The United Kingdom is considering approval of a new method of in vitro fertilization (IVF) that would allow for the correction of certain currently untreatable mitochondrial diseases.
Donation of Mitochondrial DNA from Second Mother Would Correct Certain Incurable DiseasesHealth Minister Andrew Lansley asked the Human Fertilisation and Embryology Authority to review three-parent IVF after University of Newcastle scientists reported that they had mastered the technique using a kind of cloning technology.
The potential value of this technique is in treating hereditary diseases that are passed from mother to child rather than from parents to child. Everyone inherits two sets of DNA. Genetic material from both mother and father and joined in the nucleus. Genetic material in the mitochondria, the energy making centers of each cells, however, is received exclusively from the mother.
We receive about 20,000 genes from both of our parents, and only 37 genes in the maternal mitochondrial DNA. Defects in those 37 genes, however, can be deadly, since they control the production of energy in every cell in the body.
Examples of mitochondrial defect diseases include:
• Diabetes and deafness occurring together in early childhood
• Leber's hereditary optic neuropathy, a condition causing blindness in early adulthood
• Leigh syndrome, a form of non-infectious encephalitis that can begin any time between infancy and early adulthood and several others. About 1 in 6500 babies is born with a mitochondrial defect. Only a few babies with these mitochondrial defects would live to adulthood so that having a child would be an issue, but this technology permits these women to become parents. Men cannot pass mitochrondrial defects to their offspring.
Treating Mitochondrial Defects with the Same Technology Used to Clone Dolly the SheepThe University of Newcastle reproductive technology team proposes to treat human mitochondrial diseases with the same technology used to clone Dolly the Sheep in the late 1990's. The intended parents donate sperm and an egg to be fertilized. Within a day of fertilization, the nuclear material, containing the 20,000 genes from the intentional parents, is removed from the fertilized egg and placed in a donor egg, from which the nucleus has been removed. The parents nuclear DNA then directs the growth of the embryo and later baby with the help of donor mitochondrial DNA.
Only one embryo is created. The second, donor egg is never fertilized.
British researchers have not yet attempted this procedure with any actual human volunteers. They simply report that the science is progressing to the point that this could now be done, pending approval of government regulators. The Human Fertilisation and Embryology Authority, in turn, is hesitant to grant approval for the new technique on its own, seeking to involve members of Parliament in the decision-making process as soon as possible. Review of the technique will probably take about a year.
It may well be that this new IVF technique is primarily of academic interest, since only half of the 1 in 6500 people with mitochondrial defects is a woman, and relatively few people born with these diseases reach maturity. There are no long lines of couples with mitochondrial defect issues clamoring to have IVF so they can bear healthy children. There are mutations that can cause milder, mitochondrial diseases, but no widely available method of detecting them. Continuing research, however, may yield other discoveries of greater relevance to parents seeking to conceive.