Mismatched DNA in so-called three-parent-babies may lead to problems in later life, research in mice has suggested.
Mitochondrial replacement therapy was approved by the UK Parliament last year and will allow women with genetic faults in their mitochondria — the cell’s energy generators — to have children without passing on their faulty mitochondrial DNA.
The therapy involves transferring the nucleus of the mother’s egg or fertilised embryo into an egg from an unrelated donor. The resulting child will inherit nuclear DNA from both their parents, and mitochondrial DNA from the donor.
But now a study in mice has suggested that a mismatch between mitochondrial and nuclear DNA can cause accelerated ageing and affect metabolism and obesity.
Pasieka/Science Photo Library.
Jose Antonio Enriquez, at the CNIC Research Institute in Madrid, and his team made this discovery in mice that had been specially bred to have mitochondria from a donor. When the animals were young they seemed to be in good health, but as they aged a range of problems arose, including a shortening of their telomeres — the protective caps on the ends of chromosomes — a sign of ageing.
Finding a match
However, it is not known yet whether the same effects would occur in people. The mice used in these experiments were inbred, but most people are highly outbred. “Humans are constantly mixing nuclear and mitochondrial genomes,” said Douglas Turnbull, at the University of Newcastle in the UK, whose team has pioneered mitochondrial replacement therapy.
If the findings in mice also happen in humans, then this could greatly complicate mitochondrial replacement therapy by making it necessary to find a mitochondrial donor whose DNA is a good genetic match to the mother.
“Just as with organ transplantation and blood transfusion, it is important to select mitochondrial donors [so that] the new mitochondrial DNA is genetically similar to that of the mother,” suggested Enriquez.
More studies are required before we can extrapolate Enriquez’s findings to humans, said Dusko Ilic, a stem cell researcher at King’s College London. “At that stage we can worry about whether a pre-selection of mitochondrial donor should be considered.”
Source: www.newscientist.com
