Genetic diversity and pathogenic variants as possible predictors of severity in a French sample of nonsyndromic heritable thoracic aortic aneurysms and dissections (nshTAAD)

Thoracic aortic aneurysm

Aortic medicine has undergone remarkable progress in recent decades with regard to our understanding and treatment of aortic disease. In the past decade, the scientific community has called for the aorta to be viewed as an independent organ, advocating for a holistic approach to understanding thoracic aortic disease, integrating its embryological development, wall composition, pathophysiological mechanisms, surveillance and treatment. Thoracic aortic aneurysm (TAA) is a potentially fatal disease characterized by abnormal dilation of the thoracic aorta, whereby the structural integrity of the vessel wall is compromised. Although epidemiological studies of TAA are confounded by its asymptomatic nature and diagnostic challenges, available evidence suggests that TAA prevalence and treatment outcomes vary according to race, sex and socioeconomic factors. Pathophysiological mechanisms involve interactions between vascular smooth muscle cells and the extracellular matrix, influenced by genetic predisposition and embryological factors as well as arterial hypertension. Diagnosis relies on advanced imaging techniques, with CT angiography considered to be the gold standard diagnostic tool and with genetic screening recommended for heritable conditions. Preventive measures focus on managing cardiovascular risk factors, whereas treatment includes medical management, as well as endovascular and open surgical repair. TAA has a major effect on quality of life, particularly in younger, female and genetically predisposed patients, necessitating further research and tailored interventions.

Non-canonical splice variants in thoracic aortic dissection cases and Marfan syndrome with negative genetic testing

Individuals with heritable thoracic aortic disease (HTAD) face a high risk of deadly aortic dissections, but genetic testing identifies causative variants in only a minority of cases. We explored the contribution of non-canonical splice variants (NCVAS) to thoracic aortic disease (TAD) using SpliceAI and sequencing data from diverse cohorts, including 551 early-onset sporadic dissection cases and 437 HTAD probands with exome sequencing, 57 HTAD pedigrees with whole genome sequencing, and select sporadic cases with clinical panel testing. NCVAS were identified in syndromic HTAD genes such as FBN1, SMAD3, and COL3A1, including intronic variants in FBN1 in two Marfan syndrome (MFS) families. Validation in the Penn Medicine BioBank and UK Biobank showed enrichment of NCVAS in HTAD-associated genes among dissections. These findings suggest NCVAS are an underrecognized contributor to TAD, particularly in sporadic dissection and unsolved MFS cases, highlighting the potential of advanced splice prediction tools in genetic diagnostics.

Genetic factors and management strategies in aortic health: a literature review of inherited aortopathy

Inherited aortopathies, including Marfan syndrome, Ehlers-Danlos syndrome, and Loeys-Dietz syndrome, are genetic disorders characterized by structural abnormalities of the aorta that predispose individuals to life-threatening complications like aneurysms and dissections. These conditions result from mutations in genes essential for maintaining aortic wall integrity, such as FBN1, TGFBR1, and COL3A1, affecting extracellular matrix components and the transforming growth factor-beta (TGF-β) pathway. Marfan syndrome has a prevalence of approximately 1 in 5000, while Loeys-Dietz syndrome and vascular Ehlers-Danlos syndrome are rarer, with estimated prevalences of 1 in 100 000 and 1 in 20 000, respectively. Familial thoracic aortic aneurysms and dissections (FTAAD), linked to mutations in genes like ACTA2 and MYH11, highlight the genetic heterogeneity of aortopathies. Management strategies focus on early diagnosis, risk stratification, regular imaging, lifestyle modifications, and timely surgical intervention. Advances in genetic testing and targeted therapies offer promise for personalized care. However, challenges such as genetic heterogeneity, incomplete penetrance, and variability in disease progression limit effective management. Limitations in current research include heterogeneity among studies, which complicates meta-analyses and consensus building. Future directions include exploring novel genetic interventions, optimizing treatment timing, and addressing psychosocial impacts to enhance patient outcomes. By addressing gaps in knowledge and integrating patient-reported outcomes, this study underscores the importance of a multidisciplinary approach to managing inherited aortopathies and improving the quality of life for affected individuals.

Novel variant alters splicing of TGFB2 in family with features of Loeys-Dietz syndrome

Loeys-Dietz syndrome (LDS) is a connective tissue disorder representing a wide spectrum of phenotypes, ranging from isolated thoracic aortic aneurysm or dissection to a more severe syndromic presentation with multisystemic involvement. Significant clinical variability has been noted for both related and unrelated individuals with the same pathogenic variant. We report a family of five affected individuals with notable phenotypic variability who appear to have two distinct molecular causes of LDS, one attributable to a missense variant in TGFBR2 and the other an intronic variant 6 bp upstream from a splice junction in TGFB2. We tested the functional impacts of the variant identified in the proband alongside other variants in the region reported in ClinVar using a splice reporter system, which resulted in non-canonical splicing products for several variants including the proband. Molecular validation of the splicing products suggests that the TGFB2 variants tested impact splicing by reducing efficiency of the canonical acceptor in favor of an alternate acceptor within the exon. These data combined with clinical phenotypes and segregation of the variant with disease support the conclusion that this intronic TGFB2 variant may cause LDS in this patient and her mother. These analyses demonstrate that underappreciated intronic variants that alter splicing can be relevant for clinical phenotypes of connective tissue disease. This case highlights the importance of prompt familial cascade testing, clinical evaluation with detailed dysmorphology exam, comprehensive genetic testing, and collaboration between clinicians and scientists to characterize variants of uncertain significance to properly assess risk in LDS patients.

