I am interesting in identifying the heritable component of a wide range of cardiovascular diseases which include coronary artery disease and peripheral artery disease. To this end, I am involved in utilizing genome-wide genetic and bioinformatics approaches to identify loci responsible for disease, and thereafter validating these findings by implementing a variety of molecular genetics, molecular biology and transgenic mouse models to explain the vascular biology of the identified gene or pathway.
Instructor, Surgery - Vascular Surgery
Honors & Awards
Postdoctoral Fellowship, Role: Principal Investigator, American Heart Association (2015-2017)
Jay D. Coffman Young Investigator Award Winner, Society for Vascular Medicine (2015)
Postdoctoral Travel Award, Cardiovascular Institute, Stanford University (2015)
Top Scoring Abstract, Arteriosclerosis Thrombosis Vascular Biology (2015)
Young Investigator Travel Award, Arteriosclerosis Thrombosis Vascular Biology (2015)
Dean’s List Academic Honors, Rochester Institute of Technology (2002-2005)
Boards, Advisory Committees, Professional Organizations
Early Career Member, National Postdoctoral Association (2014 - Present)
Early Career Member, American Heart Association (2010 - Present)
- Proefferocytic Therapy Promotes Transforming Growth Factor-beta Signaling and Prevents Aneurysm Formation CIRCULATION 2018; 137 (7): 750–53
Functional regulatory mechanism of smooth muscle cell-restricted LMOD1 coronary artery disease locus.
2018; 14 (11): e1007755
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
CD47-blocking antibodies restore phagocytosis and prevent atherosclerosis.
2016; 536 (7614): 86-90
Atherosclerosis is the disease process that underlies heart attack and stroke. Advanced lesions at risk of rupture are characterized by the pathological accumulation of diseased vascular cells and apoptotic cellular debris. Why these cells are not cleared remains unknown. Here we show that atherogenesis is associated with upregulation of CD47, a key anti-phagocytic molecule that is known to render malignant cells resistant to programmed cell removal, or 'efferocytosis'. We find that administration of CD47-blocking antibodies reverses this defect in efferocytosis, normalizes the clearance of diseased vascular tissue, and ameliorates atherosclerosis in multiple mouse models. Mechanistic studies implicate the pro-atherosclerotic factor TNF-α as a fundamental driver of impaired programmed cell removal, explaining why this process is compromised in vascular disease. Similar to recent observations in cancer, impaired efferocytosis appears to play a pathogenic role in cardiovascular disease, but is not a fixed defect and may represent a novel therapeutic target.
View details for PubMedID 27437576
De Novo and Rare Variants at Multiple Loci Support the Oligogenic Origins of Atrioventricular Septal Heart Defects.
2016; 12 (4)
Congenital heart disease (CHD) has a complex genetic etiology, and recent studies suggest that high penetrance de novo mutations may account for only a small fraction of disease. In a multi-institutional cohort surveyed by exome sequencing, combining analysis of 987 individuals (discovery cohort of 59 affected trios and 59 control trios, and a replication cohort of 100 affected singletons and 533 unaffected singletons) we observe variation at novel and known loci related to a specific cardiac malformation the atrioventricular septal defect (AVSD). In a primary analysis, by combining developmental coexpression networks with inheritance modeling, we identify a de novo mutation in the DNA binding domain of NR1D2 (p.R175W). We show that p.R175W changes the transcriptional activity of Nr1d2 using an in vitro transactivation model in HUVEC cells. Finally, we demonstrate previously unrecognized cardiovascular malformations in the Nr1d2tm1-Dgen knockout mouse. In secondary analyses we map genetic variation to protein-interaction networks suggesting a role for two collagen genes in AVSD, which we corroborate by burden testing in a second replication cohort of 100 AVSDs and 533 controls (p = 8.37e-08). Finally, we apply a rare-disease inheritance model to identify variation in genes previously associated with CHD (ZFPM2, NSD1, NOTCH1, VCAN, and MYH6), cardiac malformations in mouse models (ADAM17, CHRD, IFT140, PTPRJ, RYR1 and ATE1), and hypomorphic alleles of genes causing syndromic CHD (EHMT1, SRCAP, BBS2, NOTCH2, and KMT2D) in 14 of 59 trios, greatly exceeding variation in control trios without CHD (p = 9.60e-06). In total, 32% of trios carried at least one putatively disease-associated variant across 19 loci,suggesting that inherited and de novo variation across a heterogeneous group of loci may contribute to disease risk.
