SORT1 and frontotemporal dementia: Consistent with the results from mammalian cell lines and iPSC-neurons, MPEP treatment decreased SORT1 (Fig. 2D and F) and preferentially increased exPGRN (Fig. 2E and G) in the LCLs from two FTD-GRN-affected families: one termed UBC17, which carries a p.C31LfsX34 mutation, and one termed UBC15, which carries a p.R418X mutation (3,4).