Bio

Bio


Research statement:
My major fields of interest are computational biology and bioinformatics, coupled with the passion for the next-generation sequencing technologies, and a profound scientific interest in genomics, transcriptomics, regulation of gene expression, specificity of binding of transcription factors to the genome, histone modifications, nucleosome positioning, long-range genomic interactions and compartmentalization of the genome. My research lies on the frontier of the contemporary computational genomics, with the emphasis on development and testing of scripts and algorithms for the analysis of human genome and transcriptome. My focus is the improvement of methods for the various applications of the next generation sequencing, such as chromatin - immunoprecipitation sequencing or ChIP-Seq, RNA-sequencing or RNA-Seq, and probing open chromatin, DNase-Seq/ATAC-Seq, in order to answer key biological question that will ultimately help us understand better the underlying mechanisms of life. As a postdoc at Stanford?s Cardiovascular Institute, I am elucidating complex networks of interactions of transcription factors in human cardiac and vascular tissues, and molecular mechanisms that explain how cardiovascular disease risk-associated genomic loci confer disease risk. I am also employing allele specific computational pipelines to the existing next generation sequencing techniques, i.e. ChIP-Seq and RNA-Seq, in combination with the generation of eQTL data for human arterial smooth muscle cells (primary cell type of atherosclerotic lesions) to identify the causal variants that underlie disease susceptibility. In addition, I am modeling vascular SMC tissue-specific open chromatin with ATAC-Seq and DNase-Seq to understand the underlying mechanisms for cardiovascular disease causal variants. I am also active as a blogger, started a blog www.genomicscode.org and continually post UNIX and R related tips and resolve computational problems that can be applied to genomics.

Professional Education


  • Master of Science, University of Belgrade (2005)
  • Doctor of Philosophy, Universite De Lausanne (2010)

Stanford Advisors


Publications

All Publications


  • Advances in Transcriptomics: Investigating Cardiovascular Disease at Unprecedented Resolution. Circulation research Wirka, R. C., Pjanic, M., Quertermous, T. 2018; 122 (9): 1200?1220

    Abstract

    Whole-genome transcriptional profiling has become a standard genomic approach to investigate biological processes. RNA sequencing (RNAseq) in particular has witnessed myriad applications in genetics and various biomedical fields. RNAseq involves a relatively simple experimental protocol of RNA extraction and cDNA library preparation and, because of decreasing next-generation sequencing cost and lower computational burden for data processing, has obtained a central role in the modern biology. The recent application of RNAseq methodology to single-cell transcriptional profiling has enabled the more precise characterization of cell lineage and cell state genetic profiles. The development of bioinformatic and statistical tools has provided for differential gene expression analysis, RNA isoform analysis, haplotype-specific analysis of gene expression (allele-specific expression), and analysis of expression quantitative trait loci. We give an overview of these and recent developments in RNAseq methodology with emphasis on quality control, read mapping, feature counting, differential gene expression, allele-specific expression and expression quantitative trait loci analysis, and fusion transcript detection. We describe utilization of RNAseq as a diagnostic tool in Mendelian diseases, complex phenotypes, and cancer and give an overview of long read RNAseq technology. Furthermore, we discuss in detail the recent revolution in single-cell transcriptomics that is reshaping modern biology.

    View details for PubMedID 29700068

  • Genetic Regulatory Mechanisms of Smooth Muscle Cells Map to Coronary Artery Disease Risk Loci. American journal of human genetics Liu, B., Pjanic, M., Wang, T., Nguyen, T., Gloudemans, M., Rao, A., Castano, V. G., Nurnberg, S., Rader, D. J., Elwyn, S., Ingelsson, E., Montgomery, S. B., Miller, C. L., Quertermous, T. 2018

