C9orf72 and amyotrophic lateral sclerosis: More than 30 ALS-related genes have been identified, among them, the more common genes are superoxide dismutase 1 (SOD1), chromosome 9 open reading frame 72 (C9orf72), fused in sarcoma (FUS), and TAR DNA-binding protein (TDP-43/TARDBP), which are involved in a variety of cellular functions such as RNA metabolism, protein folding, autophagy and inflammation (3).