Transgenic Research

, Volume 27, Issue 4, pp 315–319 | Cite as

Unexpected mutations were expected and unrelated to CRISPR-Cas9 activity

  • Lluis MontoliuEmail author
  • C. Bruce A. WhitelawEmail author
Letter to the Editor


The scientific journal Nature Methods have just retracted a publication that reported numerous unexpected mutations after a CRISPR-Cas9 experiment based on collecting whole genome sequencing information from one control and two experimental genome edited mice. In the intervening 10 months since publication the data presented have been strongly contested and criticized by the scientific and biotech communities, through publications, open science channels and social networks. The criticism focused on the animal used as control, which was derived from the same mouse strain as the experimental individuals but from an unrelated sub-colony, hence control and experimental mice were genetically divergent. The most plausible explanation for the vast majority of the reported unexpected mutations were the expected underlying genetic polymorphisms that normally accumulate in two different colonies of the same mouse strain which occur as a result of spontaneous mutations and genetic drift. Therefore, the reported mutations were most likely not related to CRISPR-Cas9 activity.


Off target mutations CRISPR Cas9 Safety Genome editing applications Safety Gene therapy 



LM’s laboratory is funded through the Spanish Ministry of Economy and Competitiveness (MINECO) [BIO2015-70978] and the Spanish Biomedical Research Networking Centre on Rare Diseases (CIBERER) from the National Institute of Heath Carlos III (Instituto de Salud Carlos III, ISCIII). A timeline of the events and publications around this case can be easily followed from the corresponding section at the CRISPR web page at CNB-CSIC ( CBAW is funded by the Biotechnology and Biological Research Council (BBSRC) through ISP support to The Roslin Institute.


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.National Centre for Biotechnology (CNB-CSIC)Biomedical Research Networking Centre Consortium on Rare Diseases (CIBERER-ISCIII)MadridSpain
  2. 2.The Roslin Institute and Royal (Dick) School of Veterinary StudiesUniversity of EdinburghMidlothianUK

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