SLC9A6 and Parkinson disease: In a recent transcriptomic analysis of postmortem brain samples, Prasad et al. reported significantly reduced SLC9A6 expression in the substantia nigra of individuals with sporadic Parkinson's disease.35 This observation suggests that decreased SLC9A6 activity may contribute to nigral vulnerability in both familial and idiopathic PD, likely through dysregulation of vesicular pH homeostasis and impaired endosomal recycling of key synaptic and trophic components.