Thoracic Aortic Aneurysm And Dissection Patients Research Articles

Clinical Interpretation of Genetic Variants in the Evaluation and Management of Thoracic Aortic Aneurysm and Dissection

We aimed to elucidate clinical implications of genetic variant interpretation in assessing disease severity and progression in thoracic aortic aneurysm and dissection (TAAD) patients. Consecutive TAAD patients with aortic root and/or ascending aortic aneurysms seen between 2011 and 2020 were included. Serial echocardiography, family history of TAAD, and management information were retrospectively collected and analyzed. Patients were classified into gene-positive (Gen-P), variants of uncertain significance, and gene-negative (Gen-N) groups. A total of 407 patients were included: mean age 53.7±15.4 years, 64.4% women, and 38% with reported family history of TAAD. Thirty-seven (9.1%) were Gen-P; 147 (36.1%) had a variant of uncertain significance. Maximal aneurysm diameter was 4.78 mm larger in Gen-P than the other groups (P=.0003). In 162 unoperated TAAD patients with serial echocardiographic measurements, aneurysms enlarged at a significantly higher rate in the Gen-P (1.36 mm/year, 95% CI: 0.77-1.95) than variants of uncertain significance and Gen-N groups (0.83 mm/year vs 0.89 mm/year, respectively; P<.001). Aneurysms were 20% more likely to require surgical intervention for every millimeter increase in diameter. When considered on an individual basis, the highest growth rates were found in the variants of uncertain significance group. While aneurysms linked to variants of uncertain significance demonstrate average growth rates comparable to those in Gen-N, close follow-up and genetic counseling in the variants of uncertain significance group are recommended for assessment of pathogenicity on a case-by-case basis. Early familial gene testing in TAAD is important to develop individualized preventive and therapeutic criteria.

Urate-Lowering Therapy Inhibits Thoracic Aortic Aneurysm and Dissection Formation in Mice.

Thoracic aortic aneurysm and dissection (TAAD) is a highly lethal vascular disease without effective drug therapy. Whether elevated serum concentrations of uric acid are involved in TAAD development remains unclear. Serum uric acid levels were detected in different TAAD mouse models and patients. The urate-lowering drug allopurinol was administered in the drinking water of TAAD mice. Adenine diet-induced mice were established to investigate the role of hyperuricemia in TAAD formation and RNA-sequencing of thoracic aortas from these mice was performed. We found serum uric acid levels were elevated in various mouse TAAD models, including mice fed a β-aminopropionitrile diet, Marfan mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+), and ApoE-/- mice infused with Ang II (angiotensin II), as well as in patients with TAAD. Administration of urate-lowering drug allopurinol in the drinking water significantly alleviated TAAD formation in β-aminopropionitrile-treated mice, Fbn1C1041G/+ mice, and Ang II-infused ApoE-/- mice. Moreover, an adenine diet was used to induce hyperuricemia in mice. Intriguingly, a 4-week adenine diet feeding directly induced TAAD formation characterized by increased maximal thoracic aortic diameters and severe elastin degradation, which were ameliorated by allopurinol. Unbiased RNA-sequencing in mouse thoracic aortas suggested that FcγR (Fc gamma receptor) was upregulated upon adenine diet, but reciprocally repressed by allopurinol. Mechanistically, hyperuricemia activated FcγR-mediated ERK1/2 (extracellular signal-regulated kinase 1/2) phosphorylation to induce macrophage inflammation and TAAD development, which was abrogated by allopurinol or FcγR deficiency. This study uncovered an important and previously unrecognized role of hyperuricemia in mediating the pathogenesis of TAAD, and uric acid-lowering drug may represent a promising therapeutic approach for TAAD.

ADAMTS-7 deficiency attenuates thoracic aortic aneurysm and dissection in mice.

