Explore the vast range of titles available.

Background Pathogenic SMAD3 variants are responsible for a cardiovascular phenotype, mainly thoracic aortic aneurysms and dissections. Precocious identification of the vascular risk such as aortic dilatation in mutated patients has a major impact in terms of management, particularly to avoid dissection and sudden death. These vascular damages are classically associated with premature osteoarthritis and skeletal abnormalities. However, variable expressivity and incomplete penetrance are common with SMAD3 variants. Methods To investigate the clinical variability observed within SMAD3 patients, we reviewed the phenotypic and genetic data of 22 new patients from our Centre and of 133 patients reported in the literature. From this cohort of 155 mutated individuals, we first aimed to delineate an estimated frequency of the main clinical signs associated with SMAD3 pathogenic variants and, then, to look for genotype‐phenotype correlations, mainly to see if the aortic phenotype (AP) could be predicted by the SMAD3 variant type. Results We showed, herein, the absence of correlation between the SMAD3 variant type and the occurrence of an AP in patients. Conclusion Therefore, this report brings additional data for the genotype‐phenotype correlations of SMAD3 variants and the need to explore in more detail the effects of genetic modifiers that could influence the phenotype. Pathogenic SMAD3 variants are responsible for a cardiovascular phenotype, mainly thoracic aortic aneurysms and dissections, with variable expressivity and incomplete penetrance. To investigate the clinical variability observed within SMAD3 patients, we reviewed the data of 22 new patients from our Centre and of 133 patients reported in the literature. We first aimed to delineate an estimated frequency of the main clinical signs associated with SMAD3 pathogenic variants and, then, to look for genotype‐phenotype correlations. We showed herein the absence of correlation between the SMAD3 variant type and the occurrence of an aortic phenotype in patients. This report brings additional data for the genotype‐phenotype correlations of SMAD3 variants and the need to explore in more detail the effects of genetic modifiers that could influence the phenotype.

Loeys–Dietz syndrome is a connective tissue disorder predisposing individuals to aortic and arterial aneurysms. Presenting with a wide spectrum of multisystem involvement, medical management for some individuals is complex. This review of literature and expert opinion aims to provide medical guidelines for care of individuals with Loeys–Dietz syndrome. Genet Med 16 8, 576–587.

Central corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. In addition to adding support for known connective tissue-related pathways, pathway analyses uncover previously unreported gene sets. Remarkably, >20% of the CCT-loci are near or within Mendelian disorder genes. These included FBN1 , ADAMTS2 and TGFB2 which associate with connective tissue disorders (Marfan, Ehlers-Danlos and Loeys-Dietz syndromes), and the LUM-DCN-KERA gene complex involved in myopia, corneal dystrophies and cornea plana. Using index CCT-increasing variants, we find a significant inverse correlation in effect sizes between CCT and keratoconus ( r  = −0.62, P  = 5.30 × 10 −5 ) but not between CCT and primary open-angle glaucoma ( r  = −0.17, P  = 0.2). Our findings provide evidence for shared genetic influences between CCT and keratoconus, and implicate candidate genes acting in collagen and extracellular matrix regulation. Reduced central corneal thickness (CCT) is observed in common eye diseases as well as in rare Mendelian disorders. Here, in a cross-ancestry GWAS, the authors identify 19 novel genetic loci associated with CCT, a subset of which is involved in rare corneal or connective tissue disorders.

The aortic root is the predominant site for development of aneurysm caused by heterozygous loss-of-function mutations in positive effectors of the transforming growth factor-β (TGF-β) pathway. Using a mouse model of Loeys-Dietz syndrome (LDS) that carries a heterozygous kinase-inactivating mutation in TGF-β receptor I, we found that the effects of this mutation depend on the lineage of origin of vascular smooth muscle cells (VSMCs). Secondary heart field-derived (SHF-derived), but not neighboring cardiac neural crest-derived (CNC-derived), VSMCs showed impaired Smad2/3 activation in response to TGF-β, increased expression of angiotensin II (AngII) type 1 receptor (Agtr1a), enhanced responsiveness to AngII, and higher expression of TGF-β ligands. The preserved TGF-β signaling potential in CNC-derived VSMCs associated, in vivo, with increased Smad2/3 phosphorylation. CNC-, but not SHF-specific, deletion of Smad2 preserved aortic wall architecture and reduced aortic dilation in this mouse model of LDS. Taken together, these data suggest that aortic root aneurysm predisposition in this LDS mouse model depends both on defective Smad signaling in SHF-derived VSMCs and excessive Smad signaling in CNC-derived VSMCs. This work highlights the importance of considering the regional microenvironment and specifically lineage-dependent variation in the vulnerability to mutations in the development and testing of pathogenic models for aortic aneurysm.

