ORCID ID

0000-0001-7502-3141

Publication Date

2021-08-03

Document Type

Doctoral Dissertation

Academic Program

Interdisciplinary Graduate Program

Department

RNA Therapeutics Institute

First Thesis Advisor

Craig Mello

Keywords

C. elegans, CRISPR, Genome editing, HDR, Donor DNA, Precision genome editing, Chemical Modifications, Modified donors, 5′ modifications, TEG modifications, melted donors.

Abstract

CRISPR/Cas9 induced DNA breaks can be precisely repaired by cellular homology-directed repair (HDR) pathways using exogenously provided template DNA (donor). However, the full potential of precision editing is hindered in many model systems by low cutting efficiencies, low HDR efficiencies and, cytotoxicity related to Cas9 and donor DNA. In this thesis, I address these challenges and present methods that we developed to increase HDR efficiencies in multiple model organisms.

In Caenorhabditis elegans, we show that by reducing toxicity high editing efficiencies can be achieved with single stranded oligonucleotide (ssODN) donors. We demonstrate that melting dsDNA donors dramatically improves the knock-in efficiencies of longer (1kb) edits. In addition, we describe 5′-terminal modifications to the donor molecules that further increase the frequency of precision editing. With our methodology a single optimally injected animal can yield more than 100 Green Fluorescent Protein (GFP) positive progeny, dramatically enhancing efficiency of genome editing.

Next, we demonstrate the generality of 5′ modified donors by extending our studies to human cell cultures and mice zygotes. In mammalian models, 2′OMe-RNA modifications consistently increase HDR efficiencies by several fold over unmodified donors. Furthermore, end-modified donors exhibited a striking reduction in end-joining reactions including reduced concatemer formation and reduced direct ligation into the host genome. Our study demonstrates that HDR can be improved without inhibiting competing end-joining pathways and provides a platform to identify new chemical modifications that could further increase the potency and efficacy of precision genome editing.

DOI

10.13028/hs7v-w341

Rights and Permissions

Licensed under a Creative Commons license

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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