Biology subjects

Gilsbach, R.

Publications and source records attributed to Gilsbach, R..

11 recordsLinked to original sources

bioRxiv2026

Transcriptional regulation of the TASK-1 potassium channel by ETV1 -Implications for atrial excitability

BackgroundAtrial fibrillation (AF), the most common sustained arrhythmia, is driven by electrical and structural remodelling, including altered ion channel expression. The atrial-specific potassium channel TASK-1 regulates action potential duration (APD) and is differentially expressed in AF and left ventricular dysfunction, but the mechanisms controlling its expression are not well understood. ObjectiveThis study examines whether the transcription factor ETV1 regulates TASK-1 and contributes to atrial electrical remodelling. MethodsAtrial tissue from patients with and without AF was analysed to assess the relationship between ETV1 and TASK-1 (KCNK3) expression. In HL-1 cardiomyocyte-like cells and native fibroblasts, ETV1 activity was reduced using pharmacological inhibition or siRNA-mediated knockdown. TASK-1 expression, TASK-1 current, and APD at 90% repolarization were measured. Pacing experiments tested activity-dependent TASK-1 regulation. Direct transcriptional regulation was evaluated using ChIP-qPCR and ChIP-seq to detect ETV1 binding at the KCNK3 promoter. ResultsETV1 and TASK-1 levels were positively correlated in human atrial tissue. In HL-1 cells and fibroblasts, ETV1 inhibition or knockdown decreased TASK-1 expression and current and selectively prolonged APD90. Pacing-induced upregulation of TASK-1 was prevented by ETV1 inhibition, indicating a protective effect against pro-arrhythmic remodelling. ChIP-qPCR and ChIP-seq confirmed direct ETV1 binding to the KCNK3 promoter. ConclusionETV1 directly regulates TASK-1 expression and contributes to atrial electrical remodelling, identifying ETV1 as a potential upstream therapeutic target in AF. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/711402v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@3e5b25org.highwire.dtl.DTLVardef@1d1f909org.highwire.dtl.DTLVardef@34cf37org.highwire.dtl.DTLVardef@1105539_HPS_FORMAT_FIGEXP M_FIG C_FIG Translational perspectiveAtrial fibrillation is sustained by maladaptive electrical remodelling that remains insufficiently addressed by current rhythm-control therapies. Direct inhibition of individual ion channels has shown efficacy but is limited by phenotype dependence and proarrhythmic risk. The present data identify ETV1 as an upstream transcriptional regulator of the atrial-specific potassium channel TASK-1. Modulation of ETV1 reduced TASK-1 expression, prolonged atrial repolarisation, and prevented tachycardia-induced electrical remodelling in vitro. Targeting ETV1 may therefore represent a disease-modifying strategy that intervenes earlier in the remodelling cascade than conventional antiarrhythmic drugs. This approach could enable phenotype-guided therapy in atrial cardiomyopathy, particularly in patients with preserved ventricular function, and warrants validation in translational large-animal and clinical studies.

molecular biology↗

bioRxiv2026

Selective class IIa HDAC inhibition reverses diastolic dysfunction in cardiometabolic HFpEF

Heart failure with preserved ejection fraction (HFpEF) is a highly prevalent cardiometabolic syndrome with yet no effective therapies. Here, we report that selectively class IIa histone deacetylases (HDACs) but no other classes of HDACs are enzymatically activated in hearts from HFpEF patients and cardiometabolic HFpEF animal models. Cell type-specific and enzymatic activity-specific genetic loss-of-function models of the cardiomyocyte-enriched class IIa HDAC family member HDAC4 and the pharmacological class IIa HDAC-selective inhibitor TMP195 prevent and reverse diastolic dysfunction and exercise intolerance in cardiometabolic HFpEF in vivo. In contrast to pan-HDAC inhibition no adverse effects are observed. Despite its well-known non-enzymatic role as transcriptional repressor, we found that specifically enzymatic activation of HDAC4 has little direct effects on cardiomyocyte-intrinsic gene expression. Instead, non-epigenetic actions lead to endothelial activation via altered cardiocrine signaling. We discovered that selective enzymatic class IIa HDAC inhibition is a new therapeutic concept to combat cardiac HFpEF.

molecular biology↗

bioRxiv2024

The transaminase-omega-amidase pathway is a redox switch in glutamine metabolism that generates alpha-ketoglutarate