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening cardiovascular disease with severe extracellular matrix (ECM) remodeling that lacks efficient early stage diagnosis and nonsurgical therapy. A disintegrin and metalloproteinase with thrombospondin motif 7 (ADAMTS-7) is recognized as a novel locus for human coronary artery atherosclerosis. Previous work by us and others showed that ADAMTS-7 promoted atherosclerosis, postinjury neointima formation, and vascular calcification. However, whether ADAMTS-7 is involved in TAAD pathogenesis is unknown. We aimed to explore the alterations in ADAMTS-7 expression in human and mouse TAAD, and investigate the role of ADAMTS-7 in TAAD formation. A case-control study of TAAD patients (N = 86) and healthy participants (N = 88) was performed. The plasma ADAMTS-7 levels were markedly increased in TAAD patients within 24h and peaked in 7days. A TAAD mouse model was induced with 0.5% β-aminopropionitrile (BAPN) in drinking water. ELISA analysis of mouse plasma, Western blotting, and immunohistochemical staining of aorta showed an increase in ADAMTS-7 in the early stage of TAAD. Moreover, ADAMTS-7-deficient mice exhibited significantly attenuated TAAD formation and TAAD rupture-related mortality in both male and female mice, which was accompanied by reduced artery dilation and inhibited elastin degradation. ADAMTS-7 deficiency caused repressed inflammatory response and complement system activation during TAAD formation. An increase in plasma ADAMTS-7 is a novel biomarker for human TAAD. ADAMTS-7 deficiency attenuates BAPN-induced murine TAAD. ADAMTS-7 is a potential novel target for TAAD diagnosis and therapy. KEY MESSAGES: A case-control study revealed increased plasma ADAMTS-7 is a risk factor for TAAD. ADAMTS-7 was elevated in plasma and aorta at early stage of mouse TAAD. ADAMTS-7 knockout attenuated mouse TAAD formation and mortality in both sexes.

Update on the molecular landscape of thoracic aortic aneurysmal disease.

Thoracic aortic aneurysms and dissections (TAADs) are a major health problem in the Western population. This review summarises recent discoveries in the genetic landscape of TAAD disease, discusses current challenges in clinical practice, and describes the molecular road ahead in TAAD research. Disorders, in which aneurysmal disease is not observed in the thoracic aorta, are not discussed. Current gene discovery studies have pinpointed about 40 genes associated with TAAD risk, accounting for about 30% of the patients. Importantly, novel genes, and their subsequent functional characterisation, have expanded the knowledge on disease-related pathways providing crucial information on key elements in this disease, and it pinpoints new therapeutic targets. Moreover, current molecular evidence also suggests the existence of less monogenic nature of TAAD disease, in which the presentation of a diseased patient is most likely influenced by a multitude of genetic and environmental factors. Ongoing molecular genetic research continues to expand our understanding on the pathomechanisms underlying TAAD disease in order to improve molecular diagnosis, optimise risk stratification, advance therapeutic strategies and facilitate counselling of TAAD patients and their families.

Good performance of the criteria of American College of Medical Genetics and Genomics/Association for Molecular Pathology in prediction of pathogenicity of genetic variants causing thoracic aortic aneurysms and dissections

BackgroundThe identification of pathogenic variant in patients with thoracic aortic aneurysms and dissections (TAAD) was previously found to be a significant indicator pointing to earlier need for surgical intervention. In order to evaluate available methods for classifying identified genetic variants we have compared the event-free survival in a cohort of TAAD patients classified as genotype-positive versus genotype-negative by the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) criteria or by ClinVar database.MethodsWe analyzed previously unreported cohort of 132 patients tested in the routine clinical setting for genetic variants in a custom panel of 30 genes associated with TAAD or the TruSight Cardio commercial panel of 174 genes associated with cardiac disease. The identified variants were classified using VarSome platform. Kaplan–Meier survival curves were constructed to compare the event-free survival between probands defined as ‘genotype-positive’ and ‘genotype-negative’ using different classifications in order to compare their performance.ResultsOut of 107 rare variants found, 12 were classified as pathogenic/likely pathogenic by ClinVar, 38 were predicted to be pathogenic/likely pathogenic by ACMG. Variant pathogenicity as assessed by ACMG criteria was a strong predictor of event free survival (event free survival at 50 years 83% vs. 50%, for genotype positive patients vs. reference, respectively, p  = 0.00096). The performance of ACMG criteria was similar to that of ClinVar (event free survival at 50 years 87% vs. 50%, for genotype positive patients vs. reference, respectively p  = 0.023) but independent from it as shown by analysing variants with no ClinVar record (event free survival at 50 years 80% vs. 50%, p  = 0.0039). Variants classified as VUS by ACMG criteria or ClinVar did not affect event-free survival. TAAD specific custom gene panel performed similar to the larger universal cardiac panel.ConclusionsIn our cohort of unrelated TAAD patients ACMG classification tool available at VarSome was useful in assessing pathogenicity of novel genetic variants. Gene panel containing the established genes associated with the highest risk of hereditary TAAD (ACTA1, COL3A1, FBN1, MYH11, SMAD3, TGFB2, TGFBR1, TGFBR2, MYLK) was sufficient to identify prevailing majority of variants most likely to be causative of the disease.

