Somatic cell nuclear transfer is a technique to create an embryo using an enucleated oocyte and a donor nucleus. Nucleus of somatic cells must be reprogrammed in order to participate in normal development within an enucleated egg. Reprogramming refers to the erasing and remodeling of cellular epigenetic marks to a lower differentiation state. Somatic nuclei must be reprogrammed by factors in the oocyte cytoplasm to a rather totipotent state since the reconstructed embryo must initiate embryo development from the one cell stage to term. In embryos reconstructed by nuclear transfer, the donor genetic material must respond to the cytoplasmic environment of the cytoplast and recapitulate this normal developmental process. Enucleation is critically important for cloning efficiency because may affect the ultrastructure of the remaining cytoplast, thus resulting in a decline or destruction of its cellular compartments. Nonetheless, the effects of in vitro culturing are yet to be fully understood. In vitro oocyte maturation can affect the abundance of specific transcripts and are likely to deplete the developmental competence. The epigenetic modifications established during cellular differentiation are a major factor determining this low efficiency as they act as epigenetic barriers restricting reprogramming of somatic nuclei. In this review we discuss some factors that could impact cell differentiation in embryo generated by nuclear transfer.

体细胞核移植是一种使用去核卵母细胞和供体核创建胚胎的技术。为了参与去核卵内的正常发育，必须对体细胞核进行重新编程。重编程是指将细胞表观遗传标记擦除和重塑成较低分化状态。体细胞核必须通过卵母细胞细胞质中的因子重编程为相当全能的状态，因为重建的胚胎必须启动从一个细胞阶段到足月的胚胎发育。在通过核移植重建的胚胎中，供体遗传物质必须对细胞质的细胞质环境作出反应，并概括此正常发育过程。去核对于克隆效率至关重要，因为它可能会影响剩余细胞质的超微结构，因此导致其细胞室的减少或破坏。尽管如此，体外培养尚未完全了解。体外卵母细胞的成熟会影响特定转录本的数量，并可能耗尽发育能力。细胞分化过程中建立的表观遗传修饰是决定这种低效率的主要因素，因为它们充当了限制体细胞核重编程的表观遗传屏障。在这篇综述中，我们讨论了一些可能影响核移植产生的胚胎中细胞分化的因素。