LRRK2 and Parkinson disease: Increased leucine-rich repeat kinase 2 (LRRK2) kinase activity is suggested as the key risk factor associated with late onset PD (Funayama et al., 2002; Paisán-Ruíz et al., 2004; Zimprich et al., 2004a,b; Di Fonzo et al., 2005, 2006; Gilks et al., 2005; Kachergus et al., 2005; Nichols et al., 2005; Healy et al., 2008; Ross et al., 2011).