Proper reprogramming of imprinted and non-imprinted genes in cloned cattle gametogenesis
Proper reprogramming of imprinted and non-imprinted genes in cloned cattle gametogenesis
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DOI：
10.1111/asj.12846
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发表时间：
2017-11-01
影响因子：
2
通讯作者：
Nagai, Takashi
中科院分区：
文献类型：
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作者：
Kaneda, Masahiro;Watanabe, Shinya;Nagai, Takashi
克隆动物的表观遗传异常是由核移植步骤（第一次重编程）期间供体核的不完全重编程引起的。然而，在仅发生在生殖细胞中的第二个重编程步骤中，在第一步中未纠正的表观遗传错误被修复。因此，克隆动物体细胞的表观遗传异常应该在其精子或卵母细胞中被消除。克隆动物的后代在出生时或出生后发育过程中不会表现出缺陷，这一事实支持了这一点。为了在克隆牛中检验这一假设，我们比较了克隆和非克隆公牛血液和精子 DNA 中两个印记基因（H19 和 PEG3）和三个非印记基因（XIST、OCT4 和 NANOG）以及两个重复元件（卫星 I 和卫星 II）的 DNA 甲基化水平。我们发现克隆公牛和非克隆公牛之间没有差异。我们还分析了从克隆和非克隆牛中回收的卵母细胞中四种重复元件（卫星 I、卫星 II、阿尔法卫星和 Art2）的 DNA 甲基化水平。同样，克隆和非克隆之间没有观察到显着差异。这些结果表明，印记和非印记基因以及重复元件在克隆牛的配子发生过程中被正确地重新编程。因此，它们为克隆牛后代的健康做出了贡献。
Epigenetic abnormalities in cloned animals are caused by incomplete reprogramming of the donor nucleus during the nuclear transfer step (first reprogramming). However, during the second reprogramming step that occurs only in the germline cells, epigenetic errors not corrected during the first step are repaired. Consequently, epigenetic abnormalities in the somatic cells of cloned animals should be erased in their spermatozoa or oocytes. This is supported by the fact that offspring from cloned animals do not exhibit defects at birth or during postnatal development. To test this hypothesis in cloned cattle, we compared the DNA methylation level of two imprinted genes (H19 and PEG3) and three non-imprinted genes (XIST, OCT4 and NANOG) and two repetitive elements (Satellite I and Satellite II) in blood and sperm DNAs from cloned and non-cloned bulls. We found no differences between cloned and non-cloned bulls. We also analyzed the DNA methylation levels of four repetitive elements (Satellite I, Satellite II, Alpha-satellite and Art2) in oocytes recovered from cloned and non-cloned cows. Again, no significant differences were observed between clones and non-clones. These results suggested that imprinted and non-imprinted genes and repetitive elements were properly reprogramed during gametogenesis in cloned cattle; therefore, they contributed to the soundness of cloned cattle offspring.