Project description:In sickle cell disease, ischemia-reperfusion injury and intravascular hemolysis produce endothelial dysfunction and vasculopathy characterized by reduced nitric oxide (NO) and arginine bioavailability. Recent functional studies of platelets in patients with sickle cell disease reveal a basally activated state, suggesting that pathological platelet activation may contribute to sickle cell disease vasculopathy. Studies were therefore undertaken to examine transcriptional signaling pathways in platelets that may be dysregulated in sickle cell disease. We demonstrate and validate here the feasibility of comparative platelet transcriptome studies on clinical samples from single donors, by the application of RNA amplification followed by microarray-based analysis of 54,000 probe sets. Data mining an existing microarray database, we identified 220 highly abundant genes in platelets and a subset of 72 relatively platelet-specific genes, defined by more than 10-fold increased expression compared to the median of other cell types in the database with amplified transcripts. The highly abundant platelet transcripts found in the current study included 82% or 70% of platelet abundant genes identified in two previous gene expression studies on non-amplified mRNA from pooled or apheresis samples, respectively. On comparing the platelet gene expression profiles in 18 patients with sickle cell disease in steady state to 12 African American controls, at a 3-fold cut-off and 5% false discovery rate, we identified ~100 differentially expressed genes, including multiple genes involved in arginine metabolism and redox homeostasis. Further characterization of these pathways using real time PCR and biochemical assays revealed increased arginase II expression and activity and decreased platelet polyamine levels. These studies suggest a potential pathogenic role for platelet arginase and altered arginine and polyamine metabolism in sickle cell disease and provide a novel framework for the study of disease-specific platelet biology. Experiment Overall Design: There are 18 sickle cell samples and 12 control samples from healthy African American volunteers.
Project description:In sickle cell disease, ischemia-reperfusion injury and intravascular hemolysis produce endothelial dysfunction and vasculopathy characterized by reduced nitric oxide (NO) and arginine bioavailability. Recent functional studies of platelets in patients with sickle cell disease reveal a basally activated state, suggesting that pathological platelet activation may contribute to sickle cell disease vasculopathy. Studies were therefore undertaken to examine transcriptional signaling pathways in platelets that may be dysregulated in sickle cell disease. We demonstrate and validate here the feasibility of comparative platelet transcriptome studies on clinical samples from single donors, by the application of RNA amplification followed by microarray-based analysis of 54,000 probe sets. Data mining an existing microarray database, we identified 220 highly abundant genes in platelets and a subset of 72 relatively platelet-specific genes, defined by more than 10-fold increased expression compared to the median of other cell types in the database with amplified transcripts. The highly abundant platelet transcripts found in the current study included 82% or 70% of platelet abundant genes identified in two previous gene expression studies on non-amplified mRNA from pooled or apheresis samples, respectively. On comparing the platelet gene expression profiles in 18 patients with sickle cell disease in steady state to 12 African American controls, at a 3-fold cut-off and 5% false discovery rate, we identified ~100 differentially expressed genes, including multiple genes involved in arginine metabolism and redox homeostasis. Further characterization of these pathways using real time PCR and biochemical assays revealed increased arginase II expression and activity and decreased platelet polyamine levels. These studies suggest a potential pathogenic role for platelet arginase and altered arginine and polyamine metabolism in sickle cell disease and provide a novel framework for the study of disease-specific platelet biology. Keywords: Platelets, genes, enzymes, metabolism, signal transduction, sickle cell disease
Project description:Circulating platelets from Sickle cell disease (SCD) patients express distinct gene expression patterns that regulate function. The objective of this study is to identify a role of post-transcriptional regulation of the platelet transcriptional signaling by microRNAs.
Project description:Circulating platelets from Sickle cell disease (SCD) patients express distinct gene expression patterns that regulate function. The objective of this study is to identify a role of post-transcriptional regulation of the platelet transcriptional signaling by microRNAs. Comparison of microRNA expression in platelets from SCD patients and control subjects, from 2 cohorts-University of Pittsburgh and National Institutes of Health.
