RESUMEN
VASA is an evolutionarily conserved RNA helicase essential for germ cell development. The mouse PIWI family proteins MILI and MIWI2 are involved in production of Piwi-interacting RNAs (piRNAs) in fetal male germ cells through a ping-pong amplification cycle. Expression of retrotransposons is elevated in MILI- and MIWI2-deficient male germ cells due to defective de novo DNA methylation, which is presumably caused by impaired piRNA expression. Here, we report that essentially the same abnormalities are observed in MVH (mouse VASA homolog)-deficient mice. Comprehensive analysis of piRNAs in MVH-deficient fetal male germ cells showed that MVH plays crucial roles in the early phase of the ping-pong amplification cycle.
Asunto(s)
ARN Helicasas DEAD-box/genética , ARN Helicasas DEAD-box/metabolismo , Silenciador del Gen , Genes de Partícula A Intracisternal/genética , Elementos de Nucleótido Esparcido Largo/genética , ARN Interferente Pequeño/metabolismo , Animales , Proteínas Argonautas , Metilación de ADN , Regulación de la Expresión Génica , Masculino , Ratones , Ratones Noqueados , Transporte de Proteínas , Proteínas/metabolismo , ARN Interferente Pequeño/genética , Espermatogénesis/fisiología , Testículo/metabolismoRESUMEN
INTRODUCTION: Mutations in H3F3A, which encodes histone H3.3, commonly occur in pediatric glioblastoma. Additionally, H3F3A K27M substitutions occur in gliomas that arise at midline locations (eg, pons, thalamus, spine); moreover, this substitution occurs mainly in tumors in children and adolescents. Here, we sought to determine the association between H3F3A mutations and adult thalamic glioma. METHODS: Genomic H3F3A was sequenced from 20 separate thalamic gliomas. Additionally, for 14 of the 20 gliomas, 639 genes--including cancer-related genes and chromatin-modifier genes--were sequenced, and the Infinium HumanMethylation450K BeadChip was used to examine DNA methylation across the genome. RESULTS: Of the 20 tumors, 18 were high-grade thalamic gliomas, and of these 18, 11 were from patients under 50 years of age (median age, 38 y; range, 17-46), and 7 were from patients over 50 years of age. The H3F3A K27M mutation was present in 10 of the 11 (91%) younger patients and absent from all 7 older patients. Additionally, H3F3A K27M was not detected in the 2 diffuse astrocytomas. Further sequencing revealed recurrent mutations in TP53, ATRX, NF1, and EGFR. Gliomas with H3F3A K27M from pediatric or young adult patients had similar, characteristic DNA methylation profiles. In contrast, thalamic gliomas with wild-type H3F3A had DNA methylation profiles similar to those of hemispheric glioblastomas. CONCLUSION: We found that high-grade thalamic gliomas from young adults, like those from children and adolescents, frequently had H3F3A K27M.
Asunto(s)
Biomarcadores de Tumor/genética , Neoplasias Encefálicas/genética , Glioma/genética , Histonas/genética , Mutación/genética , Enfermedades Talámicas/genética , Adolescente , Adulto , Anciano , Neoplasias Encefálicas/mortalidad , Neoplasias Encefálicas/patología , Metilación de ADN , Femenino , Estudios de Seguimiento , Glioma/mortalidad , Glioma/patología , Humanos , Masculino , Persona de Mediana Edad , Clasificación del Tumor , Pronóstico , Tasa de Supervivencia , Enfermedades Talámicas/mortalidad , Enfermedades Talámicas/patología , Adulto JovenRESUMEN
Diffuse-type gastric carcinoma (DGC) is characterized by a highly malignant phenotype with prominent infiltration and stromal induction. We performed whole-exome sequencing on 30 DGC cases and found recurrent RHOA nonsynonymous mutations. With validation sequencing of an additional 57 cases, RHOA mutation was observed in 25.3% (22/87) of DGCs, with mutational hotspots affecting the Tyr42, Arg5 and Gly17 residues in RHOA protein. These positions are highly conserved among RHO family members, and Tyr42 and Arg5 are located outside the guanine nucleotide-binding pocket. Several lines of functional evidence indicated that mutant RHOA works in a gain-of-function manner. Comparison of mutational profiles for the major gastric cancer subtypes showed that RHOA mutations occur specifically in DGCs, the majority of which were histopathologically characterized by the presence of poorly differentiated adenocarcinomas together with more differentiated components in the gastric mucosa. Our findings identify a potential therapeutic target for this poor-prognosis subtype of gastric cancer with no available molecularly targeted drugs.
