Clinical utility gene card for: Hereditary thoracic aortic aneurysm and dissection including next-generation sequencing-based approaches

Whole-Exome Sequencing Identified Genes Responsible for Thoracic Aortic Aneurysms and Dissections in three Chinese Families

Thoracic aortic aneurysms and dissections are precarious conditions that often cannot be diagnosed with fatal outcomes. Over the last few years, pathogenic variants in numerous genes have been identified that predispose to heritable presentations of TAAD. An evidence-based strategy for the selection of genes to test in familial TAAD helps inform family screening and intervention to prevent life-threatening events. Using whole-exome sequencing, four members of three unrelated families clinically diagnosed with TAAD were used to identify the genetic origin of the disorder. Variant evaluation was carried out to detect the pathogenic mutation. Our studies suggest that mutations of COL3A1 and ACTA2 are responsible for familial TAAD. In addition, we highlight FBLN5, FBN1, SLC2A10, FBN2, and NOTCH1 as candidate genes. Future studies of crosstalk among the pathways may provide us a step toward understanding the pathogenic mechanism. This finding indicates the necessity of obtaining family medical history and screening of extended relatives of patients with TAAD for the early identification and treatment of TAAD.

Genetics of Ataxias in Indian Population: A Collative Insight from a Common Genetic Screening Tool

Cerebellar ataxias (CAs) represent a group of autosomal dominant and recessive neurodegenerative disorders affecting cerebellum with or without spinal cord. Overall, CAs have preponderance for tandem nucleotide repeat expansions as an etiological factor (10 TREs explain nearly 30-40% of ataxia cohort globally). The experience of 10 years of common genetic ataxia subtypes for ≈5600 patients' referrals (Pan-India) received at a single center is shared herein. Frequencies (in %, n) of SCA types and FRDA in the sample cohort are observed as follows: SCA12 (8.6%, 490); SCA2 (8.5%, 482); SCA1 (4.8%, 272); SCA3 (2%, 113); SCA7 (0.5%, 28); SCA6 (0.1%, 05); SCA17 (0.1%, 05), and FRDA (2.2%, 127). A significant amount of variability in TRE lengths at each locus is observed, we noted presence of biallelic expansion, co-occurrence of SCA-subtypes, and the presence of premutable normal alleles. The frequency of mutated GAA-FRDA allele in healthy controls is 1/158 (0.63%), thus an expected FRDA prevalence of 1:100 000 persons. The data of this study are relevant not only for clinical decision making but also for guidance in direction of genetic investigations, transancestral comparison of genotypes, and lastly provide insight for policy decision for the consideration of SCAs under rare disease category.

Long non-coding RNA HIF1A-AS2 modulates the proliferation, migration, and phenotypic switch of aortic smooth muscle cells in aortic dissection via sponging microRNA-33b

Aortic dissection (AD), also known as aortic dissecting aneurysm, is one of the most common and dangerous cardiovascular diseases with high morbidity and mortality. This study was aimed to investigate the functional role of long non-coding RNA Hypoxia-inducible factor 1 alpha-antisense RNA 2 (lncRNA HIF1A-AS2) in AD. An in vitro model of AD was established by platelet-derived growth factor-BB (PDGF-BB)-mediated human aortic Smooth Muscle Cells (SMCs). HIF1A-AS2 expression in human AD tissues was determined by quantitative real-time PCR (qRT-PCR) and fluorescence in situ hybridization (FISH) assays, followed by investigation of biological roles of HIF1A-AS2 in AD development by Cell Counting Kit-8 (CCK-8), immunofluorescence, and transwell assays. Additionally, the correlation between HIF1A-AS2, miR-33b, and high mobility group AT-hook2 (HMGA2) were identified by RNA immunoprecipitation (RIP), RNA pull-down and luciferase reporter assays. Results showed that HIF1A-AS2 was obviously increased, while the contractile-phenotype markers of vascular SMCs were significantly decreased in human AD tissues, when compared to normal tissues. Inhibition of HIF1A-AS2 attenuated SMCs proliferation and migration, whereas enhanced the phenotypic switch under the stimulation of PDGF-BB. Results from RIP, RNA pull-down and luciferase reporter assays demonstrated that miR-33b directly bound with HIF1A-AS2, and HIF1A-AS2 silencing suppressed the expression of HMGA2, which was induced by miR-33b inhibitor. In conclusion, knockdown of HIF1A-AS2 suppressed the proliferation and migration, while promoted the phenotypic switching of SMCs through miR-33b/HMGA2 axis, which laid a theoretical foundation for understanding the development of AD and shed light on a potential target for AD treatment.

