12 July 2012
Inherited mutations in mitochondrial DNA can cause a spectrum of disabling health problems with wide-ranging degrees of severity. Disorders can appear at any age from birth and often shorten the lifespan of the patient, with the most severe cases resulting in life-threatening organ failure and muscle weakness. There are currently no cures for these disorders which affect some 3,500 people in the UK, and their variability makes it difficult to provide accurate counselling and family planning advice.
A substantial body of knowledge of mitochondrial biology and pathology exists, and effective techniques have been developed that could be used to prevent the transmission of mutated mitochondrial DNA to the child. The techniques - variations of IVF procedures - use healthy mitochondria from a donor’s egg to replace damaged mitochondrial DNA that would otherwise be passed on from the mother. These methods are available for research but have yet to undergo the clinical trials necessary in order to be approved for use in patients. The new Wellcome Trust Centre for Mitochondrial Research in Newcastle is ready to move this forward if regulations allow it.
These techniques cannot yet be tested in humans because under present legislation it is illegal to implant an embryo that has been genetically modified. Researchers, clinicians and policy makers agree however that there is an urgent need for comprehensive ethical, regulatory and legal analysis of the potential for these technologies to positively impact patients’ reproductive choices and the outcomes for their offspring.
There has been much media reference recently to “three-parent” babies, with commentators discussing questions of child identity, its rights to know all biological “parents” (including the donor of the healthy mitochondrial material) and the impact of this type of genetic manipulation on future generations. What is often lost in this debate (but was specifically recognised in the recent report from the Nuffield Council of Bioethics - see previous news) is that the techniques now under consideration are aimed strictly at replacing disease-causing mitochondrial material and not manipulation of the whole germline genome; that would be a debate of entirely different scope and size.
Allowing manipulation of mitochondrial genetic material in order to prevent debilitating disease does not by any means imply germline intervention (leading to possible changes in all descendants). Such aims are far beyond those of current preventative medicine. There is a clear difference between the two types of interventions and both researchers and commentators such as the Nuffield Council have endeavoured to emphasise this demarcation.
Further initiatives to assess the legal and regulatory issues around the therapeutic application of these technologies should be considered imminently. Indeed, the Secretary of State for Health and the Secretary of State for Business, Innovation and Skills have jointly asked the Human Fertilisation and Embryology Authority (HFEA) to seek public views on this matter in a consultation to be launched in early autumn 2012.
The scale of issues around mitochondrial transfer techniques is certainly great but it is important they be tackled without delay to allow the technology to be best used for patients’ health and benefit.