C9ORF72 repeat expansions in cases with previously identified pathogenic mutations

To identify potential genetic modifiers contributing to the phenotypic variability that is detected in patients with repeat expansions in chromosome 9 open reading frame 72 (C9ORF72), we investigated the frequency of these expansions in a cohort of 334 subjects previously found to carry mutations in genes known to be associated with a spectrum of neurodegenerative diseases.A 2-step protocol, with a fluorescent PCR and a repeat-primed PCR, was...