View details for DOI 10.1371/journal.pgen.1005963
View details for PubMedID 27058611
CDKN2B Regulates TGFß Signaling and Smooth Muscle Cell Investment of Hypoxic Neovessels.
2016; 118 (2): 230-240
Genetic variation at the chromosome 9p21 cardiovascular risk locus has been associated with peripheral artery disease, but its mechanism remains unknown.To determine whether this association is secondary to an increase in atherosclerosis, or it is the result of a separate angiogenesis-related mechanism.Quantitative evaluation of human vascular samples revealed that carriers of the 9p21 risk allele possess a significantly higher burden of immature intraplaque microvessels than carriers of the ancestral allele, irrespective of lesion size or patient comorbidity. To determine whether aberrant angiogenesis also occurs under nonatherosclerotic conditions, we performed femoral artery ligation surgery in mice lacking the 9p21 candidate gene, Cdkn2b. These animals developed advanced hindlimb ischemia and digital autoamputation, secondary to a defect in the capacity of the Cdkn2b-deficient smooth muscle cell to support the developing neovessel. Microarray studies identified impaired transforming growth factor β (TGFβ) signaling in cultured cyclin-dependent kinase inhibitor 2B (CDKN2B)-deficient cells, as well as TGFβ1 upregulation in the vasculature of 9p21 risk allele carriers. Molecular signaling studies indicated that loss of CDKN2B impairs the expression of the inhibitory factor, SMAD-7, which promotes downstream TGFβ activation. Ultimately, this manifests in the upregulation of a poorly studied effector molecule, TGFβ1-induced-1, which is a TGFβ-rheostat known to have antagonistic effects on the endothelial cell and smooth muscle cell. Dual knockdown studies confirmed the reversibility of the proposed mechanism, in vitro.These results suggest that loss of CDKN2B may not only promote cardiovascular disease through the development of atherosclerosis but may also impair TGFβ signaling and hypoxic neovessel maturation.
View details for DOI 10.1161/CIRCRESAHA.115.307906
View details for PubMedID 26596284
View details for PubMedCentralID PMC4740238
Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells that Contribute to the Fibrous Cap.
2015; 5: 36-37
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
Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells That Contribute to the Fibrous Cap.
2015; 11 (5)
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
- Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells That Contribute to the Fibrous Cap PLOS GENETICS 2015; 11 (5)
Identification and Initial Functional Characterization of a Human Vascular Cell-Enriched Long Noncoding RNA
ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY
2014; 34 (6): 1249-1259
Long noncoding RNAs (lncRNAs) represent a rapidly growing class of RNA genes with functions related primarily to transcriptional and post-transcriptional control of gene expression. There is a paucity of information about lncRNA expression and function in human vascular cells. Thus, we set out to identify novel lncRNA genes in human vascular smooth muscle cells and to gain insight into their role in the control of smooth muscle cell phenotypes.RNA sequencing (RNA-seq) of human coronary artery smooth muscle cells revealed 31 unannotated lncRNAs, including a vascular cell-enriched lncRNA (Smooth muscle and Endothelial cell-enriched migration/differentiation-associated long NonCoding RNA [SENCR]). Strand-specific reverse transcription polymerase chain reaction (PCR) and rapid amplification of cDNA ends indicate that SENCR is transcribed antisense from the 5' end of the FLI1 gene and exists as 2 splice variants. RNA fluorescence in situ hybridization and biochemical fractionation studies demonstrate SENCR is a cytoplasmic lncRNA. Consistent with this observation, knockdown studies reveal little to no cis-acting effect of SENCR on FLI1 or neighboring gene expression. RNA-seq experiments in smooth muscle cells after SENCR knockdown disclose decreased expression of Myocardin and numerous smooth muscle contractile genes, whereas several promigratory genes are increased. Reverse transcription PCR and Western blotting experiments validate several differentially expressed genes after SENCR knockdown. Loss-of-function studies in scratch wound and Boyden chamber assays support SENCR as an inhibitor of smooth muscle cell migration.SENCR is a new vascular cell-enriched, cytoplasmic lncRNA that seems to stabilize the smooth muscle cell contractile phenotype.
