C9orf72 and amyotrophic lateral sclerosis: For a number of the ALS and ALSND individuals in the cohort, C9orf72 expansion carrier status was known (MCX n = 79, FCX n = 104, CER n = 115 and SCC n = 99), therefore the level of intact and non-intact L1 expression was compared in those with and without the expansion and there was no significant difference identified (MCX p = 0.61 and p = 0.81, FCX p = 0.87 and p = 0.54, CER p = 0.88 and p = 0.48 and SCC p = 0.32 and p = 0.41).