Genetic insights from a Brazilian cohort of aortopathies through targeted next-generation sequencing and FBN1 direct sequencing

Thoracic aortic diseases (or aortopathies) result from complex interactions between genetic and hemodynamic factors. Often clinically silent, these diseases can lead to lethal complications such as aortic dissection or rupture. This study focused on a Brazilian cohort of 79 individuals with thoracic aortic diseases and explored genetic factors through targeted next-generation sequencing (tNGS) of 15 priority genes and FBN1 direct sequencing. The majority of individuals had nonsyndromic aortopathy, with eight diagnosed with Marfan syndrome (MFS). Pathogenic or likely pathogenic variants (PV/LPV) were found in five genes, namely, FBN1, ACTA2, TGFBR2, MYLK, and SMAD3. Notably, novel variants in FBN1 were identified that contributed to Marfan-like phenotypes. The diagnostic yield for isolated aortopathies was 7.1%, which increased to 55.5% for syndromic cases. Variants of uncertain significance (VUS) were identified, emphasizing the need for further research and familial investigations to refine variant classifications. This study provides valuable insights into the genetic landscape of aortopathies in Brazil, aiding early diagnosis and personalized management.

Management of an elderly patient with nonsyndromic TGFBR1-related aortopathy: A case report

Key Clinical Message

Genetic variants associated with hereditary TAAD may contribute to nonsyndromic TAAD. We present the case of a 72-year-old man with nonsyndromic TAAD undergoing prophylactic surgery after a gene panel test revealed a pathogenic variant in TGFBR1, but the indication for genetic testing in such elderly-onset cases still warrants further discussion.

Abstract

Hereditary thoracic aortic aneurysm and dissection (TAAD) is a serious clinical condition resulting in a fatal outcome. Recently, variants in causative genes for syndromic hereditary TAAD, such as Marfan syndrome and Loeys-Dietz syndrome (LDS), have been reported to predispose to the development of nonsyndromic TAAD; however, genetic testing for patients with elderly-onset nonsyndromic TAAD warrants further discussion. We present a 72-year-old nonsyndromic Japanese man with moderate-sized aortic annulus ectasia (AAE) with moderate aortic regurgitation and ascending to distal arch aortic dilatation (maximum diameter: 46 mm). He had been treated for hypertension and dyslipidemia for 7 years, and his eldest son had AAE at 33 years old and type A aortic dissection at 43 years old. Surgical repair was considered a treatment option because the patient potentially had a nonsyndromic hereditary aortic disease, and genetic panel testing for TAAD identified a pathogenic missense variant in TGFBR1 (c.934G > A, p.[Gly312Ser]), previously reported in patients with LDS type 1. He was diagnosed with nonsyndromic TGFBR1-related aortopathy and underwent prophylactic surgery using a modified Bentall operation and total arch replacement with open stent graft implantation. Genetic testing was useful in guiding the treatment strategy, but further analysis is warranted to establish the clinical value in the treatment plan for patients with elderly-onset nonsyndromic TAAD.

Identification of Variants of Uncertain Significance in the Genes Associated with Thoracic Aortic Disease in Russian Patients with Nonsyndromic Sporadic Subtypes of the Disorder

Nonsyndromic sporadic thoracic aortic aneurysm (nssTAA) is characterized by diverse genetic variants that may vary in different populations. Our aim was to identify clinically relevant variants in genes implicated in hereditary aneurysms in Russian patients with nssTAA. Forty-one patients with nssTAA without dissection were analyzed. Using massive parallel sequencing, we searched for variants in exons of 53 known disease-causing genes. Patients were found to have no (likely) pathogenic variants in the genes of hereditary TAA. Six variants of uncertain significance (VUSs) were identified in four (9.8%) patients. Three VUSs [FBN1 c.7841C>T (p.Ala2614Val), COL3A1 c.2498A>T (p.Lys833Ile), and MYH11 c.4993C>T (p.Arg1665Cys)] are located in genes with "definitive" disease association (ClinGen). The remaining variants are in "potentially diagnostic" genes or genes with experimental evidence of disease association [NOTCH1 c.964G>A (p.Val322Met), COL4A5 c.953C>G (p.Pro318Arg), and PLOD3 c.833G>A (p.Gly278Asp)]. Russian patients with nssTAA without dissection examined in this study have ≥1 VUSs in six known genes of hereditary TAA (FBN1, COL3A1, MYH11, NOTCH1, COL4A5, or PLOD3). Experimental studies expanded genetic testing, and clinical examination of patients and first/second-degree relatives may shift VUSs to the pathogenic (benign) category or to a new class of rare "predisposing" low-penetrance variants causing the pathology if combined with other risk factors.

A yeast based assay establishes the pathogenicity of novel missense ACTA2 variants associated with aortic aneurysms

The ACTA2 gene codes for alpha-smooth muscle actin, a critical component of the contractile apparatus of the vascular smooth muscle cells. Autosomal dominant variants in the ACTA2 gene have been associated to familial non-syndromic thoracic aortic aneurysm/dissection (TAAD). They are thought to act through a dominant-negative mechanism. These variants display incomplete penetrance and variable expressivity, complicating the validation of ACTA2 variants pathogenicity by family segregation studies. In this study, we developed a yeast based assay to test putative TAAD-associated ACTA2 variants. We identified five new heterozygous ACTA2 missense variants in TAAD patients through next generation sequencing. We decided to test their pathogenicity in Saccharomyces cerevisiae, since yeast actin is very similar to human alpha-smooth muscle actin, and the residues at which the TAAD-associated variants occur in ACTA2 are well conserved. A wild type yeast strain was transformed with a vector expressing the different mutant alleles, to model the heterozygous condition of patients. Then, we evaluated yeast growth by spot test and cytoskeletal and mitochondrial morphology by fluorescence microscopy. We found that mutant yeast strains displayed only mild growth defects but a significant increase in the percentage of cells with abnormal mitochondrial distribution and abnormal organization of the actin cytoskeleton compared to controls. All variants appeared to interfere with the activity of wild type actin in yeast, suggesting a dominant-negative pathogenic mechanism. Our results demonstrate the utility of using the yeast actin model system to validate the pathogenicity of TAAD-associated ACTA2 variants.

