High-fidelity endonuclease variant HypaCas9 facilitates accurate allele-specific gene modification in mouse zygotes

Arisa Ikeda,Wataru Fujii,Koji Sugiura,Kunihiko Naito

doi:10.1038/s42003-019-0627-8

Abstract

CRISPR/Cas9 has been widely used for the efficient generation of genetically modified animals; however, this system could have unexpected off-target effects. In the present study, we confirmed the validity of a high-fidelity Cas9 variant, HypaCas9, for accurate genome editing in mouse zygotes. HypaCas9 efficiently modified the target locus while minimizing off-target effects even in a single-nucleotide mismatched sequence. Furthermore, by applying HypaCas9 to the discrimination of SNP in hybrid strain-derived zygotes, we accomplished allele-specific gene modifications and successfully generated mice with a monoallelic mutation in an essential gene. These results suggest that the improved accuracy of HypaCas9 facilitates the generation of genetically modified animals.

Highlights

CRISPR/Cas[9] has been widely used for the efficient generation of genetically modified animals; this system could have unexpected off-target effects
The results showed that HypaCas[9] could reduce off-target effects in mouse zygotes and the accuracy of HypaCas[9] enables the discrimination of single-nucleotide polymorphisms (SNPs) and the introduction of monoallelic mutations, and thereby the efficient generation of genetically modified mice targeting the genes essential for survival and development
To compare the specificity for target DNA between WTCas[9] and HypaCas[9], we utilized Gt(ROSA)26Sor-guide RNA (gRNA), which was previously reported to exhibit substantial off-target effects[5] (Fig. 1a), and assessed whether Cas9–gRNA introduced mutation into the on- and off-target locus by Sanger sequencing of polymerase chain reaction (PCR) products in each embryo at the blastocyst stage (Fig. 1b and Supplementary Fig. 2)

Summary

Introduction

CRISPR/Cas[9] has been widely used for the efficient generation of genetically modified animals; this system could have unexpected off-target effects. By applying HypaCas[9] to the discrimination of SNP in hybrid strain-derived zygotes, we accomplished allelespecific gene modifications and successfully generated mice with a monoallelic mutation in an essential gene. These results suggest that the improved accuracy of HypaCas[9] facilitates the generation of genetically modified animals. The results showed that HypaCas[9] could reduce off-target effects in mouse zygotes and the accuracy of HypaCas[9] enables the discrimination of single-nucleotide polymorphisms (SNPs) and the introduction of monoallelic mutations, and thereby the efficient generation of genetically modified mice targeting the genes essential for survival and development. Our finding suggests that the improved accuracy of HypaCas[9] facilitates the generation of genetically modified animals

Methods

Results

Conclusion