Winter 2015
Mitochondrial Donation And Its Future In Australia On 24 February 2015 the United Kingdom House of Lords passed legislation to allow for the use of mitochondrial donation in the IVF process for women at risk of having a child with mitochondrial DNA (mtDNA) disease. This landmark decision follows eight years of research and lobbying plus three separate expert reviews, and was passed by a majority of 232 votes. The UK Human Fertilisation and Embryology Authority is now charged with issuing a licence for these techniques to be used therapeutically on a case by case basis. The two new mitochondrial donation techniques being developed for IVF are maternal spindle transfer and pronuclear transfer. They involve transferring nuclear genetic material from the mother’s egg into a donor egg that has had its nuclear DNA removed and retains only its healthy mtDNA; the resulting child therefore does not inherit the mitochondrial disease.
Children born from a mitochondrial donor pregnancy will have DNA from three people. However, it is important to note that the donated mtDNA replaces only 37 mtDNA genes (contributing about 0.1 per cent of a person’s genetic make-up), compared with approximately 20,000 genes in the nucleus. The mtDNA contribution is important for converting food into energy but appears to make no significant contribution to appearance, behaviour or other features, which are determined by the nuclear genes and environment. Some groups have made sensationalist claims about the techniques being inappropriate because the children could
Nuclear DNA transferred into egg with healthy mitochondria
Donor’s egg containing healthy mitochondria Healthy embryo with no mitochondrial disease
Donor’s nuclear DNA removed
Mitochondrial Donation Maternal spindle transfer uses unfertilised eggs (oocytes), while pronuclear transfer uses eggs already fertilised by the father (one-cell embryos or zygotes). Unlike other IVF methods, both techniques could allow any woman carrying mitochondrial DNA disease to have healthy children who are genetically related to both parents.
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This is a simplified diagram outlining two methods for mitochondrial donation – maternal spindle transfer (prior to fertilisation) and pronuclear transfer (after fertilisation).
be said to have three parents. However, this is “misleading, inappropriate and unhelpful” according to the Nuffield Council on Bioethics in London, which in 2012 reviewed the procedures from an ethical standpoint. Australian legislation currently prohibits research involving human embryos containing genetic material (including
Research Australia grassROOTS WINTER 2015
A recent publication in the New England Journal of Medicine – Mitochondrial Donation: How Many Women Could Benefit – estimates that “the average number of births per year among women at risk for transmitting mtDNA disease is 152 in the United Kingdom”, which would correspond to approximately 56 births per year in Australia. The Australian Mitochondrial Disease Foundation (AMDF) strives to enact change in the Australian legislation concerning research on human embryos and to make mitochondrial donation available to Australian patients. Without such change, Australian families will be left with the choice of passing on potentially deadly genetic mutations, or foregoing bearing their own genetically related children.
Nuclear DNA removed from egg with unhealthy mitochondria Egg containing unhealthy mitochondria
mtDNA) from more than two persons. In 2010, an independent committee was appointed to review the Prohibition of Human Cloning for Reproduction Act 2002 and the Research Involving Human Embryos Act 2002. The report, released on 7 July 2011, recommended the legislation remain unchanged.
The AMDF has recently set up the Mitochondrial Donation Working Group, comprised of AMDF Board Members and members of its Scientific and Medical Advisory Panel. This group will take on the role of coordinating education for both politicians and the public on mitochondrial donation and its implications. From here, the working group will set out to lobby the government for the relevant changes to legislation that need to be made in order to bring these techniques to Australian women. So far, the working group has already held a useful meeting with politicians and ethicists, and has begun engaging more closely with Australian embryology and IVF researchers. The AMDF will continue to pursue what it believes to be a promising step for women at risk of passing mitochondrial disease on to their children. While this process took eight years to be passed in the UK, the AMDF is hopeful it will not be nearly as long a wait for Australian patients. www.amdf.org.au