FUS and amyotrophic lateral sclerosis: ALS is a complex disease because it has been linked to multiple aggregating proteins which include chromosome 9 open reading frame 72 (C9ORF72), superoxide dismutase 1 (SOD1), tar-DNA binding protein 43 (TDP-43), rho guanine nucleotide exchange factor (RGNEF), phosphorylated high molecular weight neurofilament protein (pNFH), fused in sarcoma (FUS), and others [7].