Targeted genetic analysis in a cohort of sporadic death from spontaneous rupture of thoracic aortic dissection in Han Chinese population

PURPOSE

Thoracic aortic dissection (TAD) is a life-threatening cardiovascular disease that often results in sudden cardiac death (SCD). However, the genetic characteristics of individuals with TAD confirmed at autopsy have been rarely studied. Our objective was to determine the prevalence of pathogenic variants in TAD-associated genes in a cohort of sporadic deaths resulting from spontaneous rupture of TAD and identify relevant genotype-phenotype relationships in Han Chinese population.

METHODS

We included sixty-one consecutive sporadic decedents whose primary cause of death was spontaneous rupture of TAD, and performed a whole exome sequencing based strategy comprising 26 known TAD-associated genes.

RESULTS

We identified 7 pathogenic or likely pathogenic (P/LP) variants in 7 cases (11.48 %) and 22 variants of uncertain significance (VUS) in 22 cases (36.07 %). The FBN1 gene was found to be the major disease-causing gene. Notably, TAD decedents with P/LP variant exhibited significantly earlier mortality. Moreover, we reported for the first time that TAD decedents with P/LP variant had a shorter diagnosis and treatment time.

CONCLUSION

Our study investigated the genetic characteristics of TAD individuals confirmed until autopsy in Han Chinese population. The findings enhanced the understanding of the genetic underpinnings of TAD and have significant implications for clinical management and forensic investigations.

Therapeutic potential of natural products and underlying targets for the treatment of aortic aneurysm

Aortic aneurysm is a vascular disease characterized by irreversible vasodilatation that can lead to dissection and rupture of the aortic aneurysm, a life-threatening condition. Thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) are two main types. The typical treatments for aortic aneurysms are open surgery and endovascular aortic repair, which are only indicated for more severe patients. Most patients with aneurysms have an insidious onset and slow progression, and there are no effective drugs to treat this stage. The inability of current animal models to perfectly simulate all the pathophysiological states of human aneurysms may be the key to this issue. Therefore, elucidating the molecular mechanisms of this disease, finding new therapeutic targets, and developing effective drugs to inhibit the development of aneurysms are the main issues of current research. Natural products have been applied for thousands of years to treat cardiovascular disease (CVD) in China and other Asian countries. In recent years, natural products have combined multi-omics, computational biology, and integrated pharmacology to accurately analyze drug components and targets. Therefore, the multi-component and multi-target complexity of natural products have made them a potentially ideal treatment for multifactorial diseases such as aortic aneurysms. Natural products have regained popularity worldwide. This review provides an overview of the known natural products for the treatment of TAA and AAA and searches for potential cardiovascular-targeted natural products that may treat TAA and AAA based on various cellular molecular mechanisms associated with aneurysm development.

Genetic architecture of thoracic aortic dissection in the female population

BACKGROUND

Sex-related differences in cardiovascular disease are now gaining much more attention and their importance is increasingly being recognized, but little is known about the genetic distribution, genotype-phenotype correlation, and outcomes in the female population with thoracic aortic dissection (TAD).

METHODS

One hundred seventy-nine Chinese female probands with TAD were enrolled from Tongji Hospital between October 2009 and October 2020. Genetic analysis was performed among 12 genes, and participants were subsequently followed up for a median of 38.2 months for TAD-related death.

RESULTS

We identified 18 pathogenic or likely pathogenic variants among 18 (10.1%) probands and 21 variants of uncertain significance in 21 (11.7%) patients. Individuals with positive variants presented with a significant risk of TAD (OR: 12.0, 95% CI: 5.87-26.8), and an association between FBN1 (p = 2.60E-11, OR = 19.8), MYLK (p = 0.006, OR = 14.0) variants and an increased risk for female TAD was identified as well. Furthermore, nearly half of the variants were found in the FBN1 gene, which was significantly linked to early aortic dissection and tended to cause death at a young age.

CONCLUSION

This study revealed the monogenic contribution of known TAD genes to the female TAD population with East Asian ancestry. Patients who tested positive for FBN1 were significantly younger at the time of aortic dissection and had a higher probability of dying at an early age.

Molecular characterization and clinical investigation of patients with heritable thoracic aortic aneurysm and dissection

OBJECTIVES

Thoracic aortic aneurysm and dissection has a genetic predisposition and a variety of clinical manifestations. This study aimed to investigate the clinical and molecular characterizations of patients with thoracic aortic aneurysm and dissection and further explore the relationship between the genotype and phenotype, as well as their postoperative outcomes.

METHODS

A total of 1095 individuals with thoracic aortic aneurysm and dissection admitted to our hospital between 2013 and 2022 were included. Next-generation sequencing and multiplex ligation-dependent probe amplification were performed, and mosaicism analysis was additionally implemented to identify the genetic causes.

RESULTS

A total of 376 causative variants were identified in 83.5% of patients with syndromic thoracic aortic aneurysm and dissection and 18.7% of patients with nonsyndromic thoracic aortic aneurysm and dissection, including 8 copy number variations and 2 mosaic variants. Patients in the "pathogenic" and "variant of uncertain significance" groups had younger ages of aortic events and higher aortic reintervention risks compared with genetically negative cases. In addition, patients with FBN1 haploinsufficiency variants had shorter reintervention-free survival than those with FBN1 dominant negative variants.

CONCLUSIONS

Our data expanded the genetic spectrum of heritable thoracic aortic aneurysm and dissection and indicated that copy number variations and mosaic variants contributed to a small proportion of the disease-causing alterations. Moreover, positive genetic results might have a possible predictive value for aortic event severity and postoperative risk stratification.

Familial Associations of Prevalence and Cause-Specific Mortality for Thoracic Aortic Disease and Bicuspid Aortic Valve in a Large-Population Database

BACKGROUND

Thoracic aortic disease and bicuspid aortic valve (BAV) likely have a heritable component, but large population-based studies are lacking. This study characterizes familial associations of thoracic aortic disease and BAV, as well as cardiovascular and aortic-specific mortality, among relatives of these individuals in a large-population database.

