Project description:The atrioventricular (AV) node is a recurrent source of potentially life-threatening arrhythmias. Nevertheless, limited data are available on its developmental control or molecular phenotype. We used a novel AV node-specific reporter mouse to gain insight into the gene programs determining the formation and phenotype of the AV node. In the transgenic reporter, green fluorescent protein (GFP) expression was driven by 160 kbp of Tbx3 and flanking sequences. GFP was selectively expressed in the AV canal of embryos, and in the AV node of adults, while all other Tbx3+ conduction system components, including the AV bundle, were devoid of GFP expression. Fluorescent AV nodal (Tbx3BAC-Egfp) and complementary working (NppaBAC336-Egfp) myocardial cell populations of E10.5 embryos and E17.5 fetuses were purified using fluorescence-activated cell sorting, and their expression profiles were assessed by microarray analysis. We constructed a comprehensive list of sodium, calcium, and potassium channels specific for the nodal or working myocard. Furthermore, the data revealed that the AV node and the working myocardium phenotypes diverge during development, but that the functional gene classes characteristic for both compartments are maintained. Interestingly, the AV node-specific gene repertoire consisted of multiple neurotrophic factors not yet appreciated to play a role in nodal development. These data present the first genome-wide transcription profiles of the AV node during development, providing valuable information concerning its molecular identity. Keywords: Tbx3, AV node, working myocardium, embryonic development, cardiac development, cardiac conduction system 24 samples: 6x working myocardium stage E10.5 (NppaBAC336-Egfp mice), 6x AV canal myocardium stage E10.5 (Tbx3BAC-Egfp mice), 6x working myocardium stage E17.5 (NppaBAC336-Egfp mice), 6x AV node myocardium stage E17.5 (Tbx3BAC-Egfp mice)
Project description:A novel assay was developed for Daudi cells in which the antiviral (AV) and antiproliferative (AP) activities of interferon (IFN) can be measured simultaneously. Using this novel assay, conditions allowing IFN AV protection but no growth inhibition were identified and selected. Daudi cells were treated under these conditions, and gene expression microarray analyses were performed. The results of the analysis identified 25 genes associated with IFN-alpha AV activity. Upregulation of 23 IFN-induced genes was confirmed by using reverse transcription-PCR. Of 25 gene products, 17 were detected by Western blotting at 24 h. Of the 25 genes, 10 have not been previously linked to AV activity of IFN-alpha. The most upregulated gene was IFIT3 (for IFN-induced protein with tetratricopeptide repeats 3). The results from antibody neutralizing experiments suggested an association of the identified genes with IFN-alpha AV activity. This association was strengthened by results from IFIT3-small interfering RNA transfection experiments showing decreased expression of IFIT3 and a reduction in the AV activity induced by IFN-alpha. Overexpression of IFIT3 resulted in a decrease of virus titer. Transcription of AV genes after the treatment of cells with higher concentrations of IFN having an AP effect on Daudi cells suggested pleiotropic functions of identified gene products. Gene expression was initially measured in four Daudi cell groups (3 x 10(6) in 10 ml of RPMI) treated for 24 h at IFN concentrations selected to allow comparison of gene activity in AV activity environments with environments in which no AV activity was observed. These treatment groups were: (i) 0.0036 ng of IFN-alpha2c/ml (n=5) (allowing AV activity only); (ii) 0.00036 ng of IFN-alpha2c/ml (n=5) (no AV observed); (iii) 0.036 ng of HY-2/ml (n=3) (allowing AV activity); and (iv) 0.0036 ng of HY-2/ml (n=3) (no AV observed). To refine the list of genes associated with AV activity, samples showing AP phenotype (achieved by treatment with IFN-alpha2c [0.36 ng/ml] (n=3) or HY-2 [36 ng/ml]) (n=3) were compared to identically treated samples manipulated to display the AV phenotype through subsequent neutralization with anti-IFNAR1 MAb 64.10 (1 ug/ml) (n=6). Further analysis of gene expression profiles after 6 h of incubation helped indicate genes associated with early roles in IFN-induced AV mechanisms (n=6).
