A Stochastic Multiscale Model of Cardiac Thin Filament Activation Using Brownian-Langevin Dynamics.

We use Brownian-Langevin dynamics principles to derive a coarse-graining multiscale myofilament model that can describe the thin-filament activation process during contraction. The model links atomistic molecular simulations of protein-protein interactions in the thin-filament regulatory unit to sarcomere-level activation dynamics. We first calculate the molecular interaction energy between tropomyosin and actin surface using Brownian dynamics simulations. This energy profile is then generalized to account for the observed tropomyosin transitions between its regulatory stable states. The generalized energy landscape then served as a basis for developing a filament-scale model using Langevin dynamics. This integrated analysis, spanning molecular to thin-filament scales, is capable of tracking the events of the tropomyosin conformational changes as it moves over the actin surface. The tropomyosin coil with flexible overlap regions between adjacent tropomyosins is represented in the model as a system of coupled stochastic ordinary differential equations. The proposed multiscale approach provides a more detailed molecular connection between tropomyosin dynamics, the trompomyosin-actin interaction-energy landscape, and the generated force by the sarcomere

Multiple Autism-Linked Genes Mediate Synapse Elimination via Proteasomal Degradation of a Synaptic Scaffold PSD-95

SummaryThe activity-dependent transcription factor myocyte enhancer factor 2 (MEF2) induces excitatory synapse elimination in mouse neurons, which requires fragile X mental retardation protein (FMRP), an RNA-binding protein implicated in human cognitive dysfunction and autism. We report here that protocadherin 10 (Pcdh10), an autism-spectrum disorders gene, is necessary for this process. MEF2 and FMRP cooperatively regulate the expression of Pcdh10. Upon MEF2 activation, PSD-95 is ubiquitinated by the ubiquitin E3 ligase murine double minute 2 (Mdm2) and then binds to Pcdh10, which links it to the proteasome for degradation. Blockade of the Pcdh10-proteasome interaction inhibits MEF2-induced PSD-95 degradation and synapse elimination. In FMRP-lacking neurons, elevated protein levels of eukaryotic translation elongation factor 1 α (EF1α), an Mdm2-interacting protein and FMRP target mRNA, sequester Mdm2 and prevent MEF2-induced PSD-95 ubiquitination and synapse elimination. Together, our findings reveal roles for multiple autism-linked genes in activity-dependent synapse elimination

Effectiveness of insecticide-treated bednets in malaria prevention in Haiti: a case-control study

Background Insecticide-treated bednets (ITNs) are eff ective in preventing malaria where vectors primarily bite indoors and late at night, but their eff ectiveness is uncertain where vectors bite outdoors and earlier in the evening. We studied the eff ectiveness of ITNs following a mass distribution in Haiti from May to September, 2012, where the Anopheles albimanus vector bites primarily outdoors and often when people are awake. Methods In this case-control study, we enrolled febrile patients presenting to outpatient departments at 17 health facilities throughout Haiti from Sept 4, 2012, to Feb 27, 2014, who were tested with malaria rapid diagnostic tests (RDTs), and administered questionnaires on ITN use and other risk factors. Cases were defi ned by positive RDT and controls were febrile patients from the same clinic with a negative RDT. Our primary analysis retrospectively matched cases and controls by age, sex, location, and date, and used conditional logistic regression on the matched sample. A sensitivity analysis used propensity scores to match patients on ITN use propensity and analyse malaria among ITN users and non-users. Additional ITN bioeffi cacy and entomological data were collected. Findings We enrolled 9317 patients, including 378 (4%) RDT-positive cases. 1202 (13%) patients reported ITN use. Post-hoc matching of cases and controls yielded 362 cases and 1201 matched controls, 19% (333) of whom reported consistent campaign net use. After using propensity scores to match on consistent campaign ITN use, 2298 patients, including 138 (7%) RDT-positive cases, were included: 1149 consistent campaign ITN users and 1149 non-consistent campaign ITN users. Both analyses revealed that ITNs did not signifi cantly protect against clinical malaria (odds ratio [OR]=0·95, 95% CI 0·68–1·32, p=0·745 for case-control analysis; OR=0·95, 95% CI 0·45–1·97, p=0·884 for propensity score analysis). ITN and entomological data indicated good ITN physical integrity and bioeffi cacy, and no permethrin resistance among local mosquitoes. Interpretation We found no evidence that mass ITN campaigns reduce clinical malaria in this observational study in Haiti; alternative malaria control strategies should be prioritised

Cryptic Eimeria genotypes are common across the southern but not northern hemisphere

