A couple received their new baby after doctors combined mitochondrial DNA from a donor and nuclear DNA from the mother to avoid genetic diseases found in the biological mother’s mitochondria. An American team carried the procedure and had to perform it in Mexico because it is illegal to do it in the United States. The “3-parent” technique is legal in the U.K., but there still debates around the issue.
The controversial technique allows parents carrying rare genetic mutations in their DNA to protect their children from them. Now that it was revealed that the method was performed successfully, embryologists hope the case would inspire nations to legalize the procedure to assure healthy babies.
John Zhang led the technique, and it was possible thanks to his team. Dr. Zhang and colleagues are from the New Hope Fertility Center in New York City and did the “3-parent” technique in Mexico to enjoy the freedom to practice the method without facing legal actions. The method and its results will be discussed at the American Society for Reproductive Medicine’s Scientific Congress in Salt Lake City in October.
The baby was born on April 6, 2016, and has shown no signs of disease or malformation. A Jordanian couple sought Dr. Zhang helps after fertility problems, four miscarriages, and two dead children. The wife has in her genes Leigh syndrome. The disease affects developing nervous systems, thus, affected her babies.
The disease is found in the mother’s mitochondria. This part of the DNA provides energy to the cells. It also carries just 37 genes that are passed to kids from their mothers. Thus, Doctors need to find a way to avoid the mitochondria carrying Leigh syndrome but including the cell’s nucleus, which contains the majority of the mother’s DNA.
Zhang had been working on a new technique wich sought only to use the biological mother’s DNA nucleus and substitute her mitochondria, using the so-called “three-parent” method, News Scientist reports. But Dr. Zhang’s original plan had to be adapted because the Jordanian parents are Muslims, and they did not agree with destroying an embryo.
The procedure: Adapting to ethical suggestions
The original method consisted of the process approved by the United Kingdom in February 2015. Physicians fertilized two eggs with the father’s sperm: one of the mother and one of a healthy donor. Then, before the fertilized eggs start to divide into early-stage embryos, each nucleus is removed. Only the mother’s nucleus is used and the other, the one of the donor’s, is discarded. This procedure is called pronuclear transfer.
To adapt to his patients’ needs, Dr. Zhang took a different approach to his technique and came up with another one called nuclear spindle transfer. This method also involves two eggs, including one from the mother and one of a donor. Doctors then removed both nucleus and inserted the one from the mother’s egg in the mitochondria from the donor. Finally, the new egg is fertilized with the father’s sperm.
What is different from the original approach is that the two eggs are not fertilized. Hence, the cell is not carrying life, and it does not interfere with the parents’ beliefs. The egg is only fertilized after a healthy mitochondria changes the unhealthy one.
Zhang and his team used the spindle nuclear transfer method in five embryos, and only one developed normally. The healthy embryo was implanted in the mother’s womb, and the child was born nine months later without complications.
The team tested the baby to make sure his mitochondria did not have Leigh syndrome. They found that less than 1 percent of the DNA in the mitochondria was carrying the mutation, which means the baby is healthy. The percentage is too low to cause any disorder. It takes at least 18 percent to start worrying about a disease.
Bert Smeets, director of the Genome Center at Maastricht University in the Netherlands, agrees that 1 percent is good news but still concerns because the percentage could grow. There is a chance that the mitochondria could replicate and gradually increase in number, the reason why the boy must be monitored continuously. Smeets says, according to New Scientist, that it is necessary to wait for more similar births and carefully judge them.
The method was adapted to the parent’s ethical values, but not to everyone’s ethic
The team avoided to destroy to embryos and fulfill a couple’s dream to have a healthy child. Some support the medical advance; others criticized it.
Sian Harding reviewed the ethics of the U.K. procedure and in his view, Dr. Zhang’s approach is ethical. He did not destroy embryos and used a healthy male embryo to avoid that the child passes any inherited mitochondrial DNA. Harding said it is as good or better than what the U.K has done.
In Britain, many leaders disagree on the issue, and it is up for debate in the House of Commons. Some people consider that the “three-parent” technique is related to “playing God,” including leading churches in the U.K. Protestant and Catholics oppose the procedure because the revolutionary method is against their religion or their ethics.
Many scientists do agree with Dr. Zhang efforts and only are concerned about the fact that the procedure was performed in Mexico.
Smeets is one of them. He said the safety of the method is convincing, but the fact that a U.S.-based team had to escape a rigid regulatory framework is a concern. Frameworks protect the introduction to the clinic and also follows up the children born after the treatment.
Dr. Smeets hopes that now that the child is born and “the heat is off,” new alternatives will become legal, and no other patients will feel the pressure to get involved in unsecured treatments.
Dr. Dusko Ilic from King’s College London said the three-parent technique is an ice-breaker in the field.
“Hopefully, this will tame the more zealous critics, accelerate the field, and we will witness soon a birth of the first mitochondrial donation baby in the U.K,” Dusko stated, according to the Independent.
Source: New Scientist