Considerable time has been spent, during the current debate in the UK Parliament on the Human Fertilisation and Embryology Bill, on the definition and generation of interspecies embryos. A free vote is most likely on this part of the proposed legislation, which is perceived by some to be highly controversial.
We are among those proposing to undertake interspecies somatic-cell nuclear transfer — in which a human cell will be transferred into an animal egg. Our studies will generate embryos in order to advance understanding of genetic reprogramming and nuclear–mitochondrial interaction. They will also generate embryonic stem cells to model certain human diseases. As embryonic stem cells can differentiate into any type of cell of the body, those harbouring a specific genetic alteration can be differentiated into cells associated with the related disease and studied in vitro.
We acknowledge the exciting progress arising from induced pluripotent stem cells, whereby a fully differentiated cell is reprogrammed to behave like an undifferentiated stem cell. However, the success of this process is highly dependent on understanding embryo-derived stem cells. It remains to be determined whether induced pluripotent cells could lead to cancer or other diseases after transplantation, and whether they are equivalent to human embryonic stem cells, as they show different patterns of gene expression1. Studying reprogramming through somatic-cell nuclear transfer may improve induced pluripotency and help to produce therapeutically useful cells.
Animal oocytes are a far more reliable source than human oocytes, which are available in very limited supply. Embryonic stem cells have been derived following intraspecies nuclear transfer in mice2 and monkeys3, and several cell lines have resulted following transfer of human nuclei into rabbit oocytes4.
We strongly recommend that scientists be allowed to generate interspecies embryos and to culture these for up to 14 days, placing them under the same restrictions as any human embryos generated under current legislation. We also hope that the new legislation will be revised to allow researchers access to banks of well-characterized tissues and cells that were donated for research but not explicitly for the production of embryonic stem cells by somatic-cell nuclear transfer or other techniques. Such experiments should be conducted in parallel with those generating induced pluripotent cells, to compare the resultant cell lines and to learn more about reprogramming, nuclear–mitochondrial interaction and certain genetic diseases. It would be a retrograde step to prevent any avenue of research, especially one with such high potential gains.
About this article
Contributions to Correspondence may be submitted to firstname.lastname@example.org. They should be no longer than 300 words, and preferably shorter. We welcome comments on publishing issues at Nautilus (http://blogs.nature.com/nautilus).