Boiani Michele, Gentile Luca, Gambles Vivian V, Cavaleri Fatima, Redi Carlo A, Schöler Hans R
Max Planck Institute for Molecular Biomedicine, Mendelstrasse 7, D-48149 Münster, Germany.
Stem Cells. 2005 Sep;23(8):1089-104. doi: 10.1634/stemcells.2004-0352. Epub 2005 Jun 14.
A prevailing view of cloning by somatic-cell nuclear transfer is that reprogramming of gene expression occurs during the first few hours after injection of the nucleus into an oocyte, that the process is stochastic, and that the type of reprogramming needed for cloning success is foreign and unlikely to be readily achieved in the ooplasm. Here, we present evidence that the release of reprogramming capacity is contingent on the culture environment of the clone while the contribution of aneuploidy to altered gene expression is marginal. In particular, the rate of blastocyst formation in clones and the regional distribution of mRNA for the pluripotent stem cell marker Oct4 in clonal blastocysts was highly dependent on the culture environment after cumulus cell nuclear transfer, unlike that in genetically equivalent zygotes. Epigenetic modifications of genetically identical somatic nuclei continue after the first cell division of the clones and are amenable to a degree of experimental control, and their development to the blastocyst stage and appropriate expression of Oct4 predict further outcome, such as derivation of embryonic stem (ES) cells, but not fetal development. This observation indicates that development to the blastocyst stage is not equivalent to full reprogramming and lends support to the novel concept that ES cells are not the equivalent of the inner cell mass, hence the discrepancy between ES cell derivability and fetal development of clones.
关于体细胞核移植克隆，一种普遍的观点认为，基因表达重编程发生在将细胞核注入卵母细胞后的最初几个小时内，该过程是随机的，且克隆成功所需的重编程类型是外来的，不太可能在卵质中轻易实现。在此，我们提供证据表明，重编程能力的释放取决于克隆的培养环境，而染色体非整倍性对基因表达改变的影响微乎其微。特别是，与基因相同的受精卵不同，克隆胚胎的囊胚形成率以及克隆囊胚中多能干细胞标志物Oct4的mRNA区域分布高度依赖于卵丘细胞核移植后的培养环境。在克隆胚胎的第一次细胞分裂后，基因相同的体细胞核的表观遗传修饰仍在继续，并且在一定程度上可进行实验控制，它们发育到囊胚阶段以及Oct4的适当表达可预测进一步的结果，如胚胎干细胞（ES细胞）的获得，但无法预测胎儿发育情况。这一观察结果表明，发育到囊胚阶段并不等同于完全重编程，这支持了一个新的概念，即ES细胞不等同于内细胞团，因此ES细胞的可获得性与克隆胎儿发育之间存在差异。
