Researchers have urged further deliberation by health authorities prior to the introduction of a potentially life-saving IVF treatment that replaces mutated mitochondrial DNA with donor material.
In an article published today in Science, evolutionary biologists from Monash University, the University of Sheffield and the University of Sussex discussed evidence, which suggests that mitochondrial replacement (MR) IVF therapy could potentially result in unintended health consequences in offspring. The UK parliament will consider green-lighting the therapy for clinical use, within the United Kingdom, next year.
Mitochondria, which exist in almost all animal cells and convert food into energy, have their own DNA, distinct from the 23 chromosome pairs that comprise the human genetic map. Mutations in the mitochondrial DNA can cause mitochondrial disease. Around 1 in 5000 Australians will develop a serious mitochondrial disease in their lifetime and there are currently no cures.
MR involves inserting the nuclear material of a prospective mother and father into a donor’s egg, which has had its own nucleus removed but still contains a healthy set of mitochondria (and mitochondrial DNA). This results in an embryo containing the genetic material of three people, with the donor egg contributing approximately 0.1 per cent of the DNA. The donor’s mitochondrial DNA would then be passed on to future generations, through daughters.
The paper’s authors – Dr Damian Dowling from Monash, lead author Dr Klaus Reinhardt of the universities of Sheffield and Tuebingen, and Dr Ted Morrow from Sussex – noted the promise of MR for preventing a variety of inherited mitochondrial conditions, ranging from mild learning difficulties to debilitating conditions such as muscular dystrophy and other life-threatening heart, muscle and brain diseases.
They then highlighted a set of research findings that have not featured prominently in debate over the safety of the therapy. Studies in model organisms have shown that MR-type techniques can profoundly alter the expression of numerous nuclear genes and affect a range of traits in the recipient including development, cognitive behaviour and physical performance. Not all combinations of nuclear and mitochondrial genetic material work well together, regardless of the health of the donor.
Dr Dowling said that in public debate, MR had been likened to replacing the batteries in a camera; however, this was an oversimplification.
“The analogy has been used to argue that mitochondria are like batteries in a camera. It doesn’t matter what brand of battery you use, the camera will function. Yet, the body of research we bring to the table suggests otherwise – the brand can affect the expression of many health-related traits,” Dr Dowling said.
“We support the premise of MR, and acknowledge the huge promise it offers to prospective mothers that suffer mitochondrial disease. We also believe that patients should have access to the full array of evidence, so they can make an informed choice that is right for them and their situation.”