Asunto(s)
Carcinoma/genética , Mutación , Neoplasias Gástricas/genética , Proteína de Unión al GTP rhoA/genética , Adenocarcinoma/genética , Secuencia de Aminoácidos , Diferenciación Celular , Análisis Mutacional de ADN , Mucosa Gástrica/patología , Biblioteca de Genes , Mutación de Línea Germinal , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Fenotipo , Pronóstico , ARN Interferente Pequeño/metabolismo , Homología de Secuencia de Aminoácido , Células del Estroma/metabolismoRESUMEN
Diverse epidemiological factors are associated with hepatocellular carcinoma (HCC) prevalence in different populations. However, the global landscape of the genetic changes in HCC genomes underpinning different epidemiological and ancestral backgrounds still remains uncharted. Here a collection of data from 503 liver cancer genomes from different populations uncovered 30 candidate driver genes and 11 core pathway modules. Furthermore, a collaboration of two large-scale cancer genome projects comparatively analyzed the trans-ancestry substitution signatures in 608 liver cancer cases and identified unique mutational signatures that predominantly contribute to Asian cases. This work elucidates previously unexplored ancestry-associated mutational processes in HCC development. A combination of hotspot TERT promoter mutation, TERT focal amplification and viral genome integration occurs in more than 68% of cases, implicating TERT as a central and ancestry-independent node of hepatocarcinogenesis. Newly identified alterations in genes encoding metabolic enzymes, chromatin remodelers and a high proportion of mTOR pathway activations offer potential therapeutic and diagnostic opportunities.
Asunto(s)
Carcinoma Hepatocelular/etnología , Carcinoma Hepatocelular/genética , Genoma Humano , Neoplasias Hepáticas/etnología , Neoplasias Hepáticas/genética , Mutación , Algoritmos , Pueblo Asiatico , Carcinoma Hepatocelular/epidemiología , Islas de CpG , Análisis Mutacional de ADN , Exoma , Regulación Neoplásica de la Expresión Génica , Genoma Viral , Hepacivirus/genética , Virus de la Hepatitis B/genética , Humanos , Japón , Neoplasias Hepáticas/epidemiología , Modelos Estadísticos , Análisis de Componente Principal , Serina-Treonina Quinasas TOR/genética , Telomerasa/genética , Estados Unidos , Población BlancaRESUMEN
Cancers of the colon and rectum, which rank among the most frequent human tumors, are currently treated by surgical resection in locally restricted tumor stages. However, disease recurrence and formation of local and distant metastasis frequently occur even in cases with successful curative resection of the primary tumor (R0). Recent technological advances in molecular diagnostic analysis have led to a wealth of knowledge about the changes in gene transcription in all stages of colorectal tumors. Differential gene expression, or transcriptome analysis, has been proposed by many groups to predict disease recurrence, clinical outcome, and also response to therapy, in addition to the well-established clinico-pathological factors. However, the clinical usability of gene expression profiling as a reliable and robust prognostic tool that allows evidence-based clinical decisions is currently under debate. In this review, we will discuss the most recent data on the prognostic significance and potential clinical application of genome wide expression analysis in colorectal cancer.
RESUMEN
Genomic imprinting causes parental origin-specific monoallelic gene expression through differential DNA methylation established in the parental germ line. However, the mechanisms underlying how specific sequences are selectively methylated are not fully understood. We have found that the components of the PIWI-interacting RNA (piRNA) pathway are required for de novo methylation of the differentially methylated region (DMR) of the imprinted mouse Rasgrf1 locus, but not other paternally imprinted loci. A retrotransposon sequence within a noncoding RNA spanning the DMR was targeted by piRNAs generated from a different locus. A direct repeat in the DMR, which is required for the methylation and imprinting of Rasgrf1, served as a promoter for this RNA. We propose a model in which piRNAs and a target RNA direct the sequence-specific methylation of Rasgrf1.
Asunto(s)
Metilación de ADN , Impresión Genómica , ARN Interferente Pequeño/genética , ARN no Traducido/genética , ras-GRF1/genética , Animales , Proteínas Argonautas , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas Mitocondriales/genética , Proteínas Mitocondriales/metabolismo , Modelos Genéticos , Mutación , Fosfolipasa D/genética , Fosfolipasa D/metabolismo , Proteínas/genética , Proteínas/metabolismo , ARN Interferente Pequeño/metabolismo , ARN no Traducido/metabolismo , Secuencias Repetitivas de Ácidos Nucleicos , Retroelementos , Espermatogonias/metabolismo , Testículo/embriología , Testículo/metabolismo , Transcripción GenéticaRESUMEN
Silencing of transposable elements occurs during fetal gametogenesis in males via de novo DNA methylation of their regulatory regions. The loss of MILI (miwi-like) and MIWI2 (mouse piwi 2), two mouse homologs of Drosophila Piwi, activates retrotransposon gene expression by impairing DNA methylation in the regulatory regions of the retrotransposons. However, as it is unclear whether the defective DNA methylation in the mutants is due to the impairment of de novo DNA methylation, we analyze DNA methylation and Piwi-interacting small RNA (piRNA) expression in wild-type, MILI-null, and MIWI2-null male fetal germ cells. We reveal that defective DNA methylation of the regulatory regions of the Line-1 (long interspersed nuclear elements) and IAP (intracisternal A particle) retrotransposons in the MILI-null and MIWI2-null male germ cells takes place at the level of de novo methylation. Comprehensive analysis shows that the piRNAs of fetal germ cells are distinct from those previously identified in neonatal and adult germ cells. The expression of piRNAs is reduced under MILI- and MIWI2-null conditions in fetal germ cells, although the extent of the reduction differs significantly between the two mutants. Our data strongly suggest that MILI and MIWI2 play essential roles in establishing de novo DNA methylation of retrotransposons in fetal male germ cells.