Oxidative stress is caused by short-lived molecules and metabolic changes belong to the fastest cellular responses. Here we studied how the endothelial cell metabolome reacts to acute oxidative challenges (menadione or H2O2) to identify redox-sensitive metabolic enzymes. H2O2 selectively increased -ketoglutaramate (KGM), a largely uncharacterized metabolite produced by glutamine transamination and a yet unrecognized intermediate of endothelial glutamine catabolism. The enzyme nitrilase-like 2 {omega}-amidase (NIT2) converts KGM to -ketoglutarate (KG). Reversible oxidation of specific cysteine in NIT2 by H2O2 inhibited its catalytic activity. Furthermore, a variant in the NIT2 gene that decreases its expression is associated with high plasma KGM level in humans. Endothelial-specific knockout mice of NIT2 exhibited increased levels of KGM and impaired angiogenesis. Knockout of NIT2 impaired endothelial cell proliferation and sprouting and induced senescence. In conclusion, we show that the glutamine transaminase-{omega}-amidase pathway is a metabolic switch in which NIT2 is the redox-sensitive enzyme. The pathway is modulated in humans and functionally important for endothelial glutamine metabolism.

physiology↗

bioRxiv2024

Long non-coding RNAs direct the SWI/SNF complex to cell-specific enhancers

The coordination of chromatin remodeling is essential for DNA accessibility and gene expression control1. The highly conserved and ubiquitously expressed SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex plays a central role in cell type- and context-dependent gene expression2. Despite the absence of a defined DNA recognition motif, SWI/SNF binds lineage specific enhancers genome-wide where it actively maintains open chromatin state2-5. It does so while retaining the ability to respond dynamically to cellular signals4. However, the mechanisms that guide SWI/SNF to specific genomic targets have remained elusive. Here we demonstrate that trans-acting long non-coding RNAs (lncRNAs) direct the SWI/SNF complex to cell type-specific enhancers. SWI/SNF preferentially binds lncRNAs and these predominantly bind DNA targets in trans. Together they localize to enhancers, many of which are cell type-specific. Knockdown of SWI/SNF- and enhancer-bound lncRNAs causes the genome-wide redistribution of SWI/SNF away from enhancers and a concomitant differential expression of spatially connected target genes. These lncRNA-SWI/SNF-enhancer networks support an enhancer hub model of SWI/SNF genomic targeting. Our findings reveal a competitive recruitment of SWI/SNF by lncRNAs which provide a specific and dynamic layer of control in chromatin accessibility and gene expression.

molecular biology↗

bioRxiv2023

In vivo silencing of regulatory elements using a single AAV-CRISPRi vector

CRISPR-Cas9 based transcriptional repressors (CRISPRi) have emerged as specific and robust tools for functional epigenetic silencing of regulatory elements. Adeno-associated viruses (AAVs) are promising CRISPRi delivery vectors for cardiovascular research and therapy. However, compact vectors enabling codelivery of all CRISPRi components by a single AAV are needed for an enhanced and consistent performance. We engineered a 4.7kb all-in-one CRISPRi construct compatible with AAV-mediated delivery and produced cardiotropic AAVi 6 and 9 particles for in vitro and in vivo application, respectively. AAVi vectors targeting the Nppa promoter (AAViNppa) reduced gene expression in cultivated cardiomyocytes (HL-1 cells) in a dose-dependent manner. The maximum effect was a >95% reduction as measured by qPCR and RNA-seq. This effect was orchestrated by loss of chromatin accessibility (ATAC-seq) and establishment of heterochromatin (H3K9me3 ChIP-seq) specifically at the target promoter region. We confirmed the broad applicability of AAVi to different cardiomyocyte cell culture systems by silencing several genes in primary neonatal rat ventricular cardiomyocytes (NRVMs), human iPSC-derived cardioids and iPSC-CMs. To demonstrate the efficacy of AAVi in vivo we injected 8-week-old C57Bl/6 WT mice with a single dose of AAViNppa and implanted osmotic minipumps releasing Phenylephrine (50 mg/kg/d) and Angiotensin II (0.45 mg/kg/d) to induce Nppa transcription. AAViNppa silenced Nppa transcription as revealed by qPCR and single nuclei RNA-seq even under stress conditions. On the epigenome layer AAViNppa induced closed chromatin at the Nppa promoter site comparable to the in vitro effect. Here, we present an efficient AAV-based method for CRISPRi-mediated epigenetic silencing of gene expression in cardiac myocytes in vivo and in vitro. This functional epigenetic approach provides an efficient way to modulate gene expression in the heart and could become a standard method for cardiovascular disease modelling and translational research.

genomics↗

bioRxiv2021

HIF1α-AS1 is a DNA:DNA:RNA triplex-forming lncRNA interacting with the HUSH complex

