What is the controversial procedure known as mitochondrial replacement?

Monday, February 22, 2016 by: Sarah Landers
Tags: mitochondrial replacement therapy, three-parent babies, biotechnology

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(NaturalNews) According to a new report by the National Academies of Sciences, Engineering, and Medicine, three-parent babies should be approved in the U.S. for boys – a controversial procedure that has already been approved in the U.K.

The report was requested by the U.S. Food and Drug Administration (FDA) and concerns a procedure known as mitochondrial replacement therapy (MRT) but it doesn't mean that the procedure will be able to go ahead immediately, as there are still concerns and safety issues that need to be addressed.

What is MRT?

Mitochondria are small, sausage-shaped structures inside a cell that generate energy. They also contain their own small genome, known as mitochondrial DNA (mtDNA) which can be prone to potentially dangerous mutation events. These events occur at a rate of around 10 times faster than those that occur in the main genome, which is housed in the cell's nucleus.

Mutations can prevent the mitochondria from functioning properly, which causes serious problems for the affected individual – including disorders that are severely debilitating and often fatal. However, there is a way to prevent children from inheriting these mutations – and this involves using MRT.

In the procedure, faulty mitochondria are replaced by those from the egg of a healthy, disease-free donor – either before or after the egg is fertilized in a test tube. Sperm cells contain hardly any mitochondria, which is why this technique involves only donor eggs and also explains why these diseases are only inherited from mothers. This is also the reason why the new report suggests that the initial clinical investigations only involve male embryos.

The problems associated with MRT

There are several reasons why this technique has been labelled as controversial and met with some opposition from various groups. Firstly, the potential psychological impacts that may result from a child that has three parents cannot be ignored, including identity issues and confusion over ancestry. These ethical complexities need to be considered in order to ensure the welfare of the child.

The Council for Responsible Genetics has reviewed the hazards of human developmental gene modification and states that they are generally categorized as either somatic (body cell) modification (in which non-reproductive tissue is affected) or germline (egg or sperm cell) modification (changes to the individual's DNA that can be passed down to future generations).

The main hazard of developmental modification is the potential transmission of undesired alterations in the germline. The hazard of germline transmission of DNA modification is not just speculative – there is a lot of literature on transgenic animals showing increased tumor incidence during adult life. Such effects may not be seen for a generation or more.

The disruption of a normal gene by inserting foreign DNA into a mouse caused lack of eye development, lack of development of the semicircular canals of the inner ear and anomalies in sense of smell.

Attempts at MRT and any other developmental gene modification will be subject to experimental error – errors which may go unnoticed for decades or several generations before we come into some real difficulties with the gene characteristics that have been passed down. The developmental process is extremely complex, and there is no scientifically accepted understanding of its overall coordination or process.

At the moment, it is still unclear as to whether the green light for MRT will ultimately be given by the FDA – the report is still undergoing a review process. But as the technique has been defined as a form of genetic modification, and modified embryos are not currently allowed to be implanted into women in the U.S., it looks like getting approval may be a timely and complicated procedure.

Sources include:

IFLScience.com

CouncilForResponsibleGenetics.org

Science.NaturalNews.com