BACKGROUND: The identification of protective immune responses to P. falciparum infection is an important goal for the development of a vaccine for malaria. This requires the identification of susceptible and resistant individuals, so that their immune responses may be studied. Time-to-infection studies are one method for identifying putative susceptible individuals (infected early) versus resistant individuals (infected late). However, the timing of infection is dependent on random factors, such as whether the subject was bitten by an infected mosquito, as well as individual factors, such as their level of immunity. It is important to understand how much of the observed variation in infection is simply due to chance.
METHODS: We analyse previously published data from a treatment-time-to-infection study of 201 individuals aged 0.5 to 78 years living in Western Kenya. We use a mathematical modelling approach to investigate the role of immunity versus random factors in determining time-to-infection in this cohort. We extend this analysis using a modelling approach to understand what factors might increase or decrease the utility of these studies for identifying susceptible and resistant individuals.
RESULTS: We find that, under most circumstances, the observed distribution of time-to-infection is consistent with this simply being a random process. We find that age, method for detection of infection (PCR versus microscopy), and underlying force of infection are all factors in determining whether time-to-infection is a useful correlate of immunity.
CONCLUSIONS: Many epidemiological studies of P. falciparum infection assume that the observed variation in infection outcomes, such as time-to-infection or presence or absence of infection, is determined by host resistance or susceptibility. However, under most circumstances, this distribution appears largely due to the random timing of infection, particularly in children. More direct measurements, such as parasite growth rate, may be more useful than time-to-infection in segregating patients based on their level of immunity.
Oncogenic transcriptional coregulators C-terminal Binding Protein (CtBP) 1 and 2 possess regulatory d-isomer specific 2-hydroxyacid dehydrogenase (D2-HDH) domains that provide an attractive target for small molecule intervention. Findings that the CtBP substrate 4-methylthio 2-oxobutyric acid (MTOB) can interfere with CtBP oncogenic activity in cell culture and in mice confirm that such inhibitors could have therapeutic benefit. Recent crystal structures of CtBP 1 and 2 revealed that MTOB binds in an active site containing a dominant tryptophan and a hydrophilic cavity, neither of which are present in other D2-HDH family members. Here, we demonstrate the effectiveness of exploiting these active site features for the design of high affinity inhibitors. Crystal structures of two such compounds, phenylpyruvate (PPy) and 2-hydroxyimino-3-phenylpropanoic acid (HIPP), show binding with favorable ring stacking against the CtBP active site tryptophan and alternate modes of stabilizing the carboxylic acid moiety. Moreover, ITC experiments show that HIPP binds to CtBP with an affinity greater than 1000-fold over that of MTOB, and enzymatic assays confirm that HIPP substantially inhibits CtBP catalysis. These results, thus, provide an important step, and additional insights, for the development of highly selective antineoplastic CtBP inhibitors.
Society for Vascular Surgery practice guidelines for atherosclerotic occlusive disease of the lower extremities: management of asymptomatic disease and claudication
Peripheral arterial disease (PAD) continues to grow in global prevalence and consumes an increasing amount of resources in the United States health care system. Overall rates of intervention for PAD have been rising steadily in recent years. Changing demographics, evolution of technologies, and an expanding database of outcomes studies are primary forces influencing clinical decision making in PAD. The management of PAD is multidisciplinary, involving primary care physicians and vascular specialists with varying expertise in diagnostic and treatment modalities. PAD represents a broad spectrum of disease from asymptomatic through severe limb ischemia. The Society for Vascular Surgery Lower Extremity Practice Guidelines committee reviewed the evidence supporting clinical care in the treatment of asymptomatic PAD and intermittent claudication (IC). The committee made specific practice recommendations using the GRADE (Grades of Recommendation Assessment, Development and Evaluation) system. There are limited Level I data available for many of the critical questions in the field, demonstrating the urgent need for comparative effectiveness research in PAD. Emphasis is placed on risk factor modification, medical therapies, and broader use of exercise programs to improve cardiovascular health and functional performance. Screening for PAD appears of unproven benefit at present. Revascularization for IC is an appropriate therapy for selected patients with disabling symptoms, after a careful risk-benefit analysis. Treatment should be individualized based on comorbid conditions, degree of functional impairment, and anatomic factors. Invasive treatments for IC should provide predictable functional improvements with reasonable durability. A minimum threshold of a > 50% likelihood of sustained efficacy for at least 2 years is suggested as a benchmark. Anatomic patency (freedom from restenosis) is considered a prerequisite for sustained efficacy of revascularization in IC. Endovascular approaches are favored for most candidates with aortoiliac disease and for selected patients with femoropopliteal disease in whom anatomic durability is expected to meet this minimum threshold. Conversely, caution is warranted in the use of interventions for IC in anatomic settings where durability is limited (extensive calcification, small-caliber arteries, diffuse infrainguinal disease, poor runoff). Surgical bypass may be a preferred strategy in good-risk patients with these disease patterns or in those with prior endovascular failures. Common femoral artery disease should be treated surgically, and saphenous vein is the preferred conduit for infrainguinal bypass grafting. Patients who undergo invasive treatments for IC should be monitored regularly in a surveillance program to record subjective improvements, assess risk factors, optimize compliance with cardioprotective medications, and monitor hemodynamic and patency status.
