Genome Editing of Expanded CTG Repeats within the Human DMPK Gene Reduces Nuclear RNA Foci in the Muscle of DM1 Mice

Mol Ther. 2019 Aug 7;27(8):1372-1388. doi: 10.1016/j.ymthe.2019.05.021. Epub 2019 Jun 5.

Abstract

Myotonic dystrophy type 1 (DM1) is caused by a CTG repeat expansion located in the 3' UTR of the DMPK gene. Expanded DMPK transcripts aggregate into nuclear foci and alter the function of RNA-binding proteins, leading to defects in the alternative splicing of numerous pre-mRNAs. To date, there is no curative treatment for DM1. Here we investigated a gene-editing strategy using the CRISPR-Cas9 system from Staphylococcus aureus (Sa) to delete the CTG repeats in the human DMPK locus. Co-expression of SaCas9 and selected pairs of single-guide RNAs (sgRNAs) in cultured DM1 patient-derived muscle line cells carrying 2,600 CTG repeats resulted in targeted DNA deletion, ribonucleoprotein foci disappearance, and correction of splicing abnormalities in various transcripts. Furthermore, a single intramuscular injection of recombinant AAV vectors expressing CRISPR-SaCas9 components in the tibialis anterior muscle of DMSXL (myotonic dystrophy mouse line carrying the human DMPK gene with >1,000 CTG repeats) mice decreased the number of pathological RNA foci in myonuclei. These results establish the proof of concept that genome editing of a large trinucleotide expansion is feasible in muscle and may represent a useful strategy to be further developed for the treatment of myotonic dystrophy.

Keywords: CRISPR-Cas9; DMPK; gene therapy; myotonic dystrophy; nucleotide repeat disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing
  • Animals
  • Base Sequence
  • CRISPR-Cas Systems
  • Cell Nucleus
  • Disease Models, Animal
  • Fluorescent Antibody Technique
  • Gene Editing*
  • Gene Expression
  • Gene Targeting
  • Genetic Vectors / genetics
  • Humans
  • Mice
  • Mice, Knockout
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / pathology
  • Myotonic Dystrophy / genetics
  • Myotonic Dystrophy / therapy
  • Myotonin-Protein Kinase / genetics*
  • RNA, Guide
  • RNA, Nuclear*
  • Transduction, Genetic
  • Trinucleotide Repeat Expansion*

Substances

  • DMPK protein, human
  • RNA, Guide
  • RNA, Nuclear
  • Myotonin-Protein Kinase