Human embryos cloned in California

Scientists at Stemgen, a La Jolla, California laboratory have published a report on the successful cloning of human embryos in the journal, Stem Cells. (The article is available free, due to the open access policy of the journal.)

The authors are very clear: these are human embryos produced by somatic cell nuclear transfer or cloning. The embryos were clones of the men who donated the fibroblast skin cells.

This study demonstrates, for the first time, that SCNT can be utilized to generate cloned human blastocysts using differentiated adult donor
nuclei remodeled and reprogrammed by human oocytes. Evidence of successful SCNT was shown with DNA fingerprinting analyses of three SCNT cloned blastocysts where embryo genomic DNA was that of the donor fibroblast cell line and were not fragmented oocytes or of parthenogenetic origin.

. . .DNA fingerprints from three SCNT blastocysts were consistent with those of the somatic cell donor employed with no evidence of contamination from the egg donors, indicating that embryonic development was being controlled by the donor cell genome.

The cloned human embryos were produced using donated oocytes less than 2 hours old and the DNA from the skin cells of men. (The eggs were donated by women for the use of other couples, see below.) The use of male donor DNA allows for easier distinction from any possible parthenogenetically produced embryos, which would be female. Any embryos that are male serve to prove the success of the experiment.

In this case, the cloned embryos were actually compared to parthenogenetically produced embryos created by stimulating oocytes to become embryos. These embryos only contain the DNA of the women who donated the eggs. Parthenotes are not clones, because of the rearrangement of genes that happens when the eggs are produced with half of the normal chromosomes which would be matched by the haploid sperm if fertilization took place.

It appears that the group had a very high success rate, with approximately 2/3 or 16 of 25 of the enucleated oocytes producing very early embryonic organisms, which (who) demonstrated cell development and division similar to embryos produced by in vitro fertilization. 10 of the embryos developed to day 3 and 5 of those went to day 5, with the formation of blastocysts. Blastocysts are embryos that have developed enough cells to form a layer of cells around a hollow center, and eventually the inner cell mass, the differentiated grouping of embryonic stem cells at one spot within the sphere. All 5 of the blastocysts formed inner cell masses. The authors do not report any stem cell lines from these embryonic stem cells, but note that they are trying to do so – either from these embryos or from additional cloning.

The Discussion includes speculation that the success rate was so high because the oocyte donors were young women who were able to produce so many eggs through stimulation of their ovaries that there were more than enough for the use by the parents (couples?) to whom they were donating for the production of embryos for implantation and pregnancy. Although the article states that all 3 of the parents were able to get pregnant from the eggs that went to them, that could not have been known at the time the eggs were taken to the experimental lab. Some went to the in vitro lab and some went to the experimenters within less than 2 hours. It takes at least a few hours after in vitro fertilization to determine whether any embryos were formed.

If embryonic stem cell lines are developed from this technique, perhaps some group will compare them to embryonic-like stem cells developed by reprogramming.

About bnuckols

Conservative Christian Family Doctor, promoting conservative news and views. (Hot Air under the right wing!)


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