Copyright © 2015 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
I trust the US Preventive Services Task Force to be unbiased and to base its recommendations on the best science available at the time (though this group clearly needs a catchier name). Despite that, I have been forced to conclude that C should, frequently, be a failing grade for the USPSTF. I am referring to issuing recommendations with a C grade...
OBJECTIVE: The roles of microRNAs (miRNAs) in coronary heart disease (CHD) have not been well characterized. This study sought to systematically characterize the complex genomic architecture of CHD by integrating whole blood miRNA and mRNA expression with genetic variation in 186 CHD cases and 186 controls.
APPROACH AND RESULTS: At false discovery rate < 0.2, 15 miRNAs were differentially expressed between CHD cases and controls. To explore regulatory mechanisms, we integrated miRNA and mRNA expression with genome-wide genotype data to investigate miRNA and mRNA associations and relationships of genetic variation with miRNAs. We identified a large number of correlated miRNA-mRNA pairs and genetic loci that seem to regulate miRNA levels. Subsequently, we explored the relationships of these complex molecular associations with CHD status. We identified a large difference in miRNA-mRNA associations between CHD cases and controls, as demonstrated by a significantly higher proportion of inversely correlated miRNA-mRNA pairs in cases versus controls (80% versus 30%; P < 1x10(-16)), suggesting a genome-wide shift in the regulatory structure of the transcriptome in CHD. The differentially coexpressed miRNA-mRNA pairs showed enrichment for CHD risk genetic variants affecting both miRNA and mRNA expression levels, implicating a putatively causal role in CHD. Furthermore, 3 miRNAs (miR-1275, miR-365a-3p, and miR-150-5p) were associated with an mRNA coexpression module that was causally linked to CHD and reflected the dysregulation of B-cell centered immune function.
CONCLUSIONS: Our results provide novel evidence that miRNAs are important regulators of biological processes involved in CHD via genetic control and via their tight coexpression with mRNAs.
Few studies have investigated simple discrimination and discrimination reversal learning by children younger than 2 years. Extant research has shown that teaching discrimination reversals may be challenging with this population. We used social reinforcement and correction procedures to teach simple simultaneous discrimination and discrimination reversal tasks involving three pairs of animal pictures displayed in a paper notebook. Participants were eight typically-developing toddlers aged 15-23 months. All learned at least one simple discrimination/discrimination reversal problem. Four children learned all problems and showed evidence of learning set formation. Perhaps surprisingly, discrimination reversals were sometimes learned more rapidly than original discriminations. The procedures suggest a potentially efficient methodology for investigating more complex aspects of relational learning in toddlers.
Drug resistance is caused by mutations that change the balance of recognition favoring substrate cleavage over inhibitor binding. Here, a structural dynamics perspective of the regained wild-type functioning in mutant HIV-1 proteases with coevolution of the natural substrates is provided. The collective dynamics of mutant structures of the protease bound to p1-p6 and NC-p1 substrates are assessed using the Anisotropic Network Model (ANM). The drug-induced protease mutations perturb the mechanistically crucial hinge axes that involve key sites for substrate binding and dimerization and mainly coordinate the intrinsic dynamics. Yet with substrate coevolution, while the wild-type dynamic behavior is restored in both p1-p6 ((LP) (1'F)p1-p6D30N/N88D) and NC-p1 ((AP) (2) (V)NC-p1V82A) bound proteases, the dynamic behavior of the NC-p1 bound protease variants (NC-p1V82A and (AP) (2) (V)NC-p1V82A) rather resemble those of the proteases bound to the other substrates, which is consistent with experimental studies. The orientational variations of residue fluctuations along the hinge axes in mutant structures justify the existence of coevolution in p1-p6 and NC-p1 substrates, that is, the dynamic behavior of hinge residues should contribute to the interdependent nature of substrate recognition. Overall, this study aids in the understanding of the structural dynamics basis of drug resistance and evolutionary optimization in the HIV-1 protease system.