Analysis of the contribution of 129 candidate genes to thoracic aortic aneurysm or dissection of a mixed cohort of sporadic and familial cases in South China

Thoracic aortic aneurysm or dissection (TAAD) is a group of life-threatening complex diseases after symptomatic onset with genetic heterogeneity accounting for approximately 20% of cases. Previously, we identified 40 rare variants in 11 TAAD-related core genes among 70 TAAD patients by next-generation sequencing. In this study, we further analyzed the variants in the disease-causing genes in 129 cases of sporadic TAAD and 22 familial cases by whole-exome sequencing. A total of 116 variants in 47 TAAD-related genes were identified, 64.7% (75/116) of which occurred in sporadic TAAD without syndromes, and among these genes, FBN1 was the most common TAAD-related gene. Of the 26.7% (31/116) that were pathogenic or likely pathogenic, almost one third were from sporadic cases without syndromes involving FBN1, SMAD3, SMAD6, MYH11, TGFBR1, MYLK, LOX and LTBP3. Interestingly, the novel VUS (variant of uncertain significance) *879Glu in MCTP2 occurred in two unrelated probands with sporadic acute aortic dissection without a bicuspid aortic valve. Furthermore, more than one variant was detected in 24 patients, and 70.8% (17/24) occurred in sporadic cases. Younger individuals were more likely to carry P/LP (pathogenic or likely pathogenic) variants and harbor more variants. P/LP carriers seem to have a larger aortic diameter, lower D-dimer levels, and a shorter ICU length of stay but longer hospitalization time. In conclusion, we expanded the candidate gene profile of TAAD, especially for sporadic cases without syndromic features. VUSs need further clarification.

New indicators for systematic assessment of aortic morphology: a narrative review

In order to prevent the occurrence of aortic adverse events in ascending thoracic aortic aneurysm patients, preventive surgery is the sole option in case of large aneurysm. Identifying high-risk patients timely and accurately requires effective predictive indicators of aortic adverse events and accurate risk stratification thresholds. Absolute diameter measured after a single imaging examination, which has been used as the predictive indicator for decades, has been proved to be ineffective for risk stratification in moderately dilated aorta. Previously, new indicators combining absolute diameters with personalized parameters have been reported to show better predictive power of aortic adverse events than absolute diameters by correcting the effect of these parameters on the diameters. Meanwhile, combining three-dimensional parameters to formulate risk stratification thresholds not only may characterize the aortic risk morphology more precisely, but also predict aortic adverse events more accurately. These new indicators may provide more systematic assessment methods of patients’ risk, formulate more personalized intervention strategies for ascending thoracic aortic aneurysm patients, and also provide a basis for researchers to develop more accurate and effective risk thresholds. We also highlight that the algorithm obtained by combining multiple indicators may be a better choice compared with single indicator, but this still requires the support of more evidence. Due to the particularity of syndromic aortic disease, whether these new indicators can be used for its risk stratification is still uncertain. Therefore, the scope of this manuscript does not include this kind of disease.

A New Variant in the MYH11 Gene in a Familial Case of Thoracic Aortic Aneurysm

MYH11 (myosin heavy chain 11) gene is involved in vascular contractility and several autosomal dominant mutations have been linked to thoracic aortic aneurysms. Three male members of the same family were found to carry a heterozygous missense variant in the MYH11 gene and all 3 individuals presented a thoracic aortic aneurysm/dilation. We identified a rare missense variant in the MYH11 gene predicted to be damaging and affecting a conserved amino acid in the myosin tail of the protein. This variant appears to be responsible for our familial case of thoracic aortic aneurysms, as the clinical expression reunited all features of genetic aneurysms.

Clinical Validity of Genes for Heritable Thoracic Aortic Aneurysm and Dissection

BACKGROUND

Thoracic aortic aneurysms progressively enlarge and predispose to acute aortic dissections. Up to 25% of individuals with thoracic aortic disease harbor an underlying Mendelian pathogenic variant. An evidence-based strategy for selection of genes to test in hereditary thoracic aortic aneurysm and dissection (HTAAD) helps inform family screening and intervention to prevent life-threatening thoracic aortic events.

OBJECTIVES

The purpose of this study was to accurately identify genes that predispose to HTAAD using the Clinical Genome Resource (ClinGen) framework.

