Additionally, PGRN is proteolytically processed into GRN peptides in the lysosome (Holler et al., 2017; Zhou et al., 2017) and both PGRN and GRN levels were found to be reduced in brain lysates from FTD patients with GRN mutation (Holler et al., 2017). This evidence concerns the gene GRN and frontotemporal dementia.