Combined deletion of Xrcc4 and Trp53 in mouse germinal center B cells leads to novel B cell lymphomas with clonal heterogeneity

Abstract Background Activated B lymphocytes harbor programmed DNA double-strand breaks (DSBs) initiated by activation-induced deaminase (AID) and repaired by non-homologous end-joining (NHEJ). While it has been proposed that these DSBs during secondary antibody gene diversification are the primary source of chromosomal translocations in germinal center (GC)-derived B cell lymphomas, this point has not been directly addressed due to the lack of proper mouse models. Methods In the current study, we establish a unique mouse model by specifically deleting a NHEJ gene, Xrcc4, and a cell cycle checkpoint gene, Trp53, in GC B cells, which results in the spontaneous development of B cell lymphomas that possess features of GC B cells. Results We show that these NHEJ deficient lymphomas harbor translocations frequently targeting immunoglobulin (Ig) loci. Furthermore, we found that Ig translocations were associated with distinct mechanisms, probably caused by AID- or RAG-induced DSBs. Intriguingly, the AID-associated Ig loci translocations target either c-myc or Pvt-1 locus whereas the partners of RAG-associated Ig translocations scattered randomly in the genome. Lastly, these NHEJ deficient lymphomas harbor complicated genomes including segmental translocations and exhibit a high level of ongoing DNA damage and clonal heterogeneity. Conclusions We propose that combined NHEJ and p53 defects may serve as an underlying mechanism for a high level of genomic complexity and clonal heterogeneity in cancers

Sistema radical en genotipos de papa, bajo condiciones de invernadero.

The objectives of this research were to study variability of growing and distribution of the root system in 10 commercial and experimental potato clones and to identify the best materials in different soil profiles. It was used a complete random block design, under greenhouse conditions at the Universidad Autónoma Agraria Antonio Narro, Saltillo, Mexico. Black polyethylene containers of 90 cm long and 30 cm diameter were used for evaluating root system. Restricted irrigation was applied to increase root growing. Experimental plot was one container with two plants. After flowering and 125 days of growing, shoot was cut. Soil in every container was divided in four sections. Shoot and roots were dried at 70 °C for 48 hours and weighted. Analysis of variance revealed highly significant differences for dry root weight among potato varieties at the four considered profiles: 0-20, 20-40, 40- 60, 60-80 cm, and for total profile (0-80 cm). Boer, Russet Burbanck and Utatlan were outstanding varieties for the total production of roots. Boer Russet Burbanck, Atlantic and Gigant varieties produced the higher amount of roots in the 60- 80 cm profile and produced a good roots growing patterns in different profiles.El presente trabajo tuvo como objetivos estudiar la variabilidad del crecimiento y distribución del sistema radical en 10 clones comerciales y experimentales de papa, e identificar los mejores materiales en diferentes perfiles de suelo. Se utilizó un diseño completamente al azar con dos repeticiones, bajo condiciones de invernadero en la Universidad Autónoma Agraria Antonio Narro., Saltillo, México. Para la evaluación del sistema radical se utilizaron bolsas de polietileno de 90 cm de largo y 30 cm de diámetro. Se aplicaron riegos restringidos para obtener mejor desarrollo radical. La parcela experimental fue una bolsa con dos plantas. Después de la floración y con un crecimiento de 125 días, se cortó el vástago. El suelo de cada bolsa que contenía las raíces fue seccionado en cuatro segmentos. Estas raíces, se recuperaron y luego se lavaron. El vástago y las raíces se secaron al horno a 70 °C durante 48 horas y se obtuvo peso seco. El análisis de varianza mostró diferencias altamente significativas entre variedades, para peso seco de sistema radical en los cuatro perfiles estudiados 0-20, 20-40, 40-60, 60-80 cm y para elperfil total (0-80 cm). Las variedades Boer, Russet Burbank y Utatlan fueron sobresalientes en la producción total de raíces. Las variedades Boer, Russet Burbank, Atlantic y Gigant mostraron mayor cantidad de raíces en el perfil de 60-80 cm y produjeron un buen patrón de crecimiento radical en diferentes perfiles

Mutations in the accessory subunit NDUFB10 result in isolated complex I deficiency and illustrate the critical role of intermembrane space import for complex I holoenzyme assembly

An infant presented with fatal infantile lactic acidosis and cardiomyopathy, and was found to have profoundly decreased activity of respiratory chain complex I in muscle, heart and liver. Exome sequencing revealed compound heterozygous mutations in NDUFB10, which encodes an accessory subunit located within the P-D part of complex I. One mutation resulted in a premature stop codon and absent protein, while the second mutation replaced the highly conserved cysteine 107 with a serine residue. Protein expression of NDUFB10 was decreased in muscle and heart, and less so in the liver and fibroblasts, resulting in the perturbed assembly of the holoenzyme at the 830 kDa stage. NDUFB10 was identified together with three other complex I subunits as a substrate of the intermembrane space oxidoreductase CHCHD4 (also known as Mia40). We found that during its mitochondrial import and maturation NDUFB10 transiently interacts with CHCHD4 and acquires disulfide bonds. The mutation of cysteine residue 107 in NDUFB10 impaired oxidation and efficient mitochondrial accumulation of the protein and resulted in degradation of non-imported precursors. Our findings indicate that mutations in NDUFB10 are a novel cause of complex I deficiency associated with a late stage assembly defect and emphasize the role of intermembrane space proteins for the efficient assembly of complex I

Functional Prostacyclin Synthase Promoter Polymorphisms. Impact in Pulmonary Arterial Hypertension

Rationale: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by elevated pulmonary artery pressure, vascular remodeling, and ultimately right ventricular heart failure. PAH can have a genetic component (heritable PAH), most often through mutations of bone morphogenetic protein receptor 2, and idiopathic and associated forms. Heritable PAH is not completely penetrant within families, with approximately 20% concurrence of inactivating bone morphogenetic protein receptor 2 mutations and delayed onset of PAH disease. Because one of the treatment options is using prostacyclin analogs, we hypothesized that prostacyclin synthase promoter sequence variants associated with increased mRNA expression may play a protective role in the bone morphogenetic protein receptor 2 unaffected carriers. Objectives: To characterize the range of prostacyclin synthase promoter variants and assess their transcriptional activities in PAH-relevant cell types. To determine the distribution of prostacyclin synthase promoter variants in PAH, unaffected carriers in heritable PAH families, and control populations. Methods: Polymerase chain reaction approaches were used to genotype prostacyclin synthase promoter variants in more than 300 individuals. Prostacyclin synthase promoter haplotypes’ transcriptional activities were determined with luciferase reporter assays. Measurements and Main Results: We identified a comprehensive set of prostacyclin synthase promoter variants and tested their transcriptional activities in PAH-relevant cell types. We demonstrated differences of prostacyclin synthase promoter activities dependent on their haplotype. Conclusions: Prostacyclin synthase promoter sequence variants exhibit a range of transcriptional activities. We discovered a significant bias for more active prostacyclin synthase promoter variants in unaffected carriers as compared with affected patients with PAH