Precision Genome Editing in the CRISPR Era

Biochem Cell Biol. 2017 Apr;95(2):187-201. doi: 10.1139/bcb-2016-0137. Epub 2016 Sep 29.


With the introduction of precision genome editing using CRISPR-Cas9 technology, we have entered a new era of genetic engineering and gene therapy. With RNA-guided endonucleases, such as Cas9, it is possible to engineer DNA double strand breaks (DSB) at specific genomic loci. DSB repair by the error-prone non-homologous end-joining (NHEJ) pathway can disrupt a target gene by generating insertions and deletions. Alternatively, Cas9-mediated DSBs can be repaired by homology-directed repair (HDR) using an homologous DNA repair template, thus allowing precise gene editing by incorporating genetic changes into the repair template. HDR can introduce gene sequences for protein epitope tags, delete genes, make point mutations, or alter enhancer and promoter activities. In anticipation of adapting this technology for gene therapy in human somatic cells, much focus has been placed on increasing the fidelity of CRISPR-Cas9 and increasing HDR efficiency to improve precision genome editing. In this review, we will discuss applications of CRISPR technology for gene inactivation and genome editing with a focus on approaches to enhancing CRISPR-Cas9-mediated HDR for the generation of cell and animal models, and conclude with a discussion of recent advances and challenges towards the application of this technology for gene therapy in humans.

Keywords: CRISPR; Cas9; DNA repair; gene therapy; genome editing; réparation d’ADN; thérapie génique; édition génique.

Publication types

  • Review

MeSH terms

  • Animals
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • CRISPR-Associated Protein 9
  • CRISPR-Cas Systems*
  • Clustered Regularly Interspaced Short Palindromic Repeats*
  • DNA Breaks, Double-Stranded
  • Endonucleases / genetics*
  • Endonucleases / metabolism
  • Gene Deletion
  • Gene Editing / methods*
  • Gene Expression
  • Genetic Engineering
  • Genetic Therapy / trends*
  • Genome, Human
  • Humans
  • Mutagenesis, Insertional
  • RNA, Guide / genetics
  • RNA, Guide / metabolism
  • Recombinational DNA Repair*


  • Bacterial Proteins
  • RNA, Guide
  • CRISPR-Associated Protein 9
  • Cas9 endonuclease Streptococcus pyogenes
  • Endonucleases