DNA:DNA:RNA triplexes that are formed through Hoogsteen base-pairing have been observed in vitro, but the extent to which these interactions occur in cells and how they impact cellular functions remains elusive. Using a combination of bioinformatic techniques, RNA/DNA pulldown and biophysical studies, we set out to identify functionally important DNA:DNA:RNA triplex-forming long non-coding RNAs (lncRNA) in human endothelial cells. The lncRNA HIF1-AS1 was retrieved as a top hit. Endogenous HIF1-AS1 reduced the expression of numerous genes, including EPH Receptor A2 and Adrenomedullin through DNA:DNA:RNA triplex formation by acting as an adapter for the repressive human silencing hub complex (HUSH). Moreover, the oxygen-sensitive HIF1-AS1 was down-regulated in pulmonary hypertension and loss-of-function approaches not only resulted in gene de-repression but also enhanced angiogenic capacity. As exemplified here with HIF1-AS1, DNA:DNA:RNA triplex formation is a functionally important mechanism of trans-acting gene expression control.

molecular biology↗

bioRxiv2021

Sequential defects in cardiac lineage commitment and maturation cause hypoplastic left heart syndrome

BackgroundComplex molecular programs in specific cell lineages govern human heart development. Hypoplastic left heart syndrome (HLHS) is the most common and severe manifestation within the spectrum of left ventricular outflow tract obstruction defects occurring in association with ventricular hypoplasia. The pathogenesis of HLHS is unknown, but hemodynamic disturbances are assumed to play a prominent role. MethodsTo identify perturbations in gene programs controlling ventricular muscle lineage development in HLHS, we performed: i) whole-exome sequencing of 87 HLHS parent-offspring trios, ii) nuclear transcriptomics of cardiomyocytes from ventricles of 4 patients with HLHS and 15 controls at different stages of heart development, iii) single cell RNA sequencing and iv) 3D modeling in iPSCs from 3 patients with HLHS and 3 controls. ResultsGene set enrichment and protein network analyses of damaging de-novo mutations and dysregulated genes from ventricles of patients with HLHS suggested alterations in specific gene programs and cellular processes critical during fetal ventricular cardiogenesis, including cell-cycle and cardiomyocyte maturation. Single-cell and 3D modeling with iPSCs demonstrated intrinsic defects in the cell-cycle/UPR/autophagy hub resulting in disrupted differentiation of early cardiac progenitor lineages leading to defective cardiomyocyte-subtype differentiation/maturation in HLHS. Additionally, premature cell-cycle exit of ventricular cardiomyocytes from HLHS patients prevented normal tissue responses to developmental signals for growth leading to multinucleation/polyploidy, accumulation of DNA damage, and exacerbated apoptosis, all potential drivers of left ventricular hypoplasia in absence of hemodynamic cues. ConclusionsOur results highlight that despite genetic heterogeneity in HLHS, many mutations converge on sequential cellular processes primarily driving cardiac myogenesis, suggesting novel therapeutic approaches.

developmental biology↗

bioRxiv2020

The landscape of SARS-CoV-2 RNA modifications

In 2019 the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the first documented cases of severe lung disease COVID-19. Since then, SARS-CoV-2 has been spreading around the globe resulting in a severe pandemic with over 500.000 fatalities and large economical and social disruptions in human societies. Gaining knowledge on how SARS-Cov-2 interacts with its host cells and causes COVID-19 is crucial for the intervention of novel therapeutic strategies. SARS-CoV-2, like other coronaviruses, is a positive-strand RNA virus. The viral RNA is modified by RNA-modifying enzymes provided by the host cell. Direct RNA sequencing (DRS) using nanopores enables unbiased sensing of canonical and modified RNA bases of the viral transcripts. In this work, we used DRS to precisely annotate the open reading frames and the landscape of SARS-CoV-2 RNA modifications. We provide the first DRS data of SARS-CoV-2 in infected human lung epithelial cells. From sequencing three isolates, we derive a robust identification of SARS-CoV-2 modification sites within a physiologically relevant host cell type. A comparison of our data with the DRS data from a previous SARS-CoV-2 isolate, both raised in monkey renal cells, reveals consistent RNA modifications across the viral genome. Conservation of the RNA modification pattern during progression of the current pandemic suggests that this pattern is likely essential for the life cycle of SARS-CoV-2 and represents a possible target for drug interventions.

genetics↗

bioRxiv2020

Genome-wide association study in European patients with congenital heart disease identifies risk loci for transposition of the great arteries and anomalies of the thoracic arteries and veins and expression of discovered candidate genes in the developing heart

