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Medulloblastoma is the most common malignant brain tumor in children with a median age of 3 to 7 years old. Human medulloblastomas are molecularly classified into four major subgroups including two with constitutive activation of developmental signaling pathways Sonic Hedgehog/Patched defining the SHH-subgroup and Wnt for the WNT-subgroup, subgroup 3 with amplification or overexpression of c-MYC and subgroup 4 with as yet undefined genetic anomalies. To date, all medulloblastomas regardless of their subgroup are treated with the same therapeutic regimen with different outcome. If children with WNT-subgroup tumors fair well, those with subgroup 3 medulloblastoma, the most aggressive form of the disease have a dismal prognosis. Most mouse models of medulloblastoma developed to date mimic the human SHH-subgroup. However, we recently developed two new mouse models that faithfully recapitulate the human WNT-subgroup and subgroup 3 (MYC). The SHH-subgroup and subgroup 3 medulloblastomas were derived from cerebellar granule progenitors in the external granule layer which sustain mutations in the SHH pathway associated with MYCN overexpression, or C-MYC amplification, respectively. In contrast, the WNT-subgroup medulloblastoma with mutations in β-Catenin originate from the lower rhombic lip, the germinal neuroepithelium surrounding the floor of the 4th ventricle, suggesting that each subgroup may originate from specific neuronal precursors within the developing cerebellum. Mouse subgroup 3 medulloblastomas, but not SHH- or WNT-subgroup tumors can be passaged indefinitely as neurospheres that express markers characterizing stem cells, including Lgr5, Oct4, Nanog, and Sox2 and induce secondary medulloblastomas with similar characteristics as the primary tumors, after orthotopic transplant into the cortices of recipient mice. These novel medulloblastoma mouse models should significantly advance our efforts to develop new therapeutic modalities for this deadly childhood cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr SY10-03. doi:1538-7445.AM2012-SY10-03