Templated repair of long bone defects in rats with bioactive spiral-wrapped electrospun amphiphilic polymer/hydroxyapatite scaffolds
Effective repair of critical-size long bone defects presents a significant clinical challenge. Electrospun scaffolds can be exploited to deliver protein therapeutics and progenitor cells, but their standalone application for long bone repair has not been explored. We have previously shown that electrospun composites of amphiphilic poly(d,l-lactic acid)-co-poly(ethylene glycol)-co-poly(d,l-lactic acid) (PELA) and hydroxyapatite (HA) guide the osteogenic differentiation of bone marrow stromal cells (MSCs), making these scaffolds uniquely suited for evaluating cell-based bone regeneration approaches. Here we examine whether the in vitro bioactivity of these electrospun scaffolds can be exploited for long bone defect repair, either through the participation of exogenous MSCs or through the activation of endogenous cells by a low dose of recombinant human bone morphogenetic protein-2 (rhBMP-2). In critical-size rat femoral segmental defects, spiral-wrapped electrospun HA-PELA with preseeded MSCs resulted in laminated endochondral ossification templated by the scaffold across the longitudinal span of the defect. Using GFP labeling, we confirmed that the exogenous MSCs adhered to HA-PELA survived at least 7 days postimplantation, suggesting direct participation of these exogenous cells in templated bone formation. When loaded with 500 ng of rhBMP-2, HA-PELA spirals led to more robust but less clearly templated bone formation than MSC-bearing scaffolds. Both treatment groups resulted in new bone bridging over the majority of the defect by 12 weeks. This study is the first demonstration of a standalone bioactive electrospun scaffold for templated bone formation in critical-size long bone defects.
Alcohol-induced miR-27a regulates differentiation and M2 macrophage polarization of normal human monocytes
Alcohol abuse is a leading cause of liver disease characterized by liver inflammation, fatty liver, alcoholic hepatitis, or liver cirrhosis. Immunomodulatory effects of alcohol on monocytes and macrophages contribute to alcoholic liver disease. Alcohol use, an independent risk factor for progression of hepatitis C virus (HCV) infection-mediated liver disease, impairs host defense and alters cytokine production and monocyte/macrophage activation. We hypothesized that alcohol and HCV have synergistic effects on the phenotype and function of monocytes. Our data show that acute alcohol binge drinking in healthy volunteers results in increased frequency of CD16(+) and CD68(+) and M2-type (CD206(+), dendritic cell [DC]-SIGN(+)-expressing and IL-10-secreting) circulating CD14(+) monocytes. Expression of HCV-induced CD68 and M2 markers (CD206 and DC-SIGN) in normal monocytes was further enhanced in the presence of alcohol. The levels of microRNA (miR)-27a was significantly upregulated in monocytes cultured in the presence of alcohol or alcohol and HCV as compared with HCV alone. The functional role of miR-27a in macrophage polarization was demonstrated by transfecting monocytes with an miR-27a inhibitor that resulted in reduced alcohol- and HCV- mediated monocyte activation (CD14 and CD68 expression), polarization (CD206 and DC-SIGN expression), and IL-10 secretion. Overexpression of miR-27a in monocytes enhanced IL-10 secretion via activation of the ERK signaling pathway. We found that miR-27a promoted ERK phosphorylation by downregulating the expression of ERK inhibitor sprouty2 in monocytes. Thus, we identified that sprouty2 is a target of miR-27a in human monocytes. In summary, our study demonstrates the regulatory role of miR-27a in alcohol-induced monocyte activation and polarization.