    Abstract

    Coronary artery disease (CAD) is the leading cause of death globally. Genome-wide association studies (GWASs) have identified more than 95 independent loci that influence CAD risk, most of which reside in non-coding regions of the genome. To interpret these loci, we generated transcriptome and whole-genome datasets using human coronary artery smooth muscle cells (HCASMCs) from 52 unrelated donors, as well as epigenomic datasets using ATAC-seq on a subset of 8 donors. Through systematic comparison with publicly available datasets from GTEx and ENCODE projects, we identified transcriptomic, epigenetic, and genetic regulatory mechanisms specific to HCASMCs. We assessed the relevance of HCASMCs to CAD risk using transcriptomic and epigenomic level analyses. By jointly modeling eQTL and GWAS datasets, we identified five genes (SIPA1, TCF21, SMAD3, FES, and PDGFRA) that may modulate CAD risk through HCASMCs, all of which have relevant functional roles in vascular remodeling. Comparison with GTEx data suggests that SIPA1 and PDGFRA influence CAD risk predominantly through HCASMCs, while other annotated genes may have multiple cell and tissue targets. Together, these results provide tissue-specific and mechanistic insights into the regulation of a critical vascular cell type associated with CAD in human populations.

    View details for PubMedID 30146127

  • TCF21 and the environmental sensor aryl-hydrocarbon receptor cooperate to activate a pro-inflammatory gene expression program in coronary artery smooth muscle cells. PLoS genetics Kim, J. B., Pjanic, M., Nguyen, T., Miller, C. L., Iyer, D., Liu, B., Wang, T., Sazonova, O., Carcamo-Orive, I., Matic, L. P., Maegdefessel, L., Hedin, U., Quertermous, T. 2017; 13 (5)

    Abstract

    Both environmental factors and genetic loci have been associated with coronary artery disease (CAD), however gene-gene and gene-environment interactions that might identify molecular mechanisms of risk are not easily studied by human genetic approaches. We have previously identified the transcription factor TCF21 as the causal CAD gene at 6q23.2 and characterized its downstream transcriptional network that is enriched for CAD GWAS genes. Here we investigate the hypothesis that TCF21 interacts with a downstream target gene, the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor that mediates the cellular response to environmental contaminants, including dioxin and polycyclic aromatic hydrocarbons (e.g., tobacco smoke). Perturbation of TCF21 expression in human coronary artery smooth muscle cells (HCASMC) revealed that TCF21 promotes expression of AHR, its heterodimerization partner ARNT, and cooperates with these factors to upregulate a number of inflammatory downstream disease related genes including IL1A, MMP1, and CYP1A1. TCF21 was shown to bind in AHR, ARNT and downstream target gene loci, and co-localization was noted for AHR-ARNT and TCF21 binding sites genome-wide in regions of HCASMC open chromatin. These regions of co-localization were found to be enriched for GWAS signals associated with cardio-metabolic as well as chronic inflammatory disease phenotypes. Finally, we show that similar to TCF21, AHR gene expression is increased in atherosclerotic lesions in mice in vivo using laser capture microdissection, and AHR protein is localized in human carotid atherosclerosis lesions where it is associated with protein kinases with a critical role in innate immune response. These data suggest that TCF21 can cooperate with AHR to activate an inflammatory gene expression program that is exacerbated by environmental stimuli, and may contribute to the overall risk for CAD.

    View details for DOI 10.1371/journal.pgen.1006750

    View details for PubMedID 28481916

  • The role of polycarbonate monomer bisphenol-A in insulin resistance. PeerJ Pjanic, M. 2017; 5: e3809

    Abstract

    Bisphenol A (BPA) is a synthetic unit of polycarbonate polymers and epoxy resins, the types of plastics that could be found in essentially every human population and incorporated into almost every aspect of the modern human society. BPA polymers appear in a wide range of products, from liquid storages (plastic bottles, can and glass linings, water pipes and tanks) and food storages (plastics wraps and containers), to medical and dental devices. BPA polymers could be hydrolyzed spontaneously or in a photo- or temperature-catalyzed process, providing widespread environmental distribution and chronic exposure to the BPA monomer in contemporary human populations. Bisphenol A is also a xenoestrogen, an endocrine-disrupting chemical (EDC) that interferes with the endocrine system mimicking the effects of an estrogen and could potentially keep our endocrine system in a constant perturbation that parallels endocrine disruption arising during pregnancy, such as insulin resistance (IR). Gestational insulin resistance represents a natural biological phenomenon of higher insulin resistance in peripheral tissues of the pregnant females, when nutrients are increasingly being directed to the embryo instead of being stored in peripheral tissues. Gestational diabetes mellitus may appear in healthy non-diabetic females, due to gestational insulin resistance that leads to increased blood sugar levels and hyperinsulinemia (increased insulin production from the pancreatic beta cells). The hypothesis states that unnoticed and constant exposure to this environmental chemical might potentially lead to the formation of chronic low-level endocrine disruptive state that resembles gestational insulin resistance, which might contribute to the development of diabetes. The increasing body of evidence supports the major premises of this hypothesis, as exemplified by the numerous publications examining the association of BPA and insulin resistance, both epidemiological and mechanistic. However, to what extent BPA might contribute to the development of diabetes in the modern societies still remains unknown. In this review, I discuss the chemical properties of BPA and the sources of BPA contamination found in the environment and in human tissues. I provide an overview of mechanisms for the proposed role of bisphenol A in insulin resistance and diabetes, as well as other related diseases, such as cardiovascular diseases. I describe the transmission of BPA effects to the offspring and postulate that gender related differences might originate from differences in liver enzyme levels, such as UDP-glucuronosyltransferase, which is involved in BPA processing and its elimination from the organism. I discuss the molecular mechanisms of BPA action through nuclear and membrane-bound ER receptors, non-monotonic dose response, epigenetic modifications of the DNA and propose that chronic exposure to weak binders, such as BPA, may mimic the effects of strong binders, such as estrogens.