METHODS

We applied the semiquantitative ClinGen framework to assess presumed gene-disease relationships between 53 candidate genes and HTAAD. Genes were classified as causative for HTAAD if they were associated with isolated thoracic aortic disease and were clinically actionable, triggering routine aortic surveillance, intervention, and family cascade screening. All gene-disease assertions were evaluated by a pre-defined curator-expert pair and subsequently discussed with an expert panel.

RESULTS

Genes were classified based on the strength of association with HTAAD into 5 categories: definitive (n = 9), strong (n = 2), moderate (n = 4), limited (n = 15), and no reported evidence (n = 23). They were further categorized by severity of associated aortic disease and risk of progression. Eleven genes in the definitive and strong groups were designated as "HTAAD genes" (category A). Eight genes were classified as unlikely to be progressive (category B) and 4 as low risk (category C). The remaining genes were recent genes with an uncertain classification or genes with no evidence of association with HTAAD.

CONCLUSIONS

The ClinGen framework is useful to semiquantitatively assess the strength of gene-disease relationships for HTAAD. Gene categories resulting from the curation may inform clinical laboratories in the development, interpretation, and subsequent clinical implications of genetic testing for patients with aortic disease.

A proposal of a new evaluation framework towards implementation of genetic tests

Background

The existing frameworks for the evaluation of genetic and genomic applications clearly address the technical and clinical value of a test, but are less concerned with the way genetic services are delivered and organized. We therefore aimed to develop a comprehensive new framework that includes an assessment of service delivery.

Methods

A new framework was built on the evaluation dimensions identified through a systematic review of the existing frameworks and a Delphi survey of Italian experts in public health genomics.

Results

Our framework has four sections. The first two sections, respectively, guide the evidence collection process for the genetic test (analytic validity; clinical validity; clinical utility; personal utility) and its delivery models (organizational aspects; economic evaluation; ethical, legal and social implications; patient perspective). The third section guides the formulation of the research priorities to be addressed in future research. Finally, the fourth section suggests three criteria to summarize the collected evidence (net benefit, cost-effectiveness, feasibility).

Conclusion

We have successfully developed an evaluation framework for the evaluation of genetic tests that includes an assessment of service delivery. It also introduces some neglected evaluation dimensions such as personal utility and patient perspective.

NGS-Based genetic testing for heritable cardiovascular diseases. Specific requirements for obtaining informed consent

Clinical genetic testing in cardiovascular genetic medicine has undergone rapid changes. Next generation sequencing allows simultaneous testing of all genes associated with any cardiovascular phenotype, and molecular genetic testing for multiple genes has become the standard of practice for cardiovascular medicine. While technical and clinical advantages of multigenic approaches are evident, informed consent procedures have become more complex and challenging to the physician ordering such a test, particularly due to the increased potential for unsolicited findings. Based on the EuroGentest "Guidelines for diagnostic next-generation sequencing" we here propose a set of disease-specific requirements for obtaining informed consent for NGS-based genetic testing in a cardiogenetic clinic. We can show that it is often not feasible to obtain informed consent for every detail and suggest, in such cases, to reach general consent beforehand and discuss specific implications of unsolicited findings after the test results are available.

Genetic testing for large-caliber vessel aneurysms

Large-caliber vessels are those with a diameter of 10 mm or more. Most aneurysms remain asymptomatic until they expand or rupture. Aortic aneurysms are of special interest for physicians and scientists because of their prevalence. Aortic aneurysms and dissections account for 1-2% of all deaths in western countries. Expansion and rupture of vascular aneurysms show a strong correlation with hyperlipidemia, hypertension, smoking, sex and age. Heritability estimates have been as high as 70%. This Utility Gene Test was developed on the basis of an analysis of the literature and existing diagnostic protocols. It is useful for confirming diagnosis, as well as for differential diagnosis, couple risk assessment and access to clinical trials.

Systematic Review of Studies That Have Evaluated Screening Tests in Relatives of Patients Affected by Nonsyndromic Thoracic Aortic Disease

