C9orf72 and amyotrophic lateral sclerosis: Despite studies which show that C9orf72 is the major gene that is mutated in the European ALS population [8, 36, 37], we did not identify pathogenic hexanucleotide (GGGGCC) repeat expansions (≥24) in C9orf72 in either fALS or sALS cases (Fig. 4).