Nolen Leisha D, Gao Shaorong, Han Zhiming, Mann Mellissa R W, Gie Chung Young, Otte Arie P, Bartolomei Marisa S, Latham Keith E
Department of Cell and Developmental Biology, Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, 415 Curie Boulevard, Philadelphia, PA 19104-6148, USA.
Dev Biol. 2005 Mar 15;279(2):525-40. doi: 10.1016/j.ydbio.2005.01.016.
Somatic cell nuclear transfer embryos exhibit extensive epigenetic abnormalities, including aberrant methylation and abnormal imprinted gene expression. In this study, a thorough analysis of X chromosome inactivation (XCI) was performed in both preimplantation and postimplantation nuclear transfer embryos. Cloned blastocysts reactivated the inactive somatic X chromosome, possibly in a gradient fashion. Analysis of XCI by Xist RNA and Eed protein localization revealed heterogeneity within cloned embryos, with some cells successfully inactivating an X chromosome and others failing to do so. Additionally, a significant proportion of cells contained more than two X chromosomes, which correlated with an increased incidence of tetraploidy. Imprinted XCI, normally found in preimplantation embryos and extraembryonic tissues, was not observed in blastocysts or placentae from later stage clones, although fetuses recapitulated the Xce effect. We conclude that, although SCNT embryos can reactivate, count, and inactivate X chromosomes, they are not able to regulate XCI consistently. These results illustrate the heterogeneity of epigenetic changes found in cloned embryos.
体细胞克隆胚胎表现出广泛的表观遗传异常，包括异常甲基化和印记基因表达异常。在本研究中，对植入前和植入后核移植胚胎的X染色体失活（XCI）进行了全面分析。克隆囊胚重新激活了失活的体细胞X染色体，可能是以梯度方式。通过Xist RNA和Eed蛋白定位分析XCI发现，克隆胚胎内存在异质性，一些细胞成功地使一条X染色体失活，而另一些细胞则未能如此。此外，相当一部分细胞含有两条以上的X染色体，这与四倍体发生率的增加相关。印记XCI通常存在于植入前胚胎和胚外组织中，但在晚期克隆的囊胚或胎盘中未观察到，尽管胎儿重现了Xce效应。我们得出结论，尽管体细胞核移植胚胎能够重新激活、计数和使X染色体失活，但它们不能始终如一地调节XCI。这些结果说明了克隆胚胎中表观遗传变化的异质性。
