Site-specific integration in CHO cells mediated by CRISPR/Cas9 and homology-directed DNA repair pathway.

Jae Seong Lee,Helene Faustrup Kildegaard,Thomas Beuchert Kallehauge,Lasse Ebdrup Pedersen

doi:10.1038/srep08572

Jae Seong Lee, Helene Faustrup Kildegaard + Show 2 more

Open Access

https://doi.org/10.1038/srep08572

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Abstract

Chinese hamster ovary (CHO) cells are the most widely used mammalian hosts for production of therapeutic proteins. However, development of recombinant CHO cell lines has been hampered by unstable and variable transgene expression caused by random integration. Here we demonstrate efficient targeted gene integration into site-specific loci in CHO cells using CRISPR/Cas9 genome editing system and compatible donor plasmid harboring a gene of interest (GOI) and short homology arms. This strategy has enabled precise insertion of a 3.7-kb gene expression cassette at defined loci in CHO cells following a simple drug-selection, resulting in homogeneous transgene expression. Taken together, the results displayed here can help pave the way for the targeting of GOI to specific loci in CHO cells, increasing the likelihood of generating isogenic cell lines with consistent protein production.

Highlights

Chinese hamster ovary (CHO) cells are the most widely used mammalian hosts for production of therapeutic proteins
We demonstrate efficient targeted gene integration into site-specific loci in CHO cells using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas[9] genome editing system and compatible donor plasmid harboring a gene of interest (GOI) and short homology arms
We show that targeting of transgenes into specific desirable sites in the CHO genome in a controlled manner reduces the variation in expression, generating a uniform population with stable transgene expression

Summary

Introduction

Chinese hamster ovary (CHO) cells are the most widely used mammalian hosts for production of therapeutic proteins. We demonstrate efficient targeted gene integration into site-specific loci in CHO cells using CRISPR/Cas[9] genome editing system and compatible donor plasmid harboring a gene of interest (GOI) and short homology arms. This strategy has enabled precise insertion of a 3.7-kb gene expression cassette at defined loci in CHO cells following a simple drug-selection, resulting in homogeneous transgene expression. Assuming that the high rate of DSB introduction will induce DNA damage repair pathways, and the concurrent introduction of a donor plasmid will be used as the repair template, the targeted integration at specific genomic sites can be feasible with high fidelity

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