Transcriptome analysis of medulloblastoma tumors in mice

The proto-oncogene MYCN is mis-expressed in various types of human brain tumors. To clarify how developmental and regional differences influence transformation, we transduced wild-type or mutationally-stabilized murine N-mycT58A into neural stem cells (NSCs) from perinatal murine cerebellum, brain stem and forebrain. Transplantation of Nmyc WT NSCs was insufficient for tumor formation. N-mycT58A cerebellar and brain stem NSCs generated medulloblastoma/primitive neuroectodermal tumors, whereas forebrain NSCs developed diffuse glioma. Expression analyses distinguished tumors generated from these different regions, with tumors from embryonic versus postnatal cerebellar NSCs demonstrating SHH-dependence and SHH-independence, respectively. These differences were regulated in-part by the transcription factor SOX9, activated in the SHH subclass of human medulloblastoma. Our results demonstrate context-dependent transformation of NSCs in response to a common oncogenic signal. 9 (total) orthotopic tumors generated from E16C, P0C, and P0F NSCs transduced with a mutation-stabilized N-Myc were compared to transduced (but not transplanted) NSCs, NSCs transduced with GFP, and cells derived from the orthotopic tumors. These were also compared to 5 normal P7 cerebella, and 32 medulloblastoma tumors from the GTML mouse model. A cell line derived from a tumor from the GTML mouse model is also included in the comparison.