Ever since I read John Holmlund’s blog entry (HERE) on mitochondrial replacement techniques (MRT) for inherited mitochondrial diseases, I have been thinking a lot about the issue of enhancement. Almost in passing, the Institute of Medicine (IOM) stipulated that MRT would not be a meaningful example of human enhancement because of the relatively limited genetic information in mitochondria.
Recall that mitochondria are the energy power houses of cells. Dysfunctional mitochondria tend to cause significant problems in tissues that require higher energy consumption, such as muscles and nerves. MRT is being proposed to prevent the birth of an individual who could develop mitochondrial myopathy, one example of the family of very debilitating and occasionally fatal mitochondrial diseases. With MRT, we are replacing en bloc defective maternal mitochondrial DNA with presumably extremely healthy mitochondrial DNA from a separate maternal donor. The resulting child is the nuclear genetic combination of her two parents plus a third healthy mitochondrial DNA donor, hence the designation “3 parent baby”.
As to whether or not MRT represents a meaningful example of human enhancement, consider the following thought experiment. Let’s stipulate that in the not-so-distant future, MRT has become routine and safe for preventing the birth of an individual with mitochondrial myopathy. Since the critical criterion for a potential maternal mitochondrial donor is a female with no genetic history of mitochondrial disease, any female meeting this condition and willing to be a donor becomes a donor candidate. Within that group, why not select a woman who also has outstanding muscle function, such as Carmelita Jeter (currently the fastest living female world record holder for the 100 meter dash). While the parental nuclear DNA undoubtedly controls much of the development of their future child’s muscle function, having Carmelita Jeter’s mitochondrial DNA certainly can not be expected to slow the child down (for if it does slow her down, then our stipulation of MRT safety fails). But does it speed her up?
Obviously the answer to the question of whether or not MRT represents an example of enhancement is – we don’t know. The IOM’s solution to determining the answer to this question (and the many other questions related to the ethics and safety of MRT) is effectively to try MRT and see what happens.
My stipulation is that MRT represents the first approved genetic enhancement therapy, despite the relatively small amount of genetic information in mitochondria.
I also think the child speeds up.