The process of deriving human embryonic stem cells, which involves embryo destruction, has caused controversy in science and politics.
Two papers published online by Nature now provide different means of deriving such cells from mice without eliminating a cloned embryo that has the potential to develop.
Rudolf Jaenisch and Alexander Meissner report that it is possible to create cloned mouse embryos that inherently lack the ability to implant in the uterus and develop further. The method involves preventing the formation of a cell layer - called the trophectoderm - that later attaches the embryo to the uterine wall. The scientists achieve this by blocking the action of Cdx2, a gene that encodes the earliest known proteins involved in the development of this layer. The cloned, Cdx2-deficient mouse embryos were morphologically abnormal, but could efficiently generate embryonic stem cells that could expand into different cell types when cultured. Because Cdx2 might be needed for therapeutic strategies using these cells, the scientists made the gene knockout reversible, so the Cdx2 gene could be turned back on once the embryonic stem cell culture was established.
Robert Lanza and his colleagues show a new way to derive mouse embryonic stem cell lines that, unlike current methods, does not disrupt the embryo's ability to implant into the womb and develop. The procedure is based on a technique used in fertility treatments, called pre-implantation genetic diagnosis, where embryos are screened for genetic defects. If healthy, they are then implanted into the uterus and develop normally. Lanza and colleagues used a single-cell biopsy taken from mouse embryos to produce five putative embryonic stem cell lines. These embryos were then implanted into mouse uteri, where they developed to birth. The authors propose that if the procedure works on human embryos it would allow the banking of such cells for children born from transferred embryos.
Rudolf Jaenisch (Whitehead Institute for Biomedical Research, Massaschusetts Institute of Technology, Cambridge, MA, USA)
Available online at: [ 1]
Bob Lanza (Advanced Cell Technology, Worcester, MA, USA)
Available online at: [Paper No. 2]
Additional contact for comment on paper:
Irving L. Weissman (Stanford University School of Medicine, Stanford, CA, USA)
(C) Nature press release.
Message posted by: Trevor M. D'Souza