Due to their heterogeneity, ALS and FTLD can be classified according to pathological subtypes and the presence of inclusions of specific aggregated proteins: for ALS, these include superoxide dismutase 1 (SOD1), fused in sarcoma (FUS), and optineurin (OPTN) [191]; for FTLD, tau and FUS are common. Here, OPTN is linked to amyotrophic lateral sclerosis.