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Egg nucleus swaps get funding and regulatory boost in the UK

British regulators today began a public consultation on experimental reproductive procedures to treat rare mitochondrial diseases.

Meanwhile, scientists conducting basic research on the procedures received £5.8 million (roughly US$9 million) to determine their safety. The procedures involve transferring the nuclear DNA of an egg with defective mitochondria to an egg with healthy mitochondria that has been stripped of its nucleus.

As many as 1 in 250 people carry a potentially disease-causing mitochondrial mutation. Mutations in mitochondrial DNA, passed from a mother to her offspring, are linked to a number of conditions, including some forms of muscular dystrophy and type 2 diabetes.

The money will pay for a new Wellcome Trust Centre for Mitochondrial Research at Newcastle University, UK. The research charity contributed £4.4 million over five years, and the university kicked in another £1.4 million. Newcastle neurology professor Doug Turnbull will head the centre. The funds will pay for research to determine the safety of two DNA-swapping procedures called pronuclear transfer and maternal spindle transfer.

Maternal spindle transfer (MST) involves transferring the chromosomes of an unfertilized egg into another woman’s egg that has been stripped of its nucleus. That hybrid cell is then fertilized in vitro. In 2009, scientists in Oregon reported that two rhesus macaques conceived this way (named Mito and Tracker) were born healthy and developed normally.

In pronuclear transfer, scientists shuttle the nucleus of a fertilized egg into another fertilized egg that lacks mitochondrial mutations and has been stripped of its nucleus. In 2010, Turnbull’s team applied this approach to fertilized human eggs that were not suitable for implant and found that 18 out of the 80 resulting embryos developed to the 8-cell stage, and a small number reached the 100-cell blastocyst stage at which implantation occurs.

There is no scientific evidence to suggest that the procedures would not be safe, according to an April 2011 report commissioned by the UK authority that regulates reproductive procedures, the Human Fertilisation and Embryology Authority (HFEA). However, the report laid out a number of experiments to conduct before the procedure can be attempted in humans.

The new Wellcome Trust grant will pay for some of that work. In particular, Turnbull, his colleague Mary Herbert and their team will test out both procedures on healthy eggs. At a press briefing today, Herbert said that the eggs would come from in vitro fertilization clinics and from altruistic donors (although UK egg donors may soon be able to receive compensation. See Give your eggs to science, get paid, suggests new report). Turnbull, Herbert and their team plan to culture the fertilized eggs to the blastocyst stage and look for signs of abnormal development.

“This is what [HFEA] wanted to see,” says Shoukhrat Mitalipov, the reproductive biologist at the Oregon Health and Science University in Portland who led the macaque work on maternal spindle transfer. “It seems like they’ve been very supportive in terms of saying what they would need to move on with clinical trials.”

The Newcastle researchers do not have plans to determine whether primates conceived through pronuclear transfer come to term and are healthy, as Mitalipov’s team did with the other procedure. The HFEA report deemed such work “critical” before clinical trials begin, and it is unclear who would conduct these experiments.

But clinical trials are clearly on the minds of scientists and regulators. In announcing a public consultation on the issue, HFEA took a step towards amending laws that now prohibit the DNA-swapping procedures. After about a year, the body will report back to Britain’s Department of Health.

At the same time, the influential Nuffield Council on Bioethics is conducting an ethical review of technologies and their implications, with a report expected this summer.

Just when clinical trials could begin is difficult to predict and will depend on the pace of research and policy decisions, Turnbull said at the briefing.

But at some point researchers and doctors will have to make a leap of faith and test the techniques in humans, Peter Braude, a reproductive biologist at King’s College London who helped put together the HFEA report, said at the briefing. “I think you have to say ‘safe enough’ with the evidence you have.”

Correction 20 January: A previous version of this post indicated that University of Newcastle professor Alison Murdoch attended the press briefing, when it was another Newcastle professor, Mary Herbert, who attended. Both scientists will be involved in the newly funded research. 

Image courtesy Wikimedia Commons


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