C9 and frontotemporal dementia: The following ALI-COs were produced: fibroblast-derived (H-L1) and cord-blood-derived (H-L2) control hiPSC lines; two fibroblast-derived C9 ALS/FTD hiPSC lines with ~50 (C9-L1) or ~1,000 (C9-L2) hexanucleotide repeat expansions; and a mutation-corrected isogenic (ISO-L2) line (Fig. 1a, Supplementary Table 1 and Extended Data Fig. 1a,b).