Mechanistic Analysis of Differential Signal Transduction Mediated by the Insulin Receptor Substrate Proteins IRS-1 and IRS-2: A Dissertation
The Insulin Receptor Substrate (IRS) proteins IRS-1 and IRS-2 are cytoplasmic adaptor proteins that organize and propagate intracellular signaling downstream of specific growth factor receptors, including the Insulin and Insulin-Like Growth Factor-1 Receptors (IR and IGF-1R, respectively). Despite sharing a high level of homology and the ability to stimulate Phosphotidylinositol-3-Kinase (PI3K) and Mitogen-Activated Protein Kinase (MAPK) signaling, IRS-1 and IRS-2 play distinct roles in mammary tumor progression. Specifically, IRS-1 promotes growth and proliferation, whereas IRS- 2 promotes motility, invasion, survival, aerobic glycolyis, and metastasis. To further understand the differences between IRS-1 and IRS-2, I investigated the mechanistic basis of IRS-2-mediated PI3K activation. I identified tyrosines in IRS-2 that mediate its recruitment and activation of PI3K in response to insulin and IGF-1 stimulation. Using a PI3K-binding deficient IRS-2 mutant, I demonstrated that IRS-2-dependent PI3K signaling promotes aerobic glycolysis through its ability to selectively regulate the phosphorylation of the Akt effector Glycogen Synthase Kinase-3β (Gsk-3β). I also performed a rigorous comparison of IRS-1 and IRS-2 signal transduction and their ability to regulate functions associated with tumor progression. These studies required the generation of a novel model system where IRS-1 and IRS-2 function could be compared in a genetically identical background. Using this model, I confirmed a role for IRS-1 in growth regulation and IRS-2 in tumor cell invasion, as well as expanded the understanding of differential IRS protein function by showing that IRS-2 more vi effectively promotes Akt activation. The model system I have established can be used for further characterization of IRS-1 and IRS-2-specific functions.
Function and Regulation of the α6 Integrins in Mammary Epithelial Biology and Breast Cancer: A Dissertation
Integrins have the ability to impact major aspects of epithelial biology including adhesion, migration, invasion, signaling and differentiation, as well as the formation and progression of cancer (Hynes 2002; Srichai and Zent 2010; Anderson et al. 2014). This thesis focuses on how integrins are regulated and function in the context of mammary epithelial biology and breast cancer with a specific focus on the α6 integrin heterodimers (α6β1 and α6β4). These integrins function primarily as receptors for the laminin family of extracellular matrix (ECM) proteins and they have been implicated in mammary gland biology and breast cancer (Friedrichs et al. 1995; Wewer et al. 1997; Mercurio et al. 2001; Margadant and Sonnenberg 2010; Muschler and Streuli 2010; Nistico et al. 2014).
The first project investigates how alternative splicing of the α6 subunit impacts the genesis and function of breast cancer stem cells (CSCs). This work revealed that the α6Bβ1 splice variant, but not α6Aβ1, is necessary for the function of breast CSCs because it activates the Hippo transducer TAZ (Zhao et al. 2008a), which is known to be essential for breast CSCs (Cordenonsi et al. 2011). My work also led to the discovery that laminin (LM) 511 is the specific ligand for α6Bβ1 and that autocrine LM511, which is mediated by TAZ, is needed to sustain breast CSCs by functioning as a ‘ECM niche’. An important aspect of this study is the finding that surface-bound LM511 characterizes a small population of cells in human breast tumors with CSC properties.
The second project of my thesis concentrated on identifying transcription factors that regulate expression of the β4 subunit. The expression of the α6β4 integrin is repressed during the epithelial-mesenchymal transition (EMT) (Yang et al. 2009) but the contribution of specific transcription factors to this repression is poorly understood. This study revealed that Snai1 is a transcriptional repressor of β4, which is responsible for establishing the PRC2 (Polycomb complex 2)- associated repressive histone mark H3K27Me3. However, I also found that the ability of Snai1 to repress transcription is abrogated by its interaction with Id2. Specifically, I identified the biochemical mechanism for how Id2 regulates Snai1. Id2 binds the SNAG domain of Snai1 that is the docking site for several corepressors (Peinado et al. 2004; Lin et al. 2010b; Dong et al. 2012a). One important consequence of Id2 interacting with Snai1 on the β4 promoter is that it prevents repressive epigenetic modifications. This finding may explain why some epithelial cells express Snai1 and β4 because they also express Id2 (Vincent et al. 2009; Bastea et al. 2012). The repression of the α6β4 integrin during the EMT is consistent with data indicating that this integrin is not expressed in CSCs (Mani et al. 2008; Goel et al. 2012; Goel et al. 2013; Goel et al. 2014). An important question going forward is to understand how the α6β4 integrin contributes to tumor formation.
