SAMBA, a plant-specific anaphase-promoting complex/cyclosome regulator is involved in early development and A-type cyclin stabilization

The anaphase-promoting complex/cyclosome (APC/C) is a large multiprotein E3 ubiquitin ligase involved in ubiquitin-dependent proteolysis of key cell cycle regulatory proteins, including the destruction of mitotic cyclins at the metaphase-to-anaphase transition. Despite its importance, the role of the APC/C in plant cells and the regulation of its activity during cell division remain poorly understood. Here, we describe the identification of a plant-specific negative regulator of the APC/C complex, designated SAMBA. In Arabidopsis thaliana, SAMBA is expressed during embryogenesis and early plant development and plays a key role in organ size control. Samba mutants produced larger seeds, leaves, and roots, which resulted from enlarged root and shoot apical meristems, and, additionally, they had a reduced fertility attributable to a hampered male gametogenesis. Inactivation of SAMBA stabilized A2-type cyclins during early development. Our data suggest that SAMBA regulates cell proliferation during early development by targeting CYCLIN A2 for APC/C-mediated proteolysis.     

Dehydroepiandrosterone (DHEA) improves pulmonary hypertension in chronic obstructive pulmonary disease (COPD): a pilot study

ObjectivesIt was previously shown that dehydroepiandrosterone (DHEA) reverses chronic hypoxia-induced pulmonary hypertension (PH) in rats, but whether DHEA can improve the clinical and hemodynamic status of patients with PH associated to chronic obstructive pulmonary disease (PH-COPD) has not been studied whereas it is a very severe poorly treated disease.Patients and methodsEight patients with PH-COPD were treated with DHEA (200 mg daily orally) for 3 months. The primary end-point was the change in the 6-minute walk test (6-MWT) distance. Secondary end-points included pulmonary hemodynamics, lung function tests and tolerance of treatment.ResultsThe 6-MWT increased in all cases, from 333 m (median [IQR]) (257; 378) to 390 m (362; 440) (P < 0.05). Mean pulmonary artery pressure decreased from 26 mmHg (25; 27) to 21.5 mmHg (20; 25) (P < 0.05) and pulmonary vascular resistance from 4.2 UI (3.5; 4.4) to 2.6 UI (2.5; 3.8) (P < 0.05). The carbon monoxide diffusing capacity of the lung (DLCO % predicted) increased significantly from 27.4% (20.1; 29.3) to 36.4% (14.6; 39.6) (P < 0.05). DHEA treatment did not change respiratory parameters of gas exchange and the 200 mg per day of DHEA used was perfectly tolerated with no side effect reported.ConclusionDHEA treatment significantly improves 6-MWT distance, pulmonary hemodynamics and DLCO of patients with PH-COPD, without worsening gas exchange, as do other pharmacological treatments of PH (trial registration NCT00581087).     

IDH2 mutations are frequent in angioimmunoblastic T-cell lymphoma

Mutations in isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) occur in most grade 2 and 3 gliomas, secondary glioblastomas, and a subset of acute myelogenous leukemias but have not been detected in other tumor types. The mutations occur at specific arginine residues and result in the acquisition of a novel enzymatic activity that converts 2-oxoglutarate to D-2-hydroxyglutarate. This study reports IDH1 and IDH2 genotyping results from a set of lymphomas, which included a large set of peripheral T-cell lymphomas. IDH2 mutations were identified in approximately 20% of angioimmunoblastic T-cell lymphomas (AITLs), but not in other peripheral T-cell lymphoma entities. These results were confirmed in an independent set of AITL patients, where the IDH2 mutation rate was approximately 45%. This is the second common genetic lesion identified in AITL after TET2 and extends the number of neoplastic diseases where IDH1 and IDH2 mutations may play a role.     

Asymmetric segregation and self-renewal of hematopoietic stem and progenitor cells with endocytic Ap2a2

The stem cell-intrinsic model of self-renewal via asymmetric cell division (ACD) posits that fate determinants be partitioned unequally between daughter cells to either activate or suppress the stemness state. ACD is a purported mechanism by which hematopoietic stem cells (HSCs) self-renew, but definitive evidence for this cellular process remains open to conjecture. To address this issue, we chose 73 candidate genes that function within the cell polarity network to identify potential determinants that may concomitantly alter HSC fate while also exhibiting asymmetric segregation at cell division. Initial gene-expression profiles of polarity candidates showed high and differential expression in both HSCs and leukemia stem cells. Altered HSC fate was assessed by our established in vitro to in vivo screen on a subcohort of candidate polarity genes, which revealed 6 novel positive regulators of HSC function: Ap2a2, Gpsm2, Tmod1, Kif3a, Racgap1, and Ccnb1. Interestingly, live-cell videomicroscopy of the endocytic protein AP2A2 shows instances of asymmetric segregation during HSC/progenitor cell cytokinesis. These results contribute further evidence that ACD is functional in HSC self-renewal, suggest a role for Ap2a2 in HSC activity, and provide a unique opportunity to prospectively analyze progeny from HSC asymmetric divisions.     

