GAP43 and glioma: Whereas glial differentiation is well marked by upregulation of GFAP (glial fibrillary acidic protein), PSD95 (postsynaptic density protein 95), MAP2 (microtubule-associated protein 2), and GAP43 (growth-associated protein 43) proteins, glioma often shows either downregulation or lack of these proteins [7,8,9,10].