RESUMEN
The full set of microRNAs (miRNAs) in the human genome is not known. Because presently known miRNAs have been identified by virtue of their abundant expression in a few cell types, many tissue-specific miRNAs remain unrevealed. To understand the role of miRNAs in B cell function and lymphomagenesis, we generated short-RNA libraries from normal human B cells at different stages of development (naive, germinal center, memory) and from a Burkitt lymphoma cell line. A combination of cloning and computational analysis identified 178 miRNAs (miRNome) expressed in normal and/or transformed B cell libraries. Most notably, the B cell miRNome included 75 miRNAs which to our knowledge have not been previously reported and of which 66 have been validated by RNA blot and/or RT-PCR analyses. Numerous miRNAs were expressed in a stage- or transformation-specific fashion in B cells, suggesting specific functional or pathologic roles. These results provide a resource for studying the role of miRNAs in B cell development, immune function, and lymphomagenesis.
Asunto(s)
Subgrupos de Linfocitos B/inmunología , MicroARNs/fisiología , Animales , Línea Celular Tumoral , Perros , Evolución Molecular , Regulación de la Expresión Génica , Haplorrinos , Humanos , Ratones , MicroARNs/análisis , MicroARNs/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , Tonsila Palatina/metabolismo , RatasRESUMEN
A balance between quiescence and proliferation is critical for proper maintenance of the hematopoietic stem cell (HSC) pool. Although a lot is known about hematopoiesis, molecular mechanisms that control HSC quiescence remain largely unknown. The ubiquitin-editing enzyme A20 functions as a central regulator of inflammation and adaptive immunity. Here, we show that a deficiency of A20 in the hematopoietic system causes anemia, lymphopenia, and postnatal lethality. Lack of A20 in HSCs results in diminished pool size, impaired radioprotection, defective repopulation, and loss of quiescence. A20-deficient HSCs display increased IFN-γ signaling, caused by augmented NF-κB activation. Strikingly, deletion of both IFN-γ and A20 in hematopoietic cells results in partial rescue of the HSC phenotype. We anticipate that our experiments will facilitate the understanding of mechanisms through which A20-mediated inflammatory signals control HSC quiescence and functions.
Asunto(s)
Ciclo Celular/genética , Cisteína Endopeptidasas/deficiencia , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Péptidos y Proteínas de Señalización Intracelular/deficiencia , Ubiquitinación/genética , Animales , Cisteína Endopeptidasas/genética , Femenino , Genes Letales , Estudios de Asociación Genética , Hematopoyesis/genética , Interferón gamma/genética , Interferón gamma/metabolismo , Péptidos y Proteínas de Señalización Intracelular/genética , Ratones , Ratones Noqueados , Mutación , FN-kappa B/metabolismo , Fenotipo , Transducción de Señal , Proteína 3 Inducida por el Factor de Necrosis Tumoral alfaRESUMEN
Autophagy is a major cellular process for bulk degradation of proteins and organelles in order to maintain metabolic homeostasis, and it represents an emerging target area for cancer. Initially proposed to be a cancer-restricting process for tumor initiation, recent studies suggest that autophagy can also promote cell survival in established tumors. ATG7 is an essential autophagy gene that encodes the E1 enzyme necessary for the lipidation of the LC3 family of ubiquitin-like proteins and autophagosome formation. In this study we identified a rare case of a cancer cell line, H1650 lung adenocarcinoma, which has lost ATG7 expression due to a focal biallelic deletion within the ATG7 locus. These cells displayed no evidence of ATG7 pathway activity; however, reconstituting the cells with wild-type ATG7 restored both LC3 lipidation and downstream autophagic consumption of autophagy substrates such as the SQSTM1/p62 protein. We characterized several phenotypes reported to be influenced by autophagy, and observed an ATG7-dependent increase in cell growth and clearance of proteasome-inhibitor induced protein aggregates. Cellular changes in mitochondrial metabolism or response to nutrient starvation were unaffected by ATG7 expression. In addition, parental H1650 cells that lacked ATG7 were still able to consume autophagy substrates SQSTM1, NBR1 and TAX1BP1 via a bafilomycin A1-sensitive pathway, suggesting that these proteins were not exclusively degraded by autophagy. Overall, these findings highlight a unique outlier instance of complete loss of ATG7-dependent autophagy in a cancer cell line. The H1650 cell line may be a useful system for future studies to further understand the role of autophagy in tumorigenesis and potential redundant pathways that allow cells to circumvent the loss of ATG7-dependent autophagy in cancer.
