Browsing by Author "Wang, Q"

Now showing 1 - 9 of 9
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    Direct and cost-efficient hyperpolarization of long-lived nuclear spin states on universal (15)N2-diazirine molecular tags.
    (Sci Adv, 2016-03) Theis, T; Ortiz, GX; Logan, AWJ; Claytor, KE; Feng, Y; Huhn, WP; Blum, V; Malcolmson, SJ; Chekmenev, EY; Wang, Q; Warren, WS
    Conventional magnetic resonance (MR) faces serious sensitivity limitations which can be overcome by hyperpolarization methods, but the most common method (dynamic nuclear polarization) is complex and expensive, and applications are limited by short spin lifetimes (typically seconds) of biologically relevant molecules. We use a recently developed method, SABRE-SHEATH, to directly hyperpolarize (15)N2 magnetization and long-lived (15)N2 singlet spin order, with signal decay time constants of 5.8 and 23 minutes, respectively. We find >10,000-fold enhancements generating detectable nuclear MR signals that last for over an hour. (15)N2-diazirines represent a class of particularly promising and versatile molecular tags, and can be incorporated into a wide range of biomolecules without significantly altering molecular function.
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    Glucose oxidase triggers gelation of N-hydroxyimide-heparin conjugates to form enzyme-responsive hydrogels for cell-specific drug delivery
    (Chemical Science, 2014-11-01) Su, T; Tang, Z; He, H; Li, W; Wang, X; Liao, C; Sun, Y; Wang, Q
    A new strategy for creating enzyme-responsive hydrogels by employing an N-hydroxyimide-heparin conjugate, designed to act as both an enzyme-mediated radical initiator and an enzyme-sensitive therapeutic carrier, is described. A novel enzyme-mediated redox initiation system involving glucose oxidase (GOx), an N-hydroxyimide-heparin conjugate and glucose is reported. The GOx-mediated radical polymerization reaction allows quick formation of hydrogels under mild conditions, with excellent flexibility in the modulation of the physical and chemical characteristics. The heparin-specific enzymatic cleavage reaction enables the delivery of cargo from the hydrogel in amounts that are controlled by the environmental levels of heparanase, which is frequently associated with tumor angiogenesis and metastasis. The formed hydrogels can realize cell-specific drug delivery by targeting cancer cells that are characterized by heparanase overexpression, whilst showing little toxicity towards normal cells. This journal is
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    Hydrogel-coated enzyme electrodes formed by GOx-mediated polymerization for glucose detecting
    (RSC Advances, 2015-01-01) Zhang, Z; Tang, Z; Su, T; Li, W; Wang, Q
    This communication reports the mild fabrication of a hydrogel-coated enzyme electrode for glucose detecting with high sensitivity (35.19 μA mM-1 cm-2) and robust stability.
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    Microgels formed by enzyme-mediated polymerization in reverse micelles with tunable activity and high stability
    (RSC Advances, 2015-01-01) Bao, S; Wu, D; Su, T; Wu, Q; Wang, Q
    This communication describes the preparation of microgels via enzyme-triggered inverse emulsion polymerization, which provides an effective method for immobilizing enzymes with tunable catalytic performance and high stability.
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    Mutation E169K in junctophilin-2 causes atrial fibrillation due to impaired RyR2 stabilization.