    View details for PubMedID 28929027

  • Genetics and Genomics of Coronary Artery Disease. Current cardiology reports Pjanic, M., Miller, C. L., Wirka, R., Kim, J. B., Direnzo, D. M., Quertermous, T. 2016; 18 (10): 102-?

    Abstract

    Coronary artery disease (or coronary heart disease), is the leading cause of mortality in many of the developing as well as the developed countries of the world. Cholesterol-enriched plaques in the heart's blood vessels combined with inflammation lead to the lesion expansion, narrowing of blood vessels, reduced blood flow, and may subsequently cause lesion rupture and a heart attack. Even though several environmental risk factors have been established, such as high LDL-cholesterol, diabetes, and high blood pressure, the underlying genetic composition may substantially modify the disease risk; hence, genome composition and gene-environment interactions may be critical for disease progression. Ongoing scientific efforts have seen substantial advancements related to the fields of genetics and genomics, with the major breakthroughs yet to come. As genomics is the most rapidly advancing field in the life sciences, it is important to present a comprehensive overview of current efforts. Here, we present a summary of various genetic and genomics assays and approaches applied to coronary artery disease research.

    View details for DOI 10.1007/s11886-016-0777-y

    View details for PubMedID 27586139

  • Integrative functional genomics identifies regulatory mechanisms at coronary artery disease loci. Nature communications Miller, C. L., Pjanic, M., Wang, T., Nguyen, T., Cohain, A., Lee, J. D., Perisic, L., Hedin, U., Kundu, R. K., Majmudar, D., Kim, J. B., Wang, O., Betsholtz, C., Ruusalepp, A., Franzén, O., Assimes, T. L., Montgomery, S. B., Schadt, E. E., Björkegren, J. L., Quertermous, T. 2016; 7: 12092-?

    Abstract

    Coronary artery disease (CAD) is the leading cause of mortality and morbidity, driven by both genetic and environmental risk factors. Meta-analyses of genome-wide association studies have identified >150 loci associated with CAD and myocardial infarction susceptibility in humans. A majority of these variants reside in non-coding regions and are co-inherited with hundreds of candidate regulatory variants, presenting a challenge to elucidate their functions. Herein, we use integrative genomic, epigenomic and transcriptomic profiling of perturbed human coronary artery smooth muscle cells and tissues to begin to identify causal regulatory variation and mechanisms responsible for CAD associations. Using these genome-wide maps, we prioritize 64 candidate variants and perform allele-specific binding and expression analyses at seven top candidate loci: 9p21.3, SMAD3, PDGFD, IL6R, BMP1, CCDC97/TGFB1 and LMOD1. We validate our findings in expression quantitative trait loci cohorts, which together reveal new links between CAD associations and regulatory function in the appropriate disease context.

