Evaluating noncoding nucleotide repeat expansions in amyotrophic lateral sclerosis

Intermediate-length polyglutamine expansions in ataxin 2 are a risk factor for amyotrophic lateral sclerosis (ALS). The polyglutamine tract is encoded by a trinucleotide repeat in a coding region of the ataxin 2 gene (ATXN2). Noncoding nucleotide repeat expansions in several genes are also associated with neurodegenerative and neuromuscular diseases. For example, hexanucleotide repeat expansions located in a noncoding region of C9ORF72 are the most common cause of ALS. We sought to assess a potential larger role of noncoding nucleotide repeat expansions in ALS. We analyzed the nucleotide repeat lengths of 6 genes (ATXN8, ATXN10, PPP2R2B, NOP56, DMPK, and JPH3) that have previously been associated with neurologic or neuromuscular disorders, in several hundred sporadic patients with ALS and healthy control subjects. We report no association between ALS and repeat length in any of these genes, suggesting that variation in the noncoding repetitive regions in these genes does not contribute to ALS.