METHODS

In this observational case-control study of the Utah Population Database, we identified probands with a diagnosis of BAV, thoracic aortic aneurysm, or thoracic aortic dissection. Age- and sex-matched controls (10:1 ratio) were identified for each proband. First-degree relatives, second-degree relatives, and first cousins of probands and controls were identified through linked genealogical information. Cox proportional hazard models were used to quantify the familial associations for each diagnosis. We used a competing-risk model to determine the risk of cardiovascular-specific and aortic-specific mortality for relatives of probands.

RESULTS

The study population included 3 812 588 unique individuals. Familial hazard risk of a concordant diagnosis was elevated in the following populations compared with controls: first-degree relatives of patients with BAV (hazard ratio [HR], 6.88 [95% CI, 5.62-8.43]); first-degree relatives of patients with thoracic aortic aneurysm (HR, 5.09 [95% CI, 3.80-6.82]); and first-degree relatives of patients with thoracic aortic dissection (HR, 4.15 [95% CI, 3.25-5.31]). In addition, the risk of aortic dissection was higher in first-degree relatives of patients with BAV (HR, 3.63 [95% CI, 2.68-4.91]) and in first-degree relatives of patients with thoracic aneurysm (HR, 3.89 [95% CI, 2.93-5.18]) compared with controls. Dissection risk was highest in first-degree relatives of patients who carried a diagnosis of both BAV and aneurysm (HR, 6.13 [95% CI, 2.82-13.33]). First-degree relatives of patients with BAV, thoracic aneurysm, or aortic dissection had a higher risk of aortic-specific mortality (HR, 2.83 [95% CI, 2.44-3.29]) compared with controls.

CONCLUSIONS

Our results indicate that BAV and thoracic aortic disease carry a significant familial association for concordant disease and aortic dissection. The pattern of familiality is consistent with a genetic cause of disease. Furthermore, we observed higher risk of aortic-specific mortality in relatives of individuals with these diagnoses. This study provides supportive evidence for screening in relatives of patients with BAV, thoracic aneurysm, or dissection.

Early-Onset Aortic Dissection: Characterization of a New Pathogenic Splicing Variation in the MYH11 Gene with Several In-Frame Abnormal Transcripts

Rare pathogenic variants in the MYH11 gene are responsible for thoracic aortic aneurysms and dissections. They are usually heterozygous missense variants or in-frame deletions of several amino acids without alteration of the reading frame and mainly affect the coiled-coil domain of the protein. Variants leading to a premature stop codon have been described in patients with another phenotype, megacystis-microcolon-intestinal hypoperistalsis syndrome, with an autosomal recessive inheritance. The physiopathological mechanisms arising from the different genetic alterations affecting the MYH11 gene are still poorly understood. Consequently, variants of unknown significance are relatively frequent in this gene. We have identified a variant affecting the consensus donor splice site of exon 29 in the MYH11 gene in a patient who suddenly died from an aortic type A dissection at the age of 23 years old. A transcript analysis on cultured fibroblasts has highlighted several abnormal transcripts including two in-frame transcripts. The first one is a deletion of the last 78 nucleotides of exon 29, corresponding to the use of a cryptic alternative donor splice site; the second one corresponds to an exon 29 skipping. Familial screening has revealed that this molecular event occurred de novo in the proband. Taken together, these experiments allowed us to classify this variant as pathogenic. This case underlines the challenging aspect of the discovery of variations in the MYH11 gene for which the consequences on splicing should be systematically studied in detail.

Smooth Muscle Heterogeneity and Plasticity in Health and Aortic Aneurysmal Disease

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the medial layer of the aorta, which plays a critical role in the maintenance of aortic wall integrity. VSMCs have been suggested to have contractile and synthetic phenotypes and undergo phenotypic switching to contribute to the deteriorating aortic wall structure. Recently, the unprecedented heterogeneity and diversity of VSMCs and their complex relationship to aortic aneurysms (AAs) have been revealed by high-resolution research methods, such as lineage tracing and single-cell RNA sequencing. The aortic wall consists of VSMCs from different embryonic origins that respond unevenly to genetic defects that directly or indirectly regulate VSMC contractile phenotype. This difference predisposes to hereditary AAs in the aortic root and ascending aorta. Several VSMC phenotypes with different functions, for example, secreting VSMCs, proliferative VSMCs, mesenchymal stem cell-like VSMCs, immune-related VSMCs, proinflammatory VSMCs, senescent VSMCs, and stressed VSMCs are identified in non-hereditary AAs. The transformation of VSMCs into different phenotypes is an adaptive response to deleterious stimuli but can also trigger pathological remodeling that exacerbates the pathogenesis and development of AAs. This review is intended to contribute to the understanding of VSMC diversity in health and aneurysmal diseases. Papers that give an update on VSMC phenotype diversity in health and aneurysmal disease are summarized and recent insights on the role of VSMCs in AAs are discussed.

HTAADVar: Aggregation and fully automated clinical interpretation of genetic variants in heritable thoracic aortic aneurysm and dissection

PURPOSE

Early detection and pathogenicity interpretation of disease-associated variants are crucial but challenging in molecular diagnosis, especially for insidious and life-threatening diseases, such as heritable thoracic aortic aneurysm and dissection (HTAAD). In this study, we developed HTAADVar, an unbiased and fully automated system for the molecular diagnosis of HTAAD.

METHODS

We developed HTAADVar (http://htaadvar.fwgenetics.org) under the American College of Medical Genetics and Genomics/Association for Molecular Pathology framework, with optimizations based on disease- and gene-specific knowledge, expert panel recommendations, and variant observations. HTAADVar provides variant interpretation with a self-built database through the web server and the stand-alone programs.

RESULTS

We constructed an expert-reviewed database by integrating 4373 variants in HTAAD genes, with comprehensive metadata curated from 697 publications and an in-house study of 790 patients. We further developed an interpretation system to assess variants automatically. Notably, HTAADVar showed a multifold increase in performance compared with public tools, reaching a sensitivity of 92.64% and specificity of 70.83%. The molecular diagnostic yield of HTAADVar among 790 patients (42.03%) also matched the clinical data, independently demonstrating its good performance in clinical application.

