细胞核重编程对克隆的影响

Nuclear reprogramming and its implication for cloning

细胞核重编程是哺乳动物正常受精胚胎和克隆胚胎发育过程中的一个重要特性,主要是对表观遗传学特征进行重新编写,包括染色质重塑、组蛋白修饰、DNA甲基化、印记基因表达、X染色体失活等表观遗传修饰的改变。通过细胞核重编程,首先,受精卵和克隆胚胎的供体核停止其特有的基因表达程序,恢复为全能状态的基因表达程序;然后,受精胚胎和克隆胚胎的细胞再从全能状态重新进入分化状态,最终形成各种组织和器官。近年来,不少研究表明,克隆胚胎的细胞核重编程存在不同程度的表观遗传修饰异常,可能对克隆及其农业和医学应用有着重要影响。本文就正常和克隆胚胎细胞核重编程的研究进展以及克隆胚胎的细胞核重编程异常对克隆的影响作一综述,并对目前有关治疗性克隆前景的不同看法进行了讨论。

Nuclear reprogramming, which involves a remodeling of epigenetic modification including chromatin remodeling, covalent modification of histone, DNA methylation, genomic imprinting and X chromosome inactivation, is an essential feature in the mammalian development of normal fertilized and cloned embryos. During the process of nuclear reprogramming, the zygotes of the normal embryos and the donor nuclei of the cloned embryos cease their unique repertoire of gene expression and reset their gene expression to the totipo- tent status, and then the normal and cloned embryos redifferentiate from the totipotent status to various differentiated states for tissue generation or organogenesis. Recent reports have shown some abnormal patterns of epigenetic modification within cloned embryos, which might represent a potentially obstacle and preclude the potential applications of cloning for agriculture and regenerative medicine. This review focuses on current progress of nuclear reprogramming in normal and cloned embryos and its implication for therapeutic cloning.