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Resistance to a CRISPR-based gene drive at an evolutionarily conserved site is revealed by mimicking genotype fixation

Fuchs, Silke; T. Garrood, William; Beber, Anna; Hammond, Andrew; Galizi, Roberto; Gribble, Matthew; Morselli, Giulia; J. Hui, Tin-Yu; Willis, Katie; Kranjc, Nace; Burt, Austin; Crisanti, Andrea; Nolan, Tony

Resistance to a CRISPR-based gene drive at an evolutionarily conserved site is revealed by mimicking genotype fixation Thumbnail


Authors

Silke Fuchs

William T. Garrood

Anna Beber

Andrew Hammond

Matthew Gribble

Giulia Morselli

Tin-Yu J. Hui

Katie Willis

Nace Kranjc

Austin Burt

Andrea Crisanti

Tony Nolan



Abstract

CRISPR-based homing gene drives can be designed to disrupt essential genes whilst biasing their own inheritance, leading to suppression of mosquito populations in the laboratory. This class of gene drives relies on CRISPR-Cas9 cleavage of a target sequence and copying ('homing') therein of the gene drive element from the homologous chromosome. However, target site mutations that are resistant to cleavage yet maintain the function of the essential gene are expected to be strongly selected for. Targeting functionally constrained regions where mutations are not easily tolerated should lower the probability of resistance. Evolutionary conservation at the sequence level is often a reliable indicator of functional constraint, though the actual level of underlying constraint between one conserved sequence and another can vary widely. Here we generated a novel adult lethal gene drive (ALGD) in the malaria vector Anopheles gambiae, targeting an ultra-conserved target site in a haplosufficient essential gene (AGAP029113) required during mosquito development, which fulfils many of the criteria for the target of a population suppression gene drive. We then designed a selection regime to experimentally assess the likelihood of generation and subsequent selection of gene drive resistant mutations at its target site. We simulated, in a caged population, a scenario where the gene drive was approaching fixation, where selection for resistance is expected to be strongest. Continuous sampling of the target locus revealed that a single, restorative, in-frame nucleotide substitution was selected. Our findings show that ultra-conservation alone need not be predictive of a site that is refractory to target site resistance. Our strategy to evaluate resistance in vivo could help to validate candidate gene drive targets for their resilience to resistance and help to improve predictions of the invasion dynamics of gene drives in field populations.

Journal Article Type Article
Acceptance Date Sep 24, 2021
Publication Date Oct 5, 2021
Publicly Available Date Mar 28, 2024
Journal PLOS Genetics
Print ISSN 1553-7404
Publisher Public Library of Science
Peer Reviewed Peer Reviewed
Article Number e1009740
DOI https://doi.org/10.1371/journal.pgen.1009740
Publisher URL https://doi.org/10.1371/journal.pgen.1009740

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