CONCLUSION

HTAADVar represents the first fully automated system for accurate variant interpretation for HTAAD. The framework of HTAADVar could also be generalized for the molecular diagnosis of other genetic diseases.

Determining the genetic contribution in patients with non-syndromic ascending thoracic aortic aneurysms: Correlation with findings from computational pathology

OBJECTIVES

This study aims to identify the clinical utility of targeted-genetic sequencing in a cohort of patients with TAA and establish a new method for regional histological characterisation of TAA disease.

METHODS

Fifty-four patients undergoing surgery for proximal TAA were recruited.

EXCLUSIONS

connective tissue disease, bicuspid aortic valves, redo surgery. All patients underwent next generation sequencing (NGS) using a custom gene panel containing 63 genes previously associated with TAA on Illumina MiSeqor NextSeq550 platforms. Explanted TAA tissue was obtained en-bloc from 34/54 patients, and complete circumferential strips of TAA tissue processed into whole slides which were subsequently digitalised. Computational pathology methods were employed to quantify elastin, cellularity and collagen in six equally divided regions across the whole aneurysm circumference.

RESULTS

Of 54 patients, clearly pathogenic or potentially pathogenic variants were found in 7.4%: namely LOX, PRKG1, TGFBR1 and SMAD3 genes. 55% had at least one variant of unknown significance (VUS) and seven of the VUSs were in genes with a strong disease association (category A) genes, whilst 15 were from moderate risk (category B) genes. Elastin and collagen abundance displayed high regional variation throughout the aneurysm circumference. In patients with <60% total elastin, the loss of elastin was more significant on the outer curve (38.0% vs 47.4%, p = 0.0094). The presence of VUS, higher pulse wave velocity and advancing age were predictors of elastin loss (regression analysis: p < 0.05).

CONCLUSIONS

These findings demonstrate the heterogeneity of TAA disease microstructure and the potential link between histological appearance and clinical factors, including genetic variation.

The critical role of the TB5 domain of Fibrillin-1 in endochondral ossification

Mutations in the Fibrillin-1 (FBN1) gene are responsible for the autosomal dominant form of Geleophysic Dysplasia (GD), which is characterized by short stature and extremities, thick skin, and cardiovascular disease. All known FBN1 mutations in GD patients are localized within the region encoding the TB5 (TGF-β binding protein-like 5) domain of this protein. Herein, we generated a knock-in mouse model, Fbn1Y1698C by introducing the p.Tyr1696Cys mutation from a GD patient into the TB5 domain of murine Fbn1 to elucidate the specific role of this domain in endochondral ossification. We found that both Fbn1Y1698C/+ and Fbn1Y1698C/Y1698C mice exhibited a reduced stature reminiscent of the human GD phenotype. The Fbn1 point mutation introduced in these mice affected the growth plate formation owing to abnormal chondrocyte differentiation such that mutant chondrocytes failed to establish a dense microfibrillar network composed of fibrillin-1. This original Fbn1 mutant mouse model offers new insight into the pathogenic events underlying GD. Our findings suggest that the etiology of GD involves the dysregulation of the ECM composed by abnormal fibrillin-1 microfibril network impacting the differentiation of the chondrocytes.

Monogenic Versus Multifactorial Inheritance in the Development of Isolated Cleft Palate: A Whole Genome Sequencing Study

Craniofacial morphogenesis is highly complex, as is the anatomical region involved. Errors during this process, resulting in orofacial clefts, occur in more than 400 genetic syndromes. Some cases of cleft lip and/or palate (CLP) are caused by mutations in single genes; however, complex interactions between genetic and environmental factors are considered to be responsible for the majority of non-syndromic CLP development. The aim of the current study was to identify genetic risk factors in patients with isolated cleft palate (CP) by whole genome sequencing. Patients with isolated CP (n = 30) recruited from the Riga Cleft Lip and Palate Centre, Institute of Stomatology, Riga, were analyzed by whole genome sequencing. Pathogenic or likely pathogenic variants were discovered in genes associated with CP (TBX22, COL2A1, FBN1, PCGF2, and KMT2D) in five patients; hence, rare disease variants were identified in 17% of patients with non-syndromic isolated CP. Our results were relevant to routine genetic counselling practice and genetic testing recommendations. Based on our data, we propose that all newborns with orofacial clefts should be offered genetic testing, at least for a panel of known CLP genes. Only if the results are negative and there is no suggestive family history or additional clinical symptoms (which would support additional exome or genome-wide investigation), should multifactorial empiric recurrence risk prediction tools be applied for families.

Genetics of Heritable Thoracic Aortic Disease

Genetic testing plays an increasing diagnostic and prognostic role in the management of patients with heritable thoracic aortic disease (HTAD). The identification of a specific variant can establish or confirm the diagnosis of syndromic HTAD, dictate extensive evaluation of the arterial tree in HTAD with known distal vasculature involvement and justify closer follow-up and earlier surgical intervention in HTAD with high risk of dissection of minimal or normal aortic size. Evolving phenotype–genotype correlations lead us towards more precise and individualized management and treatment of patients with HTAD. In this review, we present the latest evidence regarding the role of genetics in patients with HTAD.

Current state and future directions of genomic medicine in aortic dissection: A path to prevention and personalized care

Aortic dissection confers high mortality and morbidity rates despite advances in treatment, impacts quality of life, and contributes immense burden to the healthcare system globally. Efforts to prevent aortic dissection through screening and management of modifiable risk factors and early detection of aneurysms should incorporate genomic information, as it is integral to stratifying risk. However, effective integration of genomic-guided risk assessment into clinical practice will require addressing implementation barriers that currently permeate our healthcare systems. The Aortic Dissection Collaborative was established to define aortic dissection research priorities through patient engagement. Using a collaborative patient-centered feedback model, our Genomic Medicine Working Group identified related research priorities that could be investigated by pragmatic interventional studies aimed at aortic dissection prevention, utilization of genomic information to improve patient outcomes, and access to genomic medicine services. Further research is also needed to identify the genomic, lifestyle, and environmental risk factors that contribute to aortic dissection so these data can be incorporated into future comparative effectiveness studies to prevent aortic dissection.

