Production of genetically engineered mice with higher efficiency, lower mosaicism, and multiplexing capability using maternally expressed Cas9

Takayuki Sakurai,Akiko Kamiyoshi,Hisaka Kawate,Satoshi Watanabe,Takayuki Shindo,Masahiro Sato

doi:10.1038/s41598-020-57996-7

Takayuki Sakurai, Akiko Kamiyoshi + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-57996-7

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Abstract

The CRISPR/Cas9 system is widely used to generate gene-edited animals. Here, we developed an efficient system for generating genetically modified mice using maternal Cas9 from Cas9 transgenic mice. Using this system, we achieved lower mosaicism and higher rates of knock-in success, gene-editing, and birth compared to the similar parameters obtained using exogenously administered Cas9 (mRNA/protein) system. Furthermore, we successfully induced simultaneous mutations at multiple loci (a maximum of nine). Our novel gene-editing system based on maternal Cas9 could potentially facilitate the generation of mice with single and multiple gene modifications.

Highlights

The clustered regularly interspaced short palindromic repeat (CRISPR)/Cas[9] system is widely used to generate gene-edited animals
These results indicate a close relationship between the amount of mRNA incorporated into zygotes and the rate at which the mRNA is translated into proteins in the resultant embryos
We found that our system exhibits a comparably high degree of indel mutation efficiency and is superior to the other system due to a low degree of mosaicism, higher KI mutation efficiency, increased pup delivery rate, and the ability to induce mutations in multiple loci simultaneously

Summary

Introduction

The CRISPR/Cas[9] system is widely used to generate gene-edited animals. Here, we developed an efficient system for generating genetically modified mice using maternal Cas[9] from Cas[9] transgenic mice. The amount of CRISPR/ Cas[9] reagents injected into the zygote is limited as high volumes are often associated with developmental arrest of the embryos[29], reducing the possibility of simultaneous modifications in multiple genes using the CRISPR/Cas[9] system[11]. We tackled these problems by generating systemically Cas9-expressing transgenic (Tg) (sCAT) mice that produce maternal Cas[9] (maCas9), which exhibits nuclease activity, during oogenesis[30]. It has recently been reported that the delivery of CRISPR/Cas[9] reagents into the zygote by electroporation (EP) provides higher genome editing efficiency than that achieved by zygote microinjection[31,32,33]

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Conclusion