Genetic testing and clinical relevance of patients with thoracic aortic aneurysm and dissection in northwestern China.

BackgroundThoracic aortic aneurysm and dissection (TAAD) is a life‐threatening pathology that remains a challenge worldwide. Up to 40% of TAAD cases are hereditary with complex heterogeneous genetic backgrounds. The purposes of this study were to determine the diagnostic rate of patients with TAAD, investigate the molecular pathologic spectrum of TAAD by next‐generation sequencing (NGS), and explore the future preclinical prospects of genetic diagnosis in patients at high ‐risk of study.MethodsNGS was used to screen 15 genes associated with genetic TAAD in 212 patients from northwestern China. Clinical data of patients were gathered by electrocardiography, transthoracic echocardiography, and computed tomography.ResultsOf the 212 patients, 67 (31.60%) tested positive for a (likely) pathogenic variant, 42 (19.81%) had a variant of uncertain significance (VUS), and 103 (48.58%) had no variant (likely benign/benign/negative). A total of 135 reportable variants were detected in our test, among which 77 (57.04%) are first reported in this paper. A genotype–phenotype correlation of FBN1 was assessed, and the data showed that the patients with truncating and splicing mutations are more prone to developing severe aortic dissection than those with missense mutations, especially frameshift mutations (82.76% vs. 42.86%). In this study, 43 (20.28%) patients had a family history of sudden death or TAAD, whereas 132 (62.26%) did not (the remaining 37 were not available), and the positive rate of genetic testing was higher in TAAD patients with family history than in those without (76.74% vs. 18.94%).ConclusionOur study concludes that genetic variation is an important consideration in the risk stratification of individualized prediction and disease diagnosis.

Clinical manifestations and genetic characteristics in the Taiwan thoracic aortic aneurysm and dissection cohort - a prospective cohort study

Thoracic aortic aneurysm and dissection (TAAD) is a devastating but treatable disease if detected early. The clinical manifestations and genetic characteristics underlying TAAD patients in Taiwan, however, remain unclear. We consecutively recruited patients referred for TAAD screening and/or management at a tertiary medical center in Taiwan. All patients received a comprehensive survey of the clinical manifestations and a genetic testing with a 29-gene next-generation sequencing (NGS) panel. Patients (n=107) were referred for different reasons, and could be grouped into 4 categories: known aortic aneurysm or dissection (AoAD) (n=57), Marfanoid features (n=36), having family members of suspected AoAD (n=11), and ectopic lens (n=3). AoAD were confirmed in 73 (68.2%) of the entire cohort. Among all the clinical manifestations, skin striae distensae was the only physical sign that showed significant association with AoAD (p=0.007 after adjusted). Disease-causing genes/variants were identified in 46 patients (43.0%); FBN1 was the most prevalent disease-causing gene, followed by TGFBR1, TGFBR2 and FBN2. A positive genetic testing was not only an independent predictor of AoAD (hazard ratio (HR) 3.468, 95% confidence interval (CI) [1.541-7.807], p=0.003), but also had a higher chance of dissection among the patients with known dilated aorta (HR 4.552, 95% CI [1.578-13.135], p=0.005). The presence of skin striae distensae may serve as a clinical cue for physicians to search for AoAD in subjects who are at risk. The NGS panel test not only helps confirm the diagnosis, but also stratify the risk of dissection among patients with dilated aorta.

