Investigating CRISPR/Cas9 gene drive for production of disease-preventing prion gene alleles

PLoS One. 2022 Jun 7;17(6):e0269342. doi: 10.1371/journal.pone.0269342. eCollection 2022.

Abstract

Prion diseases are a group of fatal neurodegenerative disorders that includes chronic wasting disease, which affects cervids and is highly transmissible. Given that chronic wasting disease prevalence exceeds 30% in some endemic areas of North America, and that eventual transmission to other mammalian species, potentially including humans, cannot be ruled out, novel control strategies beyond population management via hunting and/or culling must be investigated. Prion diseases depend upon post-translational conversion of the cellular prion protein, encoded by the Prnp gene, into a disease-associated conformation; ablation of cellular prion protein expression, which is generally well-tolerated, eliminates prion disease susceptibility entirely. Inspired by demonstrations of gene drive in caged mosquito species, we aimed to test whether a CRISPR/Cas9-based gene drive mechanism could, in principle, promote the spread of a null Prnp allele among mammalian populations. First, we showed that transient co-expression of Cas9 and Prnp-directed guide RNAs in RK13 cells generates indels within the Prnp open-reading frame, indicating that repair of Cas9-induced double-strand breaks by non-homologous end-joining had taken place. Second, we integrated a ~1.2 kb donor DNA sequence into the Prnp open-reading frame in N2a cells by homology-directed repair following Cas9-induced cleavages and confirmed that integration occurred precisely in most cases. Third, we demonstrated that electroporation of Cas9/guide RNA ribonucleoprotein complexes into fertilised mouse oocytes resulted in pups with a variety of disruptions to the Prnp open reading frame, with a new coisogenic line of Prnp-null mice obtained as part of this work. However, a technical challenge in obtaining expression of Cas9 in the male germline prevented implementation of a complete gene drive mechanism in mice.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Animals
  • CRISPR-Cas Systems / genetics
  • Gene Drive Technology*
  • Mammals / genetics
  • Mice
  • Prion Diseases* / genetics
  • Prion Proteins / genetics
  • Prions* / genetics
  • RNA, Guide, CRISPR-Cas Systems
  • Wasting Disease, Chronic* / genetics

Substances

  • Prion Proteins
  • Prions
  • RNA, Guide, CRISPR-Cas Systems

Grants and funding

This study was supported by the Alberta Prion Research Institute (https://albertainnovates.ca/programs/alberta-prion-research-institute/) (APRIEP 201600033 and ABIBS 201600023; both awarded to D.W.) and the Canada Foundation for Innovation (https://www.innovation.ca/) (NIF21633; awarded to D.W.). The University of Alberta Transgenic core RRID:SCR_019175 receives funding from the Faculty of Medicine and Dentistry, University of Alberta and the Canada Foundation for Innovation (CFI) awards to contributing investigators. The University of Alberta Flow Cytometry core RRID:SCR_019195 receives funding from Faculty of Medicine and Dentistry, the LiKa Shing Institute of Virology and the Canada Foundation for Innovation (CFI) awards to contributing investigators. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.