    (Journal of the American College of Cardiology, 2013-11) Beavers, DL; Wang, W; Ather, S; Voigt, N; Garbino, A; Dixit, SS; Landstrom, AP; Li, N; Wang, Q; Olivotto, I; Dobrev, D; Ackerman, MJ; Wehrens, XHT
    This study sought to study the role of junctophilin-2 (JPH2) in atrial fibrillation (AF).JPH2 is believed to have an important role in sarcoplasmic reticulum (SR) Ca(2+) handling and modulation of ryanodine receptor Ca(2+) channels (RyR2). Whereas defective RyR2-mediated Ca(2+) release contributes to the pathogenesis of AF, nothing is known about the potential role of JPH2 in atrial arrhythmias.Screening 203 unrelated hypertrophic cardiomyopathy patients uncovered a novel JPH2 missense mutation (E169K) in 2 patients with juvenile-onset paroxysmal AF (pAF). Pseudoknock-in (PKI) mouse models were generated to determine the molecular defects underlying the development of AF caused by this JPH2 mutation.PKI mice expressing E169K mutant JPH2 exhibited a higher incidence of inducible AF than wild type (WT)-PKI mice, whereas A399S-PKI mice expressing a hypertrophic cardiomyopathy-linked JPH2 mutation not associated with atrial arrhythmias were not significantly different from WT-PKI. E169K-PKI but not A399A-PKI atrial cardiomyocytes showed an increased incidence of abnormal SR Ca(2+) release events. These changes were attributed to reduced binding of E169K-JPH2 to RyR2. Atrial JPH2 levels in WT-JPH2 transgenic, nontransgenic, and JPH2 knockdown mice correlated negatively with the incidence of pacing-induced AF. Ca(2+) spark frequency in atrial myocytes and the open probability of single RyR2 channels from JPH2 knockdown mice was significantly reduced by a small JPH2-mimicking oligopeptide. Moreover, patients with pAF had reduced atrial JPH2 levels per RyR2 channel compared to sinus rhythm patients and an increased frequency of spontaneous Ca(2+) release events.Our data suggest a novel mechanism by which reduced JPH2-mediated stabilization of RyR2 due to loss-of-function mutation or reduced JPH2/RyR2 ratios can promote SR Ca(2+) leak and atrial arrhythmias, representing a potential novel therapeutic target for AF.
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    Novel junctophilin-2 mutation A405S is associated with basal septal hypertrophy and diastolic dysfunction.
    (JACC. Basic to translational science, 2017-02) Quick, AP; Landstrom, AP; Wang, Q; Beavers, DL; Reynolds, JO; Barreto-Torres, G; Tran, V; Showell, J; Philippen, LE; Morris, SA; Skapura, D; Bos, JM; Pedersen, SE; Pautler, RG; Ackerman, MJ; Wehrens, XHT
    BACKGROUND:Hypertrophic cardiomyopathy (HCM), defined as asymmetric left ventricular hypertrophy, is a leading cause of cardiac death in the young. Perturbations in calcium (Ca2+) handling proteins have been implicated in the pathogenesis of HCM. JPH2-encoded junctophilin 2 is a major component of the junctional membrane complex, the subcellular microdomain involved in excitation-contraction coupling. We hypothesized that a novel JPH2 mutation identified in patients with HCM is causally linked to HCM, and alters intracellular Ca2+ signaling in a pro-hypertrophic manner. OBJECTIVES:To determine using a transgenic mouse model whether a JPH2 mutation found in a HCM patient is responsible for disease development. METHODS:Genetic interrogation of a large cohort of HCM cases was conducted for all coding exons of JPH2. Pseudo-knock-in (PKI) mice containing a novel JPH2 variant were subjected to echocardiography, cardiac MRI, hemodynamic analysis, and histology. RESULTS:A novel JPH2 mutation, A405S, was identified in a genotype-negative proband with significant basal septal hypertrophy. Although initially underappreciated by traditional echocardiographic imaging, PKI mice with this JPH2 mutation (residue A399S in mice) were found to exhibit similar basal hypertrophy using a newly developed echo imaging plane, and this was confirmed using cardiac MRI. Histological analysis demonstrated cardiomyocyte hypertrophy and disarray consistent with HCM. CONCLUSIONS:Variant A405S is a novel HCM-associated mutation in JPH2 found in a proband negative for mutations in the canonical HCM-associated genes. Studies in the analogous mouse model demonstrated for the first time a causal link between a JPH2 defect and HCM. Moreover, novel imaging approaches identified subvalvular septal hypertrophy, specific findings also reported in the human JPH2 mutation carrier.
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    Reduced junctional Na+/Ca2+-exchanger activity contributes to sarcoplasmic reticulum Ca2+ leak in junctophilin-2-deficient mice.
