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Related Concept Videos

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Related Experiment Video

Updated: Mar 27, 2026

Author Spotlight: Characterizing DNA Replication of Pathogenic Repeats to Uncover Mechanisms of Replication Fork Stalling and Expansion
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Disease-associated repeat instability and mismatch repair.

Monika H M Schmidt1, Christopher E Pearson1

  • 1Genetics & Genome Biology, The Hospital for Sick Children, Peter Gilgan Centre for Research & Learning, 686 Bay St., Toronto, Ontario M5G 0A4, Canada; Department of Molecular Genetics, University of Toronto, Medical Sciences Bldg., 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.

DNA Repair
|January 18, 2016
PubMed
Summary

DNA mismatch repair (MMR) drives repeat expansions in genetic diseases like (CAG)·(CTG) repeats. Understanding MMR regulation is key for targeting somatic expansions and developing new therapies for neurological disorders.

Keywords:
Amyotrophic lateral sclerosisDNA repair gene polymorphismError-prone repairFragile XFriedreich’s ataxiaHuntington’s diseaseMLH1MLH3MSH2MSH3MSH6Mismatch repairMutSαMutSβMyotonic dystrophyPMS2R-loopsSlipped-DNATissue-specificTrinucleotide repeat instability

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Area of Science:

  • Genetics
  • Molecular Biology
  • Genomic Instability

Background:

  • Expanded tandem repeats in DNA are linked to over 40 human genetic diseases affecting the nervous and neuromuscular systems.
  • Somatic repeat expansions influence disease onset, severity, and progression, highlighting their therapeutic potential.

Purpose of the Study:

  • To elucidate the regulatory factors governing DNA repeat expansions, with a focus on the role of DNA repair mechanisms.
  • To understand how mismatch repair (MMR) drives pathogenic repeat expansions, particularly in (CAG)·(CTG) repeats.

Main Methods:

  • Review of recent advances in understanding MMR proteins (MSH2, MSH3, MSH6, MLH1, PMS2, MLH3) involved in repeat expansions.
  • Analysis of various repeat types affected by MMR, including (CAG)·(CTG), (CGG)·(CCG), and (GAA)·(TTC).
  • Investigation into the role of slipped-DNA structures, junction conformations, and other DNA/R-loop structures in MMR-mediated instability.

Main Results:

  • Mammalian MMR paradoxically drives expansion mutations in disease-associated repeats, contrary to its typical anti-mutagenic function.
  • Mutagenic slipped-DNA structures and their conformations are implicated in MMR involvement.
  • Tissue-specific MMR expression levels correlate with repeat instability, and polymorphic variants in DNA repair genes impact disease variability.

Conclusions:

  • MMR is a critical factor in the pathogenesis of repeat expansion diseases.
  • Understanding MMR's role in repeat instability offers potential for disease prognosis and therapeutic intervention.
  • Further research into DNA repair gene variants can explain variations in disease presentation.