    View details for DOI 10.1038/ncomms12092

    View details for PubMedID 27386823

  • Nuclear Factor I genomic binding associates with chromatin boundaries BMC GENOMICS Pjanic, M., Schmid, C. D., Gaussin, A., Ambrosini, G., Adamcik, J., Pjanic, P., Plasari, G., Kerschgens, J., Dietler, G., Bucher, P., Mermod, N. 2013; 14

    Abstract

    The Nuclear Factor I (NFI) family of DNA binding proteins (also called CCAAT box transcription factors or CTF) is involved in both DNA replication and gene expression regulation. Using chromatin immuno-precipitation and high throughput sequencing (ChIP-Seq), we performed a genome-wide mapping of NFI DNA binding sites in primary mouse embryonic fibroblasts.We found that in vivo and in vitro NFI DNA binding specificities are indistinguishable, as in vivo ChIP-Seq NFI binding sites matched predictions based on previously established position weight matrix models of its in vitro binding specificity. Combining ChIP-Seq with mRNA profiling data, we found that NFI preferentially associates with highly expressed genes that it up-regulates, while binding sites were under-represented at expressed but unregulated genes. Genomic binding also correlated with markers of transcribed genes such as histone modifications H3K4me3 and H3K36me3, even outside of annotated transcribed loci, implying NFI in the control of the deposition of these modifications. Positional correlation between + and - strand ChIP-Seq tags revealed that, in contrast to other transcription factors, NFI associates with a nucleosomal length of cleavage-resistant DNA, suggesting an interaction with positioned nucleosomes. In addition, NFI binding prominently occurred at boundaries displaying discontinuities in histone modifications specific of expressed and silent chromatin, such as loci submitted to parental allele-specific imprinted expression.Our data thus suggest that NFI nucleosomal interaction may contribute to the partitioning of distinct chromatin domains and to epigenetic gene expression regulation.NFI ChIP-Seq and input control DNA data were deposited at Gene Expression Omnibus (GEO) repository under accession number GSE15844. Gene expression microarray data for mouse embryonic fibroblasts are on GEO accession number GSE15871.

    View details for DOI 10.1186/1471-2164-14-99

    View details for Web of Science ID 000316681000001

    View details for PubMedID 23402308

  • TCF21 and AP-1 interact through epigenetic modifications to regulate coronary artery disease gene expression. Genome medicine Zhao, Q., Wirka, R., Nguyen, T., Nagao, M., Cheng, P., Miller, C. L., Kim, J. B., Pjanic, M., Quertermous, T. 2019; 11 (1): 23

    Abstract

    Genome-wide association studies have identified over 160 loci that are associated with coronary artery disease. As with other complex human diseases, risk in coronary disease loci is determined primarily by altered expression of the causal gene, due to variation in binding of transcription factors and chromatin-modifying proteins that directly regulate the transcriptional apparatus. We have previously identified a coronary disease network downstream of the disease-associated transcription factor TCF21, and in work reported here extends these studies to investigate the mechanisms by which it interacts with the AP-1 transcription complex to regulate local epigenetic effects in these downstream coronary disease loci.Genomic studies, including chromatin immunoprecipitation sequencing, RNA sequencing, and protein-protein interaction studies, were performed in human coronary artery smooth muscle cells.We show here that TCF21 and JUN regulate expression of two presumptive causal coronary disease genes, SMAD3 and CDKN2B-AS1, in part by interactions with histone deacetylases and acetyltransferases. Genome-wide TCF21 and JUN binding is jointly localized and particularly enriched in coronary disease loci where they broadly modulate H3K27Ac and chromatin state changes linked to disease-related processes in vascular cells. Heterozygosity at coronary disease causal variation, or genome editing of these variants, is associated with decreased binding of both JUN and TCF21 and loss of expression in cis, supporting a transcriptional mechanism for disease risk.These data show that the known chromatin remodeling and pioneer functions of AP-1 are a pervasive aspect of epigenetic control of transcription, and thus, the risk in coronary disease-associated loci, and that interaction of AP-1 with TCF21 to control epigenetic features, contributes to the genetic risk in loci where they co-localize.

