Genetic dissection of c-Myc function during mouse organogenesis

Résumé Le gène c-myc est un des oncogènes les plus fréquemment mutés dans les tumeurs humaines. Même si plus de 70 % des cancers humains montrent une dérégulation de c-Myc, les connaissances sur son rôle physiologique pendant le développement, et dans la souris adulte restent très peu connus. Récemment, notre laboratoire a pu montrer que c-Myc contrôle l'équilibre entre le renouvellement et la différenciation des cellules souches hématopoïetiques (CSH) dans la souris adulte. Ceci est probablement dû à lacapacité de c-Myc de contrôler l'entrée et la sortie des CSH de leur niche de la moelle osseuse, en régulant plusieurs molécules d'adhésion, parmi lesquelles la cadhérine-N (Wilson et al., 2004; Wilson and Trumpp, 2006). Des études utilisant un mutant d'inactivation ont demontré que la protéine c-Myc est essentielle pour le développement au delà du jour embryonnaire E9.5. Les embryons c-Myc déficients sont plus petits que la normale et possèdent de nombreux défauts; en particulier ils ne peuvent établir un système hématopoietique embryonnaire primitif (Trumpp et al., 2001). Nous avons récemment découvert que le développement du placenta dépend de la présence de cMyc. Ceci permet de proposer que certains, sinon tous, les défauts embryonnaires puorraient dériver indirectement d'un défaut nutritionnel causé par la défaillance du placenta. Afin de répondre à cette question de manière génétique, nous avons utilisé l'allele conditionel c-mycflox (Trumpp et al., 2001) en combinaison avec l'allele Sox2-Cre (Hayashi et al., 2002). Celui-ci détermine l'expression de la récombinase Cre spécifiquement dans les cellules de l'épiblaste à partir de E6.5, tandis qu'il n'y a pas, ou seulement très peu, d'activité de la récombinase Cre dans les tissus extraembryonnaires.Alnsi, cette stratégie nous permet de générer des embryons sans c-Myc qui se développent en présence d'un compartment extraembryonnaire ou c-Myc est exprimé normalement (Sox2Cre;c-mycflox2) Ces embryons, Sox2Cre;c-mycflox2 se développent et grandissent normalement tout en formant un système vasculaire normal, mais meurent à E11.5 à cause d'un sévère manque de cellules hématopoïetiques. De façon très intéressante, la seule population qui semble être présente en nombre à peu près normal dans ces embryons est celle des précurseurs et des cellules souches. Les cellules qui forment cette population prolifèrent normalement mais ne peuvent pas former des colonies in vitro, ce qui montre que ces cellules ont perdu leur activité de cellules souches. Cependant, lorsque nous avons analysé ces cellules plus en détail en éxaminant l'expression des molécules d'intégrine nous avons découvert que l'integrine ß est sur-éxprimée à la surface des cellules c-Myc déficientes. Ceci pourrait indiquer un mécanisme par lequel c-Myc régule des molécules d'adhésion sur les cellules du sang. En conséquence, en absence de c-Myc, l'adhésion et la migration des cellules du sang de l'AGM (Aorte-Gonade-Mésonéphros) vers le foie de l'embryon, à travers le système vasculaire, est compromise. En outre, nous avons pu montrer que les hépatocytes du foie, qui constitue le site principal de formation des cellules hématopoïetiques pendant le développement, est sévèrement atteint dans des Sox2Cre;c-mycflox2 embryons. Ceci n'est pas du à un défaut propre aux cellules hépatiques qui ont perdu c-Myc, mais résulte plutôt de l'absence de cellules hématopoietïques qui normalement colonisent le foie à ce stade du développement. Ces résultats représentent la première preuve directe que le développement des hépatoblastes est dépendant de signaux provenant des cellules du sang. Summary The myc gene is one of the most frequently mutated oncogenes in human tumors. It is found to be mis-regulated in over 70% of all human cancers. However, our knowledge about its physiological role in mammalian development and adulthood remains limited. Recent work in our laboratory showed that c-Myc controls the balance between hematopoietic stem cell (HSC) self-renewal and differentiation in the adult mouse. This is likely due to the capacity of c-Myc to control entry and exit of HSCs from the bone marrow niche by regulating a number of cell adhesion molecules including N-cadherin (Wilson et al., 2004; Wilson and Trumpp 2006). During development knockout studies showed that c-Myc is required for embryonic development beyond embryonic day (E) 9.5. c-Myc deficient embryos are severely reduced in size and show multiple defects including the failure to establish a primitive hematopoietic system (Trumpp et al., 2001). Importantly, we recentry uncovered that placental development also seems to depend on normal c-Myc function, raising the possibility that some if not all of the embryonic defects observed could be mediated indirectly by a nutrition defect caused by placental failure. To address this possibility genetically, we took advantage of the conditional c-mycflox allele (Trumpp et al., 2001) in combination with the Sox2-Cre allele (Hayashi et al., 2002), in which Cre expression is specifically targeted to all epiblast cells by E6.5, while there is little or no Cre activity inextra-embryonic lineages. Thus, this strategy allows the generation of c-Myc deficient embryos, which develop within a normal c-Myc expressing extra-embryonic compartment (Sox2Cre;c-mycflox2) Such Sox2Cre;c-mycflox2 embryos develop and grow appropriately and form a normal vascular system but die at E11.5 due to a severe lack of blood cells. Interestingly, the only hematopoietic population that seems to be present in almost normal numbers in the embryo is the stem/progenitor cell population. Cells within this populatíon proliferate normal but can not give rise to hematopoietic colonies in vitro showing that functional hematopoietic stem cell (HSC) activity is lost. However, when we analyzed these phenotypic HSCs in more detail and examined integrin expression in mutant stem/progenitor cells, we observed that ß1-integrin is upregulated. This may point to a potential mechanism whereby c-Myc regulates adhesíon molecules on hematopoietic cells and thereby disturbs adhesion and migration from the AGM (aorta-gonads-mesonephros) through the vascular system to the liver. Furthermore, we uncovered that the fetal liver, the main site of hematopoietic expansion at that stage, is severely affected in Sox2Cre;c-mycflox2 embryos and that this is not due to a cell intrinsic defect of c-Myc deficient hepatocytes but rather due to the lack of hematopoietic cells that normally colonize the fetal liver at that stage of development. This provides first direct evidence that hepatoblast development depends on signals derived from blood cells.

