14 March 2011
ByAppeared in BioNews 599
Health Secretary, Andrew Lansley has asked the Human Fertilisation and Embryology Authority (HFEA) to convene an expert group 'to assess the effectiveness and safety' of a fertility treatment that would enable children to be born without potentially devastating, incurable mitochondrial diseases.
The technique replaces defective mitochondria with donated healthy mitochondria via a reverse cytoplasm (which contains the mitochondria) transfer. The procedure to replace the defective mitochondria involves a transfer of the pro-nuclei DNA belonging to the prospective parents being transferred into the donor cytoplasm. The 'reverse' aspect is because it is easier to remove the compact nuclear DNA, the sperm and egg pro-nuclei, from the defective fertilised egg (the recipient) and transfer it into the healthy donor egg's cytoplasm than it would be to essentially suck out both cells' cytoplasm and transplant the donor egg's cytoplasm into the defective egg recipient.
All cells have numerous mitochondria in the cytoplasm which surrounds the nucleus. Mitochondria are small energy-synthesising structures vital to cell function, and are only inherited maternally from the egg's cytoplasm, meaning that mitochondrial defects will be inherited by all the offspring of an affected mother.
Mitochondrial disease is rare but can be devastating, including fatal liver, neurological and heart conditions, and affects 100 children annually in Britain.
The technique is controversial because mitochondria contain a tiny amount of DNA, roughly 35 genes, involved in healthy cell and organ function, but does not encode the information to define any human attributes.
Technically any child resulting from this therapy will have the genetic information from three people: nuclear DNA from both parents and mitochondrial DNA from the donor. The resulting child is therefore almost genetically identical to their parents, but absolutely identical in attributes. The only genetic difference accounts for healthy cell function.
This genetic outcome has resulted in the media using the term 'three parent IVF'. Experts argue that the reference is a misnomer because mitochondrial DNA does not transfer any traits and therefore cannot amount to parentage any more than a liver transplant recipient would be considered to have four parents because the recipient contains the genetic DNA from four people.
The technique to transfer the parents egg and sperm pro-nuclei into a denucleated donor egg cell structure/cytoplasm is similar to the Dolly the sheep SCNT (cloning technique) but does not involve cloning. Reproductive cloning remains banned in the UK.
UK law permits the research but prohibits the clinical application of cytoplasm transplantation. When the law was updated in 2008 a provision was included to allow regulations to be introduced in the future to lift the prohibition for the prevention of mitochondrial disease.
Professor Alison Murdoch, director of reproduction at the University of Newcastle where licensed research is ongoing, says it is 'progressing very rapidly'. She estimates that the review process could take a year and should begin now.
The HFEA committee has called for evidence from experts to be submitted by 15 March 2011 for consideration on 25 March. The committee is expected to present its conclusions to the Government next month. If the Health Secretary decides to approve the procedure then the regulation will be put before Parliament for approval.