Scientists got the blastocysts homozygous for the desired mutatio in 62% of cases.
Researchers from several Moscow institutes held Russia’s first experiment on human zygotes editing using CRISPR-Cas9 and received embryos that carry a mutation in the CCR5 gene, which determines resistance to infection with the human immunodeficiency virus. The results of the research described in a scientific journal of medical University named after Pirogov, informs Rus.Media.
The human immunodeficiency virus affects the cells, namely, CD4+ lymphocytes, through interaction with the receptor on their surface, which encodes the CCR5 gene. A small portion of the human population has a mutation in this gene (delacy 32 nucleotides, CCR5Δ32), which blocks the interaction of virus with receptor, and it makes the carrier resistant to infection.
The idea of using this mutation for therapeutic purposes appeared after the story of “the Berlin patient”, a person with HIV who had bone marrow transplant from a donor with a mutation, was cured of the infection. Developed since then, the tools for genome editing allow you to effectively “turn off” CCR5 in lymphocytes, and methods of treatment using your own edited lymphocytes of a patient for clinical trials.
In 2015, Chinese scientists conducted an experiment on editing of human embryos using the CRISPR-Cas9, and in 2016 the Chinese tried to make the CCR5Δ32 mutation of the embryos. The efficiency of editing in this experiment amounted to only five percent (one embryo with 20 contain the desired mutation).
Scientists from the Research center of obstetrics, gynecology and Perinatology named Kulakov, Moscow state University and medical University named after Pirogov repeated the experiment Chinese colleagues, but modified the conditions of the experiment and obtained blastocysts homozygous for the desired mutation (i.e. contain it in all copies of the gene) in 62% of cases.
As in the previous experiment, the researchers worked with Tripropylamine defective zygotes (fertilized eggs) obtained by artificial fertilization and unsuitable for further implantation mothers. In the zygote not introduced Cas9 mRNA and Cas9 protein complex with the RNA priming and DNA matrix to make a desired mutation. A couple of the most effective gdovic RNA were selected in advance in the experiment with editing in vitro. 16 8 zygotes developed “in vitro” to the blastocyst stage (about 250 cells), after which they were used for genotyping. The analysis showed that five of the eight embryos contain the desired mutation.
In the long run such editing of embryos can help to avoid infection, for example, children of HIV-infected mothers.