iPSCs generated from a healthy individual (WTC11, referred to as MAPT WT [26]) or an FTD patient with the MAPT V337M mutation (GIH6C1, referred to as *MAPT Het [23]) were edited in previous work [17, 23] with Cas9 to generate isogenic pairs either introducing or correcting the MAPT V337M mutation (Fig. 1A). The gene discussed is MAPT; the disease is frontotemporal dementia.