TARDBP and frontotemporal dementia: ALS and FTD are pathologically defined by cytoplasmic aggregation and nuclear depletion of TAR DNA-binding protein 43 (TDP-43) in more than 97% of ALS cases and 45% of FTD cases4,5 (frontotemporal lobar degeneration (FTLD) due to TDP-43 proteinopathy (FTLD-TDP)).