Medulloblastoma, an insidious brain cancer in children, is associated with mutation (90%) of the Sonic hedgehog (Shh) receptor, Patched. In the Feb. 16th post scientists from Duke University noted that aberrant Shh signaling from a mutation in the Shh receptor gave rise to hyperproliferative granule cell precursors (GCPs) of the cerebellum which can result in brain tumors in children. In the August 12th edition of Cancer Cell, Z-J Yang et al. from Duke Univ. Med. Ctr., published their findings on a study determining the cellular origin of medulloblastoma resulting from mutation in the Shh signaling pathway. The investigators found that activation of Shh in neuronal progenitors caused medulloblastoma by 3 months of age in mice. Surprisingly, activation of Shh signaling pathway in stem cells also caused brain tumors, once the stem cells were committed to the neuronal lineage. The study results revealed that mutations in the stem cells produced a more aggressive tumor than those initiated by progenitors, with all animals succumbing to the brain tumor by 3-4 weeks. The authors concluded that their studies "suggest that medulloblastoma can be initiated in progenitors or stem cells but that Shh-induced tumorigenesis is associated with neuronal lineage commitment."