Evaluating the monogenic contribution and genotype-phenotype correlation in patients with isolated thoracic aortic aneurysm

Autonomous Epinephrine Release by KCNJ5 Mutation Drives Familial Thoracic Aortic Aneurysm and Dissection

BACKGROUND

The pathophysiology of familial thoracic aortic aneurysm and dissection (TAAD) is linked to genetic variants that affect aortic components. Although hypertension is a risk factor for TAAD, the precise genetic link remains unclear.

METHODS

A family with autosomal dominant TAAD complicated by hypertension was studied to identify candidate mutations. The effect of the identified mutation on TAAD development was investigated using a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-generated knock-in mouse model to elucidate the mechanism underlying hypertension-induced TAAD.

RESULTS

The KCNJ5 p.R242Q mutation was identified in the family and met the criteria for cosegregation, rarity, and conservation. Utilizing our mouse model, we observed that a significant proportion of heterozygous mice with the mutation displayed dilated thoracic aortas. The mutation's allele dose was positively correlated with TAAD incidence following β-aminopropionitrile monofumarate treatment. Pathological changes in the thoracic aorta, including collagen deposition and dilation, elevated transforming growth factor-β activity, and extracellular matrix remodeling, were associated with hypertension. Furthermore, the mutation was found to induce lifelong isolated systolic hypertension, attributable to autonomous epinephrine secretion from the adrenal medulla. Unlike wild-type, mutated KCNJ5 was highly expressed in the adrenal medulla instead of the adrenal cortex. Treatment with the adrenergic β-receptor blocker propranolol reduced systolic hypertension and mitigated TAAD in the heterozygous mice.

CONCLUSIONS

Familial TAAD may stem from KCNJ5 dysfunction in the G-protein-coupling domain, causing isolated systolic hypertension via increased epinephrine secretion and disruption of thoracic aortic homeostasis. These findings establish a genetic link between systolic hypertension and TAAD.

Differential Analysis of Pathogenic Variants in Thoracic Aortic Aneurysm and Dissection at Different Ages

Objective: To identify genetic variants associated with Stanford A thoracic aortic aneurysm and dissection (ATAAD) using whole-exome sequencing (WES) and analyze positive mutation rates among patients of different onset ages. Methods: WES was performed on 62 sporadic Chinese ATAAD patients (51-74 years old), and then grouped based on onset age together with 73 previously reported TAAD patients (19-50 years old): ≤35, 36-45, 46-55, and >55 years. The proportion of patients with pathogenic/likely pathogenic (P/LP) variants in TAAD causal genes was compared across groups. Results: The average onset age of the 62 patients was 57.66 years. Eight P/LP variants were identified (two novel, six previously described) in five known TAAD causal genes (FBN1, SMAD3, TGFBR2, TGFB2, and MYLK) in eight individuals. P/LP variant positive rates among patients across age groups were: 22.73% for ≤35 years, 32% for 36-45 years, 15.52% for 46-55 years, and 3.33% for >55 years. Significant differences (p = 0.0077) were observed between 36-45 and >55 years group. Conclusions: ATAAD patients aged 36-45 years old at diagnosis had a higher chance of having a P/LP variant and patients >55 years old had the lowest P/LP diagnostic rate. Therefore, gene screening in ATAAD patients ≤55 years old is key to improved diagnostic rate.

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.

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.

Exome risk score for predicting susceptibility to and severity of isolated thoracic aortic aneurysm

Isolated thoracic aortic aneurysms (TAAs) are asymptomatic before dissection or rupture and heterogeneous in clinical phenotype. It is urgent need but difficult to identify individuals at high risk to enable enhanced screening or preventive therapies. Because TAAs have a genetic component, one possible approach is to stratify individuals based on inherited DNA variations. Here, we constructed an integrated exome risk score (ERS) based on both common and rare variants found in whole exome sequencing through a machine-learning framework in discovery population consisting of 551 cases and 1071 controls. We evaluated the performance of the ERS in an independent population including 151 cases and 779 controls with a raw odds ratio (OR) per 1 standard deviation (SD) = 1.95 and area under the receiver operating characteristic curve (AUC) = 0.680. When adjusted by gender and the first four principal components, OR per SD = 1.68 and AUC reached 0.783. Individuals in the top 20% of ERS distribution had an OR of 3.20 compared with others. Finally, we found that individuals with top 20% ERS developed TAA at a younger age (P = 0.002) and with a larger diameter (P = 0.016) compared with lower ERS, and were more likely to suffer from aortic root aneurysms (P = 0.009). Our analysis provides a global view of the genetic components of isolated TAA. The exome score developed and evaluated here is the first polygenic risk score for TAA and is a promising predictor of disease risk and severity, which will facilitate the implementation of the risk-reduction strategies.

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.