GPX4 is associated with neuromelanin in SN neurons. GPX4 colocalizes with neuromelanin in SN of control brain. A. Western blot showing antibody specificity in human brain (left) and human and mouse neuroblastoma cells and mouse cortex (right). For "blocked" controls, antibody was preabsorbed with original recombinant antigen. B. Immunohistochemistry negative control with primary antibody omitted. Brown pigment is endogenous neuromelanin (black arrows). C. Robust GPX4 expression (dark grey Ni-DAB, white arrowheads) is associated with neuromelanin (brown, black arrows) and in the cytoplasm (*). D. Enlarged cell images, counterstained with methyl green to show nuclei of these neurons (white arrows). Scale bars: B, C, 20 μm, D, 10 μm.