    View details for PubMedID 31014396

  • Functional regulatory mechanism of smooth muscle cell-restricted LMOD1 coronary artery disease locus. PLoS genetics Nanda, V., Wang, T., Pjanic, M., Liu, B., Nguyen, T., Matic, L. P., Hedin, U., Koplev, S., Ma, L., Franzén, O., Ruusalepp, A., Schadt, E. E., Björkegren, J. L., Montgomery, S. B., Snyder, M. P., Quertermous, T., Leeper, N. J., Miller, C. L. 2018; 14 (11): e1007755

    Abstract

    Recent genome-wide association studies (GWAS) have identified multiple new loci which appear to alter coronary artery disease (CAD) risk via arterial wall-specific mechanisms. One of the annotated genes encodes LMOD1 (Leiomodin 1), a member of the actin filament nucleator family that is highly enriched in smooth muscle-containing tissues such as the artery wall. However, it is still unknown whether LMOD1 is the causal gene at this locus and also how the associated variants alter LMOD1 expression/function and CAD risk. Using epigenomic profiling we recently identified a non-coding regulatory variant, rs34091558, which is in tight linkage disequilibrium (LD) with the lead CAD GWAS variant, rs2820315. Herein we demonstrate through expression quantitative trait loci (eQTL) and statistical fine-mapping in GTEx, STARNET, and human coronary artery smooth muscle cell (HCASMC) datasets, rs34091558 is the top regulatory variant for LMOD1 in vascular tissues. Position weight matrix (PWM) analyses identify the protective allele rs34091558-TA to form a conserved Forkhead box O3 (FOXO3) binding motif, which is disrupted by the risk allele rs34091558-A. FOXO3 chromatin immunoprecipitation and reporter assays show reduced FOXO3 binding and LMOD1 transcriptional activity by the risk allele, consistent with effects of FOXO3 downregulation on LMOD1. LMOD1 knockdown results in increased proliferation and migration and decreased cell contraction in HCASMC, and immunostaining in atherosclerotic lesions in the SMC lineage tracing reporter mouse support a key role for LMOD1 in maintaining the differentiated SMC phenotype. These results provide compelling functional evidence that genetic variation is associated with dysregulated LMOD1 expression/function in SMCs, together contributing to the heritable risk for CAD.

    View details for PubMedID 30444878

  • Coronary artery disease genes SMAD3 and TCF21 promote opposing interactive genetic programs that regulate smooth muscle cell differentiation and disease risk. PLoS genetics Iyer, D., Zhao, Q., Wirka, R., Naravane, A., Nguyen, T., Liu, B., Nagao, M., Cheng, P., Miller, C. L., Kim, J. B., Pjanic, M., Quertermous, T. 2018; 14 (10): e1007681

    Abstract

    Although numerous genetic loci have been associated with coronary artery disease (CAD) with genome wide association studies, efforts are needed to identify the causal genes in these loci and link them into fundamental signaling pathways. Recent studies have investigated the disease mechanism of CAD associated gene SMAD3, a central transcription factor (TF) in the TGF? pathway, investigating its role in smooth muscle biology. In vitro studies in human coronary artery smooth muscle cells (HCASMC) revealed that SMAD3 modulates cellular phenotype, promoting expression of differentiation marker genes while inhibiting proliferation. RNA sequencing and chromatin immunoprecipitation sequencing studies in HCASMC identified downstream genes that reside in pathways which mediate vascular development and atherosclerosis processes in this cell type. HCASMC phenotype, and gene expression patterns promoted by SMAD3 were noted to have opposing direction of effect compared to another CAD associated TF, TCF21. At sites of SMAD3 and TCF21 colocalization on DNA, SMAD3 binding was inversely correlated with TCF21 binding, due in part to TCF21 locally blocking chromatin accessibility at the SMAD3 binding site. Further, TCF21 was able to directly inhibit SMAD3 activation of gene expression in transfection reporter gene studies. In contrast to TCF21 which is protective toward CAD, SMAD3 expression in HCASMC was shown to be directly correlated with disease risk. We propose that the pro-differentiation action of SMAD3 inhibits dedifferentiation that is required for HCASMC to expand and stabilize disease plaque as they respond to vascular stresses, counteracting the protective dedifferentiating activity of TCF21 and promoting disease risk.

