To investigate the role of a specific Asian variant of the LRRK2 gene to induce susceptibility to stress and trigger PD phenotypes with time, knock-in (KI) mice bearing the human LRRK2 R1628P risk variant have been generated and studied from 2 to 16 months of age in the presence (or absence) of stress insults, including neurotoxin injections and chronic mild stress applied at 3 months of age. The gene discussed is LRRK2; the disease is Parkinson disease.