Publications by authors named "Johan Bjorkegren"

Background: Genome-wide association studies identified a 20-Kb region of chromosome 8 (8q24.13) associated with plasma lipids, hepatic steatosis, and risk for coronary artery disease. The region is proximal to , and given its well-established role in lipid regulation in animal models, TRIB1 has been proposed to mediate the contribution of the 8q24.

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Multivariate Mendelian randomization (MVMR) is a statistical technique that uses sets of genetic instruments to estimate the direct causal effects of multiple exposures on an outcome of interest. At genomic loci with pleiotropic gene regulatory effects, that is, loci where the same genetic variants are associated to multiple nearby genes, MVMR can potentially be used to predict candidate causal genes. However, consensus in the field dictates that the genetic instruments in MVMR must be independent (not in linkage disequilibrium), which is usually not possible when considering a group of candidate genes from the same locus.

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  • Fibromuscular dysplasia (FMD) is a rare condition mostly affecting women, characterized by various arterial problems that can lead to serious health issues like hypertension and stroke.* -
  • This study used genetic data from FMD patients and healthy controls to identify 18 gene regulatory networks, with four forming an FMD-related supernetwork affecting arterial health.* -
  • By disrupting this supernetwork in mice, researchers observed symptoms of FMD, revealing insights into the disease's mechanisms and potential new treatment options.*
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Aims: Vein grafts are used for many indications, including bypass graft surgery and arteriovenous fistula (AVF) formation. However, patency following vein grafting or AVF formation is suboptimal for various reasons, including thrombosis, neointimal hyperplasia, and adverse remodelling. Recently, endothelial-to-mesenchymal transition (EndMT) was found to contribute to neointimal hyperplasia in mouse vein grafts.

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Excess abdominal fat is a sexually dimorphic risk factor for cardio-metabolic disease and is approximated by the waist-to-hip ratio adjusted for body mass index (WHR). Whereas this trait is highly heritable, few causal genes are known. We aimed to identify novel drivers of WHR using systems genetics.

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  • The study investigates the gene expression changes in vascular cells during atherosclerosis progression, emphasizing the limited understanding of their clinical significance.
  • It utilizes single-cell RNA sequencing data from both mouse models and human tissue to identify various cell subtypes involved in advanced atherosclerosis and symptomatic carotid plaques.
  • The findings highlight the association of specific gene-regulatory networks with coronary artery disease severity, suggesting pathways that may be targeted for therapeutic strategies.
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The accumulation of omics and biobank resources allows for a genome-wide understanding of the shared pathologic mechanisms between diseases and for strategies to identify drugs that could be repurposed as novel treatments. Here, we present a computational protocol, implemented as a Snakemake workflow, to identify shared transcriptional processes and screen compounds that could result in mutual benefit. This protocol also includes a description of a pharmacovigilance study designed to validate the effect of compounds using electronic health records.

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  • Multivariate Mendelian randomization (MVMR) is a statistical technique that estimates the direct causal effects of multiple genetic factors on a specific outcome, while considering gene regulatory effects in genomic loci.
  • This approach challenges the traditional requirement for genetic instruments to be independent by showing that correlated instruments can still provide valid causal estimates, confirmed through extensive simulations.
  • The application of MVMR to coronary artery disease (CAD) risk revealed twelve candidate causal genes across various tissues, though the complexity of regulatory interactions necessitates tissue-specific analyses.
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Genome-wide association studies (GWASs) have identified hundreds of risk loci for coronary artery disease (CAD). However, non-European populations are underrepresented in GWASs, and the causal gene-regulatory mechanisms of these risk loci during atherosclerosis remain unclear. We incorporated local ancestry and haplotypes to identify quantitative trait loci for expression (eQTLs) and splicing (sQTLs) in coronary arteries from 138 ancestrally diverse Americans.

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Mouse models have been used extensively to study human coronary artery disease (CAD) or atherosclerosis and to test therapeutic targets. However, whether mouse and human share similar genetic factors and pathogenic mechanisms of atherosclerosis has not been thoroughly investigated in a data-driven manner. We conducted a cross-species comparison study to better understand atherosclerosis pathogenesis between species by leveraging multiomics data.

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  • Coronary artery disease (CAD) involves the buildup of atherosclerotic plaques in arteries, with complex interactions between vascular and immune cells contributing to its progression.
  • This study integrates data from 22 single-cell RNA sequencing libraries, analyzing 118,578 cells to map human atherosclerosis and to better understand cell diversity and communication.
  • Key findings include the identification of smooth muscle cell (SMC) markers linked to CAD and atherosclerosis progression, which were validated through various analyses, aiming to inform future cardiovascular research.
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Senescent cells are a major contributor to age-dependent cardiovascular tissue dysfunction, but knowledge of their in vivo cell markers and tissue context is lacking. To reveal tissue-relevant senescence biology, we integrate the transcriptomes of 10 experimental senescence cell models with a 224 multi-tissue gene co-expression network based on RNA-seq data of seven tissues biopsies from ∼600 coronary artery disease (CAD) patients. We identify 56 senescence-associated modules, many enriched in CAD GWAS genes and correlated with cardiometabolic traits-which supports universality of senescence gene programs across tissues and in CAD.

