CDKN1B and medulloblastoma: Similar to PatchedLacZ/+ tumors, Gdf7Cre/+;SmoM2 medulloblastomas expressed the neural progenitor marker Nestin and were highly proliferative as indicated by strong expression of Ki67, CyclinD2, and phosphorylated Rb and partial loss of differentiation marker p27Kip1 (Figure 2F–H′′′).