Dexamethasone reduces the formation of thoracic aortic aneurysm and dissection in a murine model

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening vascular disease with no effective pharmaceutical therapies currently available. Inflammation plays a key role in the progression of aneurysms. Dexamethasone (DEX), a synthetic glucocorticoid, has showed alleviating effects on cells in vitro from TAAD patients. Here we performed a study aiming at investigating the protective role of DEX in a β-aminopropionitrile monofumarate (BAPN)-induced TAAD mouse model. DEX (dose: 0.04 mg/kg/day) treatment significantly reduced the aortic diameter and inhibited TAAD formation. DEX reduced infiltration of macrophages and neutrophils, apoptosis of vascular smooth muscle cells (VSMCs), expression of metalloproteinase 2/9, and extracellular matrix degradation in BAPN-treated TAAD mice. Furthermore, DEX therapy downregulated the expression of p-p65 in macrophages and VSMCs, which suggested that DEX might ameliorate BAPN-induced TAAD by suppressing NF-κB signaling. Therefore, DEX therapy attenuates the progression of BAPN-induced TAAD murine model and could be used as an effective adjuvant therapy for treating TAAD.

PKM2 Activator TEPP-46 Attenuates Thoracic Aortic Aneurysm and Dissection by Inhibiting NLRP3 Inflammasome-Mediated IL-1β Secretion.

The development of thoracic aortic aneurysm and dissection (TAAD) is mediated by inflammasome activation, which exacerbates the secretion of pro-inflammatory cytokines, chemokines, matrix metalloproteinases (MMPs), and reactive oxygen species (ROS). The glycolytic enzyme pyruvate kinase M2 (PKM2) has shown a protective role against various disorders with an inflammatory basis, such as sepsis, tumorigenesis, and diabetic nephropathy. However, its potential role in TAAD has not been investigated so far. We analyzed aortic tissues from TAAD patients and the β-aminopropionitrile fumarate (BAPN)-induced mouse model of TAAD and observed elevated levels of PKM2 in the aortic lesions of both. Treatment with the PKM2 activator TEPP-46 markedly attenuated the progression of TAAD in the mouse model as demonstrated by decreased morbidity and luminal diameter of the aorta. In addition, the thoracic aortas of the BAPN-induced mice showed reduced monocytes and macrophages infiltration and lower levels of IL-1β, MMPs, and ROS when treated with TEPP-46. Furthermore, TEPP-46 treatment also suppressed the activation of the NOD-like receptor (NLR) family and pyrin domain-containing protein 3 (NLRP3) inflammasome by downregulating p-STAT3 and HIF1-α. Pyruvate kinase M2 plays a protective role in TAAD development, and its activation is a promising therapeutic strategy against the progression of TAAD.

Correction: A functional variant of SMAD4 enhances macrophage recruitment and inflammatory response via TGF-β signal activation in Thoracic aortic aneurysm and dissection.

Thoracic aortic aneurysm and dissection (TAAD) is the most fatal macro vascular disease. The mortality of 48h after diagnosis of dissection is up to approximately 50-68%. However, the genetic factors and potential mechanism underlying sporadic TAAD remain largely unknown. Our previous study suggested rs12455792 variant of SMAD4 gene significantly contributed to the increased risk and might participated the pathological progression of TAAD. This investigation aims to test (1) the associations between rs12455792 and MO recruitment, inflammatory response in aggressiveness of TAAD, and (2) the molecular mechanism accounting for their effects. In TGF-β signaling molecular detection, rs12455792 C>T variant activated the canonical and non-canonical TGF-β mediators. It also increased the secretion of chemotactic factors of HASMCs. To confirm the impact of this change, we detected MO recruitment and infiltration in HASMCs and aortic tissues of TAAD patients. We found that MO recruitment in cells and tissues with rs12455792 variant genotypes was increased than that in wild type groups. Moreover, rs12455792 variant increased M1 type inflammatory response, which might contribute much to TAAD progression. To mimic the SMAD4 suppression effect of rs12455792 in vivo, we constructed the SMAD4 KD mouse. After induction with Ang II for 4w, the thoracic aorta dilatation and vascular remodeling were more serious than that of wild type group. In conclusion, rs12455792 increased MO recruitment, M1 type inflammatory response via activated TGF-β signaling, and further promoted vascular remodeling and pathological progress of TAAD.