View details for DOI 10.1161/ATVBAHA.114.303240
View details for Web of Science ID 000335809900022
View details for PubMedID 24578380
Leiomodin 1, a New Serum Response Factor-dependent Target Gene Expressed Preferentially in Differentiated Smooth Muscle Cells
JOURNAL OF BIOLOGICAL CHEMISTRY
2012; 287 (4): 2459-2467
Smooth muscle cell (SMC) differentiation is defined largely by a number of cell-restricted genes governed directly by the serum response factor (SRF)/myocardin (MYOCD) transcriptional switch. Here, we describe a new SRF/MYOCD-dependent, SMC-restricted gene known as Leiomodin 1 (Lmod1). Conventional and quantitative RT-PCRs indicate that Lmod1 mRNA expression is enriched in SMC-containing tissues of the mouse, whereas its two paralogs, Lmod2 and Lmod3, exhibit abundant expression in skeletal and cardiac muscle with very low levels in SMC-containing tissues. Western blotting and immunostaining of various adult and embryonic mouse tissues further confirm SMC-specific expression of the LMOD1 protein. Comparative genomic analysis of the human LMOD1 and LMOD2 genes with their respective mouse and rat orthologs shows high conservation between the three exons and several noncoding sequences, including the immediate 5' promoter region. Two conserved CArG boxes are present in both the LMOD1 and LMOD2 promoter regions, although LMOD1 displays much higher promoter activity and is more responsive to SRF/MYOCD stimulation. Gel shift assays demonstrate clear binding between SRF and the two CArG boxes in human LMOD1. Although the CArG boxes in LMOD1 and LMOD2 are similar, only LMOD1 displays SRF or MYOCD-dependent activation. Transgenic mouse studies reveal wild type LMOD1 promoter activity in cardiac and vascular SMC. Such activity is abolished upon mutation of both CArG boxes. Collectively, these data demonstrate that Lmod1 is a new SMC-restricted SRF/MYOCD target gene.
View details for DOI 10.1074/jbc.M111.302224
View details for Web of Science ID 000300292300020
View details for PubMedID 22157009
Expression and functional activity of four myocardin isoforms
2010; 464 (1-2): 1-10
Myocardin (MYOCD) is an essential component of a molecular switch for the expression of contractile genes in smooth muscle and cardiac muscle cells. The Myocd gene comprises at least fifteen exons, including two alternately spliced exons designated 2a and 10a. We investigated tissue-specific Myocd expression in mouse, rat and human tissues to determine the conservation in expression of each Myocd splice variant and to ascertain whether any functional differences exist among MYOCD isoforms. Conventional and quantitative RT-PCR revealed the dominant expression of Myocd exon 2a (Myocd_v3) in smooth muscle cell (SMC)-rich tissues (aorta and bladder) with little expression in heart across all species studied. Each species of heart showed primarily a longer version of Myocd (Myocd_v1) without exon 2a. While exclusion of exon 2a was common in all cardiac muscle samples, exon skipping of Myocd exon 10a was a rare event in both cardiac muscle and SMC tissues. In general, all four MYOCD isoforms showed comparable stimulation of SMC promoters. On the other hand, Myocd_v1 and Myocd_v2 were more active than Myocd_v3 and Myocd_v4 in stimulating cardiac muscle promoters and Myocd_v1's activity was augmented in the presence of the cardiac transcription factor, MEF2C. Importantly, whereas all four MYOCD isoforms similarly induced expression of endogenous SMC genes in a prostate tumor cell line (LNCaP), none could induce the endogenous expression of specific cardiac markers. These results are the first to show relative expression and activities of the major myocardin isoforms across disparate species. We propose a new myocardin nomenclature reflecting the dominant splice variants expressed in cardiac muscle (Myocd_v1 and v2) versus SMC-rich tissues (Myocd_v3 and v4).
View details for DOI 10.1016/j.gene.2010.03.012
View details for Web of Science ID 000281096300001
View details for PubMedID 20385216