CRISPRA few weeks ago news broke that the CRISPR gene-editing technology can introduce hundreds of unintended mutations into the genome. But in a dramatic response, two gene editing companies have hit back at the paper, claiming it is wrong, filled with errors, and that it shouldn’t have been published.

In separate letters sent to Nature Methods, scientists from Intellia Theapeutics and Editas Medicine criticised a report in the journal that claimed the gene editing tool CRISPR had caused unexpected mutations in the genomes of mice and which cast a shadow over efforts to initiate human studies using the technique, reports Technology Review.

As a result the stock market values of the two companies and CRISPR Therapeutics fell sharply, all of which together have raised more than $1 billion to pursue CRISPR treatments.

Nessan Bermingha, CEO of Intellia, called for the journal to retract the paper, effectively an effort to remove it from the scientific record.

“This publication has garnered a significant damage,” he said. “Given the issues around the designs and interpretation I believe it is appropriate that the Nature Methods editorial board retract this paper.”

In response, a spokesperson at Springer Nature, which publishes Nature Methods, said the organisation had received “a number of communications” already about the paper. “We are carefully considering all concerns that have been raised with us and are discussing them with the authors,” said the journal.

Vic Myer, chief technology officer of Editas, in a letter signed by 11 other company scientists as well as by George Church, a Harvard University professor who is a scientific co-founder and shareholder of Editas, explained, “In our opinion  the conclusions drawn from this study are unsubstantiated by the disclosed experiments.” He continued that he thought the paper should “possibly” be retracted, and at a minimum should be updated to disclose “major missing considerations.”

In conclusion, Intellia believes that the authors showed “disregard” for what’s already known about CRISPR. “It is clear the authors are not experts on the CRISPR Cas9, whole genome sequencing, nor basic genetics. Their claim of ‘unexpected mutations’ clearly demonstrates their lack of scientific acumen around this topic,” said the company.

Vinit Majhajan of Stanford University, senior author of the paper entitled, “Unexpected mutations after CRISPR-Cas9 editing in vivo,” did not immediately respond to a request for comment. Another author, Alexander Bassuck of the University of Iowa, said he was travelling and unable to respond immediately.