RSPO1 and neoplasm: The glial progenitor-like profile in NOTCH-driven CP tumor is characterized by enhanced expression of Rspo1, Zfp423, Gdf7, Msx1, Zic3/4, and Sox2, genes normally expressed in the rhombic lip progenitor pool capable of neuronal or epithelial differentiation during hindbrain development.3,6–11 Their expression and those of other glial progenitor markers were maintained as tumor cells transition through multiple differentiation states, suggesting an important role of the progenitor-like program in CP tumorigenesis.