A functional variant of SMAD4 enhances macrophage recruitment and inflammatory response via TGF-β signal activation in Thoracic aortic aneurysm and dissection.

Thoracic aortic aneurysm and dissection (TAAD) is the most fatal macro vascular disease. The mortality of 48h after diagnosis of dissection is up to approximately 50-68%. However, the genetic factors and potential mechanism underlying sporadic TAAD remain largely unknown. Our previous study suggested rs12455792 variant of SMAD4 gene significantly contributed to the increased risk and might participated the pathological progression of TAAD. This investigation aims to test (1) the associations between rs12455792 and MØ recruitment, inflammatory response in aggressiveness of TAAD, and (2) the molecular mechanism accounting for their effects. In TGF-β signaling molecular detection, rs12455792 C>T variant activated the canonical and non-canonical TGF-β mediators. It also increased the secretion of chemotactic factors of HASMCs. To confirm the impact of this change, we detected MØ recruitment and infiltration in HASMCs and aortic tissues of TAAD patients. We found that MØ recruitment in cells and tissues with rs12455792 variant genotypes was increased than that in wild type groups. Moreover, rs12455792 variant increased M1 type inflammatory response, which might contribute much to TAAD progression. To mimic the SMAD4 suppression effect of rs12455792 in vivo, we constructed the SMAD4 KD mouse. After induction with Ang II for 4w, the thoracic aorta dilatation and vascular remodeling were more serious than that of wild type group. In conclusion, rs12455792 increased MØ recruitment, M1 type inflammatory response via activated TGF-β signaling, and further promoted vascular remodeling and pathological progress of TAAD.

Identification of Novel Clinically Relevant Variants in 70 Southern Chinese patients with Thoracic Aortic Aneurysm and Dissection by Next-generation Sequencing

Thoracic Aortic Aneurysm and Dissection (TAAD) is a life-threatening pathology and remains challenging worldwide. Up to 40% of TAAD are hereditary with complex heterogeneous genetic backgrounds. Recently, next-generation sequencing (NGS) has been successfully applied to identify genetic variants in an efficient and cost-effective manner. In our study, NGS coupled with DNA target-capture array was used to screen 11 known causative genes of TAAD in 70 patients from Southern China. All the identified variants were confirmed by Sanger sequencing. We identified forty variants in 36 patients (51.4%), including three known pathogenic (7.5%), 10 likely pathogenic variants (25%, 9 in FBN1, 1 in ACTA2), and 27 variants with uncertain significance (VUS) (67.5%). Among the 27 VUS, 14 (51.9%) were in the FBN1 gene, 3 in Col5A2, 2 in ACTA2, 2 in MYH11, 2 in MYLK, 2 in SLC2A10, 1 in MSTN and 1 in SMAD3 respectively. Based on the segregation data and independent reports, five known likely pathogenic variants and four VUS were upgraded to pathogenic variant and likely pathogenic variant respectively. Our data indicate that NGS is a highly efficient genetic method for identification of pathogenic variants in TAAD patients.

Genes Associated with Thoracic Aortic Aneurysm and Dissection: An Update and Clinical Implications.

