Reprogramming within hours following nuclear transfer into mouse but not human zygotes

Abstract

Fertilized mouse zygotes can reprogram somatic cells to a pluripotent state. Human zygotes might therefore be useful for producing patient-derived pluripotent stem cells. However, logistical, legal and social considerations have limited the availability of human eggs for research. Here we show that a significant number of normal fertilized eggs (zygotes) can be obtained for reprogramming studies. Using these zygotes, we found that when the zygotic genome was replaced with that of a somatic cell, development progressed normally throughout the cleavage stages, but then arrested before the morula stage. This arrest was associated with a failure to activate transcription in the transferred somatic genome. In contrast to human zygotes, mouse zygotes reprogrammed the somatic cell genome to a pluripotent state within hours after transfer. Our results suggest that there is a previously unappreciated barrier to successful human nuclear transfer, and that future studies should focus on the requirements for genome activation.

Induction of pluripotency by defined factors

“…27),28) However, human somatic-cell-nucleartransferred cells had arrested at 8 cell stage in development. 29), 30) On the other hand, when a nuclear of somatic cell was transplanted into intact oocyte, these triploid cells succeeded to develop to the blastocyst stage. The established cell lines had pluripotency to differentiate into three germ layers.…”

MicroRNAs in regulation of pluripotency and somatic cell reprogramming

“…Since isogenic embryonic stem cell lines, known as NT-ESCs, can be derived from nucleartransferred embryos, this technology offers great hope for regenerative medicine. 40 However, due to technical restraints and ethical concerns, it is very hard to obtain patient-specific NT-ESC lines, 41 and until lately, only one research group has successfully derived hESC lines. 42 In 2006, reprogramming of mouse somatic cells into pluripotent stem cells was achieved by ectopically expressing four ESC-enriched transcription factors, namely Oct4, Sox2, Klf4, and C-myc.…”

Nuclear Reprogramming and Mitosis – how does mitosis enhance changes in gene expression?

“…6 Subsequently, they demonstrated that successful genome activation requires that the donor genome goes through a mitotic transition (which facilitates the exchange of somatic for embryonic nuclear factors on the donor nuclear material). 7 How general this phenomenon may be remains to be established. However, using a different reprogramming system, we recently demonstrated that the transcriptional response of donor cells to reprogramming stimuli varies greatly with cell cycle stage.…”