    (American journal of physiology. Heart and circulatory physiology, 2014-11) Wang, W; Landstrom, AP; Wang, Q; Munro, ML; Beavers, D; Ackerman, MJ; Soeller, C; Wehrens, XHT
    Expression silencing of junctophilin-2 (JPH2) in mouse heart leads to ryanodine receptor type 2 (RyR2)-mediated sarcoplasmic reticulum (SR) Ca(2+) leak and rapid development of heart failure. The mechanism and physiological significance of JPH2 in regulating RyR2-mediated SR Ca(2+) leak remains elusive. We sought to elucidate the role of JPH2 in regulating RyR2-mediated SR Ca(2+) release in the setting of cardiac failure. Cardiac myocytes isolated from tamoxifen-inducible conditional knockdown mice of JPH2 (MCM-shJPH2) were subjected to confocal Ca(2+) imaging. MCM-shJPH2 cardiomyocytes exhibited an increased spark frequency width with altered spark morphology, which caused increased SR Ca(2+) leakage. Single channel studies identified an increased RyR2 open probability in MCM-shJPH2 mice. The increase in spark frequency and width was observed only in MCM-shJPH2 and not found in mice with increased RyR2 open probability with native JPH2 expression. Na(+)/Ca(2+)-exchanger (NCX) activity was reduced by 50% in MCM-shJPH2 with no detectable change in NCX expression. Additionally, 50% inhibition of NCX through Cd(2+) administration alone was sufficient to increase spark width in myocytes obtained from wild-type mice. Additionally, superresolution analysis of RyR2 and NCX colocalization showed a reduced overlap between RyR2 and NCX in MCM-shJPH2 mice. In conclusion, decreased JPH2 expression causes increased SR Ca(2+) leakage by directly increasing open probability of RyR2 and by indirectly reducing junctional NCX activity through increased dyadic cleft Ca(2+). This demonstrates two novel and independent cellular mechanisms by which JPH2 regulates RyR2-mediated SR Ca(2+) leak and heart failure development.
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    Survivin as a therapeutic target in Sonic hedgehog-driven medulloblastoma.
    (Oncogene, 2015-07) Brun, SN; Markant, SL; Esparza, LA; Garcia, G; Terry, D; Huang, J-M; Pavlyukov, MS; Li, X-N; Grant, GA; Crawford, JR; Levy, ML; Conway, EM; Smith, LH; Nakano, I; Berezov, A; Greene, MI; Wang, Q; Wechsler-Reya, RJ
    Medulloblastoma (MB) is a highly malignant brain tumor that occurs primarily in children. Although surgery, radiation and high-dose chemotherapy have led to increased survival, many MB patients still die from their disease, and patients who survive suffer severe long-term side effects as a consequence of treatment. Thus, more effective and less toxic therapies for MB are critically important. Development of such therapies depends in part on identification of genes that are necessary for growth and survival of tumor cells. Survivin is an inhibitor of apoptosis protein that regulates cell cycle progression and resistance to apoptosis, is frequently expressed in human MB and when expressed at high levels predicts poor clinical outcome. Therefore, we hypothesized that Survivin may have a critical role in growth and survival of MB cells and that targeting it may enhance MB therapy. Here we show that Survivin is overexpressed in tumors from patched (Ptch) mutant mice, a model of Sonic hedgehog (SHH)-driven MB. Genetic deletion of survivin in Ptch mutant tumor cells significantly inhibits proliferation and causes cell cycle arrest. Treatment with small-molecule antagonists of Survivin impairs proliferation and survival of both murine and human MB cells. Finally, Survivin antagonists impede growth of MB cells in vivo. These studies highlight the importance of Survivin in SHH-driven MB, and suggest that it may represent a novel therapeutic target in patients with this disease.
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    Understanding GPU Programming for Statistical Computation: Studies in Massively Parallel Massive Mixtures.
    (J Comput Graph Stat, 2010-06-01) Suchard, MA; Wang, Q; Chan, C; Frelinger, J; Cron, AJ; West, M
    This article describes advances in statistical computation for large-scale data analysis in structured Bayesian mixture models via graphics processing unit (GPU) programming. The developments are partly motivated by computational challenges arising in fitting models of increasing heterogeneity to increasingly large datasets. An example context concerns common biological studies using high-throughput technologies generating many, very large datasets and requiring increasingly high-dimensional mixture models with large numbers of mixture components. We outline important strategies and processes for GPU computation in Bayesian simulation and optimization approaches, give examples of the benefits of GPU implementations in terms of processing speed and scale-up in ability to analyze large datasets, and provide a detailed, tutorial-style exposition that will benefit readers interested in developing GPU-based approaches in other statistical models. Novel, GPU-oriented approaches to modifying existing algorithms software design can lead to vast speed-up and, critically, enable statistical analyses that presently will not be performed due to compute time limitations in traditional computational environments. Supplemental materials are provided with all source code, example data, and details that will enable readers to implement and explore the GPU approach in this mixture modeling context.