American molecular biologists and physicians have published a complete protocol for the "assembly" of embryos using genetic material from three parents. This will help people with DNA defects to continue their lineage, according to an article published in the journal Reproductive BioMedicine Online.
“In the past few years, technologies have emerged that allow doctors to separate embryos with damaged mitochondria from healthy embryos using sophisticated post-conception in vitro diagnostic procedures. For the first time, the authors of the article were able to replace some of the “broken” mitochondria with normal versions in such eggs, using bodies from donated eggs,”commented Bart Fauser, editor-in-chief of the journal.
Third life
Human cells contain many separate structures - the so-called mitochondria, which play an essential role: they convert nutrients into ATP molecules, the universal cellular energy currency. Scientists associate problems in the work of mitochondria with the development of old age and decrepitude of the body.
Mitochondria are unique in that they have their own DNA, which contains instructions for its assembly and operation. Violations in it, in combination with mutations in "normal" DNA, lead to the fact that the assembly line of ATP breaks down, which causes cells to constantly starve and die. Carriers of defective mitochondria usually die at an early age, and in some cases, for example, when the mother develops Leigh syndrome, almost all embryos die in the first weeks after conception.
Seven years ago, the Kazakh-American biologist Shukhrat Mitalipov found a solution to this problem - he and his colleagues developed a special DNA transplantation technique that made it possible to “rip out” nuclear DNA from a fertilized egg with mutant mitochondria and transplant it into an empty egg.
In 2009, Mitalipov and his colleagues demonstrated almost one hundred percent efficiency of this technique in experiments on monkeys, and in September last year, Chinese scientists working in Mexico admitted that they had illegally performed such an operation on a human embryo and it was completed successfully.
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Mitochondria are unique in that they have their own DNA, which contains instructions for its assembly and operation. Violations in it, in combination with mutations in "normal" DNA, lead to the fact that the assembly line of ATP breaks down, which causes cells to constantly starve and die. Carriers of defective mitochondria usually die at an early age, and in some cases, for example, when the mother develops Leigh syndrome, almost all embryos die in the first weeks after conception.
Seven years ago, the Kazakh-American biologist Shukhrat Mitalipov found a solution to this problem - he and his colleagues developed a special DNA transplantation technique that made it possible to “rip out” nuclear DNA from a fertilized egg with mutant mitochondria and transplant it into an empty egg.
In 2009, Mitalipov and his colleagues demonstrated almost one hundred percent efficiency of this technique in experiments on monkeys, and in September last year, Chinese scientists working in Mexico admitted that they had illegally performed such an operation on a human embryo and it was completed successfully.
As the scientists emphasize, for this they used a special form of electrophoresis, which allows you to cleanly transfer genetic material from one cell to another and do without viruses that are usually used for such molecular operations. In total, Zhang's team performed four similar procedures on four eggs, about 20% of whose mitochondria were damaged.
All these procedures, according to doctors, ended successfully and the number of damaged mitochondria in the cells of future embryos decreased to 2-9%, that is, reached a relatively normal value. Having chosen one of the embryos, biologists sent it to Mexico, where the implantation of such structures into the womb is not considered illegal, as in the United States.
Pregnancy, as the researchers note, proceeded without any complications, and about a year ago, a healthy boy, Abrahim Hassan, was born, who did not suffer from Lee's syndrome and associated developmental disorders of the brain and other organs. All this, according to Zhang, indicates the safety of using the method of "conception from three parents" in clinical practice. However, Zhang and his colleagues will monitor the boy's health for the first 18 years of his life for possible negative effects.
Mitalipov and his colleagues disagree with the assertion of Zhang's team - last year they published an article in which they showed that some of the maternal mitochondria remaining in the embryo can, over time, completely replace the transplanted "energy stations" and thereby nullify the meaning of such a transplant. They urged Zhang and other doctors to stop doing such operations until they figure out why damaged mitochondria are supplanting normal versions.
Despite warnings from scientists, regulatory authorities in some countries, in particular the UK, have already approved several pilot projects to adapt this procedure to legal medical practice. In other states, including the United States, such a procedure continues to be unacceptable from the point of view of law.
