RESUMO
The Polycomb group (PcG) protein Bmi1 is an essential epigenetic regulator of stem cell function during normal development and in adult organ systems. We show that mild up-regulation of Bmi1 expression in the adult stem cells of the skeletal muscle leads to a remarkable improvement of muscle function in a mouse model of Duchenne muscular dystrophy. The molecular mechanism underlying enhanced physiological function of Bmi1 depends on the injury context and it is mediated by metallothionein 1 (MT1)-driven modulation of resistance to oxidative stress in the satellite cell population. These results lay the basis for developing Bmi1 pharmacological activators, which either alone or in combination with MT1 agonists could be a powerful novel therapeutic approach to improve regeneration in muscle wasting conditions.
Assuntos
Degeneração Macular/patologia , Degeneração Macular/fisiopatologia , Metalotioneína/metabolismo , Músculo Esquelético/fisiopatologia , Estresse Oxidativo , Complexo Repressor Polycomb 1/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Regeneração , Animais , Diferenciação Celular , Doença Crônica , Dano ao DNA , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Humanos , Degeneração Macular/genética , Camundongos Endogâmicos mdx , Camundongos Transgênicos , Desenvolvimento Muscular , Força Muscular , Músculo Esquelético/lesões , Músculo Esquelético/patologia , Fator de Transcrição PAX7/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Reprodutibilidade dos Testes , Células Satélites de Músculo Esquelético/patologia , Biologia de SistemasRESUMO
Skeletal muscle regeneration mainly depends on satellite cells, a population of resident muscle stem cells. However, our understanding of the molecular mechanisms underlying satellite cell activation is still largely undefined. Here, we show that Cripto, a regulator of early embryogenesis, is a novel regulator of muscle regeneration and satellite cell progression toward the myogenic lineage. Conditional inactivation of cripto in adult satellite cells compromises skeletal muscle regeneration, whereas gain of function of Cripto accelerates regeneration, leading to muscle hypertrophy. Moreover, we provide evidence that Cripto modulates myogenic cell determination and promotes proliferation by antagonizing the TGF-ß ligand myostatin. Our data provide unique insights into the molecular and cellular basis of Cripto activity in skeletal muscle regeneration and raise previously undescribed implications for stem cell biology and regenerative medicine.
Assuntos
Linhagem da Célula , Fator de Crescimento Epidérmico/metabolismo , Glicoproteínas de Membrana/metabolismo , Músculo Esquelético/fisiologia , Miostatina/antagonistas & inibidores , Proteínas de Neoplasias/metabolismo , Regeneração , Células Satélites de Músculo Esquelético/metabolismo , Células Satélites de Músculo Esquelético/patologia , Envelhecimento/metabolismo , Animais , Proliferação de Células , Deleção de Genes , Marcação de Genes , Hipertrofia , Camundongos , Camundongos Endogâmicos C57BL , Modelos Animais , Desenvolvimento Muscular , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Mioblastos/metabolismo , Mioblastos/patologia , Miostatina/metabolismo , Transdução de SinaisRESUMO
BACKGROUND: The Notch signaling pathway regulates a diverse array of developmental processes, and aberrant Notch signaling can lead to diseases, including cancer. To obtain a more comprehensive understanding of the genetic network that integrates into Notch signaling, we performed a genome-wide RNAi screen in Drosophila cell culture to identify genes that modify Notch-dependent transcription. RESULTS: Employing complementary data analyses, we found 399 putative modifiers: 189 promoting and 210 antagonizing Notch activated transcription. These modifiers included several known Notch interactors, validating the robustness of the assay. Many novel modifiers were also identified, covering a range of cellular localizations from the extracellular matrix to the nucleus, as well as a large number of proteins with unknown function. Chromatin-modifying proteins represent a major class of genes identified, including histone deacetylase and demethylase complex components and other chromatin modifying, remodeling and replacement factors. A protein-protein interaction map of the Notch-dependent transcription modifiers revealed that a large number of the identified proteins interact physically with these core chromatin components. CONCLUSIONS: The genome-wide RNAi screen identified many genes that can modulate Notch transcriptional output. A protein interaction map of the identified genes highlighted a network of chromatin-modifying enzymes and remodelers that regulate Notch transcription. Our results open new avenues to explore the mechanisms of Notch signal regulation and the integration of this pathway into diverse cellular processes.
Assuntos
Genoma , Interferência de RNA , Receptores Notch/metabolismo , Transdução de Sinais/genética , Transcrição Gênica , Animais , Linhagem Celular , Cromatina/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Epistasia Genética , Mutação , Mapeamento de Interação de Proteínas , Receptores Notch/genética , Ribossomos/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
The Notch signalling pathway plays a crucial role in specifying cellular fates in metazoan development by regulating communication between adjacent cells. Correlative studies suggested an involvement of Notch in intestinal development. Here, by modulating Notch activity in the mouse intestine, we directly implicate Notch signals in intestinal cell lineage specification. We also show that Notch activation is capable of amplifying the intestinal progenitor pool while inhibiting cell differentiation. We conclude that Notch activity is required for the maintenance of proliferating crypt cells in the intestinal epithelium.