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  • Histopathological studies of atherosclerotic plaques reveal that diverse lesion types necessitate improved classification methods to understand their clinical significance.
  • An analysis of gene expression in 654 human carotid plaques identified five main plaque types, each linked to specific clinical outcomes and differences in cell composition.
  • Findings suggest that a particular plaque type with severe symptoms is associated with inflammatory and fibrotic cells, and ongoing research is exploring potential biomarkers for distinguishing these plaque phenotypes.
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Coronary artery calcification (CAC), a measure of subclinical atherosclerosis, predicts future symptomatic coronary artery disease (CAD). Identifying genetic risk factors for CAC may point to new therapeutic avenues for prevention. Currently, there are only four known risk loci for CAC identified from genome-wide association studies (GWAS) in the general population.

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Genome-wide association meta-analysis (GWAMA) by the Cortisol Network (CORNET) consortium identified genetic variants spanning the locus on chromosome 14 associated with morning plasma cortisol, cardiovascular disease (CVD), and mRNA expression encoding corticosteroid-binding globulin (CBG) in the liver. These and other findings indicate that higher plasma cortisol levels are causally associated with CVD; however, the mechanisms by which variations in CBG lead to CVD are undetermined. Using genomic and transcriptomic data from The Stockholm Tartu Atherosclerosis Reverse Networks Engineering Task (STARNET) study, we identified plasma cortisol-linked single-nucleotide polymorphisms (SNPs) that are trans-associated with genes from seven different vascular and metabolic tissues, finding the highest representation of trans-genes in the liver, subcutaneous fat, and visceral abdominal fat, [false discovery rate (FDR) = 15%].

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  • Excess abdominal fat is a key risk factor for cardio-metabolic diseases, and researchers studied the waist-to-hip ratio adjusted for body mass index (WHRadjBMI) to understand fat distribution and its genetic drivers.
  • By analyzing gene expression data from male and female cohorts, they constructed networks to identify genes that regulate WHRadjBMI and could explain fat distribution differences.
  • The study uncovered 53 novel key driver genes related to fat distribution and highlighted their roles in important pathways, such as Wnt signaling and mitochondrial function, suggesting new targets for further research.
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Cancer and cardiovascular disease (CVD) are the leading causes of death worldwide. Numerous overlapping pathophysiologic mechanisms have been hypothesized to drive the development of both diseases. Further investigation of these common pathways could allow for the identification of mutually detrimental processes and therapeutic targeting to derive mutual benefit.

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Cystatin C (CyC), a secreted cysteine protease inhibitor, has unclear biological functions. Many patients exhibit elevated plasma CyC levels, particularly during glucocorticoid (GC) treatment. This study links GCs with CyC's systemic regulation by utilizing genome-wide association and structural equation modeling to determine CyC production genetics in the UK Biobank.

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  • * The study utilized RNA sequencing data to create gene regulatory networks, revealing two main SMC phenotypes in women: a vulnerable myofibroblast-like network and a contractile network, which differed in expression levels compared to males.
  • * Findings suggest that female atherosclerosis involves specific gene networks that promote plaque vulnerability, with important implications for understanding disease progression and potential treatment strategies.
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  • Scientists found that many people with heart artery problems have special gene changes called CHIP, which might make their hearts healthier or sicker.
  • They used special DNA tests to look for these changes in blood and tissue from heart patients and found a lot of them had CHIP.
  • They also discovered that the role of these CHIP changes in cells can vary; some may cause more inflammation while others affect energy use in the cells.
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Variants in genes encoding the soluble guanylyl cyclase (sGC) in platelets are associated with coronary artery disease (CAD) risk. Here, by using histology, flow cytometry and intravital microscopy, we show that functional loss of sGC in platelets of atherosclerosis-prone mice contributes to atherosclerotic plaque formation, particularly via increasing in vivo leukocyte adhesion to atherosclerotic lesions. In vitro experiments revealed that supernatant from activated platelets lacking sGC promotes leukocyte adhesion to endothelial cells (ECs) by activating ECs.

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Mouse models have been used extensively to study human coronary artery disease (CAD) or atherosclerosis and to test therapeutic targets. However, whether mouse and human share similar genetic factors and pathogenic mechanisms of atherosclerosis has not been thoroughly investigated in a data-driven manner. We conducted a cross-species comparison study to better understand atherosclerosis pathogenesis between species by leveraging multiomics data.

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Obesity is a major risk factor for cardiovascular disease, stroke, and type 2 diabetes (T2D). Excessive accumulation of fat in the abdomen further increases T2D risk. Abdominal obesity is measured by calculating the ratio of waist-to-hip circumference adjusted for the body-mass index (WHRadjBMI), a trait with a significant genetic inheritance.

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Background: People with human immunodeficiency virus (HIV) infection (PWH) are at higher risk of myocardial infarction (MI) than those without HIV. About half of MIs in PWH are type 2 (T2MI), resulting from mismatch between myocardial oxygen supply and demand, in contrast to type 1 MI (T1MI), which is due to primary plaque rupture or coronary thrombosis. Despite worse survival and rising incidence in the general population, evidence-based treatment recommendations for T2MI are lacking.

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Background: Genome-wide association studies have identified hundreds of loci associated with common vascular diseases, such as coronary artery disease, myocardial infarction, and hypertension. However, the lack of mechanistic insights for many GWAS loci limits their translation into the clinic. Among these loci with unknown functions is -four-and-a-half LIM (LIN-11, Isl-1, MEC-3) domain 5 (; chr6q16.

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