LRRK2 and Parkinson disease: The link between LRRK2 activation, tau phosphorylation and a degenerative disease state is supported by the observation that neurofibrillary tangles containing pathologically phosphorylated tau are present in a significant percentage of PD patients with LRRK2 mutations (Arima et al., 1999; Wills et al., 2010; Henderson et al., 2019).