RESUMO
Mutations in the Drosophila trol gene cause cell cycle arrest of neuroblasts in the larval brain. Here, we show that trol encodes the Drosophila homolog of Perlecan and regulates neuroblast division by modulating both FGF and Hh signaling. Addition of human FGF-2 to trol mutant brains in culture rescues the trol proliferation phenotype, while addition of a MAPK inhibitor causes cell cycle arrest of the regulated neuroblasts in wildtype brains. Like FGF, Hh activates stem cell division in the larval brain in a Trol-dependent fashion. Coimmunoprecipitation studies are consistent with interactions between Trol and Hh and between mammalian Perlecan and Shh that are not competed with heparin sulfate. Finally, analyses of mutations in trol, hh, and ttv suggest that Trol affects Hh movement. These results indicate that Trol can mediate signaling through both of the FGF and Hedgehog pathways to control the onset of stem cell proliferation in the developing nervous system.
Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/crescimento & desenvolvimento , Fator 2 de Crescimento de Fibroblastos/genética , Proteoglicanas de Heparan Sulfato/genética , Alelos , Sequência de Aminoácidos , Animais , Encéfalo/citologia , Encéfalo/crescimento & desenvolvimento , Divisão Celular/efeitos dos fármacos , DNA/genética , Proteínas de Drosophila/fisiologia , Drosophila melanogaster/genética , Drosophila melanogaster/fisiologia , Inibidores Enzimáticos/farmacologia , Fator 2 de Crescimento de Fibroblastos/fisiologia , Flavonoides/farmacologia , Regulação da Expressão Gênica no Desenvolvimento , Genes de Insetos , Proteínas Hedgehog , Proteoglicanas de Heparan Sulfato/fisiologia , Humanos , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Dados de Sequência Molecular , Mutação , Neurônios/citologia , Fenótipo , RNA Mensageiro/genética , Transdução de Sinais , Células-Tronco/citologiaRESUMO
We have used serial analysis of gene expression (SAGE) to investigate the influence of the von Hippel-Lindau (VHL) gene on global gene expression profiles. SAGE libraries were prepared from renal cell carcinoma (RCC) lines that either lack (parental) or express wild-type VHL (wtVHL). Comparison of these libraries revealed some differentially expressed genes (Glut-1, for example) that were known to be influenced by VHL, but the majority of genes had not previously been reported to be affected by the cell's VHL status. The identification of several genes involved in TNFalpha-mediated events prompted us to compare the sensitivity of cells with different VHL status in TNFalpha cytotoxicity assays. Strikingly, VHL-deficient cells were much more resistant to the toxic influence of TNFalpha. We propose that VHL-dependent sensitization of RCC cells to TNFalpha-mediated killing may contribute to VHL's growth suppressive function.
