C9orf72 and amyotrophic lateral sclerosis: Around 10% of ALS cases are caused by autosomal dominant mutations of varying penetrance to one or more known genes including C9ORF72 (C9-ALS) [17, 64], SOD1 (ALS-SOD1) [68], FUS (ALS-FUS) [43] and TARDBP [81], with some mutations appearing to predispose patients towards an upper (UMN) or lower (LMN) motor neuron predominant phenotype [29, 60, 65, 79].