C9orf72 and amyotrophic lateral sclerosis: Although our evidence and others demonstrate that C9ORF72 deficiency cannot by itself cause ALS, it was recently shown in mice and rats that decreasing C9ORF72 predisposes animals to the development of motor neuron disease (Shao et al., 2019; Dong et al., 2020a,b; Zhu et al., 2020).