It has been demonstrated that midbrain organoids generated from LRRK2(G2019S) or PRKN patients (Kim et al., 2019a) recapitulate the principal hallmarks of neurodegeneration observed in vivo and show alterations in novel biochemical pathways with abnormal phenotypes of LRRK2 sporadic PD and alpha-synuclein-mediated gene alteration. Here, LRRK2 is linked to Parkinson disease.