Microfibril-associated glycoprotein 4 forms octamers that mediate interactions with elastogenic proteins and cells.

Microfibril-associated glycoprotein 4 (MFAP4) is a 36-kDa extracellular matrix glycoprotein with critical roles in organ fibrosis, chronic obstructive pulmonary disease, and cardiovascular disorders, including aortic aneurysms. MFAP4 multimerises and interacts with elastogenic proteins, including fibrillin-1 and tropoelastin, and with cells via integrins. Structural details of MFAP4 and its potential interfaces for these interactions are unknown. Here, we present a cryo-electron microscopy structure of human MFAP4. In the presence of calcium, MFAP4 assembles as an octamer, where two sets of homodimers constitute the top and bottom halves of each octamer. Each homodimer is linked together by an intermolecular disulphide bond. A C34S missense mutation prevents disulphide-bond formation between monomers but does not prevent octamer assembly. The atomic model, built into the 3.55 Å cryo-EM map, suggests that salt-bridge interactions mediate homodimer assembly, while non-polar residues form the interface between octamer halves. In the absence of calcium, an MFAP4 octamer dissociates into two tetramers. Binding studies with fibrillin-1, tropoelastin, LTBP4, and small fibulins show that MFAP4 has multiple surfaces for protein-protein interactions, most of which depend upon MFAP4 octamer assembly. The C34S mutation does not affect these protein interactions or cell interactions. MFAP4 assemblies with fibrillin-1 abrogate MFAP4 interactions with cells.

Multidisciplinary follow-up in a patient with Morgagni hernia leads to diagnosis of Marfan syndrome.

BACKGROUND: congenital diaphragmatic hernia (CDH) is a birth defect occurring in isolated or syndromic (chromosomal or monogenic) conditions. The diaphragmatic defect can be the most common one: left-sided posterolateral, named Bochdalek hernia; or it can be an anterior-retrosternal defect, named Morgagni hernia. Marfan syndrome (MFS) is a rare autosomal dominant inherited condition that affects connective tissue, caused by mutations in fibrillin-1 gene on chromosome 15. To date various types of diaphragmatic defects (about 30 types) have been reported in association with MFS, but they are heterogeneous, including CDH and paraesophageal hernia. CASE PRESENTATION: We describe the case of a child incidentally diagnosed with Morgagni hernia through a chest X-ray performed due to recurrent respiratory tract infections. Since the diagnosis of CDH, the patient underwent a clinical multidisciplinary follow-up leading to the diagnosis of MFS in accordance with revised Ghent Criteria: the child had typical clinical features and a novel heterozygous de novo single-base deletion in exon 26 of the FBN1 gene, identified by Whole-Exome Sequencing. MFS diagnosis permitted to look for cardiovascular complications and treat them, though asymptomatic, in order to prevent major cardiovascular life-threatening events. CONCLUSION: Our case shows the importance of a long-term and multidisciplinary follow-up in all children with diagnosis of CDH.

In vivo phenotypic vascular dysfunction extends beyond the aorta in a mouse model for fibrillin-1 (Fbn1) mutation.

In individuals with Marfan Syndrome (MFS), fibrillin-1 gene (FBN1) mutations can lead to vascular wall weakening and dysfunction. The experimental mouse model of MFS (Fbn1C1041G/+) has been advantageous in investigating MFS-associated life-threatening aortic aneurysms. It is well established that the MFS mouse model exhibits an accelerated-aging phenotype in elastic organs like the aorta, lung, and skin. However, the impact of Fbn1 mutations on the in vivo function and structure of various artery types with the consideration of sex and age, has not been adequately explored in real-time and a clinically relevant context. In this study, we investigate if Fbn1 mutation contributes to sex-dependent alterations in central and cerebral vascular function similar to phenotypic changes associated with normal aging in healthy control mice. In vivo ultrasound imaging of central and cerebral vasculature was performed in 6-month-old male and female MFS and C57BL/6 mice and sex-matched 12-month-old (middle-aged) healthy control mice. Our findings confirm aortic enlargement (aneurysm) and wall stiffness in MFS mice, but with exacerbation in male diameters. Coronary artery blood flow velocity (BFV) in diastole was not different but left pulmonary artery BFV was decreased in MFS and 12-month-old control mice regardless of sex. At 6 months of age, MFS male mice show decreased posterior cerebral artery BFV as compared to age-matched control males, with no difference observed between female cohorts. Reduced mitral valve early-filling velocities were indicated in MFS mice regardless of sex. Male MFS mice also demonstrated left ventricular hypertrophy. Overall, these results underscore the significance of biological sex in vascular function and structure in MFS mice, while highlighting a trend of pre-mature vascular aging phenotype in MFS mice that is comparable to phenotypes observed in older healthy controls. Furthermore, this research is a vital step in understanding MFS's broader implications and sets the stage for more in-depth future analyses, while providing data-driven preclinical justification for re-evaluating diagnostic approaches and therapeutic efficacy.

