Meet Alana Saarinen, one of only a handful of people in the world who have three biological parents. No, she’s not the result of some weird genetic engineering experiment, but a pioneering infertility treatment which has now been banned. The procedure involved transferring part of a donor’s cell to her mother’s egg which contains tiny structures called mitochondria. Since these structures possess their own genome, Alana consequently has DNA from three parents.
Mitochondria are sausage-shaped organelles that are sometimes referred to as cellular powerhouses. These structures produce energy in the form of ATP which serves as the energy currency of life. Mitochondria are odd because they replicate independently of cell division and also have their own small genome. It’s estimated that the human genome has around 30,000 genes; all but 37 of these are located in the nuclear genome, the rest are found in the mitochondrial genome. Mitochondrial DNA is only passed down from the mother, probably because eggs contain far more molecules of this DNA than sperm.
A variety of diseases can result from faulty mitochondria which mainly affect cells of the brain, heart, skeletal muscles and respiratory system. The diseases vary in severity depending on which tissues are primarily affected, but in general they are severely debilitating and often fatal. This is why the UK is now considering legalizing mitochondrial replacement to prevent these diseases from being passed on. However, this is not the reason that Alana’s parents underwent the procedure.
Alana’s mother had been trying to conceive through IVF for 10 years. As a last resort, she turned to the St. Barnabas Institute in New Jersey, which pioneered a procedure called cytoplasmic transfer back in the 1990s. Since it was possible that faulty mitochondria could be to blame for her inability to conceive, embryologists swapped the part of her egg that contains the mitochondria—the cytoplasm—with that from a donor.
17 babies were born as a result of cytoplasmic transfer at this particular clinic, but concerns were raised as one woman experienced a miscarriage, another baby was born with a missing X chromosome, and two other children had developmental disorders. However, it’s difficult to tell whether these problems arose because of the procedure.
After three extensive reviews to scrutinize the safety of mitochondrial replacement, the UK’s Human Fertilization and Embryology Authority concluded that the procedure is “not unsafe.” Therefore, its approval in the UK is currently being debated amongst politicians, but it is likely that more studies will be required before a decision is made.
Some are concerned that legalizing the procedure could eventually lead to designer babies, and is humans attempting to “play God,” whereas others have raised safety concerns because some animal studies yielded offspring with altered cognitive abilities and patterns of aging. However, it has been argued that the studies were invalid because they were conducted on inbred animals. Furthermore, mitochondrial replacement has been scrutinized to a much greater extent than other assisted reproduction techniques that are now widely used.
While it is possible to improve the lives of individuals suffering with mitochondrial diseases, they are incurable. Approval of this procedure could therefore help to prevent debilitating diseases that currently affect some 5,000 people in the UK.
[Via BBC News]