LRRK2 and Parkinson disease: PD-associated mutant variants with altered GTPase activity demonstrated markedly increased cytotoxicity when compared with cultures expressing wild-type GTPase fragments, underlining the notion that altered GTPase activity of Lrrk2 is an important factor determining neuronal cell loss during PD progression (Gloeckner et al., 2006; Xiong et al., 2010).