Flow cytometry analyses showed that DsRed+ GBM cells and Tbx18::H2B-GFP+ mural cells were separate populations, with only very few double-labeled cells detected (Fig. 2A), the latter of which could be rare trans-differentiation events or misexpression of Tbx18 by some GBM cells. The gene discussed is TBX18; the disease is glioblastoma.