ITGB4 and ependymoma: 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.