Function of TRADD in tumor necrosis factor receptor 1 signaling and in TRIF-dependent inflammatory responses.

Tumor necrosis factor receptor 1 (TNFR1) and Toll-like receptors (TLRs) regulate immune and inflammatory responses. Here we show that the TNFR1-associated death domain protein (TRADD) is critical in TNFR1, TLR3 and TLR4 signaling. TRADD deficiency abrogated TNF-induced apoptosis, prevented recruitment of the ubiquitin ligase TRAF2 and ubiquitination of the adaptor RIP1 in the TNFR1 signaling complex, and considerably inhibited but did not completely abolish activation of the transcription factor NF-kappaB and mitogen-activated protein kinases 'downstream' of TNFR1. TRIF-dependent cytokine production induced by the synthetic double-stranded RNA poly(I:C) and lipopolysaccharide was lower in TRADD-deficient mice than in wild-type mice. Moreover, TRADD deficiency inhibited poly(I:C)-mediated RIP1 ubiquitination and activation of NF-kappaB and mitogen-activated protein kinase signaling in fibroblasts but not in bone marrow macrophages. Thus, TRADD is an essential component of TNFR1 signaling and has a critical but apparently cell type-specific function in TRIF-dependent TLR responses.

Progressive decline of decision-making performances during multiple sclerosis.

