Wednesday, February 26, 2014

Mitochondrial replacement / 3-parent babies: opening the door to human enhancement

This week the NY Times had an interesting opinion column on mitochondrial replacement, a procedure currently under review by the FDA. The idea is that there is a cohort of inheritable diseases based on defects in the mitochondrial genome. In the embryo the mitochondria are all derived from the fertilized egg so the defects are passed from the female partner. Thus the approach for potential parents where the woman has a mitochondrial defect would be for in vitro fertilization followed by transfer of the fertilized nucleus to an enucleated egg from a healthy donor. Thus the embryo would have three parents, the male and female who contribute the nuclear genome and the female who contributes the mitochondrial genome. 

It is hard to argue with the use of mitochondrial replacement to prevent the passing of defective mitochondrial genomes to children. In the current situation women who know they posses such defects must choose between refraining from having children or passing their defects to their offspring. However, if this approach is to be approved by the FDA it is important to go forward with the understanding that it will open the door to widespread use in other contexts. Mitochondrial transfer will become yet another tool in the growing armamentarium of human enhancement technologies, where advances made in the name of disease treatment are subsequently applied to enhance the physical or cognitive abilities of healthy individuals. A possible additional use is improving success rates for older women during in vitro fertility treatments. Beyond that application looms a whole range of other possibilities. The most obvious, given the connection between mitochondrial energy generation and muscle function, is to seek to enhance the athletic prowess of offspring. Sequencing mitochondrial genomes is trivial with current ‘deep sequencing’ machines and it would be quite easy to sort through the mitochondrial genomes of thousands of individuals seeking genetic patterns associated with outstanding athletic capabilities. The ethical and societal implications of such efforts are very hazy, but what is clear is that it will happen if given the chance. 

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