Project description:Room temperature whole blood mRNA stabilization procedures, such as the PAX gene system, are critical for the application of transcriptional analysis to population-based clinical studies. Global transcriptome analysis of whole blood RNA using microarrays has proven to be challenging due to the high abundance of globin transcripts that constitute 70% of whole blood mRNA in the blood. This is a particular problem in patients with sickle-cell disease, secondary to the high abundance of globin-expressing nucleated red blood cells and reticulocytes in the circulation . In order to more accurately measure the steady state whole blood transcriptome in sickle-cell patients, we evaluated the efficacy of reducing globin transcripts in PAXgene stabilized RNA samples for genome-wide transcriptome analyses using oligonucleotide arrays. We demonstrate here by both microarrays and Q-PCR that the globin mRNA depletion method resulted in 55-65 fold reduction in globin transcripts in whole blood collected from healthy volunteers and sickle-cell disease patients. This led to an improvement in microarray data quality with increased detection rate of expressed genes and improved overlap with the expression signatures of isolated peripheral blood mononuclear (PBMC) preparations. The differentially modulated genes from the globin depleted samples had a higher correlation coefficient to the 112 genes identified to be significantly altered in our previous study on sickle-cell disease using PBMC preparations. Additionally, the analysis of differences between the whole blood transcriptome and PBMC transcriptome reveals important erythrocyte genes that participate in sickle-cell pathogenesis and compensation. The combination of globin mRNA reduction after whole-blood RNA stabilization represents a robust clinical research methodology for the discovery of biomarkers for hematologic diseases and in multicenter clinical trials investigating a wide range of nonhematologic disorders where fractionation of cell types is impracticable. Keywords: Microarrays, PAXgene, globin reduction, whole blood, PBMC There are 10 samples for each of PBMC, PAX and PAX globin-reduced, where 5 samples come from sickle-cell patients and 5 from healthy controls.
Project description:We analyzed expression of miRNAs in Exhaled Breath Condensates from pediatric patients with sickle cell disease, asthma, sickle cell disease and asthma, and controls
Project description:To analyze expression of inflammatory cytokines in Exhaled Breath Condensates from pediatric patients with sickle cell disease, asthma, sickle cell disease and asthma, and controls
Project description:Clinical variability in sickle cell disease (SCD) suggests a role for extra-erythrocytic factors in the pathogenesis of vasoocclusion. We hypothesized that one potential factor, endothelial dysfunction, results from induction of phenotypic changes by circulating factors in SCD patients. The database reports gene expression in cultured human pulmonary artery endothelial cells (HPAEC) exposed to plasma from: a) sickle acute chest syndrome (ACS) patients (samples ; b) SCD patients at steady-state and c) normal volunteers using microarrays (U133A-B GeneChip Affymetrix).
Project description:Sickle cell disease (SCD) is caused by a pathogenic hemoglobin (Hb) mutation, yet patients can have dramatically variable clinical manifestations. Here we address the genetic basis of this clinical heterogeneity. Using a systems genetics approach, we performed whole blood gene expression analysis and eQTL analysis on different clinical phenotypes in SCD patients. We generated whole blood gene expression profiles for 311 West-African children recruited from the National Sickle Cell Disease Centre in Cotonou, Benin which included 250 patients with varying degrees of SCD severities and 61 age-matched controls. SCD is caused by a point-mutation in the beta-hemoglobin gene that changes the normal HbAA protein into, most often, an abnormal HbSS or HbSC protein. The SCD patients recruited in the study either had HbSS or HbSC phenotypes and were categorized into different 3 clinical states based on follow-up status (Rahimy, MC, et al. Effect of a comprehensive clinical care program on disease course in severely ill children with sickle cell anemia in sub-Saharan African setting. Bood 102, 834-838. 2002). When patients are refered to the clinic, they are enrolled when they are in steady-state condition, and are labeled as entry (E). Patients followed at the SCD clinic are labeled as FU. Control patients were recruited and are labeled as C. Patients were also assigned a severity score (Sebastiani, P. et al. A network model to predict the risk of death in sickle cell disease. Blood 110, 2727-2735, 2007). Hemoglobin protein status (Hb phenotype) was confirmed for each patient using standard electrophoretic techniques. We generated genotypes for 263 of these individuals and performed principal component analysis (PCA) which identified 2 signigicant genotypic principal components (gPC1 and gPC2). Using the gene expression and genotyping data, we performed an eSNP analysis. . Gene expression data presented in this study.