TP53 and medulloblastoma: These authors provide evidence that constitutive activation of the Wnt/β-catenin pathway in BLBP expressing cerebellar precursors causes a defect in cell migration from the lower rhombic lip - which manifests eventually as medulloblastoma if tumour suppressor TP53 is also deactivated - while cell populations arising from the ventricular zone and rhombic lip do not show evidence for any developmental defect.