Four baby monkeys created in a laboratory in the United States could hold the key to the eradication of a class of incurable genetic diseases, scientists revealed today.
In an experiment that brings the creation of babies with three biological parents a step closer, Spindler, Spindly and twins Mito and Tracker were born through IVF using a technique that should make it possible to prevent women who carry genetic disorders of the mitochondria from passing them on to their children.
Defects in mitochondria – tiny structures known as the power houses or batteries of a cell because they convert food into energy – affect about one in 6,500 births in the UK and can cause about 50 known diseases, such as fatal liver failure, stroke-like episodes, blindness, muscular dystrophy, diabetes and deafness. Mitochondrial DNA also plays a role in neurodegenerative diseases such as Alzheimer’s, Parkinson’s and Huntington’s.
The team of scientists from the Oregon National Primate Research Centre in effect swapped the mitochondrial DNA (mDNA) from the macaque monkey mother’s egg for the mDNA of a donor egg. Reconstructed eggs were then fertilised with the father’s sperm and the healthy offspring were born. Tests showed that no mDNA from the mother’s egg had been transferred.
This is the first time that primates have been genetically modified in this way. The fact that healthy offspring have been produced, paves the way for the use of the techniques in humans. But the research, published in the journal Nature today, will reignite the debate over genetic engineering and so-called “designer babies”.
Babies born using the new technique would inherit most of their genetic material from their mother and father. But a tiny amount – mitochondrial DNA accounts for less than 1% of all the DNA in a human body – would come from the donor of the mDNA. This genetic material would be passed on to future generations.
British scientists who developed a similar technique using mice provoked controversy last year when they revealed they had created 10 human embryos each containing DNA from one man and two women. The one-celled embryos, created at the University of Newcastle, were destroyed within days, as required by law.
Recognising the “devastating effects” of mitochondrial diseases, the new Human Fertilisation and Embryology Act, which comes into force on 1 October, allows for secondary legislation to permit treatment of mitochondrial diseases should therapies become available.
Mitochondria, which are strewn throughout the cell body, contain their own DNA separate from that in the nucleus. Like nuclear DNA, mDNA harbours genes that can mutate and cause disease. However, mDNA can only be passed on to offspring via mothers’ eggs. It is not transmitted by sperm.
Dr Shoukhrat Mitalipov, who led the research team, said: “With the proper governmental approvals, our work can rapidly be translated into clinical trials for humans, and, eventually, approved therapies.” He accepted the research was controversial because it involved making the genetic changes that could be passed down generations. He said: “We are talking about birth defects that cause terrible diseases. The only way to treat them is to replace these genes.”
Peter Braude, head of the department of women’s health at King’s College London and director of the centre for preimplantation genetic diagnosis at Guy’s hospital, London, described the work as “very exciting”. These were “just the sort of procedures that were anticipated when parliament left the door open for transfer of genetic material to avoid mitochondrial disease in the latest revision of the Human Fertilisation and Embryology Act”.
Dr Marita Pohlschmidt, director of research at the Muscular Dystrophy Campaign, said: “We welcome these new advances and believe affected families should be offered the choice of having a healthy child.”
Professor Sir Ian Wilmut, of the medical research centre for regenerative diseases in Edinburgh, who created Dolly the cloned sheep, welcomed the research tonight: “The authors are to be congratulated for being the first to demonstrate in primates a new route to therapy. This brings us an important step nearer to being able to prevent the birth of children with a particular type of inherited disease.”
Gene genie: New front in search for cures
Mitochondrial DNA mutations are linked to a growing list of human diseases including neurodegenerative diseases, diabetes, cancer and infertility.
Mitochondrial diseases with neuromuscular disease symptoms are often referred to as a mitochondrial myopathy and, say the Muscular Dystrophy Campaign, around 3,500 people in the UK are affected by this type of the disease. Other conditions caused by defective mDNA include diabetes mellitus and deafness – although the combination can occur for other reasons – multiple sclerosis-type diseases, Leber’s hereditary optic neuropathy, where sight loss can begin in young adulthood, Leigh syndrome, marked by seizures and dementia. Mutations are increasingly implicated in a range of prevalent conditions such as Alzheimer’s and Parkinson’s. Since the distribution of the defective mDNA may vary from organ to organ, and each mutation is affected by other variants in the genetic make up, the effects of mitochondrial disease can be quite varied. A mutation that in one individual may cause liver disease might cause brain disorder in another.