An effective way of DNA editing has been found
Scientists from the Institute of Fundamental Research in South Korea have created a new technology based on the CRISPR/Cas system, which allows you to make mutations in DNA with an accuracy of one nucleotide. It can be used to treat such severe hereditary diseases as cystic fibrosis, phenylketonuria or Huntington's disease. The biologists' article was published in the journal Nature Biotechnology (Kim et al., Highly efficient RNA-guided base editing in mouse embryos).
The CRISPR/Cas9 system is used to change the nucleotide sequence of DNA. Cas9 is a protein that cuts a double chain at a certain site. This location is determined by a guide RNA (sgRNA), which binds complementarily to a specific recognition site. The nucleic acid torn by molecular "scissors" is then restored, but as a result, part of the sequence is lost, which prevents the exact change of DNA.
To solve this problem, the researchers modified the system by combining Cas9 with another enzyme, cytidine deaminase. This made it possible to obtain a molecular complex capable of replacing one nucleotide with another. It cuts only one chain in the double helix and converts the nucleotide cytosine into thymine.
The new technology was tested on mouse embryos, creating mutants that had mutations either in the genes encoding the protein dystrophin, or in the genes of tyrosinase, which is involved in the synthesis of melanin. To do this, the complex was injected into fertilized eggs by injection and microporation, after which the embryos were transplanted to surrogate mothers. The rodents that were born did not synthesize dystrophin in muscle cells (in humans, this leads to Duchenne dystrophy) or were albinos.
The ability to artificially introduce point mutations is necessary for technologies aimed at correcting harmful mutations. This will allow the development of new therapies for hereditary diseases associated with single-nucleotide substitutions.
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28.02.2017