28 August 2017

The failure of a CRISPR/Cas9 competitor

The author of the publication about the editing of the genome by the NgAgo protein withdrew the article

Daria Spasskaya, N+1

The author of the publication about the editing of the genome by the NgAgo protein, under pressure from the scientific community, withdrew the article from the journal Nature Biotechnology, where it was published in May 2016. This is reported by Nature and the Retraction Watch website. 

A year ago, an article appeared in the journal Nature Biotechnology offering an alternative to the CRISPR/Cas9 system for genome editing. As a nuclease, that is, a protein that cleaves DNA, it was proposed to use a protein from the family Argonauts from the archaebacterium Natronobacterium gregoryi — NgAgo. The article was prepared by a research team from the Chinese University of Hebei under the leadership of Chunyu Han.

The system of directed genome editing includes a protein that cleaves DNA, and a seed that "tells" him where to make the incision. In the case of CRISPR/Cas9, such a seed is a guide RNA. In addition, in order for the Cas9 protein to bind to DNA, there must be a short sequence, designated as PAM, near the site of the intended incision. The requirement to have PAM limits the editing space. In addition, the use of RNA as a seed slightly reduces the selectivity of Cas9.

An alternative editing option with NgAgo promised to become even more popular than CRISPR/Cas9. Firstly, according to the authors, NgAgo did not require PAM to recognize the gap site, and secondly, it used short single-stranded DNA as a seed, which should have greatly simplified the editing technology and increased its accuracy.

The first doubts that NgAgo works at all appeared among scientists within a month and a half after the publication was published. There were special online communities where researchers discussed their experience using NgAgo. As a result, in the year since the publication of the original article, four publications have been published refuting Khan's data. 

In response to criticism, Khan promised to check his protocol and release additions to it. However, the story ended with the Chinese team withdrawing the article, admitting that no one had yet managed to reproduce the key results. 

It is unknown whether Chinese scientists made a mistake or deliberately falsified the data, but the new technology managed to arouse not only scientific interest. According to Nature, Novozymes, the largest enzyme manufacturing company, has already paid a large sum to Hebei University for its use. 

In 2014, the story of non-reproducible results on obtaining pluripotent stem cells ended badly for the Japanese scientist Yoshiki Sasai. As a result of the scandal that broke out after being accused of falsifying the results, he committed suicide. 

However, according to the magazine Science, at least half of scientific research is not reproduced in the field of psychology.

Portal "Eternal youth" http://vechnayamolodost.ru  28.08.2017

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