GRN and frontotemporal dementia: This study does not support the idea of exercise as a strategy to raise brain progranulin levels in symptomatic patients with FTD due to GRN mutations, as we observed no effects on progranulin levels in Grn+/−mice at 4–8 months of age, the age range in which these mice begin to develop abnormal behavior and neuronal dysfunction (Filiano et al., 2013).