Thoracic aortic aneurysm (TAA) is a lethal disease, with a natural history of enlarging progressively until dissection or rupture occurs. Since the discovery almost 20 years ago that ascending TAAs are highly familial, our understanding of the genetics of thoracic aortic aneurysm and dissection (TAAD) has increased exponentially. At least 29 genes have been shown to be associated with the development of TAAD, the majority of which encode proteins involved in the extracellular matrix, smooth muscle cell contraction or metabolism, or the transforming growth factor-β signaling pathway. Almost one-quarter of TAAD patients have a mutation in one of these genes. In this review, we provide a summary of TAAD-associated genes, associated clinical features of the vasculature, and implications for surgical treatment of TAAD. With the widespread use of next-generation sequencing and development of novel functional assays, the future of the genetics of TAAD is bright, as both novel TAAD genes and variants within the genes will continue to be identified.

Next-generation sequencing for diagnosis of thoracic aortic aneurysms and dissections: diagnostic yield, novel mutations and genotype phenotype correlations.

BackgroundThoracic aortic aneurysms and dissections (TAAD) are silent but possibly lethal condition with up to 40 % of cases being hereditary. Genetic background is heterogeneous. Recently next-generation sequencing enabled efficient and cost-effective examination of gene panels. Aim of the study was to define the diagnostic yield of NGS in the 51 TAAD patients and to look for genotype–phenotype correlations within families of the patients with TAAD.Methods51 unrelated TAAD patients were examined by either whole exome sequencing or TruSight One sequencing panel. We analyzed rare variants in 10 established thoracic aortic aneurysms-associated genes. Whenever possible, we looked for co-segregation in the families. Kaplan–Meier survival curve was constructed to compare the event-free survival depending on genotype. Aortic events were defined as acute aortic dissection or first planned aortic surgery.Results and discussionIn 21 TAAD patients we found 22 rare variants, 6 (27.3 %) of these were previously reported, and 16 (73.7 %) were novel. Based on segregation data, functional analysis and software estimations we assumed that three of novel variants were causative, nine likely causative. Remaining four were classified as of unknown significance (2) and likely benign (2). In all, 9 (17.6 %) of 51 probands had a positive result when considering variants classified as causative only and 18 (35.3 %) if likely causative were also included. Genotype-positive probands (n = 18) showed shorter mean event free survival (41 years, CI 35–46) than reference group, i.e. those (n = 29) without any plausible variant identified (51 years, CI 45–57, p = 0.0083). This effect was also found when the ‘genotype-positive’ group was restricted to probands with ‘likely causative’ variants (p = 0.0092) which further supports pathogenicity of these variants. The mean event free survival was particularly low (37 years, CI 27–47) among the probands with defects in the TGF beta signaling (p = 0.0033 vs. the reference group).ConclusionsThis study broadens the spectrum of genetic background of thoracic aneurysms and dissections and supports its potential role as a prognostic factor in the patients with the disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0870-4) contains supplementary material, which is available to authorized users.

Recurrent Rare Genomic Copy Number Variants and Bicuspid Aortic Valve Are Enriched in Early Onset Thoracic Aortic Aneurysms and Dissections.

Thoracic Aortic Aneurysms and Dissections (TAAD) are a major cause of death in the United States. The spectrum of TAAD ranges from genetic disorders, such as Marfan syndrome, to sporadic isolated disease of unknown cause. We hypothesized that genomic copy number variants (CNVs) contribute causally to early onset TAAD (ETAAD). We conducted a genome-wide SNP array analysis of ETAAD patients of European descent who were enrolled in the National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions (GenTAC). Genotyping was performed on the Illumina Omni-Express platform, using PennCNV, Nexus and CNVPartition for CNV detection. ETAAD patients (n = 108, 100% European American, 28% female, average age 20 years, 55% with bicuspid aortic valves) were compared to 7013 dbGAP controls without a history of vascular disease using downsampled Omni 2.5 data. For comparison, 805 sporadic TAAD patients with late onset aortic disease (STAAD cohort) and 192 affected probands from families with at least two affected relatives (FTAAD cohort) from our institution were screened for additional CNVs at these loci with SNP arrays. We identified 47 recurrent CNV regions in the ETAAD, FTAAD and STAAD groups that were absent or extremely rare in controls. Nine rare CNVs that were either very large (>1 Mb) or shared by ETAAD and STAAD or FTAAD patients were also identified. Four rare CNVs involved genes that cause arterial aneurysms when mutated. The largest and most prevalent of the recurrent CNVs were at Xq28 (two duplications and two deletions) and 17q25.1 (three duplications). The percentage of individuals harboring rare CNVs was significantly greater in the ETAAD cohort (32%) than in the FTAAD (23%) or STAAD (17%) cohorts. We identified multiple loci affected by rare CNVs in one-third of ETAAD patients, confirming the genetic heterogeneity of TAAD. Alterations of candidate genes at these loci may contribute to the pathogenesis of TAAD.