Genetic Variation in LRP1 Associates with Stanford Type B Aortic Dissection Risk and Clinical Outcome

Genetic variation in LRP1 (low-density lipoprotein receptor-related protein 1) was reported to be associated with thoracic aortic dissections and aneurysms. The aims of this study were to confirm this association in a prospective single-center patient cohort of patients with acute Stanford type B aortic dissections (STBAD) and to assess the impact of LRP1 variation on clinical outcome. The single nucleotide variation (SNV) rs11172113 within the LRP1 gene was genotyped in 113 STBAD patients and 768 healthy control subjects from the same population. The T-allele of rs11172113 was more common in STBAD patients as compared to the reference group (72.6% vs. 59.6%) and confirmed to be an independent risk factor for STBAD (p = 0.002) after sex and age adjustment in a logistic regression model analyzing diabetes, smoking and hypertension as additional risk factors. Analysis of clinical follow-up (median follow-up 2.0 years) revealed that patients with the T-allele were more likely to suffer aorta-related complications (T-allele 75.6% vs. 63.8%; p = 0.022). In this study sample of STBAD patients, variation in LRP1 was an independent risk factor for STBAD and affected clinical outcome.

Cooperative Mechanism of ADAMTS/ ADAMTSL and Fibrillin-1 in the Marfan Syndrome and Acromelic Dysplasias

The term “fibrillinopathies” gathers various diseases with a wide spectrum of clinical features and severity but all share mutations in the fibrillin genes. The first described fibrillinopathy, Marfan syndrome (MFS), is a multisystem disease with a unique combination of skeletal, thoracic aortic aneurysm (TAA) and ocular features. The numerous FBN1 mutations identified in MFS are located all along the gene, leading to the same pathogenic mechanism. The geleophysic/acromicric dysplasias (GD/AD), characterized by short stature, short extremities, and joint limitation are described as “the mirror image” of MFS. Previously, in GD/AD patients, we identified heterozygous FBN1 mutations all affecting TGFβ-binding protein-like domain 5 (TB5). ADAMTS10, ADAMTS17 and, ADAMTSL2 are also involved in the pathogenic mechanism of acromelic dysplasia. More recently, in TAA patients, we identified mutations in THSD4, encoding ADAMTSL6, a protein belonging to the ADAMTSL family suggesting that ADAMTSL proteins are also involved in the Marfanoid spectrum. Together with human genetic data and generated knockout mouse models targeting the involved genes, we provide herein an overview of the role of fibrillin-1 in opposite phenotypes. Finally, we will decipher the potential biological cooperation of ADAMTS-fibrillin-1 involved in these opposite phenotypes.

Sudden death due to a novel nonsense mutation in Marfan syndrome

BACKGROUND

Marfan syndrome is a hereditary connective tissue disease accompanied by autosomal dominant inheritance; that mainly arises from a mutation in the fibrillin-1 gene (FBN1). Aortic dissection and rupture are the common and lethal complications of MFS and may cause sudden unexpected death.

METHOD

A man aged 34 was admitted to the hospital due to persistent pain in his abdomen 12 h post-drinking and suddenly died 10 h later. A forensic autopsy was performed to identify the underlying mechanism of death. Due to the high suspected of MFS, Sanger sequencing was performed, and a novel mutation was detected in the deceased. To clarify the underlying mechanism of this mutation, real-time quantitative polymerase chain reaction was conducted and Western blot analysis was performed in vitro.

RESULTS

A novel PTC mutation c.933C > A in FBN1 was found. Through family history inspection and Sanger sequencing, other MFS patients in the present family were confirmed. The pathologic changes in the aorta in the present case showed media cystic degeneration, disordered arrangement of elastic fibers and a significant reduction in fibrillin 1 compared with the control. The mutation led to significant reduction inFBN1 mRNA and fibrillin-1 in cells in vitro, and overexpression of phospho-Smad2 was observed.

CONCLUSION

We confirmed a novel pathogenic PTC mutation in the FBN1gene through Sanger sequencing, and the pathological changes and underlying mechanisms were also identified. The present work not only extends the pathogenic mutation spectrum of MFS, but also stresses the role of forensic autopsy, genetic analysis and functional validation of novel mutations in cases of sudden death associated with congenital diseases.

A +3 variant at a donor splice site leads to a skipping of the MYH11 exon 32, a recurrent RNA defect causing Heritable Thoracic Aortic Aneurysm and Dissection and/or Patent Ductus Arteriosus

Background

Pathogenic variants in MYH11 are associated with either heritable thoracic aortic aneurysm and dissection (HTAAD), patent ductus arteriosus (PDA) syndrome, or megacystis‐microcolon‐intestinal hypoperistalsis syndrome (MMIHS).

Methods and Results

We report a family referred for molecular diagnosis with HTAAD/PDA phenotype in which we found a variant at a non‐conserved position of the 5’ donor splice site of intron 32 of MYH11 potentially altering splicing (NM_002474.3:c.4578+3A>C). Although its cosegregation with disease was observed, it remained of unknown significance. Later, aortic surgery in the proband gave us the opportunity to perform a transcript analysis. This showed a skipping of the exon 32, an RNA defect previously reported to be translated to an in‐frame loss of 71 amino acids and a dominant‐negative effect in the smooth muscle myosin rod. This RNA defect is also reported in 3 other HTAAD/PDA pedigrees.

Conclusion

This report confirms that among rare variants in MYH11, skipping of exon 32 is recurrent. This finding is of particular interest to establish complex genotype–phenotype correlations where some alleles are associated with autosomal dominant HTAAD/PDA, while others result in recessive or dominant visceral myopathies.

