PIN1 and Parkinson disease: Indeed, Pin1 has been reported to be significantly upregulated in postmortem human midbrain of PD patients in comparison with aged-matched controls [19], as well as in vitro in dopaminergic MN9D neurons, treated with 1-methyl-4-phenylpyridinium (MPP+), and in the substantia nigra of the 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine (MPTP)–induced PD mouse model [19].