    View details for PubMedID 30307970

  • From Locus Association to Mechanism of Gene Causality: The Devil Is in the Details. Arteriosclerosis, thrombosis, and vascular biology Miller, C. L., Pjanic, M., Quertermous, T. 2015; 35 (10): 2079-2080

    View details for DOI 10.1161/ATVBAHA.115.306366

    View details for PubMedID 26399919

    View details for PubMedCentralID PMC4594207

  • Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells that Contribute to the Fibrous Cap. Genomics data Nurnberg, S. T., Cheng, K., Raiesdana, A., Kundu, R., MILLER, C. L., Kim, J. B., Arora, K., Carcamo-Oribe, I., Xiong, Y., Tellakula, N., Nanda, V., Murthy, N., Boisvert, W. A., HEDIN, U., Perisic, L., Aldi, S., Maegdefessel, L., Pjanic, M., Owens, G. K., Tallquist, M. D., Quertermous, T. 2015; 5: 36-37

    Abstract

    TCF21 is a basic helix-loop-helix transcription factor that has recently been implicated as contributing to susceptibility to coronary heart disease based on genome wide association studies. In order to identify transcriptionally regulated target genes in a major disease relevant cell type, we performed siRNA knockdown of TCF21 in in vitro cultured human coronary artery smooth muscle cells and compared the transcriptome of siTCF21 versus siCONTROL treated cells. The raw (FASTQ) as well as processed (BED) data from 3 technical replicates per treatment has been deposited with Gene Expression Omnibus (GSE44461).

    View details for PubMedID 26090325

  • Characterization of TCF21 Downstream Target Regions Identifies a Transcriptional Network Linking Multiple Independent Coronary Artery Disease Loci. PLoS genetics Sazonova, O., Zhao, Y., Nürnberg, S., Miller, C., Pjanic, M., Castano, V. G., Kim, J. B., Salfati, E. L., Kundaje, A. B., Bejerano, G., Assimes, T., Yang, X., Quertermous, T. 2015; 11 (5)

    Abstract

    To functionally link coronary artery disease (CAD) causal genes identified by genome wide association studies (GWAS), and to investigate the cellular and molecular mechanisms of atherosclerosis, we have used chromatin immunoprecipitation sequencing (ChIP-Seq) with the CAD associated transcription factor TCF21 in human coronary artery smooth muscle cells (HCASMC). Analysis of identified TCF21 target genes for enrichment of molecular and cellular annotation terms identified processes relevant to CAD pathophysiology, including "growth factor binding," "matrix interaction," and "smooth muscle contraction." We characterized the canonical binding sequence for TCF21 as CAGCTG, identified AP-1 binding sites in TCF21 peaks, and by conducting ChIP-Seq for JUN and JUND in HCASMC confirmed that there is significant overlap between TCF21 and AP-1 binding loci in this cell type. Expression quantitative trait variation mapped to target genes of TCF21 was significantly enriched among variants with low P-values in the GWAS analyses, suggesting a possible functional interaction between TCF21 binding and causal variants in other CAD disease loci. Separate enrichment analyses found over-representation of TCF21 target genes among CAD associated genes, and linkage disequilibrium between TCF21 peak variation and that found in GWAS loci, consistent with the hypothesis that TCF21 may affect disease risk through interaction with other disease associated loci. Interestingly, enrichment for TCF21 target genes was also found among other genome wide association phenotypes, including height and inflammatory bowel disease, suggesting a functional profile important for basic cellular processes in non-vascular tissues. Thus, data and analyses presented here suggest that study of GWAS transcription factors may be a highly useful approach to identifying disease gene interactions and thus pathways that may be relevant to complex disease etiology.

    View details for DOI 10.1371/journal.pgen.1005202

    View details for PubMedID 26020271

  • Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells That Contribute to the Fibrous Cap. PLoS genetics Nurnberg, S. T., Cheng, K., Raiesdana, A., Kundu, R., Miller, C. L., Kim, J. B., Arora, K., Carcamo-Oribe, I., Xiong, Y., Tellakula, N., Nanda, V., Murthy, N., Boisvert, W. A., Hedin, U., Perisic, L., Aldi, S., Maegdefessel, L., Pjanic, M., Owens, G. K., Tallquist, M. D., Quertermous, T. 2015; 11 (5)