The purpose of this study was to evaluate longitudinally, using the Iowa Gambling Task (IGT), the dynamics of decision-making capacity at a two-year interval (median: 2.1 years) in a group of patients with multiple sclerosis (MS) (n = 70) and minor neurological disability [Expanded Disability Status Scale (EDSS) < or = 2.5 at baseline]. Cognition (memory, executive functions, attention), behavior, handicap, and perceived health status were also investigated. Standardized change scores [(score at retest-score at baseline)/standard deviation of baseline score] were computed. Results showed that IGT performances decreased from baseline to retest (from 0.3, SD = 0.4 to 0.1, SD = 0.3, p = .005). MS patients who worsened in the IGT were more likely to show a decreased perceived health status and emotional well-being (SEP-59; p = .05 for both). Relapsing rate, disability progression, cognitive, and behavioral changes were not associated with decreased IGT performances. In conclusion, decline in decision making can appear as an isolated deficit in MS.

How to Measure Scope Variables when no Metrics Exist : Application to Landscape Quality Measurement and Hedonic Price Evaluation

Landscape is an example of a non-market good where no metrics exist to measure its quality. The paper proposes an original methodology to nevertheless estimate scope variables in those circumstances, allowing then to better test if people's willingnesstopay for such good is sensitive to the scope. The methodology is based on techniques developed in the context of multicriteria decision analysis. It is applied to assess the quality of the landscape of several Swiss alpine resorts. This assessment is then used as an explanatory variable in a hedonic price function to explain the rent of apartments and to derive an implicit price of the landscape quality.

Permanent pacemaker implantation after transcatheter aortic valve implantation: impact on late clinical outcomes and left ventricular function.

BACKGROUND Very few data exist on the clinical impact of permanent pacemaker implantation (PPI) after transcatheter aortic valve implantation. The objective of this study was to assess the impact of PPI after transcatheter aortic valve implantation on late outcomes in a large cohort of patients. METHODS AND RESULTS A total of 1556 consecutive patients without prior PPI undergoing transcatheter aortic valve implantation were included. Of them, 239 patients (15.4%) required a PPI within the first 30 days after transcatheter aortic valve implantation. At a mean follow-up of 22±17 months, no association was observed between the need for 30-day PPI and all-cause mortality (hazard ratio, 0.98; 95% confidence interval, 0.74-1.30; P=0.871), cardiovascular mortality (hazard ratio, 0.81; 95% confidence interval, 0.56-1.17; P=0.270), and all-cause mortality or rehospitalization for heart failure (hazard ratio, 1.00; 95% confidence interval, 0.77-1.30; P=0.980). A lower rate of unexpected (sudden or unknown) death was observed in patients with PPI (hazard ratio, 0.31; 95% confidence interval, 0.11-0.85; P=0.023). Patients with new PPI showed a poorer evolution of left ventricular ejection fraction over time (P=0.017), and new PPI was an independent predictor of left ventricular ejection fraction decrease at the 6- to 12-month follow-up (estimated coefficient, -2.26; 95% confidence interval, -4.07 to -0.44; P=0.013; R(2)=0.121). CONCLUSIONS The need for PPI was a frequent complication of transcatheter aortic valve implantation, but it was not associated with any increase in overall or cardiovascular death or rehospitalization for heart failure after a mean follow-up of ≈2 years. Indeed, 30-day PPI was a protective factor for the occurrence of unexpected (sudden or unknown) death. However, new PPI did have a negative effect on left ventricular function over time.

