GRN and frontotemporal dementia: Given that there is currently no feasible way to pharmacologically manipulate PGRN levels in the brain and that recombinant PGRN is too large to cross the blood–brain barrier (BBB) for protein replacement, the development of bio-available, BBB permeable PGRN enhancers will be a valuable tool to determine whether therapeutically modulating or increasing PGRN levels can alleviate the pathogenesis associated with FTD-GRN.