The phylum Apicomplexa includes parasites of medical, zoonotic and veterinary significance. Understanding the global distribution and genetic diversity of these protozoa is of fundamental importance for efficient, robust and long-lasting methods of control. Eimeria spp. cause intestinal coccidiosis in all major livestock animals and are the most important parasites of domestic chickens in terms of both economic impact and animal welfare. Despite having significant negative impacts on the efficiency of food production, many fundamental questions relating to the global distribution and genetic variation of Eimeria spp. remain largely unanswered. Here, we provide the broadest map yet of Eimeria occurrence for domestic chickens, confirming that all the known species (Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox, Eimeria tenella) are present in all six continents where chickens are found (including 21 countries). Analysis of 248 internal transcribed spacer sequences derived from 17 countries provided evidence of possible allopatric diversity for species such as E. tenella (FST values ⩽0.34) but not E. acervulina and E. mitis, and highlighted a trend towards widespread genetic variance. We found that three genetic variants described previously only in Australia and southern Africa (operational taxonomic units x, y and z) have a wide distribution across the southern, but not the northern hemisphere. While the drivers for such a polarised distribution of these operational taxonomic unit genotypes remains unclear, the occurrence of genetically variant Eimeria may pose a risk to food security and animal welfare in Europe and North America should these parasites spread to the northern hemisphere

Feasibility and safety of a 6-month exercise program to increase bone and muscle strength in children with juvenile idiopathic arthritis

Background: Arthritis in childhood can be associated with muscle weakness around affected joints, low bone mass and low bone strength. Exercise is recognized as an important part of management of children with juvenile idiopathic arthritis (JIA) but the exercise prescription to best promote bone and muscle health is unknown. We therefore aimed to: 1. assess feasibility and safety of a 6-month home- and group-based exercise program for children with JIA; 2. estimate the effect of program participation on bone mass and strength, muscle function and clinical outcomes and 3. determine if any positive changes in bone and muscle outcomes are maintained 6 months later. Methods: We recruited 24 children with JIA who were part of the Linking Exercise, Physical Activity and Pathophysiology in Childhood Arthritis (LEAP) study to participate in a 6-month home-based exercise program involving jumping and handgrip exercises, resistance training and one group exercise session per month. We assessed lumbar spine bone mass (dual energy X-ray absorptiometry), distal tibia and radius bone microarchitecture and strength (high-resolution peripheral quantitative computed tomography), muscle function (jumping mechanography, dynamometry) and clinical outcomes (joint assessment, function, health-related quality of life) at baseline, 6- and 12-months. Adherence was assessed using weekly activity logs. Results: Thirteen children completed the 6-month intervention. Participants reported 9 adverse events and post-exercise pain was rare (0.4%). Fatigue improved, but there were no other sustained improvements in muscle, bone or clinical outcomes. Adherence to the exercise program was low (47%) and decreased over time. Conclusion: Children with JIA safely participated in a home-based exercise program designed to enhance muscle and bone strength. Fatigue improved, which may in turn facilitate physical activity participation. Prescribed exercise posed adherence challenges and efforts are needed to address facilitators and barriers to participation in and adherence to exercise programs among children with JIA. Trial registration: Data of the children with JIA are from the LEAP study (Canadian Institutes of Health Research (CIHR; GRANT# 107535). http://www.leapjia.com/

The risk and nature of flares in juvenile idiopathic arthritis: Results from the ReACCh-Out cohort

Objective To describe probabilities and characteristics of disease flares in children with juvenile idiopathic arthritis ( JIA) and to identify clinical features associated with an increased risk of flare. Methods We studied children in the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) prospective inception cohort. A flare was defined as a recurrence of disease manifestations after attaining inactive disease and was called significant if it required intensification of treatment. Probability of first flare was calculated with Kaplan-Meier methods, and associated features were identified using Cox regression. Results 1146 children were followed up a median of 24 months after attaining inactive disease. We observed 627 first flares (54.7% of patients) with median active joint count of 1, physician global assessment (PGA) of 12 mm and duration of 27 weeks. Within a year after attaining inactive disease, the probability of flare was 42.5% (95% CI 39% to 46%) for any flare and 26.6% (24% to 30%) for a significant flare. Within a year after stopping treatment, it was 31.7% (28% to 36%) and 25.0% (21% to 29%), respectively. A maximum PGA \u3e30 mm, maximum active joint count \u3e4, rheumatoid factor (RF)-positive polyarthritis, antinuclear antibodies (ANA) and receiving disease-modifying antirheumatic drugs (DMARDs) or biological agents before attaining inactive disease were associated with increased risk of flare. Systemic JIA was associated with the lowest risk of flare. Conclusions In this real-practice JIA cohort, flares were frequent, usually involved a few swollen joints for an average of 6 months and 60% led to treatment intensification. Children with a severe disease course had an increased risk of flare

Predicting which children with juvenile idiopathic arthritis will not attain early remission with conventional treatment: Results from the Reacch-out cohort

