IF data showed that ~98% of Tbx18::H2B-GFP cells co-expressed GBM markers SOX2 and/or OLIG2, and exhibited a clustered distribution consistent with clonal propagation, suggesting that Tbx18 was being misexpressed by a subset of GBM cells that retained expression of GBM markers (Fig. S2D and S2E). Here, H2BC21 is linked to glioblastoma.