RationaleGenetic factors undoubtedly contribute to the development of congenital heart disease (CHD), but still remain mostly ill-defined. ObjectiveIdentification of genetic risk factors associated with CHD and functional analysis of SNP-carrying genes. Methods and ResultsGenetic association study of 1,440 Caucasian CHD patients from the German Heart Center Munich collected from March 2009 to June 2016, 2,594 patients of previous studies provided by the Newcastle University and 8,486 controls underwent meta-analysis to detect single nucleotide polymorphisms (SNPs) associated with CHD. Results4,034 Caucasian CHD patients strictly classified according to the Society of Thoracic Surgeons nomenclature and 8,486 controls were included. One SNP on chromosome 5 reached genome-wide significance across all CHD phenotypes (rs185531658,OR:2.16, p=5.28x10-9) and was also indicative for septal defects (OR:2.16, p=6.15x10-8). One region on chromosome 20 pointing to the MACROD2 locus, identified four SNPs (rs150246290,OR:3.78, p=1.27x10-10; rs149890280,OR:3.74, p=1.8x10-10; rs149467721,OR:3.53; p=1.39x10-9, rs77094733,OR:3.53, p=1.73x10-9) in patients with transposition of the great arteries (TGA). A second region was detected on chromosome 8 located at ZBTB10 (rs148563140,OR:3.42, p=3.28x10-8; rs143638934,OR:3.42, p=3.51x10-8) in the same subgroup. Three highly significant risk variants on chromosome 17 (rs76774446,OR:1.60, p=9.95x10-8; rs11874,OR:1.60, p=6.64x10-8; rs17677363,OR:1.60, p=9.81x10-8) within the GOSR2 locus were identified in patients with anomalies of thoracic arteries and veins (ATAV). Genetic variants associated with ATAV are suggested to influence expression of WNT3, and variant rs870142 related to septal defects is proposed to influence expression of MSX1. Cardiac differentiation of human and murine induced pluripotent stem cells and single cell RNAseq analyses of developing murine and human hearts show essential functional roles for MACROD2, GOSR2, WNT3 and MSX1 at all developmental stages. ConclusionsFor the first time genetic risk factors in CHD patients with TGA and ATAV were identified. Several candidate genes play an essential functional role in heart development at the embryonic, newborn and adult stage.

genomics↗

bioRxiv2020

Specificity of Gβ and γ subunits to SNARE complex both at rest and after α2aadrenergic receptor stimulation

Though much is known about the various physiological functions of each GPCR and the specificity of G subunits, the specificity of G{beta}{gamma} activated by a given GPCR and activating each effector in vivo is not known. Previously, we identified different G{beta} and G{gamma} subunits interacting specifically with 2a-adrenergic receptors (2aAR). In this study, we examined its in vivo specificity to the soluble NSF attachment proteins (SNARE) complex in adrenergic (auto-2aAR) and non-adrenergic (hetero-2aAR) neurons. We applied a quantitative targeted multiple reaction monitoring proteomic analysis of G{beta} and G{gamma} subunits bound to the SNARE complex, and found only a subset of G{beta} and G{gamma} bound. Without stimulation of auto-2aAR, G{beta}1 and G{gamma}3 interacted with the SNARE complex. When auto-2aAR were activated, G{beta}1, G{beta}2, and G{gamma}3 were found. Further understanding of in vivo G{beta}{gamma} specificity to its effectors provides new insights into the multiplicity of genes for G{beta} and G{gamma}. SummarySpecific G{beta}{gamma} dimers interact with the SNARE complex following presynaptic 2aAR activation in both adrenergic and non-adrenergic neurons.

biochemistry↗

bioRxiv2017

Distinct epigenetic programs regulate cardiac myocyte development and disease in the human heart in vivo

Epigenetic mechanisms and transcription factor networks essential for differentiation of cardiac myocytes have been uncovered. However, reshaping of the epigenome of these terminally differentiated cells during fetal development, postnatal maturation and in disease remains unknown. Thus, the aim of this study was to determine the dynamics of the cardiac myocyte epigenome during development and in chronic heart failure. Prenatal development and postnatal maturation are characterized by a cooperation of active CpG methylation and histone marks at cis-regulatory and genic regions to shape the cardiac myocyte transcriptome. In contrast, pathological gene expression in terminal heart failure is accompanied by changes in active histone marks without major alterations in CpG methylation and repressive chromatin marks. Notably, cis-regulatory regions in cardiac myocytes are significantly enriched for cardiovascular disease-associated variants. This study uncovers distinct layers of epigenetic regulation not only during prenatal development and postnatal maturation but also in diseased human cardiac myocytes.

genomics↗