An increase in dysfunctional mitochondria was identified in 26 independent hiPSC-PD studies using LRRK2, PRKN, PINK1, GBA, and SNCA patient-derived neuronal lines24,27,31,32,37–39,52,55,57,59,61,62,64,67,68,70,71,73,74,77,85,89,90. Here, PINK1 is linked to Parkinson disease.