Gene expression analysis indicates that transcription of integrin β4 (ITGB4), but not β1 (ITGB1), is significantly up-regulated in PFA compared to ZFTA ependymoma and normal brain samples (Supplementary Fig. 4g, h), suggesting that the integrin α6β4 heterodimer is the functional form relevant for PFA tumors. The gene discussed is ITGB1; the disease is ependymoma.