C9orf72 and amyotrophic lateral sclerosis: While most cases of ALS have no known genetic cause, more than 30 genes have been linked to ALS with the most common causative mutations identified in C9orf72 and SOD1, with rarer mutations occurring in a number of other genes such as TARDBP and FUS, most of which are ubiquitously expressed (Akçimen et al., 2023).