In summary, my thesis provides novel insights into the biology of the α6 integrins that has important implications for the function of these integrins in mammary gland biology and breast cancer, especially our understanding of breast CSCs.
Wolfram syndrome is a genetic disorder characterized by diabetes and neurodegeneration. Two causative genes have been identified so far, WFS1 and WFS2, both encoding endoplasmic reticulum (ER) localized transmembrane proteins. Since WFS1 is involved in the ER stress pathway, Wolfram syndrome is considered an ER disease. Despite the underlying importance of ER dysfunction in Wolfram syndrome, the molecular mechanism linking ER to the death of β cells and neurons has not been elucidated.
The endoplasmic reticulum (ER) is an organelle that forms a network of enclosed sacs and tubes that connect the nuclear membrane and other organelles including Golgi and mitochondria. ER plays critical functions in protein folding, protein transport, lipid metabolism, and calcium regulation. Dysregulation of ER function disrupts normal cell metabolism and activates an array of anti-survival pathways, eventually leading to disease state.
Here we show that calpain is involved in both prototypes of Wolfram syndrome. Calpain 2 activity is negatively regulated by WFS2 protein, and hyper-activation of calpain 2 by WFS2-knockdown leads to cell death. Calpain hyper-activation is also present in WFS1 loss of function cells due to the high cytosolic calcium. Extensive calpain activation exists in the Wolfram syndrome mouse model as well as in patient cells. A compound screen targeting ER homeostasis reveals that dantrolene, a ryanodine receptor inhibitor, can prevent cell death in cell models of Wolfram syndrome. Our results demonstrate that the pathway leading to calpain activation provides potential therapeutic targets for Wolfram syndrome and other ER diseases.
A Tale of Two Projects: Basis for Centrosome Amplification after DNA Damage and Practical Assessment of Photodamage in Live-Cell Imaging: A Dissertation
This thesis comprises two separate studies that focus on the consequences of cellular damage. The first investigates the effects of DNA damage on centriole behavior and the second characterizes phototoxicity during live-cell imaging.
Cancer treatments such as ionizing radiation and/or chemotherapeutic DNA damaging agents are intended to kill tumor cells, but they also damage normal proliferating cells. Although centrosome amplification after DNA damage is a well-established phenomenon for transformed cells, it is not fully understood in untransformed cells. The presence of extra centrosomes in normal cell populations raises the chances of genomic instability, thus posing additional threats to patients undergoing these therapies. I characterized centriole behavior after DNA damage in synchronized untransformed (RPE1) human cells. Treatment with the radiomimetic drug, Doxorubicin, prolongs G2 phase by at least 72hrs, where 52% of cells display disengaged centrioles and 10% contain extra centrioles. This disengagement is mediated by Plk and APC/C activities both singly and in combination. Disengaged centrioles are associated with maturation markers suggesting they are capable of organizing spindle poles. Despite the high incidence of centriole disengagement, only a small percentage of centrioles reduplicate due to p53/p21 dependent inhibition of Cdk2 activity. Although all cells become prolonged in G2 phase, 14% eventually go through mitosis, of which 26% contain disengaged or extra centrioles.
In addition to cancer treatments, cellular damage can be acquired from various external conditions. Short wavelengths of light are known to be toxic to living cells, but are commonly used during live-cell microscopy to excite fluorescent proteins. I characterized the phototoxic effects of blue (488nm) and green (546nm) light on cell cycle progression in RPE1. For unlabeled cells, I found that exposure to green light is far less toxic than blue light, but is not benign. However, the presence of fluorescent proteins led to increased sensitivity to both blue and green light. For 488nm irradiations, spreading the total irradiation durations out into a series of 10s pulses or conducting single longer, but lower intensity, exposures made no significant changes in phototoxicity. However, reducing oxidative stress by culturing cells at physiological (~3%) oxygen, or treatment with a water-soluble antioxidant, Trolox, greatly improved the cells tolerance to blue light.
