RESUMO
c-Myc and phosphatidylinositol 3-OH kinase (PI3K) both participate in diverse cellular processes, including cell cycle control and tumorigenic transformation. They also contribute to preserving embryonic stem cell (ESC) characteristics. However, in spite of the vast knowledge, the molecular relationship between c-Myc and PI3K in ESCs is not known. Herein, we demonstrate that c-Myc and PI3K function cooperatively but independently to support ESC self-renewal when murine ESCs are cultured under conventional culture condition. Interestingly, culture of ESCs in 2i-condition including a GSK3ß and MEK inhibitor renders both PI3K and Myc signaling dispensable for the maintenance of pluripotent properties. These results suggest that the requirement for an oncogenic proliferation-dependent mechanism sustained by Myc and PI3K is context dependent and that the 2i-condition liberates ESCs from the dependence of this mechanism.
Assuntos
Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Animais , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/biossíntese , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Diferenciação Celular/fisiologia , Proliferação de Células/fisiologia , Sistema de Sinalização das MAP Quinases , Camundongos , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Fator 2 Relacionado a NF-E2/biossíntese , Fator 2 Relacionado a NF-E2/genética , Fosfatidilinositol 3-Quinases/genética , Inibidores de Fosfoinositídeo-3 Quinase , Células-Tronco Pluripotentes/citologia , Células-Tronco Pluripotentes/metabolismo , Proteínas Proto-Oncogênicas c-myc/genéticaRESUMO
c-Myc participates in diverse cellular processes including cell cycle control, tumorigenic transformation, and reprogramming of somatic cells to induced pluripotent cells. c-Myc is also an important regulator of self-renewal and pluripotency of embryonic stem cells (ESCs). We recently demonstrated that loss of the Max gene, encoding the best characterized partner for all Myc family proteins, causes loss of the pluripotent state and extensive cell death in ESCs strictly in this order. However, the mechanisms and molecules that are responsible for these phenotypes remain largely obscure. Here, we show that Sirt1, p53, and p38(MAPK) are crucially involved in the detrimental phenotype of Max-null ESCs. Moreover, our analyses revealed that these proteins are involved at varying levels to one another in the hierarchy of the pathway leading to cell death in Max-null ESCs.
Assuntos
Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/biossíntese , Células-Tronco Embrionárias/citologia , Células-Tronco Embrionárias/metabolismo , Células-Tronco Pluripotentes/citologia , Células-Tronco Pluripotentes/metabolismo , Sirtuína 1/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Antioxidantes/farmacologia , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Morte Celular/fisiologia , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Doxiciclina/farmacologia , Células-Tronco Embrionárias/efeitos dos fármacos , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Fenótipo , Células-Tronco Pluripotentes/efeitos dos fármacos , Inibidores de Proteínas Quinases/farmacologia , Sirtuína 1/antagonistas & inibidores , Sirtuína 1/genética , Transfecção , Proteína Supressora de Tumor p53/genética , Proteínas Quinases p38 Ativadas por Mitógeno/antagonistas & inibidores , Proteínas Quinases p38 Ativadas por Mitógeno/genéticaRESUMO
It is widely believed that cellular senescence plays a critical role in both aging and cancer, and that senescence is a fundamental, permanent growth arrest that somatic cells cannot avoid. Here we show that Myc plays an important role in self-renewal of esophageal epithelial cells, contributing to their resistance to cellular senescence. Myc is homogeneously expressed in basal cells of the esophageal epithelium and Myc positively regulates their self-renewal by maintaining their undifferentiated state. Indeed, Myc knockout induced a loss of the undifferentiated state of esophageal epithelial cells resulting in cellular senescence while forced MYC expression promoted oncogenic cell proliferation. A superoxide scavenger counteracted Myc knockout-induced senescence, therefore suggesting that a mitochondrial superoxide takes part in inducing senescence. Taken together, these analyses reveal extremely low levels of cellular senescence and senescence-associated phenotypes in the esophageal epithelium, as well as a critical role for Myc in self-renewal of basal cells in this organ. This provides new avenues for studying and understanding the links between stemness and resistance to cellular senescence.
