C9orf72 and amyotrophic lateral sclerosis: First, genes that are involved in SG regulation are potent modifiers of the toxicity of mutant ALS genes, including TDP-43, Profilin 1 and C9orf72, in yeast and Drosophila (Couthouis et al., 2011; Kim et al., 2014; Lee et al., 2016).