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Wednesday 6 February 2008

RAPID ROUNDUP: Embryos with three parents – Australian experts respond.

Scientists in the UK are reported to have created human embryos containing DNA from two women and one man in the hope of one day treating inherited mitochondrial disorders. Australian experts respond.

Feel free to use these quotes in your stories. If you wish to speak to one of these or another expert, contact the AusSMC on 08 8207 7415.

David Thorburn is Associate Professor of Mitochondrial and Metabolic Research at the Murdoch Children's Research Institute, Melbourne

“Mitochondrial disorders are problems in converting food into energy and so can affect any and every organ in the body. Most commonly they affect the brain, which is the most energy demanding organ but also heart, muscle, liver and other organs. They can cause mental retardation or developmental delay, epilepsy, movement disorders and a very wide range of conditions. The unique thing about mitochondrial disorders is that some of the disorders are not caused by mutations in genes in the nucleus – which is what we normally think of when we think of genetic disease, but are instead caused by genes within the mitochondria. Your mitochondria are inherited from your mother so you mitochondrial genes come solely down the maternal line.

About 1 in 5000 children will develop mitochondrial disorders at some stage in their life. Our unit has diagnosed about 400 kids with these diseases in the last 15 years. These are diseases with a high degree of morbidity and mortality with over 50% of children dying in the first few years of life. We did a review of treatment in 2006 and found there is no evidence that any of the currently available treatments have any proven efficacy or a prolonged effect. These are very serious disorders which are all but untreatable and so there is a big incentive to offer families ways to prevent these diseases. This research is important because it is investigating ways of allowing families to have their own genetic children who will not be at risk of developing these severe diseases.

Mitochondrial DNA is very specialised, really all it does is code for 13 proteins used to generate energy in the cell. In total there are 37 mitochondrial genes compared with 1000 times that many in the nucleus. There is no evidence mitochondrial genes effect physical features like hair colour and there is not expected to be any implications from mixing 2 types of mitochondrial DNA in terms of physical features or any impact on intelligence except that the disabling effect of the disorders can be prevented.

This is a promising approach but so far the researchers have not published this data so it still needs to be subjected to scientific scrutiny, there are some theoretical risks that need to be addressed and at the moment we don’t know what stage the research is at and whether this has been done.”

Prof Bob Williamson is Professor of Medical Genetics, University of Melbourne

“A small number of babies are born with handicaps because the energy system in their cells, the mitochondria, do not work properly, leading to serious handicap affecting the brain and muscles. The Newcastle, U.K. group has shown that it is possible to take the nucleus from an affected embryo, put it into an egg with functional mitochondria, and grow it to a point where it might be able to implant in the mother’s womb and grow normally.

The headlines say 'DNA from 3 people', and this is strictly correct, since normal mitochondria have their own DNA. However, if a baby is born using this technique, the things that we usually think of as genetic (contributing to appearance, ability and personality) would be from the couple who provide the egg and sperm, since the mitochondria are just an energy factory, the equivalent of the electricity supply that allows cells to work properly.

One of the objectives of good medicine is to help couples who are at risk of having a severely handicapped child to avoid this by using the best ethical research techniques. Couples who are at risk of having a child with a severe handicap usually choose not to have children unless they can reduce this risk. New techniques, such as these, have to be considered by an ethics committee with community representatives. I think it is completely ethical to use new genetic techniques to help couples have their own, healthy children.”

Wendy Rogers is Associate Professor of Medical Ethics and Health Law at Flinders University, Adelaide

“This comes back to how you define a parent. The people who raise a child and are there day after day caring for them are the most important people in that child’s life. Someone who donates an egg without a nucleus cannot be called a ‘parent’. A cytoplasm donor would have even less parental status with that child than someone who donates sperm to a sperm bank. In terms of the ethical issues, the important question is how and where therapists harvest healthy eggs. Obtaining healthy eggs for such procedures must be done under strict ethical guidelines.”