Background Nonsyndromic thoracic aortic diseases ( NS - TADs ) are often silent entities until they present as life-threatening emergencies. Despite familial inheritance being common, screening is not the current standard of care in NS - TAD s. We sought to determine the incidence of aortic diseases, the predictive accuracy of available screening tests, and the effectiveness of screening programs in relatives of patients affected by NS - TADs . Methods and Results A systematic literature search on PubMed/ MEDLINE , Embase, and the Cochrane Library was conducted from inception to the end of December 2017. The search was supplemented with the Online Mendelian Inheritance in Man database. A total of 53 studies were included, and a total of 2696 NS - TAD relatives were screened. Screening was genetic in 49% of studies, followed by imaging techniques in 11% and a combination of the 2 in 40%. Newly affected individuals were identified in 33%, 24%, and 15% of first-, second-, and third-degree relatives, respectively. Familial NS - TAD s were primarily attributed to single-gene mutations, expressed in an autosomal dominant pattern with incomplete penetrance. Specific gene mutations were observed in 25% of the screened families. Disease subtype and genetic mutations stratified patients with respect to age of presentation, aneurysmal location, and aortic diameter before dissection. Relatives of patients with sporadic NS - TAD s were also found to be affected. No studies evaluated the predictive accuracy of imaging or genetic screening tests, or the clinical or cost-effectiveness of an NS - TAD screening program. Conclusions First- and second-degree relatives of patients affected by both familial and sporadic NS - TAD s may benefit from personalized screening programs.

Genetic diagnostics of inherited aortic diseases : Medical strategy analysis

Genetic aortic syndromes (GAS) include Marfan, Loeys-Dietz, vascular Ehlers-Danlos, and Turner syndrome as well as congenital bicuspid aortic valve. The clinical management of these diseases has certain similarities and differences. We employed medical strategy analysis to test the utility of genetic diagnostics in the management of GAS. We chose the standpoint of the cardiologist for our analysis. In the first step, the medical goals in the management of GAS are specified. In the second step, the accuracy of genetic diagnostics for GAS is examined. Finally, conclusions can be drawn about the utility of genetic diagnostics in managing GAS. We found that genetic diagnostics is necessary to exclude GAS, to diagnose GAS, and to specify disease types. Second, combining phenotype with genotype information maximizes the predictability of the course of disease. Third, with genetic diagnostics it is possible to predict the birth of children with causative mutations for GAS and to initiate drug therapy to prevent the onset of aortic dilatation or to slow down its progression to aortic aneurysm. Finally, genetic diagnostics improves prognostic predictions and thereby contributes to a better timing of elective surgery and to a better choice of procedures. The findings of our medical strategy analysis indicate the high utility of genetic diagnostics for managing GAS.

Navigating the Phenotype Frontier: The Monarch Initiative

The principles of genetics apply across the entire tree of life. At the cellular level we share biological mechanisms with species from which we diverged millions, even billions of years ago. We can exploit this common ancestry to learn about health and disease, by analyzing DNA and protein sequences, but also through the observable outcomes of genetic differences, i.e. phenotypes. To solve challenging disease problems we need to unify the heterogeneous data that relates genomics to disease traits. Without a big-picture view of phenotypic data, many questions in genetics are difficult or impossible to answer. The Monarch Initiative (https://monarchinitiative.org) provides tools for genotype-phenotype analysis, genomic diagnostics, and precision medicine across broad areas of disease.

Postmortem genetic testing should be recommended in sudden cardiac death cases due to thoracic aortic dissection

BACKGROUND

Acute thoracic aortic dissections and ruptures, the main life-threatening complications of the corresponding aneurysms, are an important cause of sudden cardiac death. Despite the usefulness of the molecular diagnosis of these conditions in the clinical setting, the corresponding forensic field remains largely unexplored. The main goal of this study was to explore and validate a new massive parallel sequencing candidate gene​ assay as a diagnostic tool for acute thoracic aortic dissection autopsy cases.

MATERIALS AND METHODS

Massive parallel sequencing of 22 thoracic aortic disease candidate genes performed in 17 cases of thoracic aortic dissection using AmpliSeq and Ion Proton technologies. Genetic variants were filtered by location, type, and frequency at the Exome Aggregation Consortium and an internal database and further classified based on the American College of Medical Genetics and Genomics (ACMG) recommendations published in 2015. All prioritized results were confirmed by traditional sequencing.

RESULTS

From the total of 10 potentially pathogenic genetic variants identified in 7 out of the 17 initial samples, 2 of them were further classified as pathogenic, 2 as likely pathogenic, 1 as possibly benign, and the remaining 5 as variants of uncertain significance, reaching a molecular autopsy yield of 23%, approximately.

CONCLUSIONS

This massive parallel sequencing candidate gene approach proved useful for the molecular autopsy of aortic dissection sudden cardiac death cases and should therefore be progressively incorporated into the forensic field, being especially beneficial for the anticipated diagnosis and risk stratification of any other family member at risk of developing the same condition.