CRISPR/Cas9 in zebrafish: An attractive model for FBN1 genetic defects in humans

Background

Mutations in the fibrillin‐1 gene (FBN1) are associated with various heritable connective tissue disorders (HCTD). The most studied HCTD is Marfan syndrome. Ninety percent of Marfan syndrome is caused by mutations in the FBN1 gene. The zebrafish share high genetic similarity to humans, representing an ideal model for genetic research of human diseases. This study aimed to generate and characterize fbn1^+/− mutant zebrafish using the CRISPR/Cas9 gene‐editing technology.

Methods

CRISPR/Cas9 was applied to generate an fbn1 frameshift mutation (fbn1^+/−) in zebrafish. F1 fbn1^+/− heterozygotes were crossed with transgenic fluorescent zebrafish to obtain F2 fbn1^+/− zebrafish. Morphological abnormalities were assessed in F2 fbn1^+/− zebrafish by comparing with the Tuebingen (TU) wild‐type controls at different development stages.

Results

We successfully generated a transgenic line of fbn1^+/− zebrafish. Compared with TU wild‐type zebrafish, F2 fbn1^+/− zebrafish exhibited noticeably decreased pigmentation, increased lengths, slender body shape, and abnormal cardiac blood flow from atrium to ventricle.

Conclusion

We generated the first fbn1^+/− zebrafish model using CRISPR/Cas9 gene‐editing approach to mimic FBN1 genetic defects in humans, providing an attractive model of Marfan syndrome and a method to determine the pathogenicity of gene mutation sites.

Identification of COL3A1 variants associated with sporadic thoracic aortic dissection: a case-control study

Thoracic aortic dissection (TAD) without familial clustering or syndromic features is known as sporadic TAD (STAD). So far, the genetic basis of STAD remains unknown. Whole exome sequencing was performed in 223 STAD patients and 414 healthy controls from the Chinese Han population (N = 637). After population structure and genetic relationship and ancestry analyses, we used the optimal sequence kernel association test to identify the candidate genes or variants of STAD. We found that COL3A1 was significantly relevant to STAD (P = 7.35 × 10^-6) after 10 000 times permutation test (P = 2.49 × 10^-3). Moreover, another independent cohort, including 423 cases and 734 non-STAD subjects (N = 1157), replicated our results (P = 0.021). Further bioinformatics analysis showed that COL3A1 was highly expressed in dissected aortic tissues, and its expression was related to the extracellular matrix (ECM) pathway. Our study identified a profile of known heritable TAD genes in the Chinese STAD population and found that COL3A1 could increase the risk of STAD through the ECM pathway. We wanted to expand the knowledge of the genetic basis and pathology of STAD, which may further help in providing better genetic counseling to the patients.

Marfan syndrome resulting from a rare pathogenic FBN1 variant, ascertained through a proband with IgG4-related arteriopathy

A 57-year-old man with a family history of aortic aneurysm was found, during assessment of unexplained fever, to have an infrarenal aortic aneurysm requiring immediate repair. Dilatation of popliteal and iliac arteries was also present. Progressive aortic root dilatation with aortic regurgitation was documented from 70 years leading to valve-sparing aortic root replacement at 77 years, at which time genetic studies identified a likely pathogenic FBN1 missense variant c.6916C > T (p.Arg2306Cys) in exon 56. The proband's lenses were normally positioned and the Marfan syndrome (MFS) systemic score was 0/20. Cascade genetic testing identified 15 other family members with the FBN1 variant, several of whom had unsuspected aortic root dilatation; none had ectopia lentis or MFS systemic score ≥ 7. Segregation analysis resulted in reclassification of the FBN1 variant as pathogenic. The combination of thoracic aortic aneurysm and dissection (TAAD) and a pathogenic FBN1 variant in multiple family members allowed a diagnosis of MFS using the revised Ghent criteria. At 82 years, the proband's presenting abdominal aortic aneurysm was diagnosed retrospectively to have resulted from IgG4-related inflammatory aortopathy.

Role of Clinical Genetic Testing in the Management of Aortopathies

PURPOSE OF REVIEW

Thoracic aortic aneurysms (TAA) have a strong heritable basis, and identification of a genetic etiology has important implications for patients with TAA and their relatives. This review provides an overview of Mendelian causes of TAA, discusses important considerations for genetic testing, and summarizes the impact a genetic diagnosis may have on a patient's medical care.

RECENT FINDINGS

Thoracic aortic disease may be non-syndromic or seen as part of a genetic syndrome, such as Marfan syndrome, Loeys-Dietz syndrome, or vascular Ehlers-Danlos syndrome. Expanded access to genetic testing has revealed the wide and overlapping phenotypic spectrum of these conditions, highlighting the need for genetic testing to establish an accurate diagnosis. Important aspects of genetic evaluation include thorough phenotyping through family history and physical examination, selection of an appropriate genetic test driven by the patient's phenotype, and careful interpretation of genetic test results. Improved understanding of the natural history of these conditions has led to tailored management recommendations, including gene-based recommendations for prophylactic surgical repair. Identification of a genetic etiology allows for careful monitoring of disease progression, informs the timing of prophylactic surgical repair, and facilitates the identification of other at-risk relatives through cascade genetic testing.

Pregnancy outcome in thoracic aortic disease data from the Registry Of Pregnancy And Cardiac disease

Background

Cardiovascular disease is the leading cause of death during pregnancy with thoracic aortic dissection being one of the main causes. Thoracic aortic disease is commonly related to hereditary disorders and congenital heart malformations such as bicuspid aortic valve (BAV). Pregnancy is considered a high risk period in women with underlying aortopathy.

Methods

The ESC EORP Registry Of Pregnancy And Cardiac disease (ROPAC) is a prospective global registry that enrolled 5739 women with pre-existing cardiac disease. With this analysis, we aim to study the maternal and fetal outcome of pregnancy in women with thoracic aortic disease.

