Expanded ATXN2 CAG repeat size in ALS identifies genetic overlap between ALS and SCA2

Neurology. 2011 Jun 14;76(24):2066-72. doi: 10.1212/WNL.0b013e31821f445b. Epub 2011 May 11.


Objectives: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of motor neurons that results in progressive muscle weakness and limits survival to 2-5 years after disease onset. Intermediate CAG repeat expansions in ataxin 2 (ATXN2), the causative gene of spinocerebellar ataxia type 2 (SCA2), have been implicated in sporadic ALS. We studied ATXN2 in a large cohort of patients with sporadic and familial ALS.

Methods: We determined ATXN2 CAG repeat size in 1,948 sporadic and familial ALS cases and 2,002 controls from Belgium and the Netherlands.

Results: In controls, the maximal ATXN2 repeat size was 31. In sporadic ALS, a significant amount of longer repeat sizes (≥ 32, range 32-39) were encountered (in 0.5% or 10/1,845 ALS cases, vs 0% in controls, p = 0.0006). Receiver operating characteristic analysis showed that a cutoff of ≥ 29 appeared optimal to discriminate ALS from control (p = 0.036, odds ratio [OR] 1.92, 95% confidence interval [CI] 1.04-3.64). A meta-analysis with the previously published results from the United States showed that the association between a repeat length of ≥ 29 and ALS became stronger (p < 0.0001, OR 2.93, 95% CI 1.73-4.98). In unexplained familial ALS, we found an intermediate repeat expansion of 31 and a homozygous repeat expansion of 33 each in 1.1% of families. The phenotype of patients with ALS with expanded repeat sizes ranged from rapidly progressive typical ALS to slowly progressive ALS with reduced sensory nerve action potentials.

Conclusion: Our data reveal a novel genetic overlap between ALS and SCA2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age of Onset
  • Aged
  • Aged, 80 and over
  • Amyotrophic Lateral Sclerosis / genetics*
  • Amyotrophic Lateral Sclerosis / pathology
  • Amyotrophic Lateral Sclerosis / physiopathology
  • Ataxins
  • Belgium
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nerve Tissue Proteins / genetics*
  • Netherlands
  • Pedigree
  • Spinocerebellar Ataxias / genetics*
  • Spinocerebellar Ataxias / pathology
  • Spinocerebellar Ataxias / physiopathology
  • Trinucleotide Repeat Expansion*


  • Ataxins
  • Nerve Tissue Proteins