Role of the donor nuclei in cloning efficiency: can the ooplasm reprogram any nucleus?

Abstract

Cloning efficiency has not been dramatically improved after the first success of somatic cell nuclear transfer (SCNT) in sheep in 1997. The reasons for the low efficiency of SCNT embryos must be attributed to the insufficient reprogramming of the donor nucleus in ooplasm. It has been clarified that the methylation and acetylation status are disordered in SCNT embryos and the gene expression pattern is different and widely varied in SCNT embryos, compared with fertilized embryos. In this paper, we focused on the role of the donor nuclei in cloning efficiency, and discuss whether ooplasm can reprogram any nucleus.

A comparative study on expression profile of developmentally important genes during pre-implantation stages in buffalo hand-made cloned embryos derived from adult fibroblasts and amniotic fluid derived stem cells

“…It has also been opined that a low OCT4 expression level at the blastocyst stage is associated with the low developmental potential of NT embryos (Li et al 2005). The down-regulation of OCT4 gene is considered to be a candidate marker for the low potential of NT embryos to develop healthy offspring (Kato and Tsunoda 2010). Our data indicate that an abnormal pattern of OCT4 expression in NT embryos might lead to their compromised developmental competence.…”

“…This finding implies that de-regulated gene expression is a common phenomenon in bovine cloning. Markers that will be useful for predicting the potential of NT embryos to develop healthy offspring are needed (Kato and Tsunoda 2010).…”

“…State of donor cells is one of the most important factors for cloning efficiency (Kato and Tsunoda 2010). Many attempts have been made to establish the most competent donor cell type, especially for the mouse.…”

Differential developmental competence and gene expression patterns in buffalo (Bubalus bubalis) nuclear transfer embryos reconstructed with fetal fibroblasts and amnion mesenchymal stem cells

“…State of donor cells is one of the most significant factors for cloning efficiency (Kato and Tsunoda 2010). Many attempts have been made to establish the most competent donor cell type, especially for the mouse.…”

rRNA Genes Are Not Fully Activated in Mouse Somatic Cell Nuclear Transfer Embryos

“…As a kind of somatic cell NT embryo, CCNT embryos had relatively more active NORs and almost the same nucleolar-related genes expression level when compared with ESNT embryos. This may be one of the reasons why CCs always yielded better cloning outcomes than other somatic cells and were wildly used in NT experiments of different animals (50). Because the oocytes were supposed to have the same reprogramming competence against different donor cells, we believed that the rDNA methylation level and active NOR numbers in 4-cell embryos were determined by the rDNA epigenetic status of donor cells.…”