The LRRK2 G2019S mutation is one of the most common genetic causes of familial PD, contributing to both familial and sporadic forms of the disease.[23] However, it is still unclear how LRRK2 kinase activity is regulated at the cellular and molecular levels, as well as how the activity of abnormal LRRK2 kinase results in PD. This evidence concerns the gene LRRK2 and Parkinson disease.