PTCH1 and Mobius syndrome: The increase of expression of CD15, a marker of brain tumor stem cells, detected by qRT-PCR in the Ptch1+/−/Btg1KO MBs compared with Ptch1+/−/Btg1WT MBs (Figure 7A), was confirmed at protein level by immunohistochemical analysis of tumor sections from MBs of the two different genotypes under study (Figures 7C,D).