New Techniques in Reproductive Medicine: Mitochondrial Transfer
by Megha Murthy
After a certain point in life, people just want to settle down and start a family. They look forward to having kids. However, not every family is able to create a child that is perfectly healthy. In some cases, the mother might have reproductive issues that inhibit the parents from having a child. Or the mother could have passed down a rare genetic condition she inherited through the mitochondria to the child which could affect the development of the child. In these situations, the parents might opt for adoption. However, there are other methods that might enable the family to reproduce a healthy child.
The mitochondrion plays an important role in the body by creating energy to help the cells in the body function. Babies normally inherit their mitochondrial DNA from only the mother. If the mother has a defect or mutation in the genes of the mitochondrial DNA, the mutated DNA will be passed on to the child. In some cases, these mutations can prove fatal to the baby by causing problems in the respiratory, endocrine, heart, muscles, and nervous system. Usually, these defects can either cause a miscarriage or they can kill the baby either shortly after birth, or after a few years. The mother will most likely not know she has unhealthy mitochondria until she goes to a doctor to figure out why she cannot produce a healthy baby. Doctors can confirm this by looking into the family history of diseases and the characteristics of fiber tissues in the body, which appear ragged red when the mitochondria is mutated. These results will expose if the genetic defect lies in the mitochondrial genome. Once the doctors determine that the mother has unhealthy mitochondria, which could affect the development of her child, she can decide how she wants to start a family of her own. If the mother is set on conceiving her own child as opposed to adopting a child, then she could look into mitochondrial transfer to ensure her child develops healthy mitochondria.
The mitochondria are essential to the body by providing the body with energy. In normal conception, the child’s DNA comes from both the mother and the father with all of the mitochondrial DNA coming from the mother. If there is a mutation in the mitochondrial DNA, then the child will be at risk of lack of energy. Therefore, the child might not fully develop. The regular DNA is in the nucleus, while the mitochondrial DNA is in the cytoplasm but still inside the mother’s egg cell. However, with mitochondrial transfer, a tiny 0.1 percent of the child’s DNA comes from a healthy mitochondrial DNA donor. In this process, the nucleus, which is the body’s main control center, is removed from the egg cell containing the unhealthy mitochondria. The egg cell is where the embryo will develop. The donor’s nucleus is then removed from the donor’s egg cell, which contains the healthy mitochondria. The mother’s nucleus is then inserted into the donor’s healthy egg cell. The egg cell is then transferred back into the mother’s uterus, where the embryo will develop. Now, this egg can be fertilized by the sperm and the parents can have a healthy baby.
The first successful mitochondrial transfer procedure was tested out on a Jordanian couple by physician John Zhang in a Mexican clinic back in 2011. The couple had initially traveled from Jordan to New York University and met with Dr. James Grifo who had tested mitochondria transfer on mice. He then directed them to D. Zhang, who had been working on this technique. They had lost their first two children due to mitochondrial associated Leigh Syndrome disease, so they decided to try out the mitochondrial transfer method. Luckily for them, this method was successful and they had a baby boy who inherited nuclear DNA from both his parents and healthy mitochondrial DNA from the donor.
According to researchers, there are still some issues that need to be resolved with mitochondrial transfer therapy. Some of the diseased mitochondrial DNA can be transferred from the mother into the healthy donor’s nucleus. This technique involves sucking up the mother’s nucleus with a tiny glass straw and transferring it the donor egg cell, which doesn’t contain a nucleus. However, some disease containing mitochondria can be sucked up in this process, and therefore transferred to the donor egg as well. Even a small amount of mutated DNA might cause further problems in the following generations. The mutated DNA could change the structure of the mitochondrial DNA which could essentially then lead to a variety of problems, such as Leigh syndrome, which could fatally affect the child. However, others say that mitochondrial transfer would ensure that deadly diseases aren’t passed onto the next generation.
Some researchers are claiming that altering the DNA of an embryo is not ethical. In fact, the United States Congress banned the FDA from using federal funds to review these practices because altering a human embryo is deemed as unethical. While some argue that altering the genes could cure life threatening diseases, others feel that this would pave the way for so called “designer babies.” The genes of these babies could be altered to look a certain way that would enable the child to adhere to beauty standards. Or, the genes could be altered to ensure the child have a high IQ, which would give the child an unfair advantage in society.
Aside from the scientific community, the public have also voiced their concern on the ethics of this procedure. They believe that people who aren’t born yet are unable to give their consent to having this treatment given to them if they aren’t born yet. Catholic ethicists have complained that this method “dilutes parenthood” because some of the DNA is coming from a donor. Altering this genome is permanent and this alteration could be passed down onto future generations. There is also no way to identify the long-term impact of mitochondrial transfer because there could be other problems in the genome that might affect the baby in the future.
While research is still being done on this practice, there is not enough evidence to ensure its complete safety. While it could cure one disease, it could also cause other diseases in the process because the genome is altered. However, with a bit more work, this technique could be utilized to treat those one in four thousand women who suffer from mitochondrial diseases. However, mitochondrial transfer therapy first has to be approved by the government. This can only be accomplished through multiple successful trials. Only then can this procedure become more commonly used.