Identification and Surgical Repair of Familial Thoracic Aortic Aneurysm and Dissection Caused by TGFBR1 Mutation

This study aimed at exploring the causative gene and summarizing the clinical characteristics in a Chinese thoracic aortic aneurysm and dissection (TAAD) family. Family members were examined for features of syndromic genetic diseases by clinician and geneticist. Genomic DNA was extracted from 2 distantly related members with definite TAAD for exome sequencing. A pathogenic mutation (rs111426349, c.1459C >T) of transforming growth factor β receptor 1 (TGFBR1) was confirmed, which result in the amino acid substitution p.R487W. Fourteen TGFBR1 mutation carriers were detected among 39 tested members in this family. The average age at diagnosis of aortic root dilatation or aneurysm was 23.2 ± 12.6 years (range 3-37 years). Early onset of aortic root dilatation was significant in this family without reported phenotypes. The David procedure was performed prophylactically in 3 carriers of this family. Familial TAAD caused by TGFBR1 mutation (c.1459C >T) was confirmed in a large Chinese Han ethnic family using exome sequencing. Aggressively prophylactic David procedure may be not necessary at a smaller aortic size in familial TAAD patients with TGFBR1 mutation and further observation is warranted.

Abstract 34: Myh11 R247C is a Modifier Allele for Aortic Disease

Thoracic aortic aneurysms and dissections (TAAD) affect more than 30,000 Americans annually. TAAD can be inherited due to mutations in a number of genes, including MYH11, which encodes the smooth muscle myosin heavy chain. In non-familial TAAD patients, hypertension is the most common risk factor, but genetic contributors have not been explored. Exome sequencing has identified non-synonymous variants of unknown significance in MYH11 in the population, and these variants are enriched in TAAD patients without a family history. The goal of this study was to determine if rare MYH11 variants contribute to TAAD. A knock-in mouse model of one recurrent rare variant, Myh11 R247C, shows no structural or pathologic abnormalities of the aorta, but does have decreased aortic contractility. We sought to determine if the Myh11 R247C allele could modify aortic disease due to another gene mutation. The Myh11R247C allele was bred into Acta2-/- mice, which develop aortic aneurysms, and into Acta2+/- mice, which do not. In both cases, the R247C allele significantly increases aortic diameter and accelerates elastin fragmentation and proteoglycan deposition; however the aneurysms do not progress to aortic dissection. Treatment of Myh11R247C/R247C mice with a combination of L-NAME and high salt diet induced a sustained increase in systolic blood pressure from 130mmHg to 180mmHg. Approximately 25% of Myh11R247C/R247C mice on treatment died spontaneously with evidence of aortic dissections at necropsy, but without aortic dilation. The surviving mice also show no aneurysm formation. Aortic pathology shows significant fragmentation and thinning of elastin fibers, medial thickening, and a unique pattern of proteoglycan deposition along the elastin layers in the hypertensive Myh11R247C/R247C mice. These data indicate that the Myh11R247C allele in mice increases severity of Acta2-/- associated aortic aneurysms and induces aortic disease when added to a known risk factor for TAAD, hypertension. Therefore, patients with the Myh11R247C rare variant and a disease-causing mutation may have earlier disease onset and increased severity; co-occurrence of the Myh11R247C allele in individuals with other benign genetic variants or risk factors like hypertension may induce TAAD.

