RESUMEN
Members of the PRDM protein family have been shown to play important roles during embryonic development. Previous in vitro and in situ analyses indicated a function of Prdm6 in cells of the vascular system. To reveal physiological functions of Prdm6, we generated conditional Prdm6-deficient mice. Complete deletion of Prdm6 results in embryonic lethality due to cardiovascular defects associated with aberrations in vascular patterning. However, smooth muscle cells could be regularly differentiated from Prdm6-deficient embryonic stem cells and vascular smooth muscle cells were present and proliferated normally in Prdm6-deficient embryos. Conditional deletion of Prdm6 in the smooth muscle cell lineage using a SM22-Cre driver line resulted in perinatal lethality due to hemorrhage in the lungs. We thus identified Prdm6 as a factor that is essential for the physiological control of cardiovascular development.
Asunto(s)
Sistema Cardiovascular/embriología , Proteínas Represoras/fisiología , Animales , Secuencia de Bases , Northern Blotting , Southern Blotting , Tipificación del Cuerpo , Diferenciación Celular , Proliferación Celular , Cartilla de ADN , Ratones , Ratones Noqueados , Músculo Liso/citología , Neovascularización Fisiológica , Análisis de Secuencia por Matrices de Oligonucleótidos , Reacción en Cadena de la Polimerasa , Proteínas Represoras/genéticaRESUMEN
Chromosomal translocations involving the immunoglobulin heavy chain (IGH) locus define common subgroups of B-cell lymphoma but are rare in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Recent fluorescent in situ hybridization and molecular cloning studies have identified several novel IGH translocations involving genes that play important roles in normal hemopoiesis, including the cytokine receptor genes CRLF2 and EPOR, all members of the CCAAT enhancer-binding protein gene family, as well as genes not normally expressed in hemopoietic cells including inhibitor of DNA binding 4. IGH translocation results in deregulated target gene expression because of juxtaposition with IGH transcriptional enhancers. However, many genes targeted by IGH translocations are also more commonly deregulated in BCP-ALL as a consequence of other genetic or epigenetic mechanisms. For example, interstitial genomic deletions also result in deregulated CRLF2 expression, whereas EPOR expression is deregulated as a consequence of the ETV6-RUNX1 fusion. The possible clinical importance of many of the various IGH translocations in BCP-ALL remains to be determined from prospective studies, but CRLF2 expression is associated with a poor prognosis. Despite their rarity, IGH chromosomal translocations in BCP-ALL therefore define not only new mechanisms of B-cell transformation but also clinically important subgroups of disease and suggest new targeted therapeutic approaches.
Asunto(s)
Linfocitos B/metabolismo , Transformación Celular Neoplásica/metabolismo , Cadenas Pesadas de Inmunoglobulina/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras B/metabolismo , Sitios de Carácter Cuantitativo , Translocación Genética , Enfermedad Aguda , Animales , Transformación Celular Neoplásica/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/biosíntesis , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Regulación Leucémica de la Expresión Génica/genética , Hematopoyesis/genética , Humanos , Cadenas Pesadas de Inmunoglobulina/genética , Proteínas Inhibidoras de la Diferenciación/biosíntesis , Proteínas Inhibidoras de la Diferenciación/genética , Proteínas de Fusión Oncogénica/biosíntesis , Proteínas de Fusión Oncogénica/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras B/diagnóstico , Leucemia-Linfoma Linfoblástico de Células Precursoras B/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras B/terapia , Pronóstico , Receptores de Citocinas/biosíntesis , Receptores de Citocinas/genética , Receptores de Eritropoyetina/biosíntesis , Receptores de Eritropoyetina/genéticaRESUMEN
Integrative genomic and gene-expression analyses have identified amplified oncogenes in B-cell non-Hodgkin lymphoma (B-NHL), but the capability of such technologies to localize tumor suppressor genes within homozygous deletions remains unexplored. Array-based comparative genomic hybridization (CGH) and gene-expression microarray analysis of 48 cell lines derived from patients with different B-NHLs delineated 20 homozygous deletions at 7 chromosome areas, all of which contained tumor suppressor gene targets. Further investigation revealed that only a fraction of primary biopsies presented inactivation of these genes by point mutation or intragenic deletion, but instead some of them were frequently silenced