In addition, an analysis of freshly frozen post-mortem human brain samples revealed increased GPNMB levels in the substantia nigra of sporadic Parkinson’s disease (PD) patients compared to healthy control subjects [47] and transgenic overexpression of GPNMB reduced gliosis and microglial morphological changes in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD [48]. Here, GPNMB is linked to Parkinson disease.