RESUMO
The smooth and precise transition from totipotency to pluripotency is a key process in embryonic development, generating pluripotent stem cells capable of forming all cell types. While endogenous retroviruses (ERVs) are essential for early development, their precise roles in this transition remains mysterious. Using cutting-edge genetic and biochemical techniques in mice, we identify MERVL-gag, a retroviral protein, as a crucial modulator of pluripotent factors OCT4 and SOX2 during lineage specification. MERVL-gag tightly operates with URI, a prefoldin protein that concurs with pluripotency bias in mouse blastomeres, and which is indeed required for totipotency-to-pluripotency transition. Accordingly, URI loss promotes a stable totipotent-like state and embryo arrest at 2C stage. Mechanistically, URI binds and shields OCT4 and SOX2 from proteasome degradation, while MERVL-gag displaces URI from pluripotent factor interaction, causing their degradation. Our findings reveal the symbiotic coevolution of ERVs with their host cells to ensure the smooth and timely progression of early embryo development.
Assuntos
Retrovirus Endógenos , Células-Tronco Pluripotentes , Feminino , Gravidez , Animais , Camundongos , Retrovirus Endógenos/genética , Embrião de Mamíferos , Desenvolvimento Embrionário/genéticaRESUMO
The biological purpose of long non-coding RNAs (lncRNAs) is poorly understood. Haploinsufficient mutations in HNF1A homeobox A (HNF1A), encoding a homeodomain transcription factor, cause diabetes mellitus. Here, we examine HASTER, the promoter of an lncRNA antisense to HNF1A. Using mouse and human models, we show that HASTER maintains cell-specific physiological HNF1A concentrations through positive and negative feedback loops. Pancreatic ß cells from Haster mutant mice consequently showed variegated HNF1A silencing or overexpression, resulting in hyperglycaemia. HASTER-dependent negative feedback was essential to prevent HNF1A binding to inappropriate genomic regions. We demonstrate that the HASTER promoter DNA, rather than the lncRNA, modulates HNF1A promoter-enhancer interactions in cis and thereby regulates HNF1A transcription. Our studies expose a cis-regulatory element that is unlike classic enhancers or silencers, it stabilizes the transcription of its target gene and ensures the fidelity of a cell-specific transcription factor program. They also show that disruption of a mammalian lncRNA promoter can cause diabetes mellitus.
Assuntos
Fator 1-alfa Nuclear de Hepatócito , Regiões Promotoras Genéticas , RNA Longo não Codificante , Animais , Humanos , Camundongos , Fator 1-alfa Nuclear de Hepatócito/genética , Mamíferos , RNA Longo não Codificante/genética , Transcrição Gênica/genética , Transcrição Gênica/fisiologiaRESUMO
By whole exome sequencing, we recently identified a missense mutation (p.R703C) in the human ATP4a gene, which encodes the proton pump responsible for gastric acidification. This mutation causes an aggressive familial type I gastric neuroendocrine tumor in homozygous individuals. Affected individuals show an early onset of the disease, characterized by gastric hypoacidity, hypergastrinemia, iron-deficiency anemia, gastric intestinal metaplasia and, in one case, an associated gastric adenocarcinoma. Total gastrectomy was performed as the definitive treatment in all affected individuals. We now describe the generation and characterization of a knockin mouse model for the ATP4a(R703C) mutation to better understand the tumorigenesis process. Homozygous mice recapitulated most of the phenotypical alterations that were observed in human individuals, strongly suggesting that this mutation is the primary alteration responsible for disease development. Homozygous mice developed premalignant condition with severe hyperplasia, dysplasia and glandular metaplasia in the stomach. Interestingly, gastric acidification in homozygous mice, induced by treatment with 3% HCl acid in the drinking water, prevented (if treated from birth) or partially reverted (if treated during adulthood) the development of glandular metaplasia and dysplasia in the stomach and partially rescued the abnormal biochemical parameters. We therefore suggest that, in this model, achlorhydria contributes to tumorigenesis to a greater extent than hypergastrinemia. Furthermore, our mouse model represents a unique and novel tool for studying the pathologies associated with disturbances in gastric acid secretion.