RESUMO
Mammals have limited regenerative capacity, whereas some vertebrates, like fish and salamanders, are able to regenerate their organs efficiently. The regeneration in these species depends on cell dedifferentiation followed by proliferation. We generate a mouse model that enables the inducible expression of the four Yamanaka factors (Oct-3/4, Sox2, Klf4, and c-Myc, or 4F) specifically in hepatocytes. Transient in vivo 4F expression induces partial reprogramming of adult hepatocytes to a progenitor state and concomitantly increases cell proliferation. This is indicated by reduced expression of differentiated hepatic-lineage markers, an increase in markers of proliferation and chromatin modifiers, global changes in DNA accessibility, and an acquisition of liver stem and progenitor cell markers. Functionally, short-term expression of 4F enhances liver regenerative capacity through topoisomerase2-mediated partial reprogramming. Our results reveal that liver-specific 4F expression in vivo induces cellular plasticity and counteracts liver failure, suggesting that partial reprogramming may represent an avenue for enhancing tissue regeneration.
Assuntos
Reprogramação Celular , Fígado , Animais , Desdiferenciação Celular , Hepatócitos/metabolismo , Fígado/metabolismo , Regeneração Hepática , Mamíferos , CamundongosRESUMO
To clarify the molecular mechanism of adipocyte differentiation, we previously isolated a novel gene, factor for adipocyte differentiation (fad) 158, whose expression was induced during the earliest stages of adipogenesis, and its product was localized to the endoplasmic reticulum. We found that the knockdown of fad158 expression prevented the differentiation of 3T3-L1 cells into adipocytes. In addition, over-expression of fad158 promoted the differentiation of NIH-3T3 cells, which do not usually differentiate into adipocytes. Although these findings strongly suggest that fad158 has a crucial role in regulating adipocyte differentiation, the physiological role of the gene is still unclear. In this study, we generated mice in which fad158 expression was deleted. The fad158-deficient mice did not show remarkable changes in body weight or the weight of white adipose tissue on a chow diet, but had significantly lower body weights and fat mass than wild-type mice when fed a high-fat diet. Furthermore, although the disruption of fad158 did not influence insulin sensitivity on the chow diet, it improved insulin resistance induced by the high-fat diet. These results indicate that fad158 is a key factor in the development of obesity and insulin resistance caused by a high-fat diet.
Assuntos
Adipócitos/citologia , Adipogenia/genética , Tecido Adiposo Branco/metabolismo , Gorduras na Dieta/efeitos adversos , Resistência à Insulina/genética , Proteínas de Membrana/genética , Obesidade/genética , Aumento de Peso/genética , Células 3T3-L1 , Animais , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/metabolismoRESUMO
Identification of the precise molecular pathways involved in oncogene-induced transformation may help us gain a better understanding of tumor initiation and promotion. Here, we demonstrate that SOX2+ foregut epithelial cells are prone to oncogenic transformation upon mutagenic insults, such as KrasG12D and p53 deletion. GFP-based lineage-tracing experiments indicate that SOX2+ cells are the cells-of-origin of esophagus and stomach hyperplasia. Our observations indicate distinct roles for oncogenic KRAS mutation and P53 deletion. p53 homozygous deletion is required for the acquisition of an invasive potential, and KrasG12D expression, but not p53 deletion, suffices for tumor formation. Global gene expression analysis reveals secreting factors upregulated in the hyperplasia induced by oncogenic KRAS and highlights a crucial role for the CXCR2 pathway in driving hyperplasia. Collectively, the array of genetic models presented here demonstrate that stratified epithelial cells are susceptible to oncogenic insults, which may lead to a better understanding of tumor initiation and aid in the design of new cancer therapeutics.
Assuntos
Neoplasias Esofágicas/metabolismo , Mutação , Receptores de Interleucina-8B/metabolismo , Fatores de Transcrição SOXB1/metabolismo , Animais , Proliferação de Células , Neoplasias Esofágicas/patologia , Feminino , Masculino , Camundongos , Camundongos Mutantes , Transdução de Sinais , Células Tumorais CultivadasRESUMO
Embryonic stem cells (ESCs) can self-renew indefinitely under the governance of ESC-specific transcriptional circuitries in which each transcriptional factor regulates distinct or overlapping sets of genes with other factors. c-Myc is a key player that is crucially involved in maintaining the undifferentiated state and the self-renewal of ESCs. However, the mechanism by which c-Myc helps preserve the ESC status is still poorly understood. Here we addressed this question by performing loss-of-function studies with the Max gene, which encodes the best-characterized partner protein for all Myc family proteins. Although Myc/Max complexes are widely regarded as crucial regulators of the ESC status, our data revealed that ESCs do not absolutely require these complexes in certain contexts and that this requirement is restricted to empirical ESC culture conditions without a MAPK inhibitor.