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TR: Scientists here in the United States have tried cloning using rabbit eggs, with no success. Does that suggest that the method won't work?
IW: Those results are disappointing, but they aren't surprising. Very small changes in these procedures can be critical. For example, many labs that successfully cloned farm animals could not get the technique to work in mice.
We've already learned certain lessons about how to go about it. One group in Japan has used rabbit eggs to generate stem cells from macaque monkeys. They discovered that cells should first be grown in the medium used for rabbit cells, then later in the medium used for macaque cells. Simple changes like that can dramatically change success.
TR: In the past year, scientists made a breakthrough in "reprogramming"--turning back the clock on an adult cell to produce stem cells without using eggs. Simply triggering expression of four genes seemed to create stem-cell-like cells, which could obviate the need for human eggs. Are you also pursuing this type of research?
IW: I first suggested something like that back in 1997: I said it would be the offspring of Dolly. I'm sure a lot of other people were thinking that way as well, but it's been a very difficult experiment to do.
The efficiency for that method [the reprogramming method described earlier this year] was very low, so there should be lots of room for improvement. We just developed an assay in which we add an extract from mouse embryonic stem cells onto human cells, which triggers expression of those four genes. We plan to use that system to figure out which factors in the extract are crucial for turning on gene expression.
TR: The U.S. administration, which has hindered embryonic stem-cell research with drastic funding restrictions, has suggested that advancements in reprogramming technologies are a reason to move away from traditional embryonic stem-cell research. What do you think?
IW: In the short term, we don't know which approach will work best, so I think we should pursue both. But in the end, I think reprogramming will be preferable.
A lack of human eggs has created a major roadblock in one of the most promising areas of stem-cell research.
Researchers want to make patient-matched stem cells, but success could depend on gaining a reliable source of human eggs.
In the wake of scientific fraud in South Korea, researchers are renewing their race to clone stem cells.
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hmnelson
1 Comment
Cross-species viral transmission
My first concern whenever I hear of any sort of human-animal tissue combinations is whether or not the practice might create new human diseases through cross-species transmission of animal viruses.
For example:
http://www.niaid.nih.gov/dait/cross-species/page3.htm
"The doomsday scenario is... that you take a porcine organ, you transplant it into a person, a porcine cell expresses a retrovirus, it infects a human cell... (and) produces a virus capable of transmission to the general public. Complex recombinations do occur, but they are not common."
Since this research is concerned with eggs, not adult cells and organs, and there is only a very small amount of animal DNA left in the cell, such worries wouldn't seem to apply.
Still, is there such a thing as an inherited retrovirus? If so, is there any chance that the small amount of residual animal DNA could harbor such a virus, and that it might be expressed later on?
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cretin001
35 Comments
Re: Cross-species viral transmission
apart from the chance of something like that hapening this is immoral and wrong and wierd and wrong and freaky and wrong. If there is an afterlife wer the hel wud they go? wud they go to limbo or somthin caus som freak of a person decided to try something freaky and wrong? u can try it if u find som martians and mix them with animals...
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