    Abstract

    Recent genome wide association studies have identified a number of genes that contribute to the risk for coronary heart disease. One such gene, TCF21, encodes a basic-helix-loop-helix transcription factor believed to serve a critical role in the development of epicardial progenitor cells that give rise to coronary artery smooth muscle cells (SMC) and cardiac fibroblasts. Using reporter gene and immunolocalization studies with mouse and human tissues we have found that vascular TCF21 expression in the adult is restricted primarily to adventitial cells associated with coronary arteries and also medial SMC in the proximal aorta of mouse. Genome wide RNA-Seq studies in human coronary artery SMC (HCASMC) with siRNA knockdown found a number of putative TCF21 downstream pathways identified by enrichment of terms related to CAD, including "vascular disease," "disorder of artery," and "occlusion of artery," as well as disease-related cellular functions including "cellular movement" and "cellular growth and proliferation." In vitro studies in HCASMC demonstrated that TCF21 expression promotes proliferation and migration and inhibits SMC lineage marker expression. Detailed in situ expression studies with reporter gene and lineage tracing revealed that vascular wall cells expressing Tcf21 before disease initiation migrate into vascular lesions of ApoE-/- and Ldlr-/- mice. While Tcf21 lineage traced cells are distributed throughout the early lesions, in mature lesions they contribute to the formation of a subcapsular layer of cells, and others become associated with the fibrous cap. The lineage traced fibrous cap cells activate expression of SMC markers and growth factor receptor genes. Taken together, these data suggest that TCF21 may have a role regulating the differentiation state of SMC precursor cells that migrate into vascular lesions and contribute to the fibrous cap and more broadly, in view of the association of this gene with human CAD, provide evidence that these processes may be a mechanism for CAD risk attributable to the vascular wall.

    View details for DOI 10.1371/journal.pgen.1005155

    View details for PubMedID 26020946

  • Molecular Characterization of a Human Matrix Attachment Region Epigenetic Regulator PLOS ONE Arope, S., Harraghy, N., Pjanic, M., Mermod, N. 2013; 8 (11)

    Abstract

    Matrix attachment regions (MAR) generally act as epigenetic regulatory sequences that increase gene expression, and they were proposed to partition chromosomes into loop-forming domains. However, their molecular mode of action remains poorly understood. Here, we assessed the possible contribution of the AT-rich core and adjacent transcription factor binding motifs to the transcription augmenting and anti-silencing effects of human MAR 1-68. Either flanking sequences together with the AT-rich core were required to obtain the full MAR effects. Shortened MAR derivatives retaining full MAR activity were constructed from combinations of the AT-rich sequence and multimerized transcription factor binding motifs, implying that both transcription factors and the AT-rich microsatellite sequence are required to mediate the MAR effect. Genomic analysis indicated that MAR AT-rich cores may be depleted of histones and enriched in RNA polymerase II, providing a molecular interpretation of their chromatin domain insulator and transcriptional augmentation activities.

    View details for DOI 10.1371/journal.pone.0079262

    View details for Web of Science ID 000327143800050

    View details for PubMedID 24244463

  • Nuclear factor I revealed as family of promoter binding transcription activators BMC GENOMICS Pjanic, M., Pjanic, P., Schmid, C., Ambrosini, G., Gaussin, A., Plasari, G., Mazza, C., Bucher, P., Mermod, N. 2011; 12

    Abstract

    Multiplex experimental assays coupled to computational predictions are being increasingly employed for the simultaneous analysis of many specimens at the genome scale, which quickly generates very large amounts of data. However, inferring valuable biological information from the comparisons of very large genomic datasets still represents an enormous challenge.As a study model, we chose the NFI/CTF family of mammalian transcription factors and we compared the results obtained from a genome-wide study of its binding sites with chromatin structure assays, gene expression microarray data, and in silico binding site predictions. We found that NFI/CTF family members preferentially bind their DNA target sites when they are located around transcription start sites when compared to control datasets generated from the random subsampling of the complete set of NFI binding sites. NFI proteins preferably associate with the upstream regions of genes that are highly expressed and that are enriched in active chromatin modifications such as H3K4me3 and H3K36me3. We postulate that this is a causal association and that NFI proteins mainly act as activators of transcription. This was documented for one member of the family (NFI-C), which revealed as a more potent gene activator than repressor in global gene expression analysis. Interestingly, we also discovered the association of NFI with the tri-methylation of lysine 9 of histone H3, a chromatin marker previously associated with the protection against silencing of telomeric genes by NFI.Taken together, we illustrate approaches that can be taken to analyze large genomic data, and provide evidence that NFI family members may act in conjunction with specific chromatin modifications to activate gene expression.

    View details for DOI 10.1186/1471-2164-12-181

    View details for Web of Science ID 000289898900001

    View details for PubMedID 21473784

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