GRN and frontotemporal dementia: There are both familial and sporadic forms of FTD, with the most common variants discovered in genes encoding for the microtubule-associated protein Tau (MAPT; FTLD-TAU), progranulin (GRN; FTLD-TDP), and C9orf72 (FTLD-TDP) (Mackenzie and Neumann, 2016).