Dysregulation of glutamate transmission in VKI mice resembles that reported in LRRK2 G2019S knock-in mouse models of parkinsonism; however, the failure of LRRK2 kinase inhibition to reverse glutamate phenotypes in VKI mice suggests VPS35 D620N mutation effects do not result from ongoing LRRK2 kinase activity or are not rapidly reversible. This evidence concerns the gene VPS35 and Parkinson disease.