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Title: Targeting double-strand break indel byproducts with secondary guide RNAs improves Cas9 HDR-mediated genome editing efficiencies

Programmable double-strand DNA breaks (DSBs) can be harnessed for precision genome editing through manipulation of the homology-directed repair (HDR) pathway. However, end-joining repair pathways often outcompete HDR and introduce insertions and deletions of bases (indels) at the DSB site, decreasing precision outcomes. It has been shown that indel sequences for a given DSB site are reproducible and can even be predicted. Here, we report a general strategy (the “double tap” method) to improve HDR-mediated precision genome editing efficiencies that takes advantage of the reproducible nature of indel sequences. The method simply involves the use of multiple gRNAs: a primary gRNA that targets the wild-type genomic sequence, and one or more secondary gRNAs that target the most common indel sequence(s), which in effect provides a “second chance” at HDR-mediated editing. This proof-of-principle study presents the double tap method as a simple yet effective option for enhancing precision editing in mammalian cells.

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Nature Publishing Group
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Nature Communications
Medium: X
Sponsoring Org:
National Science Foundation
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    Basic Protocol 1: Constructing the Cas9/sgRNA transient expression vector

    Alternate Protocol 1: Shortcut to generating single and pooled Cas9/sgRNA expression vectors

    Basic Protocol 2: Designing the oligonucleotide‐based homology‐directed repair (HDR) template

    Alternate Protocol 2: Designing the plasmid‐based HDR template

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    Basic Protocol 4: Identifying edited plants.

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