In 2016, the three-parent baby born in Mexico made headlines. According to a study published by doctors who worked on the project, the success came after scraping through many areas of potential defeat.
The treatment leading to the conception of the baby was led by Dr. John Zhang of New York's New Hope Fertility Center. The details have been published in the journal Reproductive BioMedicine Online.
The process involved in vitro fertilization (IVF) with mitochondrial replacement therapy (MRT).
In the paper, Dr. Zhang and colleagues gave a detailed account of the treatment and discussed the barriers they faced. One was the risk of a child carrying a 2.36 percent to 9.23 percent mitochondrial DNA (mtDNA) mutational load in samples tested.
Some mutated mtDNA indeed passed into the embryo, which may cause health problems to the child later in his life. For the conception, the egg carried DNA from the boy's mother and minor amounts of mitochondrial DNA from another healthy female donor.
The MRT done was mainly to thwart the transmission of defective mitochondria that carried the fatal nervous system disorder Leigh syndrome.
Success From Jaws Of Defeat
Top stem cell biologist Professor Robin Lovell-Badge of London's Francis Crick Institute hailed the move and called it good news. He said the woman treated was able to have an apparently healthy child without any mitochondrial disease was laudable, but he observed that it was apparent that Zhang and the team were "sailing very close to the wind," and luck also played a good part in the successful outcome.
However, Lovell-Badge criticized the American doctors for using electrofusion as a method for moving nuclear DNA, which was being shunned by other researchers because it leads to abnormal embryos.
The treatment involved the complex transfer of a nuclear DNA from the mother's egg to a donor egg. In the donor egg, the nuclear DNA from the boy's mother and donor's healthy mitochondrial DNA were housed and facilitated its fertilization by the sperm of the father for developing the embryo.
The DNA present in mitochondria has a role in metabolism, but it will not impact appearance and personality.
Risk Of Abnormal Mitochondrial DNA
The study says the successful outcome brushed through many risk areas, including the passing of abnormal mitochondria to the embryo, though it stayed below the threshold to initiate any disease.
Lovell-Badge told a parliamentary committee that there is some concern, though by luck it led to pregnancy, and the abnormal mitochondrial DNA was also low in most tissues.
Since many steps in the creation of three-parent baby would have violated the U.S. federal law, final steps, including the implantation of the embryo into the womb, were done in Mexico.
However, in the UK, MRT has got a legal stamp.
Hailing the positive side of the treatment, Professor Sir Doug Turnbull, director of the University of Newcastle's Wellcome Centre for Mitochondrial Research, said mitochondrial donation has become an important part in new IVF technique helping women with a mitochondrial DNA mutation issues.
In the UK, mitochondrial donation is set to thrive, as the regulatory framework has come in place. A New Castle clinic has been issued a license to start mitochondrial donation for women facing a risk for offspring.
