LRRK2 and Parkinson disease: A previous study reported the mutation of LRRK2 resulted in cell toxicity and apoptosis in PD.[11] Meanwhile, ER stress is a universal intracellular stress response caused by a range of situations that disrupt cellular homeostasis and leads to cell death.[12] We further studied whether LRRK2 mutation could affect the ER stress in iPSC‐induced DA neurons.