by epigenetic mechanisms. Notably, the pattern of genetic and epigenetic inactivation differed among B-NHL subtypes. Thus, the P53-inducible PIG7/LITAF was silenced by homozygous deletion in primary mediastinal B-cell lymphoma and by promoter hypermethylation in germinal center lymphoma, the proapoptotic BIM gene presented homozygous deletion in mantle cell lymphoma and promoter hypermethylation in Burkitt lymphoma, the proapoptotic BH3-only NOXA was mutated and preferentially silenced in diffuse large B-cell lymphoma, and INK4c/P18 was silenced by biallelic mutation in mantle-cell lymphoma. Our microarray strategy has identified novel candidate tumor suppressor genes inactivated by genetic and epigenetic mechanisms that substantially vary among the B-NHL subtypes.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Proteínas Portadoras/genética , Inhibidor p18 de las Quinasas Dependientes de la Ciclina/genética , Genes Supresores de Tumor , Proteínas de Homeodominio/genética , Linfoma de Células B/genética , Proteínas de la Membrana/genética , Proteínas Nucleares/genética , Proteínas Proto-Oncogénicas c-bcl-2/genética , Proteínas Proto-Oncogénicas/genética , Eliminación de Secuencia , Factores de Transcripción/genética , Proteínas de Transporte Vesicular/genética , Proteínas Adaptadoras Transductoras de Señales , Apoptosis/genética , Proteína 11 Similar a Bcl2 , Biopsia , Línea Celular Tumoral , Mapeo Cromosómico , Cromosomas Humanos/genética , Cromosomas Humanos/ultraestructura , Metilación de ADN , Análisis Mutacional de ADN , ADN de Neoplasias/genética , Epigénesis Genética , Dosificación de Gen , Regulación Neoplásica de la Expresión Génica , Silenciador del Gen , Homocigoto , Humanos , Linfoma de Células B/clasificación , Linfoma de Células B/inmunología , Linfoma de Células B/patología , Hibridación de Ácido Nucleico , Análisis de Secuencia por Matrices de Oligonucleótidos , Mutación Puntual , Regiones Promotoras Genéticas/genética , Proteínas de Unión al ARN , Nexinas de ClasificaciónRESUMEN
CCAAT enhancer-binding protein (CEBP) transcription factors play pivotal roles in proliferation and differentiation, including suppression of myeloid leukemogenesis. Mutations of CEBPA are found in a subset of acute myeloid leukemia (AML) and in some cases of familial AML. Here, using cytogenetics, fluorescence in situ hybridization (FISH), and molecular cloning, we show that 5 CEBP gene family members are targeted by recurrent IGH chromosomal translocations in BCP-ALL. Ten patients with t(8;14)(q11;q32) involved CEBPD on chromosome 8, and 9 patients with t(14;19)(q32;q13) involved CEBPA, while a further patient involved CEBPG, located 71 kb telomeric of CEBPA in chromosome band 19q13; 4 patients with inv(14)(q11q32)/t(14;14)(q11;q32) involved CEBPE and 3 patients with t(14;20)(q32;q13) involved CEBPB. In 16 patients the translocation breakpoints were cloned using long-distance inverse-polymerase chain reaction (LDI-PCR). With the exception of CEBPD breakpoints, which were scattered within a 43-kb region centromeric of CEBPD, translocation breakpoints were clustered immediately 5' or 3' of the involved CEBP gene. Except in 1 patient with t(14;14)(q11;q32), the involved CEBP genes retained germ-line sequences. Quantitative reverse transcription (RT)-PCR showed overexpression of the translocated CEBP gene. Our findings implicate the CEBP gene family as novel oncogenes in BCP-ALL, and suggest opposing functions of CEBP dysregulation in myeloid and lymphoid leukemogenesis.
Asunto(s)
Linfoma de Burkitt/genética , Proteínas Potenciadoras de Unión a CCAAT/genética , Cromosomas Humanos/genética , Cadenas Pesadas de Inmunoglobulina/genética , Familia de Multigenes/genética , Oncogenes/genética , Translocación Genética , Centrómero/genética , Humanos , Hibridación Fluorescente in Situ , Reacción en Cadena de la Polimerasa , Telómero/genéticaRESUMEN
Many subtypes of B-cell malignancy are characterized by chromosomal translocations that target the immunoglobulin loci. Molecular cloning of such translocations continues to allow the identification of genes whose deregulated expression plays a pivotal role in the pathogenesis of B-cell malignancy. The clustering of breakpoints within the immunoglobulin loci has allowed the development of rapid and robust polymerase chain reaction methods for cloning. We discuss in this chapter the use of long-distance inverse polymerase chain reaction methods to clone immunoglobulin chromosomal translocation breakpoints from clinical material. These methods have been successfully applied to several other types of chromosomal translocation including those involving other genes such as BCL6, ETV6, and MYC.