Alteration in neuromuscular function after a 5 km running time trial

The aim of this study was to characterize the effect of a 5 km running time trial on the neuromuscular properties of the plantar flexors. Eleven well-trained triathletes performed a series of neuromuscular tests before and immediately after the run on a 200 m indoor track. Muscle activation (twitch interpolation) and normalized EMG activity were assessed during maximal voluntary contraction (MVC) of plantar flexors. Maximal soleus H-reflexes and M-waves were evoked at rest (i.e. H (MAX) and M (MAX), respectively) and during MVC (i.e. H (SUP) and M (SUP), respectively). MVC significantly declined (-27%; P < 0.001) after the run, due to decrease in muscle activation (-8%; P < 0.05) and M (MAX)-normalized EMG activity (-13%; P < 0.05). Significant reductions in M-wave amplitudes (M (MAX): -13% and M (SUP): -16%; P < 0.05) as well as H (MAX)/M (MAX) (-37%; P < 0.01) and H (SUP)/M (SUP) (-25%; P < 0.05) ratios occurred with fatigue. Following exercise, the single twitch was characterized by lower peak torque (-16%; P < 0.001) as well as shorter contraction (-19%; P < 0.001) and half-relaxation (-24%; P < 0.001) times. In conclusion, the reduction in plantar flexors strength induced by a 5 km running time trial is caused by peripheral adjustments, which are attributable to a failure of the neuromuscular transmission and excitation-contraction coupling. Fatigue also decreased the magnitude of efferent motor outflow from spinal motor neurons to the plantar flexors and part of this suboptimal neural drive is the result of an inhibition of soleus motoneuron pool reflex excitability.

Insulin and NPY pathways and the control of GnRH function and puberty onset.

Energy balance exerts a critical influence on reproductive function. Leptin and insulin are among the metabolic factors signaling the nutritional status of an individual to the hypothalamus, and their role in the overall modulation of the activity of GnRH neurons is increasingly recognized. As such, they participate to a more generalized phenomenon: the signaling of peripheral metabolic changes to the central nervous system. The physiological importance that the interactions occurring between peripheral metabolic factors and the central nervous system bear for the control of food intake is increasingly recognized. The central mechanisms implicated are the focus of attention of very many research groups worldwide. We review here the experimental data that suggest that similar mechanisms are at play for the metabolic control of the neuroendocrine reproductive function. It is appearing that metabolic signals are integrated at the levels of first-order neurons equipped with the proper receptors, ant that these neurons send their signals towards hypothalamic GnRH neurons which constitute the integrative element of this network.

Impaired left ventricular function as a predictive factor for mid-term survival in octogenarians after primary coronary artery bypass surgery.

BACKGROUND: The impact of preoperative impaired left ventricular ejection fraction (EF) in octogenarians following coronary bypass surgery on short-term survival was evaluated in this study. METHODS: A total of 147 octogenarians (mean age 82.1 ± 1.9 years) with coronary artery diseases underwent elective coronary artery bypass graft between January 2000 and December 2009. Patients were stratified into: Group I (n = 59) with EF >50%, Group II (n = 59) with 50% > EF >30% and in Group III (n = 29) with 30% > EF. RESULTS: There was no difference among the three groups regarding incidence of COPD, renal failure, congestive heart failure, diabetes, and preoperative cerebrovascular events. Postoperative atrial fibrillation was the sole independent predictive factor for in-hospital mortality (odds ratio (OR), 18.1); this was 8.5% in Group I, 15.3% in Group II and 10.3% in Group III. Independent predictive factors for mortality during follow up were: decrease of EF during follow-up for more that 5% (OR, 5.2), usage of left internal mammary artery as free graft (OR, 18.1), and EF in follow-up lower than 40% (OR, 4.8). CONCLUSIONS: The results herein suggest acceptable in-hospital as well short-term mortality in octogenarians with impaired EF following coronary artery bypass grafting (CABG) and are comparable to recent literature where the mortality of younger patients was up to 15% and short-term mortality up to 40%, respectively. Accordingly, we can also state that in an octogenarian cohort with impaired EF, CABG is a viable treatment with acceptable mortality.

