Gene therapy of eggs instead of "three-parent" children?
An alternative to the method of creating children from three parents
will be the destruction of defective DNA
This technology involves replacing defective maternal mitochondrial DNA, which can be a carrier of a mass of dangerous mutations, with the mtDNA of another woman – in fact, the second mother (mtDNA differs from nuclear DNA – ed.). Such clinical practice may be the optimal method of ridding future children of various genetic diseases.
Now, scientists have told in a new article published in the journal Cell about a possible alternative to "three parents" (Reddy et al., Selective Elimination of Mitochondrial Mutations in the Germline by Genome Editing). A team of researchers claims that one day mothers will have a chance to rid their children of inheritance of mitochondrial defects.
The therapy developed by scientists involves the modification of diseased eggs in such a way that faulty mitochondria in them could be destroyed, or, more precisely, neutralized. Some researchers say that such an approach would avoid resolving a lot of ethical issues that may be associated with the birth of children from three parents.
And yet, this technique relates to gene editing, and a lot of discussions have already broken out around this initiative.
Approximately 1 in 5,000 people worldwide has disorders caused by faulty mitochondria – the components of cells that are responsible for their energy supply. Defective mitochondria can also worsen the course of diseases that are not directly related to malfunctions in themselves – for example, aggravate some types of cancer.
"For the disease to develop, 60-95% of all mitochondria must be defective. However, in most cases, only a small fraction of the hundreds of thousands of mitochondria in the egg turn out to be faulty," explains lead author of the new study Alejandro Ocampo, a molecular biologist at the Salk Institute for Biological Research in La Jolla, California.
Ocampo and his colleague Juan Carlos Belmonte concluded that reducing the amount of mutant mitochondrial DNA in eggs or in an already fertilized embryo can reduce the likelihood of developing genetic diseases in the future.
In the course of their experiment, the scientists introduced RNA segments into the cells that possessed a special enzyme endonuclease. It can reconstruct mtDNA. Endonuclease searches for mitochondria with a certain mutation and destroys their DNA, thus neutralizing the cell.
Ocampo and Belmonte conducted an experiment on mouse eggs and unicellular fertilized rodent embryos, the latter of which contained mitochondrial DNA from two different mice. They injected RNA into the cells aimed at creating an endonuclease that would destroy the DNA of one of the mice, but would leave the other. The embryos were transplanted to surrogate mothers.
Tests showed that about 60% of the mitochondrial DNA from the target mouse was destroyed. As described in the press release (Gene-editing technique offers hope for hereditary diseases), as a result, quite healthy mice were born.
A picture from an article in Cell – VM.
Scientists also repeated their success in another experiment: the mitochondria of people with diseases were planted in the eggs of mice and saw that the introduction of "programmed" RNA led to the destruction of 20-50% of damaged mitochondrial DNA.
Experts who did not participate in this work say that before it comes to clinical practice, the team of Ocampo and Belmonte has yet to prove that their technique is safe for human embryos and will not lead to unpredictable mutations in other parts of the genome.
Portal "Eternal youth" http://vechnayamolodost.ru24.04.2015