Work during the past several years has significantly increased our understanding of the genetic basis of ALS and has led to the identification of disease-causing mutations in various genes including chromosome 9 open reading frame 72 (C9orf72), fused in sarcoma (FUS), optineurin (OPTN), profilin 1 (PFN1), sequestosome 1 (SQSTM1), superoxide dismutase 1 (SOD1), TANK-binding kinase 1 (TBK1), TAR DNA-binding protein 43 (TARDBP), ubiquilin 2 (UBQLN2), vesicle-associated membrane protein-associated protein B and C (VAPB) and valosin-containing protein (VCP) [65]. Here, PFN1 is linked to amyotrophic lateral sclerosis.