"Early failure to perform correct XCI is likely to lead to the demise of the embryo. A recent publication showed that the sex ratio of children born after blastocyst transfer in IVF/ICSI treatments is altered in favour of males. As a result of our finding that XCI occurs at the pre-implantation stage, further research should be able to clarify whether culture conditions in the laboratory influence the growth rate and survival of female embryos and whether this can be improved."
She said that her results also had implications for human embryo stem (ES) cell research. "Human embryonic stem cell lines are derived from blastocysts that, we know now, already have, or still have, a form of XCI. While mouse embryos reactivate the X chromosome in the inner cell mass at the blastocyst stage so that the derived embryonic stem cells are completely undifferentiated, it is not yet known whether this occurs in human embryos. The onset and subsequent steps of XCI in human pre-implantation embryos occur at a later stage than in mouse embryos. Thus, it is possible that reactivation of the X chromosome happens also at a later stage, after the usual time for ES cell derivation. The current human ES cell lines may, therefore, still have the first wave of XCI. Indeed, the majority of human ES cells have XCI features."
This might mean that human embryonic stem cells could behave in a different and possibly unpredictable way to
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| Contact: Mary Rice mary@mrcommunication.org European Society for Human Reproduction and Embryology Source:Eurekalert |