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Contracting CAG/CTG repeats using the CRISPR-Cas9 nickase

Cinzia Cinesi1, Lorène Aeschbach1, Bin Yang1

  • 1Center for Integrative Genomics, University of Lausanne, 1015 Lausanne, Switzerland.

Nature Communications
|November 10, 2016
PubMed

Insights

Scientists discovered a new method to contract CAG/CTG repeats, which are linked to neurological diseases. This CRISPR-Cas9 nickase approach shows promise for developing treatments by reducing harmful repeat expansions in vivo.

Area of Science:

  • Genetics
  • Molecular Biology
  • Neuroscience

Background:

  • CAG/CTG repeat expansions are associated with over 13 incurable neurological diseases.
  • Disease severity correlates with repeat tract length, suggesting repeat contraction as a therapeutic strategy.

Purpose of the Study:

  • To investigate methods for specifically inducing CAG/CTG repeat contractions.
  • To understand the mechanisms underlying repeat instability and contraction.

Main Methods:

  • Utilized a GFP-based chromosomal reporter to monitor repeat expansions and contractions.
  • Employed CRISPR-Cas9 D10A nickase to induce targeted DNA damage within repeat tracts.
  • Investigated the roles of DNA damage response kinases (ATM, ATR) and repair proteins (MSH2, XPA).

Main Results:

  • Inducing double-strand breaks caused instability in both expansion and contraction directions.
  • CRISPR-Cas9 D10A nickase primarily induced contractions, independent of single-strand break repair.
  • Nickase-induced contractions were dependent on the ATM kinase.
  • ATR inhibition, in a MSH2- and XPA-dependent manner, increased both expansions and contractions.

Conclusions:

  • DNA gaps within repeat tracts promote contractions.
  • The type of DNA damage dictates the direction and extent of CAG/CTG repeat instability.
  • This study provides a foundation for inducing CAG/CTG repeat contractions in vivo for therapeutic purposes.

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