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Updated: Jan 28, 2026

Preparing and Injecting Embryos of Culex Mosquitoes to Generate Null Mutations using CRISPR/Cas9
Published on: September 10, 2020
A large CRISPR-induced bystander mutation causes immune dysregulation
Dimitre R Simeonov1,2,3,4, Alexander J Brandt4,5, Alice Y Chan3,6
1Biomedical Sciences Graduate Program, University of California, San Francisco, CA, 94143, USA.
Abstract:
A persistent concern with CRISPR-Cas9 gene editing has been the potential to generate mutations at off-target genomic sites. While CRISPR-engineering mice to delete a ~360 bp intronic enhancer, here we discovered a founder line that had marked immune dysregulation caused by a 24 kb tandem duplication of the sequence adjacent to the on-target deletion. Our results suggest unintended repair of on-target genomic cuts can cause pathogenic "bystander" mutations that escape detection by routine targeted genotyping assays.
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