Results

Thoracic aortic disease was reported in 189 women (3.3%). Half of them were patients with Marfan syndrome (MFS), 26% had a BAV, 8% Turner syndrome, 2% vascular Ehlers-Danlos syndrome and 11% had no underlying genetic defect or associated congenital heart defect. Aortic dilatation was reported in 58% of patients and 6% had a history of aortic dissection. Four patients, of whom three were patients with MFS, had an acute aortic dissection (three type A and one type B aortic dissection) without maternal or fetal mortality. No complications occurred in women with a history of aortic dissection. There was no significant difference in median fetal birth weight if treated with a beta-blocker or not (2960 g (2358–3390 g) vs 3270 g (2750–3570 g), p value 0.25).

Conclusion

This ancillary analysis provides the largest prospective data review on pregnancy risk for patients with thoracic aortic disease. Overall pregnancy outcomes in women with thoracic aortic disease followed according to current guidelines are good.

Cardiogenetics: genetic testing in the diagnosis and management of patients with aortic disease

Thoracic aortic aneurysm and aortic dissection have a potent genetic underpinning with 20% of individuals having an affected relative. Heritable thoracic aortic diseases (HTAD) may be classified as syndromic (including Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome and others) or non-syndromic (without recognisable phenotypes) and relate to pathogenic variants in multiple genes affecting extracellular matrix proteins, transforming growth factor-beta (TGF-β) signalling and smooth muscle contractile function. Clinical and imaging characteristics may heighten likelihood of an underlying HTAD. HTAD should be investigated in individuals with thoracic aortic aneurysm or aortic dissection, especially when occurring in younger individuals, in those with phenotypic features and in those with a family history of aneurysm disease. Screening family members for aneurysm disease is important. Consultation with a medical geneticist and genetic testing of individuals at increased risk for HTAD is recommended. Medical management and prophylactic aortic surgical thresholds are informed by an accurate clinical and molecular diagnosis.

[Gene mutation analysis of 19 Uighur families with aortic disease in Kashgar, China]

OBJECTIVE

To explore genetic mutation types and their correlation with clinical phenotypes in Uighur patients with aortic disease in Kashgar (Xinjiang Uighur Autonomous Region, China).

METHODS

We examined 37 pathogenic genes in 19 Uighur families with aortic diseases including Marfan syndrome from Kashgar using next generation sequencing, and the results were confirmed by Sanger sequence in the first relatives.

RESULTS

This study included 19 families with aortic diseases, in whom a total of 23 variants were identified, and 11 (57.89%) probands had one or more variants. Among them, definite pathogenic mutation was detected in one patient (5.26%), variants of uncertain significance (VUS) were found in 8 (42.11%), and benign/likely benign variants were detected in 7 (36.84%). The 23 variants identified included one (5.26%) pathogenic variant, 14 (60.87%) VUS, and 8 (34.78%) benign/likely benign variants. The 14 VUS were analyzed by prediction with SIFT and Polyphen2 HDIV, which identified 6 (42.86%) variants as deleterious/possibly damaging; all the 8 benign/likely benign variants were predicted to be deleterious/possibly damaging.

CONCLUSIONS

We detected 23 genetic variants in the 19 Uighur families with aortic diseases, and 22 of these variants remain to be verified by more patient data in future studies.

Inherited Thoracic Aortic Disease: New Insights and Translational Targets

Inherited thoracic aortopathies denote a group of congenital conditions that predispose to disease of the thoracic aorta. Aortic wall weakness and abnormal aortic hemodynamic profiles predispose these patients to dilatation of the thoracic aorta, which is generally silent but can precipitate aortic dissection or rupture with devastating and often fatal consequences. Current strategies to assess the future risk of aortic dissection or rupture are based primarily on monitoring aortic diameter. However, diameter alone is a poor predictor of risk, with many patients experiencing dissection or rupture below current intervention thresholds. Developing tools that improve the risk assessment of those with aortopathy is internationally regarded as a research priority. A robust understanding of the molecular pathways that lead to aortic wall weakness is required to identify biomarkers and therapeutic targets that could improve patient management. Here, we summarize the current understanding of the genetically determined mechanisms underlying inherited aortopathies and critically appraise the available blood biomarkers, imaging techniques, and therapeutic targets that have shown promise for improving the management of patients with these important and potentially fatal conditions.

The Genetics of Thoracic Aortic Aneurysms and Dissection: A Clinical Perspective

Thoracic aortic aneurysm and dissection (TAAD) affects many patients globally and has high mortality rates if undetected. Once thought to be solely a degenerative disease that afflicted the aorta due to high pressure and biomechanical stress, extensive investigation of the heritability and natural history of TAAD has shown a clear genetic basis for the disease. Here, we review both the cellular mechanisms and clinical manifestations of syndromic and non-syndromic TAAD. We particularly focus on genes that have been linked to dissection at diameters <5.0 cm, the current lower bound for surgical intervention. Genetic screening tests to identify patients with TAAD associated mutations that place them at high risk for dissection are also discussed.

A new mutational hotspot in the SKI gene in the context of MFS/TAA molecular diagnosis

SKI pathogenic variations are associated with Shprintzen-Goldberg Syndrome (SGS), a rare systemic connective tissue disorder characterized by craniofacial, skeletal and cardiovascular features. So far, the clinical description, including intellectual disability, has been relatively homogeneous, and the known pathogenic variations were located in two different hotspots of the SKI gene. In the course of diagnosing Marfan syndrome and related disorders, we identified nine sporadic probands (aged 2-47 years) carrying three different likely pathogenic or pathogenic variants in the SKI gene affecting the same amino acid (Thr180). Seven of these molecular events were confirmed de novo. All probands displayed a milder morphological phenotype with a marfanoid habitus that did not initially lead to a clinical diagnosis of SGS. Only three of them had learning disorders, and none had intellectual disability. Six out of nine presented thoracic aortic aneurysm, which led to preventive surgery in the oldest case. This report extends the phenotypic spectrum of variants identified in the SKI gene. We describe a new mutational hotspot associated with a marfanoid syndrome with no intellectual disability. Cardiovascular involvement was confirmed in a significant number of cases, highlighting the importance of accurately diagnosing SGS and ensuring appropriate medical treatment and follow-up.