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We’ve come a long way when it comes to redefining what it means to be a family. I mean, remember when My Two Dads seemed like a strange scenario? Not anymore. Given what scientists can do with DNA, the evolution of the family unit is just the tip of the iceberg. Even babies who were born as a result of infertility treatments or who were conceived in test tubes aren’t that unusual anymore. Soon, kids who have DNA from three people won’t be all that unusual either. Right now, there are somewhere between 30-50 people in the world who were made from the DNA of three different individuals.
Using mitochondria (the energy-producing bits of the cell) is part of an infertility treatment called cytoplasmic transfer. The process has been around for over 15 years and was developed by an embryologist at New Jersey’s St. Barnabus Institute. The pioneering doctor, Jacques Cohen, figured that some infertility was caused by malfunctions in the cytoplasm, which contains a cell’s nucleus and mitochondria. There was a good chance the problem was with the mitochondria itself, so he came up with the technique of implanting mitochondria from a female donor into the would-be mother’s egg, which he then fertilized with the would-be father’s sperm. Thus, some of the female donor’s DNA ends up in the embryo, and technically, the child has parts from three different people.
Cohen successfully performed the procedure a number of times, resulting in the birth of seventeen babies at his clinic, and more at other clinics that adopted his technique. Of the pregnancies at Cohen’s clinic, there was a miscarriage and a twin pregnancy in which one of the twins didn’t have an X chromosome. Even though the numbers were still positive, Cohen was a bit concerned, especially when a few years later, some of the babies who had been fine at birth began displaying symptoms of various developmental disorders and cognitive diseases, including autism.
It’s unclear whether the cytoplasmic transfer was the cause of these conditions, or whether it was a coincidence. Still, in 2002, the FDA requested that practitioners stop using the procedure because of safety, as well as ethical issues. Some people feel that the process is essentially genetic modification, as it does affect one’s “germ line,” or the genes passed on to offspring (since mitochondria comes from mothers, this only pertains to females). Now, Cohen’s clinic has started a program to follow up on other children born from the process.
In even bigger news, the UK is considering making legal a similar process that involves harvesting the mitochondria of a female donor, but not for infertility treatment. Instead, the process will be used for people who don’t want to pass on genetic diseases.
There are two different ways this might happen—one involves fertilizing only a donor egg that has the nucleus of the mother’s egg in it, and the other involves fertilizing both the donor and the mother’s eggs and replacing the donor embryo with the mother’s embryo. The Human Fertilisation and Embryology Authority in the UK found that the process is “not unsafe” for a “specific and defined group of patients.” Not exactly a ringing endorsement, but it’s a start. We’ll be keeping our eyes on this one.