Open AccessAnalysis of off-target effects in CRISPR-based gene drives in the human malaria mosquito
Author(s) -
William T. Garrood,
Nace Kranjc,
Karl Petri,
Daniel Y. Kim,
Jimmy A. Guo,
Andrew Hammond,
Ioanna Morianou,
Vikram Pattanayak,
J. Keith Joung,
Andrea Crisanti,
Alekos Simoni
Publication year - 2021
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.2004838117
Subject(s) - crispr , biology , cas9 , genetics , gene drive , guide rna , gene , anopheles gambiae , genome editing , population , computational biology , gene knockout , malaria , demography , sociology , immunology
CRISPR-Cas9 nuclease-based gene drives have been developed toward the aim of control of the human malaria vectorAnopheles gambiae . Gene drives are based on an active source of Cas9 nuclease in the germline that promotes super-Mendelian inheritance of the transgene by homology-directed repair (“homing”). Understanding whether CRISPR-induced off-target mutations are generated inAnopheles mosquitoes is an important aspect of risk assessment before any potential field release of this technology. We compared the frequencies and the propensity of off-target events to occur in four different gene-drive strains, including a deliberately promiscuous set-up, using a nongermline restricted promoter for SpCas9 and a guide RNA with many closely related sites (two or more mismatches) across the mosquito genome. Under this scenario we observed off-target mutations at frequencies no greater than 1.42%. We witnessed no evidence that CRISPR-induced off-target mutations were able to accumulate (or drive) in a mosquito population, despite multiple generations’ exposure to the CRISPR-Cas9 nuclease construct. Furthermore, judicious design of the guide RNA used for homing of the CRISPR construct, combined with tight temporal constriction of Cas9 expression to the germline, rendered off-target mutations undetectable. The findings of this study represent an important milestone for the understanding and managing of CRISPR-Cas9 specificity in mosquitoes, and demonstrates that CRISPR off-target editing in the context of a mosquito gene drive can be reduced to minimal levels.