Abstract 67: A Rare Variant in Myh11, R247C, Affects Smooth Muscle Cell Phenotype and Acts as a Modifier for Aortic Disease

Thoracic aortic aneurysms and dissections (TAAD) affect more than 30,000 Americans annually. One-fifth of TAAD patients have a first-degree relative with the disease, suggesting a genetic component to its pathogenesis. Missense mutations in a number of genes lead to TAAD, including MYH11 ,which encodes the smooth muscle isoform of myosin heavy chain. However, potential genetic contributors in the four-fifths of patients without affected relatives have not been explored. Variants of unknown significance in MYH11 are prevalent in the population, and are enriched in patients with TAAD and other vascular diseases. The goal of this study was to evaluate one of these variants as a potential contributor to TAAD. A knock-in mouse model of the Myh11 R247C rare variant was generated, and these mice survive and reproduce normally. They have no structural abnormalities of the aorta or signs of aortic disease, but do have decreased aortic contractility. Myh11 R247C/R247C mice also have increased neointimal proliferation following carotid ligation and increased proliferation of vascular smooth muscle cells (SMCs) in vitro. Myh11 R247C/R247C SMCs have decreased contractile gene and protein expression and are dedifferentiated. In fibroblasts, myosin force generation is required for maturation of focal adhesions, and enhancers of RhoA activity replace enhancers of Rac1 activity as maturation occurs. Consistent with these previous findings, adhesions are smaller in Myh11 R247C/R247C SMCs, and there is increased Rac1 and focal adhesion kinase (FAK) activation with decreased RhoA activation. A RhoA activator (CN03) rescues the dedifferentiated phenotype of Myh11 R247C/R247C SMCs, and FAK inhibition reduces proliferation. Since this rare variant occurs in the general population, we sought to determine if it acts as a modifier gene for aortic disease. The Myh11 R247C allele was bred into Acta2 -/- mice, which develop aortic aneurysms, and into Acta2 +/- mice, which do not. In both cases, the presence of the R247C allele increases aortic diameter. These preliminary data suggest that the MYH11 R247C rare variant may be a genetic contributor to TAAD in patients without an inherited mutation, or may affect the clinical presentation of TAAD in patients with Mendelian disease.

Systemic mutational analysis of the TGFβ signalling pathway in thoracic aortic aneurysms and dissections

PurposeExcessive activation of the TGFβ signalling pathway caused by genetic mutations is known to be responsible for the inherited thoracic aortic aneurysms and dissections (TAAD) that is life-threatening and characterised...

Recurrent Chromosome 16p13.1 Duplications Are a Risk Factor for Aortic Dissections

Chromosomal deletions or reciprocal duplications of the 16p13.1 region have been implicated in a variety of neuropsychiatric disorders such as autism, schizophrenia, epilepsies, and attention-deficit hyperactivity disorder (ADHD). In this study, we investigated the association of recurrent genomic copy number variants (CNVs) with thoracic aortic aneurysms and dissections (TAAD). By using SNP arrays to screen and comparative genomic hybridization microarrays to validate, we identified 16p13.1 duplications in 8 out of 765 patients of European descent with adult-onset TAAD compared with 4 of 4,569 controls matched for ethnicity (P = 5.0×10−5, OR = 12.2). The findings were replicated in an independent cohort of 467 patients of European descent with TAAD (P = 0.005, OR = 14.7). Patients with 16p13.1 duplications were more likely to harbor a second rare CNV (P = 0.012) and to present with aortic dissections (P = 0.010) than patients without duplications. Duplications of 16p13.1 were identified in 2 of 130 patients with familial TAAD, but the duplications did not segregate with TAAD in the families. MYH11, a gene known to predispose to TAAD, lies in the duplicated region of 16p13.1, and increased MYH11 expression was found in aortic tissues from TAAD patients with 16p13.1 duplications compared with control aortas. These data suggest chromosome 16p13.1 duplications confer a risk for TAAD in addition to the established risk for neuropsychiatric disorders. It also indicates that recurrent CNVs may predispose to disorders involving more than one organ system, an observation critical to the understanding of the role of recurrent CNVs in human disease and a finding that may be common to other recurrent CNVs involving multiple genes.