Dysfonction endothéliale et risque cardiovasculaire : l'exercice protège la fonction endothéliale et prévient la maladie cardiovasculaire [Endothelial dysfunction and cardiovascular risk : xercise protects endothelial function and prevents cardiovascular disease]

Objectifs : Décrire les caractéristiques de la dysfonction endothéliale associée au risque cardiovasculaire et expliciter les mécanismes biologiques par lesquels l'exercice stimule et/ou restaure la fonction endothéliale. Actualités : La fonction endothéliale, via les effets vasculoprotecteurs du monoxyde d'azote (NO), préserve la santé cardiovasculaire. Le dysfonctionnement endothélial est un facteur prédictif de la survenue des événements cardiovasculaires. L'endothélium est donc un organe cible préventif et thérapeutique prioritaire pour diminuer le risque cardiovasculaire. Perspectives : Les études épidémiologiques mettent en évidence les bienfaits de l'exercice régulier sur la fonction endothéliale, via une action endothéliale directe. L'approche expérimentale permet aujourd'hui de mieux cerner les mécanismes biologiques protecteurs de l'exercice. L'exercice, via l'élévation des forces de cisaillement, protège et/ou normalise la fonction endothéliale en augmentant la biodisponibilité en NO soit par une stimulation de la production de NO et/ou, soit par une augmentation des défenses antioxydantes et/ou une atténuation des enzymes prooxydantes. Conclusion : La connaissance des mécanismes biologiques protecteurs de l'exercice doit permettre d'encourager la pratique d'un exercice régulier par tous pour prévenir et réduire la mortalité cardiovasculaire.

Gene-lifestyle interaction and type 2 diabetes: the EPIC interact case-cohort study.

BACKGROUND Understanding of the genetic basis of type 2 diabetes (T2D) has progressed rapidly, but the interactions between common genetic variants and lifestyle risk factors have not been systematically investigated in studies with adequate statistical power. Therefore, we aimed to quantify the combined effects of genetic and lifestyle factors on risk of T2D in order to inform strategies for prevention. METHODS AND FINDINGS The InterAct study includes 12,403 incident T2D cases and a representative sub-cohort of 16,154 individuals from a cohort of 340,234 European participants with 3.99 million person-years of follow-up. We studied the combined effects of an additive genetic T2D risk score and modifiable and non-modifiable risk factors using Prentice-weighted Cox regression and random effects meta-analysis methods. The effect of the genetic score was significantly greater in younger individuals (p for interaction  = 1.20×10-4). Relative genetic risk (per standard deviation [4.4 risk alleles]) was also larger in participants who were leaner, both in terms of body mass index (p for interaction  = 1.50×10-3) and waist circumference (p for interaction  = 7.49×10-9). Examination of absolute risks by strata showed the importance of obesity for T2D risk. The 10-y cumulative incidence of T2D rose from 0.25% to 0.89% across extreme quartiles of the genetic score in normal weight individuals, compared to 4.22% to 7.99% in obese individuals. We detected no significant interactions between the genetic score and sex, diabetes family history, physical activity, or dietary habits assessed by a Mediterranean diet score. CONCLUSIONS The relative effect of a T2D genetic risk score is greater in younger and leaner participants. However, this sub-group is at low absolute risk and would not be a logical target for preventive interventions. The high absolute risk associated with obesity at any level of genetic risk highlights the importance of universal rather than targeted approaches to lifestyle intervention.

Telehealth system (e-CUIDATE) to improve quality of life in breast cancer survivors: rationale and study protocol for a randomized clinical trial.

