70 A small number of mutations also occur in the N-terminus of TDP-43, a domain that is necessary for TDP-43 to self-associate into oligomers that can correctly function in RNA processing.13 Impaired TDP-43 dimerisation is also observed in brain tissue from patients with ALS, and expression of N-terminal dimerisation-impaired TDP-43 has been shown to cause TDP-43 pathology in vitro.49 These mutation-related effects are likely to be different when wild-type TDP-43 is mislocalised in non-TARDBP mutation related ALS and idiopathic ALS. This evidence concerns the gene TARDBP and amyotrophic lateral sclerosis.