Loeys-Dietz syndrome (LDS) is a connective tissue disorder that is characterized by a high risk for aneurysm and dissection throughout the arterial tree and phenotypically resembles Marfan syndrome. LDS is caused by heterozygous missense mutations in either TGF-β receptor gene (TGFBR1 or TGFBR2), which are predicted to result in diminished TGF-β signaling; however, aortic surgical samples from patients show evidence of paradoxically increased TGF-β signaling. We generated 2 knockin mouse strains with LDS mutations in either Tgfbr1 or Tgfbr2 and a transgenic mouse overexpressing mutant Tgfbr2. Knockin and transgenic mice, but not haploinsufficient animals, recapitulated the LDS phenotype. While heterozygous mutant cells had diminished signaling in response to exogenous TGF-β in vitro, they maintained normal levels of Smad2 phosphorylation under steady-state culture conditions, suggesting a chronic compensation. Analysis of TGF-β signaling in the aortic wall in vivo revealed progressive upregulation of Smad2 phosphorylation and TGF-β target gene output, which paralleled worsening of aneurysm pathology and coincided with upregulation of TGF-β1 ligand expression. Importantly, suppression of Smad2 phosphorylation and TGF-β1 expression correlated with the therapeutic efficacy of the angiotensin II type 1 receptor antagonist losartan. Together, these data suggest that increased TGF-β signaling contributes to postnatal aneurysm progression in LDS.

Loeys-Dietz syndrome is a rare connective tissue disorder characterized by life-threatening aortic aneurysm and distinctive craniofacial anomalies. It is caused by mutations along the transforming growth factor beta (TGF-β) signaling pathway (LDS1-6). We previously showed that craniofacial anomalies varied among LDS subtypes and that LDS2, caused by mutations in the TGFBR2 gene, exhibited the most severe and variable phenotype. In this study, we performed a thorough qualitative and quantitative analysis of craniofacial anomalies in a mouse model for LDS2, through micro computed tomography and 3D geometric morphometric analysis at multiple postnatal stages. We show that craniofacial shape in Tgfbr2 G357W/ + mice strongly deviates from their WT littermates from an early age and exhibit high variability and evidence of left–right asymmetry despite the pure genetic background. Cranial doming, shortening of the anterior part of the skull, widening of the space between orbits, reduction of mandibular size, suture fusion in the cranial vault and palate, and abnormal condylar shape were among features that were consistent with the phenotype seen in patients with LDS. Interestingly, several of these features were more prevalent and severe in females than in males, indicating potential sexual dimorphism, further supported by the trend observed in our revisited clinical data.

Bart Loeys and colleagues identify mutations or deletions of TGFB2 in individuals with thoracic aortic aneurysm and other features of Loeys-Dietz syndrome. TGFB2 encodes the transforming growth factor-β2 ligand. Loeys-Dietz syndrome (LDS) associates with a tissue signature for high transforming growth factor (TGF)-β signaling but is often caused by heterozygous mutations in genes encoding positive effectors of TGF-β signaling, including either subunit of the TGF-β receptor or SMAD3, thereby engendering controversy regarding the mechanism of disease. Here, we report heterozygous mutations or deletions in the gene encoding the TGF-β2 ligand for a phenotype within the LDS spectrum and show upregulation of TGF-β signaling in aortic tissue from affected individuals. Furthermore, haploinsufficient Tgfb2 +/− mice have aortic root aneurysm and biochemical evidence of increased canonical and noncanonical TGF-β signaling. Mice that harbor both a mutant Marfan syndrome (MFS) allele ( Fbn1 C1039G/+ ) and Tgfb2 haploinsufficiency show increased TGF-β signaling and phenotypic worsening in association with normalization of TGF-β2 expression and high expression of TGF-β1. Taken together, these data support the hypothesis that compensatory autocrine and/or paracrine events contribute to the pathogenesis of TGF-β–mediated vasculopathies.