Collectively, my work offers an explanation for centrosome amplification after DNA damage and demonstrates the importance of proper centriole regulation in untransformed human cells. Further, it provides a practical assessment of photodamage during live-cell imaging.
Depression is the leading cause of disability among women of reproductive age worldwide. Upwards of 1 in 5 women suffer from perinatal depression. This condition has deleterious effects on several birth outcomes, infant attachment, and children’s behavior/development. Maternal suicide causes 20% of postpartum deaths in depressed women. Although the vast majority of perinatal women are amenable to being screened for depression, screening alone does not improve treatment rates or patient outcomes. Obstetrics/Gynecology (Ob/Gyn) clinics need supports in place to adequately address depression in their patient populations. The primary goal of this thesis is to develop, refine, and pilot test a new low-cost and sustainable stepped care program for Ob/Gyn clinics that will improve perinatal women’s depression treatment rates and outcomes. We developed and beta tested the Rapid Access to Perinatal Psychiatric Care in Depression (RAPPID) Program, to create a comprehensive intervention that is proactive, multifaceted, and practical. RAPPID aims to improve perinatal depression treatment and treatment response rates through: (1) access to immediate resource provision/referrals and psychiatric telephone consultation for Ob/Gyn providers; (2) clinic-specific implementation of depression care, including training support and toolkits; and (3) proactive depression screening, assessment, and treatment in OB/Gyn clinics. RAPPID builds on a low-cost and widely disseminated population-based model for delivering psychiatric care in primary care settings. Formative data and feedback from key stakeholders also informed the development of RAPPID. Our formative and pilot work in real-world settings suggests RAPPID is feasible and has the potential to improve depression detection and treatment in Ob/Gyn settings. The next step will be to compare two active interventions, RAPPID vs. enhanced usual care (access to resource provision/referrals and psychiatric telephone consultation) in a cluster-randomized trial in which we will randomize 12 Ob/Gyn clinics to either RAPPID or enhanced usual care.
A Population-Based Perspective on Clinically Recognized Venous Thromboembolism: Contemporary Trends in Clinical Epidemiology and Risk Assessment of Recurrent Events: A Dissertation
Background: Venous thromboembolism (VTE), comprising the conditions of deep vein thrombosis (DVT) and pulmonary embolism (PE), is a common acute cardiovascular event associated with increased long-term morbidity, functional disability, all-cause mortality, and high rates of recurrence. Major advances in identification, prophylaxis, and treatment over the past 3-decades have likely changed its clinical epidemiology. However, there are little published data describing contemporary, population-based, trends in VTE prevention and management.
Objectives: To examine recent trends in the epidemiology of clinically recognized VTE and assess the risk of recurrence after a first acute episode of VTE.
Methods: We used population-based surveillance to monitor trends in acute VTE among residents of the Worcester, Massachusetts, metropolitan statistical area (WMSA) from 1985 through 2009, including in-hospital and ambulatory settings.
Results: Among 5,025 WMSA residents diagnosed with acute PE and/or lower-extremity DVT between 1985 and 2009 (mean age = 65 years), 46% were men and 95% were white. Age- and sex-adjusted annual event rates (per 100, 000) of clinically recognized acute first-time and recurrent VTE was 142 overall, increasing from 112 in 1985/86 to 168 in 2009, due primarily to increases in PE occurrence. During this period, non-invasive diagnostic VTE testing increased, vi while treatment shifted from the in-hospital (chiefly with warfarin and unfractionated heparin) to out-patient setting (chiefly with low-molecular-weight heparins and newer anticoagulants). Among those with community-presenting first-time VTE, subsequent 3-year cumulative event rates of key outcomes decreased from 1999 to 2009, including all-cause mortality (41% to 26%), major bleeding episodes (12% to 6%), and recurrent VTE (17% to 9%). Active-cancer (with or without chemotherapy), a hypercoagulable state, varicose vein stripping, and Inferior vena cava filter placement were independent predictors of recurrence during short- (3-month) and long-term (3-year) follow-up after a first acute episode of VTE. We developed risk score calculators for VTE recurrence based on a 3-month prognostic model for all patients and separately for patients without active cancer.