Project description:The atrioventricular (AV) node is a recurrent source of potentially life-threatening arrhythmias. Nevertheless, limited data are available on its developmental control or molecular phenotype. We used a novel AV node-specific reporter mouse to gain insight into the gene programs determining the formation and phenotype of the AV node. In the transgenic reporter, green fluorescent protein (GFP) expression was driven by 160 kbp of Tbx3 and flanking sequences. GFP was selectively expressed in the AV canal of embryos, and in the AV node of adults, while all other Tbx3+ conduction system components, including the AV bundle, were devoid of GFP expression. Fluorescent AV nodal (Tbx3BAC-Egfp) and complementary working (NppaBAC336-Egfp) myocardial cell populations of E10.5 embryos and E17.5 fetuses were purified using fluorescence-activated cell sorting, and their expression profiles were assessed by microarray analysis. We constructed a comprehensive list of sodium, calcium, and potassium channels specific for the nodal or working myocard. Furthermore, the data revealed that the AV node and the working myocardium phenotypes diverge during development, but that the functional gene classes characteristic for both compartments are maintained. Interestingly, the AV node-specific gene repertoire consisted of multiple neurotrophic factors not yet appreciated to play a role in nodal development. These data present the first genome-wide transcription profiles of the AV node during development, providing valuable information concerning its molecular identity. Keywords: Tbx3, AV node, working myocardium, embryonic development, cardiac development, cardiac conduction system
Project description:Heart failure is associated with atrioventricular (AV) node dysfunction, and AV node dysfunction in the setting of heart failure is associated with an increased risk of mortality and heart failure hospitalisation. This study aims to understand the causes of AV node dysfunction in heart failure by studying changes in the whole nodal transcriptome. The mouse transverse aortic constriction model of heart failure was studied; functional changes were assessed using electrocardiography and echocardiography and the transcriptome of the AV node was quantified using RNA-seq. Heart failure was associated with a significant increase in the PR interval, indicating a slowing of AV node conduction and AV node dysfunction, and significant changes in 3,077 transcripts (5.6% of the transcriptome). Many systems were affected: transcripts supporting AV node conduction were downregulated and there were changes in transcripts identified by GWAS as determinants of the PR interval. In addition, there was evidence of remodelling of the sarcomere, a shift from fatty acid to glucose metabolism, and remodelling of the extracellular matrix. There was evidence of the causes of this widespread remodelling of the AV node: evidence of dysregulation of multiple intracellular signalling pathways, dysregulation of 109 protein kinases and 148 transcription factors, and an immune response with a proliferation of neutrophils, monocytes, macrophages and B lymphocytes and a dysregulation of 40 cytokines. In conclusion, inflammation and a widespread transcriptional remodelling of the AV node underlies AV node dysfunction in heart failure.
Project description:Phenotypic heterogeneity is an important mechanism to regulate bacterial virulence, where a single regulatory switch is typically activated to generate virulent and avirulent subpopulations. The opportunistic pathogen Acinetobacter baumannii can transition at high-frequency between virulent (VIR-O) and avirulent (AV-T) subpopulations, distinguished by cells that form opaque or translucent colonies. We demonstrate that expression of twelve TetR-type transcriptional regulators (TTTRs) can drive cells from the VIR-O subpopulation to the AV-T state. Remarkably, in a subpopulation of VIR-O cells, four of these TTTRs were stochastically activated in different combinations to drive cells to the AV-T state, with each resulting AV-T subvariant exhibiting unique phenotypic differences. Due to their functional redundancy, a quadruple mutant with all four of these TTTRs inactivated was required to see a loss of VIR-O to AV-T switching. Further, we demonstrate a small RNA, SrvS, acts as a “rheostat”, where the levels of SrvS expression influences both the VIR-O to AV-T switching frequency and which TTTR is activated when VIR-O cells switch to AV-T. In summary, this work has revealed a new paradigm for phenotypic switching in bacteria, where an unprecedented number of related transcriptional regulators are activated in different combinations to control virulence and generate unique AV-T subvariants with distinct phenotypic properties.
Project description:Tissue-resident macrophages abound in the distal atrioventricular (AV) node of the heart, electrically couple to conducting cardiomyocytes via Connexin (Cx) 43-containing gap junctions and are implicated in normal and aberrant cardiac conduction. Moreover, conditional deletion of Cx43 in macrophages (tamoxifen-inducible Cx3cr1 Cx43-/- mice) delays AV conduction and acute depletion of macrophages in Cd11bDTR mice induces progressive AV block.
Project description:A novel assay was developed for Daudi cells in which the antiviral (AV) and antiproliferative (AP) activities of interferon (IFN) can be measured simultaneously. Using this novel assay, conditions allowing IFN AV protection but no growth inhibition were identified and selected. Daudi cells were treated under these conditions, and gene expression microarray analyses were performed. The results of the analysis identified 25 genes associated with IFN-alpha AV activity. Upregulation of 23 IFN-induced genes was confirmed by using reverse transcription-PCR. Of 25 gene products, 17 were detected by Western blotting at 24 h. Of the 25 genes, 10 have not been previously linked to AV activity of IFN-alpha. The most upregulated gene was IFIT3 (for IFN-induced protein with tetratricopeptide repeats 3). The results from antibody neutralizing experiments suggested an association of the identified genes with IFN-alpha AV activity. This association was strengthened by results from IFIT3-small interfering RNA transfection experiments showing decreased expression of IFIT3 and a reduction in the AV activity induced by IFN-alpha. Overexpression of IFIT3 resulted in a decrease of virus titer. Transcription of AV genes after the treatment of cells with higher concentrations of IFN having an AP effect on Daudi cells suggested pleiotropic functions of identified gene products.