By generating transgenic mice expressing tv-a under the control of tissue specific promoters, exclusive infection by RCAS has been obtained to tv-a-expressing cells, allowing the generation of several mouse glioma models, including PDGF-B-driven tumors [18, 19] and demonstrating that abnormal PDGF signaling can contribute to the etiology of brain tumors. The gene discussed is PDGFB; the disease is infection.