RET and central nervous system cancer: To functionally assess the role of pericytes in glioma development and progression, we stereotactically injected GBM cells into the subventricular zone (SVZ) of wild-type mice or of mice carrying a homozygous Pdgfb allele that is missing the PDGF-B heparan sulfate proteoglycan binding motif sequence (Pdgfbret/ret mice)31.