RESUMEN
Subsets of rodent neurons are reported to express major histocompatibility complex class I (MHC-I), but such expression has not been reported in normal adult human neurons. Here we provide evidence from immunolabel, RNA expression and mass spectrometry analysis of postmortem samples that human catecholaminergic substantia nigra and locus coeruleus neurons express MHC-I, and that this molecule is inducible in human stem cell-derived dopamine (DA) neurons. Catecholamine murine cultured neurons are more responsive to induction of MHC-I by gamma-interferon than other neuronal populations. Neuronal MHC-I is also induced by factors released from microglia activated by neuromelanin or alpha-synuclein, or high cytosolic DA and/or oxidative stress. DA neurons internalize foreign ovalbumin and display antigen derived from this protein by MHC-I, which triggers DA neuronal death in the presence of appropriate cytotoxic T cells. Thus, neuronal MHC-I can trigger antigenic response, and catecholamine neurons may be particularly susceptible to T-cell-mediated cytotoxic attack.
Asunto(s)
Neuronas Adrenérgicas/metabolismo , Neuronas Dopaminérgicas/metabolismo , Genes MHC Clase I , Antígenos de Histocompatibilidad Clase I/genética , Locus Coeruleus/metabolismo , Microglía/metabolismo , ARN Mensajero/metabolismo , Sustancia Negra/metabolismo , Neuronas Adrenérgicas/efectos de los fármacos , Anciano , Anciano de 80 o más Años , Animales , Supervivencia Celular , Dopamina/metabolismo , Neuronas Dopaminérgicas/efectos de los fármacos , Femenino , Perfilación de la Expresión Génica , Antígenos de Histocompatibilidad Clase I/efectos de los fármacos , Antígenos de Histocompatibilidad Clase I/metabolismo , Humanos , Interferón gamma/farmacología , Masculino , Melaninas/metabolismo , Ratones , Persona de Mediana Edad , Estrés Oxidativo , Enfermedad de Parkinson/genética , Enfermedad de Parkinson/metabolismo , ARN Mensajero/efectos de los fármacos , Linfocitos T Citotóxicos , alfa-Sinucleína/metabolismoRESUMEN
Diffuse large B cell lymphoma (DLBCL) is a heterogeneous disease composed of at least two distinct subtypes: germinal center B cell-like (GCB) and activated B cell-like (ABC) DLBCL. These phenotypic subtypes segregate with largely unique genetic lesions, suggesting the involvement of different pathogenetic mechanisms. In this report we show that the BLIMP1/PRDM1 gene is inactivated by multiple mechanisms, including homozygous deletions, truncating or missense mutations, and transcriptional repression by constitutively active BCL6, in â¼53% of ABC-DLBCL. In vivo, conditional deletion of Blimp1 in mouse B cells promotes the development of lymphoproliferative disorders recapitulating critical features of the human ABC-DLBCL. These results demonstrate that BLIMP1 is a bona fide tumor-suppressor gene whose loss contributes to lymphomagenesis by blocking plasma cell differentiation.
Asunto(s)
Genes Supresores de Tumor , Linfoma de Células B Grandes Difuso/genética , Factores de Transcripción/genética , Animales , Proteínas de Unión al ADN/metabolismo , Epigénesis Genética , Humanos , Linfoma de Células B Grandes Difuso/etiología , Ratones , Ratones Endogámicos C57BL , Mutación Missense , Factor 1 de Unión al Dominio 1 de Regulación Positiva , Proteínas Proto-Oncogénicas c-bcl-6RESUMEN
S1P(2) sphingosine 1-phosphate receptor signaling can regulate proliferation, survival, morphology, and migration in many cell types in vitro. Here, we report that S1P(2)(-/-) mice develop clonal B-cell lymphomas with age, such that approximately half of the animals display this neoplasm by 1.5 to 2 years of age. Histologic, immunophenotypic, and molecular analyses revealed a uniform tumor phenotype with features of germinal center (GC)-derived diffuse large B-cell lymphoma (DLBCL). Tumor formation was preceded by increases in GC B cells and CD69(+) T cells, as well as an increased formation of spontaneous GCs, suggesting that S1P(2) loss may promote lymphomagenesis in part by disrupting GC B-cells homeostasis. With the sole exception of rare lung tumors, the effect of S1P(2) gene disruption is remarkably restricted to DLBCL. In humans, 28 of 106 (26%) DLBCL samples were found to harbor multiple somatic mutations in the 5' sequences of the S1P(2) gene. Mutations displayed features resembling those generated by the IgV-associated somatic hypermutation mechanism, but were not detected at significant levels in normal GC B cells, indicating a tumor-associated aberrant function. Collectively, our data suggest that S1P(2) signaling may play a critical role in suppressing DLBCL formation in vivo. The high incidence of DLBCL in S1P(2)(-/-) mice, its onset at old age, and the relative lack of other neoplasms identify these mice as a novel, and potentially valuable, model for this highly prevalent and aggressive human malignancy.