LRRK2 and Parkinson disease: For mouse models used to study gene overexpression involving some familial PD forms, such as α-synuclein and leucine-rich repeat kinase 2, since they do not experience dopaminergic cell loss, LID cannot be induced with levodopa treatment (120), and there is currently no single PD animal model that perfectly replicates all the core features of PD (121).