Additionally, the most common genetic subtype of ALS is caused by the expansion of a hexanucleotide repeat (GGGGCC) within the C9orf72 (chromosome 9 open reading frame 72) gene, which has also been associated with TDP-43 abnormalities (DeJesus-Hernandez et al., 2011; Renton et al., 2011). Here, C9orf72 is linked to amyotrophic lateral sclerosis.