A bit more about “3-parent babies”

It is reported that the UK’s Human Fertilisation and Embryology Authority (HFEA) issued guidelines last week to govern the practice of mitochondrial transfer, which the UK government approved in February.  In this case, the term “mitochondrial transfer” refers to any of several possible techniques that could be used to allow women with certain rare but debilitating diseases of the mitochondria—the “energy factories” of the cell—to have unaffected children.

I and other contributors to this blog have posted several times on this topic over the last two years.  Among these:  I linked to several resources on February 27 of this year, and had proposed a number of ethical issues posed by the practice on May 29 of last year, among other postings.

I have not been able to locate the draft guidelines on the Web, but an approving editorial in Nature comments that they are due to take effect next month.  The editorial says that the UK will limit the practice solely for the purpose of avoiding serious disease, at licensed centers that will be required to get separate approval on a case-by-case basis, with monitoring (with parental consent) of the health of any children born as a result.  This is important because mitochondrial transfer or donation has been suggested as a treatment for infertility, not just to avoid rare mitochondrial disease.  It is estimated that 150 people in the UK and, if eventually FDA-approved in the US, 800 people here would be eligible annually. 

If the approach is ethical, these guidelines, as stated, seem wise.    However, to implement this technique requires that the egg nucleus of an affected woman, who desires her own genetic child, would have to be implanted into an egg donated by an unaffected woman, after the nucleus of that egg has been removed.  Perhaps the most immediate ethical issue here—if, indeed, one is concerned about protecting human life from the point of conception—is that the nucleus transferred would likely not come from the egg, but from a fertilized embryo, leading to the destruction of that embryo to create a new one. 

But the Nature editors are responding to a separate concern—about unknown risks to the health of the child that would be born after mitochondrial transfer/donation.  The concern is this:  while mitochondria have only about 3 dozen genes (compared to about 20,000 in the human nucleus), the function of which has been thought to be limited, it turns out that, in some species anyway, there are more complex and really interesting interactions between what the mitochondrial genes and the nuclear genes do.  Examples:  learning behavior and brain anatomy in mice, survival in fruit flies, and general health in crustaceans.  Read about it here

The implication is that combining mitochondria from one woman with nuclear genetic material from another (plus a father’s genome) could, in humans, lead to currently unpredictable and profound implications for resulting children.  The journal editors are sanguine: experience with normal human outbreeding, and the limited scope and oversight of what is proposed in the UK, will keep the risks limited.  An unborn child could not consent, of course, but the prospective parents could, on that child’s behalf, in the belief that in the individual case the benefits outweigh the risks, maybe substantially.  Still, some scientists most knowledgeable in the field think the UK is moving too fast.

Note that this would be rather less the case were the UK to countenance trying this for infertility in general, as is said to be offered by some clinics in Canada.  We certainly should not rush into that.

It looks like, sometime in the not-to-distant future, a “3-parent Louise Brown,” if you will, will sally forth.  But it might take rather some time for enough such people to be born and followed for mitochondrial donation for infertility to gather steam.

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