Objective. To estimate the probability of early remission with conventional treatment for each child with juvenile idiopathic arthritis (JIA). Children with a low chance of remission may be candidates for initial treatment with biologics or triple disease-modifying antirheumatic drugs (DMARD). Methods. We used data from 1074 subjects in the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) cohort. The predicted outcome was clinically inactive disease for ≥ 6 months starting within 1 year of JIA diagnosis in patients who did not receive early biologic agents or triple DMARD. Models were developed in 200 random splits of 75% of the cohort and tested on the remaining 25% of subjects, calculating expected and observed frequencies of remission and c-index values. Results. Our best Cox logistic model combining 18 clinical variables a median of 2 days after diagnosis had a c-index of 0.69 (95% CI 0.67-0.71), better than using JIA category alone (0.59, 95% CI 0.56-0.63). Children in the lowest probability decile had a 20% chance of remission and 21% attained remission; children in the highest decile had a 69% chance of remission and 73% attained remission. Compared to 5% of subjects identified by JIA category alone, the model identified 14% of subjects as low chance of remission (probability \u3c 0.25), of whom 77% failed to attain remission. Conclusion. Although the model did not meet our a priori performance threshold (c-index \u3e 0.70), it identified 3 times more subjects with low chance of remission than did JIA category alone, and it may serve as a benchmark for assessing value added by future laboratory/imaging biomarkers

Characterization of Notch1 Antibodies That Inhibit Signaling of Both Normal and Mutated Notch1 Receptors

Notch receptors normally play a key role in guiding a variety of cell fate decisions during development and differentiation of metazoan organisms. On the other hand, dysregulation of Notch1 signaling is associated with many different types of cancer as well as tumor angiogenesis, making Notch1 a potential therapeutic target.Here we report the in vitro activities of inhibitory Notch1 monoclonal antibodies derived from cell-based and solid-phase screening of a phage display library. Two classes of antibodies were found, one directed against the EGF-repeat region that encompasses the ligand-binding domain (LBD), and the second directed against the activation switch of the receptor, the Notch negative regulatory region (NRR). The antibodies are selective for Notch1, inhibiting Jag2-dependent signaling by Notch1 but not by Notch 2 and 3 in reporter gene assays, with EC(50) values as low as 5+/-3 nM and 0.13+/-0.09 nM for the LBD and NRR antibodies, respectively, and fail to recognize Notch4. While more potent, NRR antibodies are incomplete antagonists of Notch1 signaling. The antagonistic activity of LBD, but not NRR, antibodies is strongly dependent on the activating ligand. Both LBD and NRR antibodies bind to Notch1 on human tumor cell lines and inhibit the expression of sentinel Notch target genes, including HES1, HES5, and DTX1. NRR antibodies also strongly inhibit ligand-independent signaling in heterologous cells transiently expressing Notch1 receptors with diverse NRR "class I" point mutations, the most common type of mutation found in human T-cell acute lymphoblastic leukemia (T-ALL). In contrast, NRR antibodies failed to antagonize Notch1 receptors bearing rare "class II" or "class III" mutations, in which amino acid insertions generate a duplicated or constitutively sensitive metalloprotease cleavage site. Signaling in T-ALL cell lines bearing class I mutations is partially refractory to inhibitory antibodies as compared to cell-penetrating gamma-secretase inhibitors.Antibodies that compete with Notch1 ligand binding or that bind to the negative regulatory region can act as potent inhibitors of Notch1 signaling. These antibodies may have clinical utility for conditions in which inhibition of signaling by wild-type Notch1 is desired, but are likely to be of limited value for treatment of T-ALLs associated with aberrant Notch1 activation

A Mouse Model of the Human Fragile X Syndrome I304N Mutation

The mental retardation, autistic features, and behavioral abnormalities characteristic of the Fragile X mental retardation syndrome result from the loss of function of the RNA–binding protein FMRP. The disease is usually caused by a triplet repeat expansion in the 5′UTR of the FMR1 gene. This leads to loss of function through transcriptional gene silencing, pointing to a key function for FMRP, but precluding genetic identification of critical activities within the protein. Moreover, antisense transcripts (FMR4, ASFMR1) in the same locus have been reported to be silenced by the repeat expansion. Missense mutations offer one means of confirming a central role for FMRP in the disease, but to date, only a single such patient has been described. This patient harbors an isoleucine to asparagine mutation (I304N) in the second FMRP KH-type RNA–binding domain, however, this single case report was complicated because the patient harbored a superimposed familial liver disease. To address these issues, we have generated a new Fragile X Syndrome mouse model in which the endogenous Fmr1 gene harbors the I304N mutation. These mice phenocopy the symptoms of Fragile X Syndrome in the existing Fmr1–null mouse, as assessed by testicular size, behavioral phenotyping, and electrophysiological assays of synaptic plasticity. I304N FMRP retains some functions, but has specifically lost RNA binding and polyribosome association; moreover, levels of the mutant protein are markedly reduced in the brain specifically at a time when synapses are forming postnatally. These data suggest that loss of FMRP function, particularly in KH2-mediated RNA binding and in synaptic plasticity, play critical roles in pathogenesis of the Fragile X Syndrome and establish a new model for studying the disorder