Control and C9orf72 ALS/FTD iPSC-MGs were labeled with the live cell nuclear marker Hoechst (Figures 6A–I) to identify individual cells followed by treatment with hSN fluorescently tagged with pHrodo succinimidyl ester (hSN-rodo; Figures 6A, J–Q). Here, FSCN1 is linked to frontotemporal dementia.