BACKGROUND Breast cancer survivors suffer physical impairment after oncology treatment. This impairment reduces quality of life (QoL) and increase the prevalence of handicaps associated to unhealthy lifestyle (for example, decreased aerobic capacity and strength, weight gain, and fatigue). Recent work has shown that exercise adapted to individual characteristics of patients is related to improved overall and disease-free survival. Nowadays, technological support using telerehabilitation systems is a promising strategy with great advantage of a quick and efficient contact with the health professional. It is not known the role of telerehabilitation through therapeutic exercise as a support tool to implement an active lifestyle which has been shown as an effective resource to improve fitness and reduce musculoskeletal disorders of these women. METHODS / DESIGN This study will use a two-arm, assessor blinded, parallel randomized controlled trial design. People will be eligible if: their diagnosis is of stages I, II, or IIIA breast cancer; they are without chronic disease or orthopedic issues that would interfere with ability to participate in a physical activity program; they had access to the Internet and basic knowledge of computer use or living with a relative who has this knowledge; they had completed adjuvant therapy except for hormone therapy and not have a history of cancer recurrence; and they have an interest in improving lifestyle. Participants will be randomized into e-CUIDATE or usual care groups. E-CUIDATE give participants access to a range of contents: planning exercise arranged in series with breathing exercises, mobility, strength, and stretching. All of these exercises will be assigned to women in the telerehabilitation group according to perceived needs. The control group will be asked to maintain their usual routine. Study endpoints will be assessed after 8 weeks (immediate effects) and after 6 months. The primary outcome will be QoL measured by The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 version 3.0 and breast module called The European Organization for Research and Treatment of Cancer Breast Cancer-Specific Quality of Life questionnaire. The secondary outcomes: pain (algometry, Visual Analogue Scale, Brief Pain Inventory short form); body composition; physical measurement (abdominal test, handgrip strength, back muscle strength, and multiple sit-to-stand test); cardiorespiratory fitness (International Fitness Scale, 6-minute walk test, International Physical Activity Questionnaire-Short Form); fatigue (Piper Fatigue Scale and Borg Fatigue Scale); anxiety and depression (Hospital Anxiety and Depression Scale); cognitive function (Trail Making Test and Auditory Consonant Trigram); accelerometry; lymphedema; and anthropometric perimeters. DISCUSSION This study investigates the feasibility and effectiveness of a telerehabilitation system during adjuvant treatment of patients with breast cancer. If this treatment option is effective, telehealth systems could offer a choice of supportive care to cancer patients during the survivorship phase. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT01801527.

Gain-of-function mutations in PDR1, a regulator of antifungal drug resistance in Candida glabrata, control adherence to host cells.

Candida glabrata is an emerging opportunistic pathogen that is known to develop resistance to azole drugs due to increased drug efflux. The mechanism consists of CgPDR1-mediated upregulation of ATP-binding cassette transporters. A range of gain-of-function (GOF) mutations in CgPDR1 have been found to lead not only to azole resistance but also to enhanced virulence. This implicates CgPDR1 in the regulation of the interaction of C. glabrata with the host. To identify specific CgPDR1-regulated steps of the host-pathogen interaction, we investigated in this work the interaction of selected CgPDR1 GOF mutants with murine bone marrow-derived macrophages and human acute monocytic leukemia cell line (THP-1)-derived macrophages, as well as different epithelial cell lines. GOF mutations in CgPDR1 did not influence survival and replication within macrophages following phagocytosis but led to decreased adherence to and uptake by macrophages. This may allow evasion from the host's innate cellular immune response. The interaction with epithelial cells revealed an opposite trend, suggesting that GOF mutations in CgPDR1 may favor epithelial colonization of the host by C. glabrata through increased adherence to epithelial cell layers. These data reveal that GOF mutations in CgPDR1 modulate the interaction with host cells in ways that may contribute to increased virulence.

Decision fusion for the classification of hyperspectral data: Outcome of the 2008 GRS-S data fusion contest

The 2008 Data Fusion Contest organized by the IEEE Geoscience and Remote Sensing Data Fusion Technical Committee deals with the classification of high-resolution hyperspectral data from an urban area. Unlike in the previous issues of the contest, the goal was not only to identify the best algorithm but also to provide a collaborative effort: The decision fusion of the best individual algorithms was aiming at further improving the classification performances, and the best algorithms were ranked according to their relative contribution to the decision fusion. This paper presents the five awarded algorithms and the conclusions of the contest, stressing the importance of decision fusion, dimension reduction, and supervised classification methods, such as neural networks and support vector machines.

Fast calculation of the CAC convolution algorithm using the multinomial distribution function

The authors focus on one of the methods for connection acceptance control (CAC) in an ATM network: the convolution approach. With the aim of reducing the cost in terms of calculation and storage requirements, they propose the use of the multinomial distribution function. This permits direct computation of the associated probabilities of the instantaneous bandwidth requirements. This in turn makes possible a simple deconvolution process. Moreover, under certain conditions additional improvements may be achieved