Assuntos
Técnicas de Introdução de Genes , ATPase Trocadora de Hidrogênio-Potássio/genética , Mutação/genética , Tumores Neuroendócrinos/genética , Tumores Neuroendócrinos/terapia , Neoplasias Gástricas/genética , Neoplasias Gástricas/terapia , Anemia/sangue , Anemia/complicações , Anemia/patologia , Animais , Modelos Animais de Doenças , Ácido Gástrico/metabolismo , Gastrinas/sangue , Homozigoto , Humanos , Ácido Clorídrico/farmacologia , Hiperplasia , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Tumores Neuroendócrinos/sangue , Tumores Neuroendócrinos/prevenção & controle , Fenótipo , Estômago/patologia , Neoplasias Gástricas/sangue , Neoplasias Gástricas/prevenção & controleRESUMO
Genetic diseases associated with defects in primary cilia are classified as ciliopathies. Pancreatic lesions and ductal cysts are found in patients with ciliopathic polycystic kidney diseases suggesting a close connection between pancreatic defects and primary cilia. Here we investigate the role of two genes whose deletion is known to cause primary cilium defects, namely Hnf6 and Lkb1, in pancreatic ductal homeostasis. We find that mice with postnatal duct-specific deletion of Hnf6 or Lkb1 show duct dilations. Cells lining dilated ducts present shorter cilia with swollen tips, suggesting defective intraciliary transport. This is associated with signs of chronic pancreatitis, namely acinar-to-ductal metaplasia, acinar proliferation and apoptosis, presence of inflammatory infiltrates, fibrosis and lipomatosis. Our data reveal a tight association between ductal ciliary defects and pancreatitis with perturbed acinar homeostasis and differentiation. Such injuries can account for the increased risk to develop pancreatic cancer in Peutz-Jeghers patients who carry LKB1 loss-of-function mutations.
Assuntos
Cílios/patologia , Fator 6 Nuclear de Hepatócito/metabolismo , Pancreatite Crônica/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Quinases Ativadas por AMP , Animais , Apoptose/fisiologia , Diferenciação Celular , Cílios/genética , Células Epiteliais/patologia , Fator 6 Nuclear de Hepatócito/genética , Lipomatose/genética , Lipomatose/metabolismo , Metaplasia/genética , Metaplasia/metabolismo , Camundongos , Pâncreas/patologia , Ductos Pancreáticos/metabolismo , Neoplasias Pancreáticas/genética , Pancreatite Crônica/genética , Proteínas Serina-Treonina Quinases/genéticaRESUMO
Polycomb proteins are known to be of great importance in human cancer pathogenesis. SUZ12 is a component of the Polycomb PRC2 complex that, along with EZH2, is involved in embryonic stem cell differentiation. EZH2 plays an essential role in many cancer types, but an equivalent involvement of SUZ12 has not been as thoroughly demonstrated. Here we show that SUZ12 is anomalously expressed in human primary tumors, especially in mantle cell lymphoma (MCL), pulmonary carcinomas and melanoma, and is associated with gene locus amplification in some cases. Using MCL as a model, functional and genomic studies demonstrate that SUZ12 loss compromises cell viability, increases apoptosis, and targets genes involved in central oncogenic pathways associated with MCL pathogenesis. Our results support the hypothesis that the abnormal expression of SUZ12 accounts for some of the unexplained features of MCL, such as abnormal DNA repair and increased resistance to apoptosis.
Assuntos
Proteínas de Transporte , Regulação Neoplásica da Expressão Gênica , Linfoma de Célula do Manto , Proteínas Nucleares , Apoptose , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Diferenciação Celular/genética , Linhagem Celular , Reparo do DNA , Perfilação da Expressão Gênica , Humanos , Linfoma de Célula do Manto/genética , Linfoma de Célula do Manto/metabolismo , Proteínas de Neoplasias , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Complexo Repressor Polycomb 2 , Fatores de TranscriçãoRESUMO
The Ras homolog enriched in striatum, Rhes, is the product of a thyroid hormone-regulated gene during brain development. Rhes and the dexamethasone-induced Dexras1 define a novel distinct subfamily of proteins within the Ras family, characterized by an extended variable domain in the carboxyl terminal region. We have carried this study because there is a complete lack of knowledge on Rhes signaling. We show that in PC12 cells, Rhes is targeted to the plasma membrane by farnesylation. We demonstrate that about 30% of the native Rhes protein is bound to GTP and this proportion is unaltered by typical Ras family nucleotide exchange factors. However, Rhes is not transforming in murine fibroblasts. We have also examined the role of Rhes in cell signaling. Rhes does not stimulate the ERK pathway. By contrast, it binds to and activates PI3K. On the other hand, we demonstrate that Rhes impairs the activation of the cAMP/PKA pathway by thyroid-stimulating hormone, and by an activated beta2 adrenergic receptor by a mechanism that suggests uncoupling of the receptor to its cognate heterotrimeric complex. Overall, our results provide the initial insights into the role in signal transduction of this novel Ras family member.