CTSD and frontotemporal dementia: A control line was generated in parallel to GRN KO cells using guide RNA targeting LacZ. GRN KO HEK-293 cells exhibited lysosomal abnormalities such as an increase in levels of mature cathepsin D (Fig. 1a, b), which has also been reported in brain tissue from patients with FTD-GRN30,39 and Grn–/– mice33,39.