Rare copy number variants disrupt genes regulating vascular smooth muscle cell adhesion and contractility in sporadic thoracic aortic aneurysms and dissections

Abstract

Thoracic aortic aneurysms and dissections (TAAD) cause significant morbidity and mortality, but the genetic origins of TAAD remain largely unknown. In a genome-wide analysis of 418 sporadic TAAD cases, we identified 47 copy number variant (CNV) regions that were enriched in or unique to TAAD patients compared to population controls. Gene ontology, expression profiling, and network analysis showed that genes within TAAD CNVs regulate smooth muscle cell adhesion or contractility and interact with the smooth muscle-specific isoforms of α-actin and β-myosin, which are known to cause familial TAAD when altered. Enrichment of these gene functions in rare CNVs was replicated in independent cohorts with sporadic TAAD (STAAD, n = 387) and inherited TAAD (FTAAD, n = 88). The overall prevalence of rare CNVs (23%) was significantly increased in FTAAD compared with STAAD patients (Fisher's exact test, p = 0.03). Our findings suggest that rare CNVs disrupting smooth muscle adhesion or contraction contribute to both sporadic and familial disease.

Figure 1

Flow Diagram of CNV Analysis The following abbreviations are used: STAAD, sporadic thoracic aortic aneurysms and dissections; BCM, Baylor College of Medicine; UTHSCH, University of Texas Health Science Center; dbGAP, Database of Genotypes and Phenotypes. Samples that did not meet quality thresholds were identified and excluded via functions implemented in the PennCNV package. Rare events larger than 1 Mb were analyzed separately.

Figure 2

Network of Interacting TAAD CNV Genes Genes within TAAD-associated CNVs are colored green (FTAAD), orange (BCM), or blue (UTHSCH); lines indicate functional or physical interactions between gene products; not all genes in the network are shown. All CNVs represented in this network are rare and occur in one or none of 4922 control individuals. The following abbreviations are used: ABRA, actin-binding Rho-activating protein; ABLIM, actin-binding LIM protein family; ACAN, aggrecan; ACTR2, actin-related protein 2 homolog; AFAP1, actin filament-associated protein 1; AKAP12, A kinase anchor protein12; ALOX5, 5-lipoxygenase; ARHGAP26, GTPase regulator associated with FAK; ATF2, activating transcription factor 2; BGN, biglycan; BMP4, bone morphogenetic protein 4; BMPR1B, bone morphogenetic protein receptor 1B; BMPER, BMP-binding endothelial cell precursor-derived regulator; EPHA5, ephrin type A receptor 5; EMMPRIN, extracellular matrix metalloproteinase inducer; CAPZA1, capping protein muscle Z-line, alpha 1; CCDC88A, coiled-coil domain containing 88A; CD36, thrombospondin receptor; CLDN, claudins; COL18A1, collagen type 18, alpha 1 and endostatin; CSRP2, cysteine-rich protein 2; FAK, focal adhesion kinase; FOG2, friend of GATA2; GDF5, growth differentiation factor 5; HAND1, heart and neural crest derivatives expressed 1; ID1, inhibitor of DNA binding 1; ILKAP, integrin-linked kinase-associated phosphatase; JAG, jagged homolog; JAM3, junctional adhesion molecule 3; JNK, JUN N-terminal kinase; LIMK1, LIM domain kinase 1; MIB2, mindbomb homolog 2; MMP9, matrix metalloproteinase 9; MT1-MMP, matrix metalloproteinase 14; MRTFs, myocardin- related transcription factors; MYH11, myosin heavy chain, smooth muscle isoform; MYL9, myosin regulatory light chain 2, smooth muscle isoform; MYOCD, myocardin; NID2, nidogen 2; OVOL2, Ovo-like 2; PARD3, partitioning defective 3 homolog; PMP22, peripheral myelin protein 22; POSH, plenty of SH3s; PRKAR2A, cAMP-dependent protein kinase, regulatory subunit alpha 2; PPIA, cyclophilin A; PRKACA, cAMP-dependent protein kinase catalytic subunit alpha; PTPRA, protein tyrosine phosphatase, receptor type, alpha polypeptide; RGNEF, Rho guanine nucleotide exchange factor; RHOC, Ras homolog gene family, member C; ROCK, Rho-associated, coiled-coil domain-containing protein kinase; SMAD, mothers against decapentaplegic homolog; SMYD1, set and MYND domain-containing 1; SPRY2, sprouty homolog 2; SRF, serum response factor; TJP1, tight junction protein ZO-1; TNC, tenascin C; VCAN, versican; WASL, Wiskott-Aldrich syndrome gene-like protein; WIPF1, WAS/WASL-interacting protein family member 1. Figure was derived from IPA analysis (version 8.1) and created with Cytoscape (version 2.6.3).

Figure 3

Gene Ontology Processes in BCM, UTHSC, and FTAAD Cohorts Negative logarithms of p values are plotted on the x axis. Green: FTAAD; orange: BCM; blue: UTHSCH. Graph was generated with Microsoft Excel with data from GeneGo MetaCore pathway analysis software. P values are for enrichment of the specific GO terms. For calculation of p values, please refer to Subjects and Methods.