RESUMO
Diffuse intrinsic pontine glioma (DIPG) is an incurable brain tumor of childhood characterized by histone mutations at lysine 27, which results in epigenomic dysregulation. There has been a failure to develop effective treatment for this tumor. Using a combined RNAi and chemical screen targeting epigenomic regulators, we identify the polycomb repressive complex 1 (PRC1) component BMI1 as a critical factor for DIPG tumor maintenance in vivo. BMI1 chromatin occupancy is enriched at genes associated with differentiation and tumor suppressors in DIPG cells. Inhibition of BMI1 decreases cell self-renewal and attenuates tumor growth due to induction of senescence. Prolonged BMI1 inhibition induces a senescence-associated secretory phenotype, which promotes tumor recurrence. Clearance of senescent cells using BH3 protein mimetics co-operates with BMI1 inhibition to enhance tumor cell killing in vivo.
Assuntos
Envelhecimento/genética , Glioma Pontino Intrínseco Difuso/genética , Complexo Repressor Polycomb 1/metabolismo , Astrocitoma/genética , Neoplasias do Tronco Encefálico/tratamento farmacológico , Neoplasias do Tronco Encefálico/genética , Diferenciação Celular/genética , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Criança , Pré-Escolar , Cromatina/genética , Glioma Pontino Intrínseco Difuso/tratamento farmacológico , Glioma Pontino Intrínseco Difuso/metabolismo , Epigenômica , Feminino , Glioma/tratamento farmacológico , Glioma/genética , Glioma/patologia , Histonas/metabolismo , Humanos , Lisina/metabolismo , Masculino , Mutação , Recidiva Local de Neoplasia/tratamento farmacológico , Recidiva Local de Neoplasia/genética , Complexo Repressor Polycomb 1/antagonistas & inibidores , Complexo Repressor Polycomb 1/genéticaRESUMO
Medulloblastoma (MB) is the most prevalent malignant brain tumor in children, accounting for 20% of all childhood brain tumors. The molecular profiling of MB into 4 major subgroups (WNT, SHH, Grp3, and Grp4) emphasizes the heterogeneity of MB and opens paths in which treatments may be targeted to molecularly aggressive and distinct tumors. Current therapeutic strategies for Group 3 MB are challenging and can be accompanied by long-term side effects from treatment. The involvement of altered epigenetic machinery in neoplastic transformation in MB has become more evident. Thus, we performed an epigenomic RNAi and chemical screen and identified SETD8/PRE-SET7/KMT5a as a critical player in maintaining proliferation and cell survival of MB cells. We have found that inhibition of SETD8 effects the migration/invasive ability of MB cells. SETD8 alters H4K20me chromatin occupancy at key genes involved in tumor invasiveness and pluripotency. Interestingly, these results link the aggressive and metastatic behavior of MYC-driven MB with SETD8 activity. Based on our results, we suggest that SETD8 has a critical role mediating Group 3 MB tumorigenesis. Establishing a role for SETD8 as a factor in MYC-driven MB has potential to lead to more effective therapies needed to improve outcomes in high-risk patients.
RESUMO
The Caenorhabditis elegans gene sup-26 encodes a well-conserved RNA-recognition motif-containing RNA-binding protein (RBP) that functions in dendrite morphogenesis of the PVD sensory neuron. The Drosophila ortholog of sup-26, alan shepard (shep), is expressed throughout the nervous system and has been shown to regulate neuronal remodeling during metamorphosis. Here, we extend these studies to show that sup-26 and shep are required for the development of diverse cell types within the nematode and fly nervous systems during embryonic and larval stages. We ascribe roles for sup-26 in regulating dendrite number and the expression of genes involved in mechanosensation within the nematode peripheral nervous system. We also find that in Drosophila, shep regulates dendrite length and branch order of nociceptive neurons, regulates the organization of neuronal clusters of the peripheral nervous system and the organization of axons within the ventral nerve cord. Taken together, our results suggest that shep/sup-26 orthologs play diverse roles in neural development across animal species. Moreover, we discuss potential roles for shep/sup-26 orthologs in the human nervous system.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Proteínas de Drosophila/genética , Embrião não Mamífero/metabolismo , Sistema Nervoso/metabolismo , Proteínas de Ligação a RNA/genética , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans/embriologia , Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Proteínas de Caenorhabditis elegans/metabolismo , Dendritos/genética , Dendritos/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriologia , Drosophila melanogaster/genética , Drosophila melanogaster/crescimento & desenvolvimento , Embrião não Mamífero/embriologia , Regulação da Expressão Gênica no Desenvolvimento , Hibridização In Situ , Larva/genética , Larva/crescimento & desenvolvimento , Larva/metabolismo , Metamorfose Biológica/genética , Microscopia Confocal , Morfogênese/genética , Sistema Nervoso/embriologia , Sistema Nervoso/crescimento & desenvolvimento , Interferência de RNA , Proteínas de Ligação a RNA/metabolismoRESUMO
The large number of RNA-binding proteins and translation factors encoded in the Drosophila and other metazoan genomes predicts widespread use of post-transcriptional regulation in cellular and developmental processes. Previous studies identified roles for several RNA-binding proteins in dendrite branching morphogenesis of Drosophila larval sensory neurons. To determine the larger contribution of post-transcriptional gene regulation to neuronal morphogenesis, we conducted an RNA interference screen to identify additional Drosophila proteins annotated as either RNA-binding proteins or translation factors that function in producing the complex dendritic trees of larval class IV dendritic arborization neurons. We identified 88 genes encoding such proteins whose knockdown resulted in aberrant dendritic morphology, including alterations in dendritic branch number, branch length, field size, and patterning of the dendritic tree. In particular, splicing and translation initiation factors were associated with distinct and characteristic phenotypes, suggesting that different morphogenetic events are best controlled at specific steps in post-transcriptional messenger RNA metabolism. Many of the factors identified in the screen have been implicated in controlling the subcellular distributions and translation of maternal messenger RNAs; thus, common post-transcriptional regulatory strategies may be used in neurogenesis and in the generation of asymmetry in the female germline and embryo.