Hongbin He3 and Yanjun Huan1
1College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, Shandong Province, China
2College of Life Science, Northeast Agricultural University, Harbin, Heilongjiang Province, China
3College of Life Science, Shandong Normal University, Jinan, Shandong Province, China
*These authors contributed equally to this work
Yanjun Huan, email: [email protected]
Keywords: imprinting, donor cell, somatic cell nuclear transfer, cloned embryo, pig
Received: June 20, 2017 Accepted: August 06, 2017 Published: August 22, 2017
Imprinting disorder during somatic cell nuclear transfer usually leads to the abnormality of cloned animals and low cloning efficiency. However, little is known about the role of donor cell imprinting in the development of cloned embryos. Here, we demonstrated that the imprinting (H19/Igf2) in porcine fetus fibroblasts derived from the morphologically abnormal cloned fetuses (the abnormal imprinting group) was more hypomethylated, and accordingly, significantly higher H19 transcription and lower Igf2 expression occurred in comparison with those in fibroblasts derived from morphologically normal cloned fetuses (the normal imprinting group) or donor fetus fibroblasts (the control group). When these fibroblasts were used as donor cells, the abnormal imprinting group displayed an even lower imprinting methylation level, in correspondence to the significantly downregulated expression of Dnmt1, Dnmt3a and Zfp57, and a markedly reduced blastocyst rate, while the normal imprinting group took on the similar patterns of imprinting, gene expression and embryo development to the control group. When 5-aza-dC was applied to reduce the fibroblasts imprinting methylation level in the normal imprinting group, cloned embryos displayed the more severely impaired imprinting and significantly lower blastocyst rate. While the upregulated H19 transcription in the abnormal imprinting group was knocked down, the imprinting statuses were partly rescued, and the cleavage and blastocyst rates significantly increased in cloned embryos. In all, donor cell imprinting disorder reduced the developmental efficiency of cloned embryos. This work provides a new insight into understanding the molecular mechanism of donor cells regulating the cloned embryo development.
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