In addition, mRNA levels of lysosome-related genes, including lysosomal membrane protein (LAMP1 and LAMP2), lysosomal proteinase cathepsins (CTSB and CTSD), lysosomal acidification (ATPase H + transporting lysosomal accessory protein 2, ATP6AP2), and damaged lysosomes (LGALS3, gene coding Gal-3) were significantly increased in iMGs from FTD–GRN patients compared to those in control-derived iMGs (Fig. 4E). Here, CTSD is linked to frontotemporal dementia.