ATXN2 trinucleotide repeat length correlates with risk of ALS

We investigated a CAG trinucleotide repeat expansion in the ATXN2 gene in amyotrophic lateral sclerosis (ALS). Two new case-control studies, a British dataset of 1474 ALS cases and 567 controls, and a Dutch dataset of 1328 ALS cases and 691 controls were analyzed. In addition, to increase power, we systematically searched PubMed for case-control studies published after 1 August 2010 that investigated the association between ATXN2 intermediate repeats and ALS. We conducted a meta-analysis of the new and existing studies for the relative risks of ATXN2 intermediate repeat alleles of between 24 and 34 CAG trinucleotide repeats and ALS. There was an overall increased risk of ALS for those carrying intermediate sized trinucleotide repeat alleles (odds ratio 3.06 [95% confidence interval 2.37–3.94]; p = 6 × 10−18), with an exponential relationship between repeat length and ALS risk for alleles of 29–32 repeats (R2 = 0.91, p = 0.0002). No relationship was seen for repeat length and age of onset or survival. In contrast to trinucleotide repeat diseases, intermediate ATXN2 trinucleotide repeat expansion in ALS does not predict age of onset but does predict disease risk.This work was supported by the EU Joint Programme for Neurodegenerative Disease Research projects SOPHIA, STRENGTH, and NETCALS. Christopher E. Shaw, Ammar Al-Chalabi, and Daniel Stahl receive salary support from the National Institute for Health Research Dementia Biomedical Research Unit at South London and Maudsley NHS Foundation Trust and King's College London. Philip Van Damme holds a senior clinical investigatorship of FWO-Flanders and is supported by the Belgian ALS ligue. William Sproviero, Richard Orrell, John Hardy, and Maryam Shoai are funded by the MND Association