Three Person Mitochondrial Manipulation

Author:  Jessica Johnson

Institution:  University of Washington

On February 3rd 2016, the Institute of Medicine (IOM) in the United States deemed Mitochondrial Replacement Techniques (MRT) as ethically permissible and gave a green light for MRT clinical trials.  While this medical technique is critical for women with mitochondrial diseases to have healthy children, the committee’s decision has brought up multiple ethical discussions.

Women with mitochondrial diseases have the possibility of passing their disease on to their children.  Fathers do not face this risk because mitochondrial DNA is only passed on through the maternal line and is separate from nuclear DNA.  

Mitochondrial diseases can cause a wide range of complications including muscle weakness, loss of muscle, eye problems, and retarded growth.

To prevent the inheritance of these sometimes fatal mitochondrial diseases, scientists have developed Mitochondrial Replacement Techniques.  MRT replaces the faulty mitochondrial DNA and inserts healthy mitochondrial DNA in its place.  In the process, a woman’s eggs are collected and the mitochondrial DNA is removed.  A donor egg’s healthy mitochondria are then inserted into the woman’s eggs, after which the modified eggs can be fertilized and inserted into the woman attempting to conceive.

MRT is a seemingly straightforward genetic replacement therapy, but here’s the catch: MRT requires a donor egg from a healthy individual who is not the mother. MRT uses healthy mitochondrial DNA from a donor egg to replace the problematic mitochondrial DNA in the egg.  In essence, any child born from this technique has genetic material from three individuals: their father, their mother, and the healthy donor.

The ethical debates surrounding MRT center on the idea of “three parents” to an offspring.   The affect such alterations could have on future generations has not been studied. As a result, the ICM has proposed only male children be conceived and treated with MRT to avoid passing on the altered mitochondrial DNA. This could prevent the altered mitochondrial DNA from causing complications in future generations.

IOM also recommends that scientists track the lifelong health of children born through this method.  This recommendation has raised concerns because it forces unborn children into a lifelong tracking procedure without their consent.   However, if such tracking procedures are not implemented, the long-term effects of MRT may be difficult to determine.

The people who will benefit from MRT are not as numerous as the widespread news coverage might suggest.  Mitochondrial diseases are fairly rare in the human population, only occurring in approximately 8.5 people per 100,000.   In addition, many of these mitochondrial diseases are a result of issues with the nuclear DNA, not the mitochondrial DNA, thus making MRT ineffective on those individuals.

Allowing MRT to go to clinical trials is a bold move on the part of the IOM.  Such a decision opens up discussion about allowing more gene therapy techniques to enter clinical trials.  The public will continue to discuss the ethical implications of gene therapy techniques such as MRT, and this discussion is crucial for the future of afflicted individuals who cannot otherwise have healthy children.