Studies using mutant KI mouse models with endogenous level and pattern of LRRK2 expression, have revealed dysfunction in several key pathological aspects of PD, mediated by pathogenic variants of LRRK2. Despite the relevance and usefulness of LRRK2 KI mouse models in understanding disease pathogenesis, it must be emphasized that PD is a multifactorial disease. This evidence concerns the gene LRRK2 and Parkinson disease.