In addition, studies have demonstrated that mutations in TAR DNA-binding protein (TARDBP), variants of angiogenin (ANG), polymorphisms within axon guidance pathway genes, expanded ataxin 2 (ATXN2) repeats and hexanucleotide repeat expansions in C9ORF72 gene are involved in both PD and ALS [11]–[18]. This evidence concerns the gene ATXN2 and amyotrophic lateral sclerosis.