European Society of Hypertension scientific newsletter: hypertension and aortic diseases

Hypertension, one of the major cardiovascular risk factors, promotes the formation of atheromatous lesions in the large arteries, including the aorta. It also favors aortic aneurysm and acute aortic syndrome such as aortic dissection or hematoma. In patients with aortic disease, beta-blockers and/or renin-angiotensin-aldosterone system inhibitors should be preferentially used to decrease blood pressure and improve arterial wall properties.     

Hemoglobin sickle cell disease complications: a clinical study of 179 cases

Background

Hemoglobin sickle cell disease is one of the most frequent hemoglobinopathies. Surprisingly, few studies have been dedicated to this disease, currently considered to be a mild variant of homozygous sickle cell disease. The aim of this study was to update our knowledge about hemoglobin sickle cell disease.

Design and Methods

The study involved a single center series of 179 patients. Clinical and biological data were collected with special attention to the assessment of pulmonary arterial hypertension and nephropathy.

Results

Hemoglobin sickle cell diagnosis was delayed and performed in adulthood in 29% of cases. Prevalence of hospitalized painful vasoocclusive crisis, acute chest syndrome and priapism was 36%, 20% and 20%, respectively. The most common chronic organ complications were retinopathy and sensorineural otological disorders in 70% and 29% of cases. Indeed, prevalence of complications reported in homozygous sickle cell disease, such as nephropathy, suspicion of pulmonary hypertension, strokes and leg ulcers was rather low (13%, 4% and 1%, respectively). Phlebotomy performed in 36% of this population (baseline hemoglobin 11.5 g/dL) prevented recurrence of acute events in 71% of cases.

Conclusions

Our data suggest that hemoglobin sickle cell disease should not be considered as a mild form of sickle cell anemia but as a separate disease with a special emphasis on viscosity-associated otological and ophthalmological disorders, and with a low prevalence of vasculopathy (strokes, pulmonary hypertension, ulcers and nephropathy). Phlebotomy was useful in reducing acute events and a wider use of this procedure should be further investigated.     

Genetic Variants in Toll-Like Receptor 2 (TLR2), TLR4, TLR9, and FCγ Receptor II Are Associated with Antibody Response to Quadrivalent Meningococcal Conjugate Vaccine in HIV-Infected Youth

This study examined the association of host genetic variants with the antibody response to the quadrivalent meningococcal conjugate vaccine (MCV4) in HIV-infected youth. Genetic variants associated with severity of meningococcal disease, including the IgG Fc receptor (FCγRII)-A484T, interleukin-10 (IL-10)-A1082G, -C819T, and -C627A, IL-4-C589T, mannose binding lectin-2 (MBL2)-A/O, -H/L, -P/Q, and -X/Y, toll-like receptor 2 (TLR2)-G2408A, TLR4-A12874G and -C13174T, and TLR9-T1237C and -T1486C were determined by real-time PCR (RT-PCR) for 271 HIV-infected subjects (median, 17 years). Response was defined as a ≥4-fold increase from entry in bactericidal antibody titers to each serogroup. Generalized estimating equation (GEE) models were used to evaluate the association of allelic variants with the immunologic response to all serogroups within each subject with and without adjusting for CD4 percentage and HIV viral load. At week 4, but not after, subjects with TLR2-2408-G/A versus -G/G genotypes and the TLR4-12874-A/A genotype were more likely to achieve a ≥4-fold increase overall in the four serogroups (unadjusted P of 0.006 and adjusted P of 0.008 and unadjusted P of 0.008 and adjusted P of 0.019, respectively). At week 28, the TLR9-1237 T allele was associated with enhanced antibody response (T allele versus C/C, unadjusted P of 0.014 and adjusted P of 0.009), which was maintained at week 72 (unadjusted and adjusted P of 0.008). At week 72, the FcγRII-131Arg allotype was associated with a ≥4-fold increase in antibody titer versus those with His/His (unadjusted P of 0.009; adjusted P of <0.001). These findings suggest that for HIV-infected youth, the initial antibody response to MCV4 is associated with variants in TLR2 and TLR4 while the long-term response is associated with genetic polymorphisms in TLR9 and FcγRIIa.