In this section, we address the evidence for DA release defects in animal and human-based cell models of major monogenic forms of autosomal dominant (SNCA, LRRK2 and VPS35) and autosomal recessive [PRKN (parkin), PINK1 and PARK7 (DJ-1)] familial Parkinson’s disease and those carrying the major genetic risk factor for Parkinson’s disease onset (GBA1). The gene discussed is LRRK2; the disease is Parkinson disease.