Conclusions: Despite advances in identification, prophylaxis, and treatment between 1985 and 2009, the disease burden from VTE in residents of central Massachusetts remains high, with increasing annual events. Declines in the frequency of major adverse outcomes between 1999 and 2009 were reassuring. Still, mortality, major bleeding, and recurrence rates remained high, suggesting opportunities for improved prevention and treatment. Clinicians may be able to use the identified predictors of recurrence and risk score calculators to estimate the risk of VTE recurrence and tailor outpatient treatments to individual patients.
The immune system can recognize virtually any antigen, yet T cell responses against several pathogens, including Mycobacterium tuberculosis, are restricted to a limited number of immunodominant epitopes. The host factors that affect immunodominance are incompletely understood. Whether immunodominant epitopes elicit protective CD8+ T cell responses or instead act as decoys to subvert immunity and allow pathogens to establish chronic infection is unknown. Here we show that anatomically distinct human granulomas contain clonally expanded CD8+ T cells with overlapping T cell receptor (TCR) repertoires. Similarly, the murine CD8+ T cell response against M. tuberculosis is dominated by TB10.44-11-specific T cells with extreme TCRβ bias. Using a retrogenic model of TB10.44-11-specific CD8+ T cells, we show that TCR dominance can arise because of competition between clonotypes driven by differences in affinity. Finally, we demonstrate that TB10.4-specific CD8+ T cells mediate protection against tuberculosis, which requires interferon-γ production and TAP1-dependent antigen presentation in vivo. Our study of how immunodominance, biased TCR repertoires, and protection are inter-related, provides a new way to measure the quality of T cell immunity, which if applied to vaccine evaluation, could enhance our understanding of how to elicit protective T cell immunity.
RNAi has become an essential tool in C. elegans research. This unit describes procedures for RNAi in C. elegans by microinjecting with dsRNA, feeding with bacteria expressing dsRNA, and soaking in dsRNA solution, as well as high-throughput methods for RNAi-based screens. (c) 2015 by John Wiley and Sons, Inc.
Let a hundred flowers bloom: the role of context dependence in creating phenotypic diversity following targeted therapy
Using a newly developed computational platform, COSPER, Litvin et al. (2015) identify context-dependent interactions between MEK and interferon signaling that underlie sensitivity and resistance to MEK inhibition in melanoma.
In addition to mediating sister chromatid cohesion during the cell cycle, the cohesin complex associates with CTCF and with active gene regulatory elements to form long-range interactions between its binding sites. Genome-wide chromosome conformation capture had shown that cohesin's main role in interphase genome organization is in mediating interactions within architectural chromosome compartments, rather than specifying compartments per se. However, it remains unclear how cohesin-mediated interactions contribute to the regulation of gene expression. We have found that the binding of CTCF and cohesin is highly enriched at enhancers and in particular at enhancer arrays or "super-enhancers" in mouse thymocytes. Using local and global chromosome conformation capture, we demonstrate that enhancer elements associate not just in linear sequence, but also in 3D, and that spatial enhancer clustering is facilitated by cohesin. The conditional deletion of cohesin from noncycling thymocytes preserved enhancer position, H3K27ac, H4K4me1, and enhancer transcription, but weakened interactions between enhancers. Interestingly, approximately 50% of deregulated genes reside in the vicinity of enhancer elements, suggesting that cohesin regulates gene expression through spatial clustering of enhancer elements. We propose a model for cohesin-dependent gene regulation in which spatial clustering of enhancer elements acts as a unified mechanism for both enhancer-promoter "connections" and "insulation."
How disease-associated mutations impair protein activities in the context of biological networks remains mostly undetermined. Although a few renowned alleles are well characterized, functional information is missing for over 100,000 disease-associated variants. Here we functionally profile several thousand missense mutations across a spectrum of Mendelian disorders using various interaction assays. The majority of disease-associated alleles exhibit wild-type chaperone binding profiles, suggesting they preserve protein folding or stability. While common variants from healthy individuals rarely affect interactions, two-thirds of disease-associated alleles perturb protein-protein interactions, with half corresponding to "edgetic" alleles affecting only a subset of interactions while leaving most other interactions unperturbed. With transcription factors, many alleles that leave protein-protein interactions intact affect DNA binding. Different mutations in the same gene leading to different interaction profiles often result in distinct disease phenotypes. Thus disease-associated alleles that perturb distinct protein activities rather than grossly affecting folding and stability are relatively widespread.