Project description:Sonic hedgehog (Shh) signals via Gli transcription factors to stimulate proliferation of granule neuron precursor cells (GNPs) in the cerebellum. Deregulation of Shh target genes often results in unrestrained GNP proliferation and eventually medulloblastoma, the most common pediatric brain malignancy. Transcription factor binding location analysis (chIP-chip) revealed 510 and 1,060 genomic loci bound by Gli1 with high confidence in murine GNP and medulloblastoma cells, respectively. In primary tumors, Gli1 associated with only one-third of the Gli1-bound regions in GNPs. Gene expression profiling, coupled with our binding results, indicated that there were more than one hundred target genes in common between the two cell populations, and importantly, there was an equivalent number of tumor-specific targets. These results indicate that the transformation of normal GNPs into deadly tumor cells is accompanied by some changes in the battery of genes regulated by Gli1.
Project description:Origins of the brain tumor, medulloblastoma, from stem cells or restricted pro-genitor cells are unclear. To investigate this, we activated oncogenic Hedgehog signaling in multipotent and lineage-restricted CNS progenitors. We observed that normal unipo-tent cerebellar granule neuron precursors (CGNP) derive from hGFAP+ and Olig2+ rhombic lip progenitors. Hedgehog activation in a spectrum of early and late stage CNS progenitors generated similar medulloblastomas, but not other brain cancers, indicating that acquisition of CGNP identity is essential for tumorigenesis. We show in human and mouse medulloblastoma that cells expressing the glia-associated markers Gfap and Olig2 are neoplastic and that they retain features of embryonic-type granule lineage progenitors. Thus, oncogenic Hedgehog signaling promotes medulloblastoma from lineage-restricted granule cell progenitors. Gene expression profiling of cerebellar tumors generated from various early and late stage CNS progenitor cells.