After acute (Figure 4A) or chronic (Figure 4B) MPTP induction of PD, although α‐syn mRNA was further increased in AQP4−/− mouse midbrains, α‐syn protein levels did not show any detectable increase in either AQP4+/+ or AQP4−/− mouse midbrains in acute (Figure 4C,D) or chronic (Figure 4E,F) MPTP‐induced PD mouse models. The gene discussed is AQP4; the disease is Parkinson disease.