Cas9 conjugate complex delivering donor DNA for efficient gene editing by homology-directed repair

Delivery of the CRISPR ribonucleoprotein (RNP) for homology-directed repair (HDR) has been challenging due to the low efficiency. Herein, we developed a Cas9 conjugate complex system which can induce efficient HDR editing with the use of a minimal amount of carrier material. Cas9 from Streptococcus pyogenes was purified and conjugated with low molecular weight polymer (LP). The Cas9-LP conjugates were complexed with single guide RNA (sgRNA) and donor DNA, which showed greatly enhanced internalization into cells compared to native Cas9 complexes, as well as a high extent of co-localization of Cas9 with sgRNA. The cytotoxicity of Cas9-LP complexes was evaluated, demonstrating low cytotoxicity compared to the conventional lipofectamine formulation. Finally, the treatment of Cas9-LP complexes to HEK293T reporter cell line expressing a mutant red fluorescent protein (RFP) results in efficient base correction of the RFP gene (up to 31%), leading to restoration of RFP expression and fluorescence. We anticipate that the current method can be widely used as a platform for efficient HDR editing via 'minimal carrier assisted' delivery without the aid of any external physical stimuli, which can be potentially applied for in vivo and ex vivo editing of cellular targets. (c) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

A Cas9 conjugate complex system was developed to induce efficient HDR editing with minimal carrier material. The Cas9-LP complexes showed lower cytotoxicity compared to conventional lipofectamine formulations and achieved efficient base correction of the RFP gene in HEK293T cells.