A recent gene expression study on 6-hydroxydopamine animal models of PD revealed that GPNMB (as well as other genes belonging to regeneration-associated genes) was highly upregulated in SN early after the lesion.112 This upregulation could be a response associated with axodegenerative process of SN neurons after lesions, and could also exhibit axoprotective or regenerative properties.112. Here, GPNMB is linked to Parkinson disease.