GRN and Alzheimer disease: Amyloid beta precursor protein (APP) [6], presenilin 1 (PSEN1) [7], and presenilin 2 (PSEN2) [8, 9] are AD familial risk genes explaining < 0.5% of AD cases with age of onset typically between 30–50 years of age, while progranulin (GRN) [10] and microtubule-associated protein tau (MAPT) [11–13] are FTD familial risk genes [2].