In an attempt to recapitulate our in vivo findings in cell cultures, a more amendable system for the future mechanistic studies, we also performed preliminary studies on primary cultured SPNs derived from the Lrrk2+/+ and Lrrk2−/− mice as well as the PD-related G2019S and R1441C mutant mice. This evidence concerns the gene LRRK2 and late-onset Parkinson disease.