The role of advanced echocardiography and cardiovascular magnetic resonance in the assessment of myocardial function in Marfan syndrome-An update

Cardiovascular assessment of patients with Marfan syndrome has normally focused on the aortic root and vascular manifestations of the disease due to the high risk of aortic dissection. Although primary myocardial impairment has long been suspected in these patients, the evidence has been controversial. Advanced echocardiography and cardiovascular magnetic resonance imaging have proven to be effective, accurate, and more sensitive in the detection of subtle cardiac dysfunction. The application of these techniques to Marfan syndrome over the last 10 years has made significant progress in demonstrating the presence of primary myocardial impairment in these patients, but further work is still required to obtain confirmatory molecular, pathophysiological, and prognostic clinical data. Phenotypic expression of the disease has prognostic value, also suggesting potential effective medical therapy.

[Diagnostics in human genetics : Integration of phenotypic and genomic data]

The development of reliable methods for annotation of clinical phenotypes and algorithms to calculate similarity values for clinical phenotype profiles will be a major challenge for genomic personalized medicine, since combined analysis of phenotypic features and genetic variants can increase diagnostic yield, especially with exome or genome sequencing. The Human Phenotype Ontology project (HPO; www.human-phenotype-ontology.org ) provides an ontology for capturing phenotypic abnormalities in human disease in a precise and comprehensive fashion. The HPO not only enables reliable integration of disease-relevant information from numerous databases, but it also allows for similarity between patients or between patients and disease descriptions to be calculated algorithmically. The HPO thereby represents a solid foundation for differential diagnostic applications as well as for translational research and prioritization of novel disease genes in exome or genome sequencing projects.

The role of the multidisciplinary health care team in the management of patients with Marfan syndrome

Marfan syndrome (MFS) is a rare, severe, chronic, life-threatening disease with multiorgan involvement that requires optimal multidisciplinary care to normalize both prognosis and quality of life. In this article, each key team member of all the medical disciplines of a multidisciplinary health care team at the Hamburg Marfan center gives a personal account of his or her contribution in the management of patients with MFS. The authors show how, with the support of health care managers, key team members organize themselves in an organizational structure to create a common meaning, to maximize therapeutic success for patients with MFS. First, we show how the initiative and collaboration of patient representatives, scientists, and physicians resulted in the foundation of Marfan centers, initially in the US and later in Germany, and how and why such centers evolved over time. Then, we elucidate the three main structural elements; a team of coordinators, core disciplines, and auxiliary disciplines of health care. Moreover, we explain how a multidisciplinary health care team integrates into many other health care structures of a university medical center, including external quality assurance; quality management system; clinical risk management; center for rare diseases; aorta center; health care teams for pregnancy, for neonates, and for rehabilitation; and in structures for patient centeredness. We provide accounts of medical goals and standards for each core discipline, including pediatricians, pediatric cardiologists, cardiologists, human geneticists, heart surgeons, vascular surgeons, vascular interventionists, orthopedic surgeons, ophthalmologists, and nurses; and of auxiliary disciplines including forensic pathologists, radiologists, rhythmologists, pulmonologists, sleep specialists, orthodontists, dentists, neurologists, obstetric surgeons, psychiatrist/psychologist, and rehabilitation specialists. We conclude that a multidisciplinary health care team is a means to maximize therapeutic success.

WES/WGS Reporting of Mutations from Cardiovascular "Actionable" Genes in Clinical Practice: A Key Role for UMD Knowledgebases in the Era of Big Databases

High-throughput next-generation sequencing such as whole-exome and whole-genome sequencing are being rapidly integrated into clinical practice. The use of these techniques leads to the identification of secondary variants for which decisions about the reporting or not to the patient need to be made. The American College of Medical Genetics and Genomics recently published recommendations for the reporting of these variants in clinical practice for 56 "actionable" genes. Among these, seven are involved in Marfan Syndrome And Related Disorders (MSARD) resulting from mutations of the FBN1, TGFBR1 and 2, ACTA2, SMAD3, MYH11 and MYLK genes. Here, we show that mutations collected in UMD databases for MSARD genes (UMD-MSARD) are rarely reported, including the most frequent ones, in global scale initiatives for variant annotation such as the NHLBI GO Exome Sequencing Project (ESP), the Exome Aggregation Consortium (ExAC), and ClinVar. The predicted pathogenic mutations reported in global scale initiatives but absent in locus-specific databases (LSDBs) mainly correspond to rare events. UMD-MSARD databases are therefore the only resources providing access to the full spectrum of known pathogenic mutations. They are the most comprehensive resources for clinicians and geneticists to interpret MSARD-related variations not only primary variants but also secondary variants.