C9orf72 and amyotrophic lateral sclerosis: A significant ALS association was detected only for C9orf72, involving (i) alleles limited by fragment length (P < 2.2 × 10–16), (ii) alleles with read counts five times above or below average (P < 2.2 × 10–16), and (iii) alleles supported by a single consistent read (P = 5.8 × 10–6).