The finding that LRRK2-mediated Rab10 phosphorylation is significantly elevated in neutrophils (Figure 5) and monocytes (Figure 7) derived from patients with PD associated with a single copy of the VPS35[D620N] allele confirms that the heterozygous mutation is sufficient to potently activate LRRK2 kinase activity in humans. The gene discussed is LRRK2; the disease is Parkinson disease.