TARDBP and frontotemporal dementia: In addition to the cases caused by these gene mutations, many sporadic ALS/FTD cases of unknown genetic factors show TDP-43 disappearance from the nuclei and abnormal depositions in the cytoplasm of neurons, indicating that these diseases form a common pathological spectrum in terms of TDP-43 pathology (Arai et al., 2006; Neumann et al., 2006).