BackgroundPathogenic variants in TGFB3 may lead to a syndromic genetic aortopathy. Heritable thoracic aortic disease (HTAD) and arterial events may occur in TGFB3-related disease but there are limited outcomes data on vascular events in this condition.MethodsClinical data, phenotypical features and aortic outcomes in individuals with pathogenic/likely pathogenic (P/LP) TGFB3 variants enrolled in the Montalcino Aortic Consortium registry were reviewed.Results34 individuals (56% male, median age 42 years, IQR 17–49, range 3–74 years) with P/LP TGFB3 variants were studied. Craniofacial, cutaneous and musculoskeletal features seen in Loeys-Dietz syndrome were variably present. Extra-aortic cardiovascular features included arterial tortuosity (25%), extra-aortic arterial aneurysms (6%) and mitral valve prolapse (21%).Aortic dilation (Z-Score>2) was present in 10 individuals (29%) and aortic dissection occurred in 2 (6%). Type A aortic dissection occurred in two patients (aged between 55 years and 60 years), and one of these patients experienced a type B aortic dissection 6 years later. Seven adults (median age 62 years, range 32–69 years) with aortic root dilation (41–49 mm) are being followed. No patients have undergone prophylactic aortic surgery. Twenty-five per cent of children have aortic dilation. Sixty-eight per cent of the entire cohort remains free of aortic disease. No deaths have occurred.ConclusionsTGFB3-related HTAD is characterised by late-onset and less penetrant thoracic aortic and arterial disease compared with other transforming growth factor β HTAD. Based on our data, a larger aortic size threshold for prophylactic aortic surgery is appropriate in patients with TGFB3-related HTAD compared with HTAD due to TGFBR1 or TGFBR2 variants.

Background: Pathogenic variants within the gene encoding transforming growth factor β (TGF-β) are responsible for Loeys-Dietz syndrome (LDS), a heritable thoracic aortic disease sharing clinical features with Marfan syndrome, including craniofacial and skeletal abnormalities as well as aortic root aneurysms and dissections. In contrast to Marfan syndrome patients, who rarely develop aneurysms or dissections beyond the aortic root, LDS patients frequently exhibit vessel aneurysms in locations other than the aortic root. Here, we report the case of a 61-year-old patient who initially presented with marfanoid characteristics and an aortic root aneurysm and was presumed to have Marfan syndrome two decades ago. Later, the patient developed an abdominal aorta aneurysm, necessitating endovascular repair and stent placement. That fact raised doubts regarding the initial diagnosis of Marfan syndrome, and we decided to investigate the genetic cause of the disorder. Methods: Genetic testing was performed using WES analysis and Sanger sequencing. Results: The genetic analysis detected a de novo heterozygous pathogenic variant c.896G>A in exon 5 of the TGFB2 gene, resulting in the amino acid substitution p. Arg299Gln that has devastating destabilizing structural effects on 3D folding of the protein, as demonstrated by the molecular modeling study we performed. This variant is pathogenic for LDS type 4, partially consistent with the patient’s clinical presentation. Conclusions: Our case emphasizes the significance of precise clinical assessment and genetic verification in patients exhibiting marfanoid characteristics. Furthermore, our findings contribute to the understanding of the diverse clinical spectrum associated with this specific pathogenic variant of TGFB2, underscoring the importance of detailed clinical assessment in expanding knowledge of genotype-phenotype correlations. Accurate diagnosis is crucial for tailored and appropriate management of individuals with heritable thoracic aortic diseases.

Pathogenic variants in TGFBR1 are a common cause of Loeys-Dietz syndrome (LDS) characterized by life-threatening aortic and arterial disease. Generally, these are missense changes in highly conserved amino acids in the serine–threonine kinase domain. Conversely, nonsense, frameshift, or specific missense changes in the ligand-binding extracellular domain cause multiple self-healing squamous epithelioma (MSSE) lacking the cardiovascular phenotype. Here, we report on two novel variants in the penultimate exon 8 of TGFBR1 were identified in 3 patients from two unrelated LDS families: both were predicted to cause frameshift and premature stop codons (Gln448Profs*15 and Cys446Asnfs*4) resulting in truncated TGFBR1 proteins lacking the last 43 and 56 amino acid residues, respectively. These were classified as variants of uncertain significance based on current criteria. Transcript expression analyses revealed both mutant alleles escaped nonsense-mediated mRNA decay. Functional characterization in patient’s dermal fibroblasts showed paradoxically enhanced TGFβ signaling, as observed for pathogenic missense TGFBR1 changes causative of LDS. In summary, we expanded the allelic repertoire of LDS-associated TGFBR1 variants to include truncating variants escaping nonsense-mediated mRNA decay. Our data highlight the importance of functional studies in variants interpretation for correct clinical diagnosis.