Cloning and Mitochondrial Disease

by Brian on November 26, 2003

In his paper “Dolly: The Age of Biological Control”, Ian Wilmut suggests one interesting use for cloning technology. In that paper Wilmut basically opposes what we normally think of as reproductive cloning. (In a recent paper with Glenn McGee he has slightly softened his attitude.) But he thinks the following procedure, which as far as I can tell would be illegal under current anti-cloning legislation, would be entirely appropriate if provably safe. I agree with Wilmut, and I think there’s a very strong argument for amending the legislation to ensure this procedure is permissible.

But there is one way nuclear transfer technology might be used in procreation that I do find attractive. This is its use to replace the mitochondrial DNA in an egg. Mitochondria are the small bodies in each of our cells which supply energy. They contain DNA, which is subject to error (mutation) leading to diseases in just the same way that chromosomal mutation may cause disease. However, in the case of mitochondria we inherit those only from our mothers. A woman suffering from mitochondrial disease knows that her children will inherit the same condition. In principle, there is no reason why the embryo nucleus could not be removed from the defective egg and be placed in a recipient egg cell, itself enucleated. The recipient egg would be provided by a woman known not to have similar damage to her mitochondria, with her full informed consent. The resulting child would be exactly as it would have developed, except that it would not suffer the disease associated with mitochondria. The catch with this is that it would be possible to make multiple copies of the embryo—you might start with a thirty-cell embryo and end up with six fertilized eggs. Done thoughtfully, however, this method of nuclear transfer could provide a way to treat currently untreatable mitochondrially carried diseases.

If you think 30 cell embryos are worthy of legal defence, then I guess you shouldn’t like this idea. But that is very much a minority position, and I can’t see why anyone else should oppose Wilmut’s proposal, provided it is safe.



Brett Bellmore 11.26.03 at 2:18 pm

This confirms what I’ve thought all along: That cloning, by it self, is quite boring. Won’t have much impact on society at all. It’s the key technology needed for germ line genetic engineering, though, and THAT is interesting.


Chris 11.26.03 at 4:13 pm

I would submit that viewing an emryo as a person (and therefore entitled to a person’s rights) may be ‘very much a minority position’ in some areas of the world, but that one should apply such broad claims to the world as a whole tentatively, if at all. If you are arguing for laws in a particular location (county, state, country, wherever), I’ll concede that the view of embryo=person in that location may very well fall into the ‘fringe’ category; otherwise, I would argue that the ‘minority’ to which you refer is much larger than you might imagine.


john c. halasz 11.26.03 at 7:09 pm

Yes, that’s been the point all along. Cloning as a viable reproductive technique is doubtful and of dubious benefit, but, as a research tool in developing and maintaining cell lines and in developing treatments/cures for congenital or degenerative diseases or conditions such as paralysis, it has immense promise. Misfocusing the issue is misordering priorities.


Brian Weatherson 11.26.03 at 8:41 pm

John, but this would count as reproductive cloning under the definitions currently in play. After all, the result of cloning would be a healthy baby girl (or boy). The point here, I think, is that the boundary between reproductive cloning and cloning for research is fuzzier than is often acknowledged. (Actually this may be a point that anti-cloning forces agree with me about.)


john c. halasz 11.27.03 at 12:32 am

Sorry, if I missed the fine print somewhere, but, no, I think the relevant points in the mitochondrial case are 1) it is being done with fetal/embryological tissue, and thus both does not have the same risks/drawbacks as cloning using adult cellular DNA and is much more likely to prove feasible in the nearer term, and 2) it is being done to prevent the occurrance of a genetic disease, even if it does so before rather than after the point of conception, so it does resemble the case of medicinal rather than strictly reproductive uses of cloning, which also involve nuclear DNA and thus short-curcuit the genetic exchange involved in all other forms of reproduction, which would be one of the core objections as to its degree of intrusion into the “naturalness” of the process and the risks and damages that could result. Part of what is at issue in your framing of the debate is whether mere personal preference should count as a sufficient reason for such an agressive, risky and expensive intrusion/manipulation into underlying biological processes, were it even to prove really possible, or whether other interests, or proxy-interests, such as respecting natural constraints, acknowledging human limits and considering social effects and consequences should be given stronger weight. As of now, human reproductive cloning is really a speculative issue, part of notional humanist/posthumanist debates, inspired by a kind of “technological fiction”, (since fiction = making.) But the mitochondrial case is much more clearly cut, from both a humanistic and a naturalistic point of view.

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