LRRK2 and Parkinson disease: Through the reprogramming of fibroblasts from PD patients with the LRRK2 G2019S mutation into induced pluripotent stem cells (iPSCs) and their differentiation into dopaminergic neurons, it was found that under the G2019S mutation condition, the sensitivity of dopaminergic neurons to ERS increased, manifested as the upregulation of the expression of ERS-related molecules such as GRP78 and CHOP, accompanied by impaired mitochondrial function [69].