[Clinical phenotype and genetic analysis of six Chinese patients affected with Acromicric dysplasia due to variants of FBN1 gene].

OBJECTIVE: To retrospectively analyze the clinical and genetic characteristics of six patients with Acromicric dysplasia due to variants of the FBN1 gene. METHODS: Six patients who had visited the Affiliated Hospital of Qingdao University between February 2018 and October 2020 were selected as the study subjects. Clinical data of the patients were collected. High-throughput sequencing was carried out. And candidate variants were verified by Sanger sequencing. RESULTS: All of the six patients had presented with severe short stature (< 3s), brachydactyly, short and broad hands and feet. Other manifestations included joint stiffness, facial dysmorphism, delayed bone age, liver enlargement, coracoid femoral head, and lumbar lordosis. Genetic testing revealed that all had harbored heterozygous variants of the FBN1 gene. Patient 1 had harbored a c.5183C>T (p.A1728V) missense variant in exon 42, which had derived from his father (patient 2). Patient 3 had harbored a c.5284G>A (p.G1762S) missense variant in exon 43, which had derived from her mother (patient 4). Patient 5 had harbored a c.5156G>T (p.C1719F) missense variant in exon 42, which was de novo in origin. Patient 6 had harbored a c.5272G>T (p.D1758Y) missense variant in exon 43, which was also de novo in origin. The variants carried by patients 1, 3 and 6 were known to be pathogenic. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the FBN1: c.5156G>T was rated as a pathogenic variant (PS2+PM1+PM2_Supporting +PM5+PP3). CONCLUSION: All of the six patients had severe short stature and a variety of other clinical manifestations, which may be attributed to the variants of the FBN1 gene.

Pathogenic variants affecting the TB5 domain of the fibrillin-1 protein: not only in geleophysic/acromicric dysplasias but also in Marfan syndrome.

BACKGROUND: Marfan syndrome (MFS) is a multisystem disease with a unique combination of skeletal, cardiovascular and ocular features. Geleophysic/acromicric dysplasias (GPHYSD/ACMICD), characterised by short stature and extremities, are described as 'the mirror image' of MFS. The numerous FBN1 pathogenic variants identified in MFS are located all along the gene and lead to the same final pathogenic sequence. Conversely, in GPHYSD/ACMICD, the 28 known heterozygous FBN1 pathogenic variants all affect exons 41-42 encoding TGFß-binding protein-like domain 5 (TB5). METHODS: Since 1996, more than 5000 consecutive probands have been referred nationwide to our laboratory for molecular diagnosis of suspected MFS. RESULTS: We identified five MFS probands carrying distinct heterozygous pathogenic in-frame variants affecting the TB5 domain of FBN1. The clinical data showed that the probands displayed a classical form of MFS. Strikingly, one missense variant affects an amino acid that was previously involved in GPHYSD. CONCLUSION: Surprisingly, pathogenic variants in the TB5 domain of FBN1 can lead to two opposite phenotypes: GPHYSD/ACMICD and MFS, suggesting the existence of different pathogenic sequences with the involvement of tissue specificity. Further functional studies are ongoing to determine the precise role of this domain in the physiopathology of each disease.

The role of genetic testing in Marfan syndrome.

PURPOSE OF REVIEW: This review aims to delineate the genetic basis of Marfan syndrome (MFS) and underscore the pivotal role of genetic testing in the diagnosis, differential diagnosis, genotype-phenotype correlations, and overall disease management. RECENT FINDINGS: The identification of pathogenic or likely pathogenic variants in the FBN1 gene, associated with specific clinical features such as aortic root dilatation or ectopia lentis, is a major diagnostic criterion for MFS. Understanding genotype-phenotype correlations is useful for determining the timing of follow-up, guiding prophylactic aortic root surgery, and providing more precise information to patients and their family members during genetic counseling. Genetic testing is also relevant in distinguishing MFS from other conditions that present with heritable thoracic aortic diseases, allowing for tailored and individualized management. SUMMARY: Genetic testing is essential in different steps of the MFS patients' clinical pathway, starting from the phase of diagnosis to management and specific treatment.

Aqueous humor TGFß and fibrillin-1 in Tsk mice reveal clues to POAG pathogenesis.

Aqueous humor (AH) and blood levels of transforming growth factor ß (TGFß) are elevated in idiopathic primary open angle glaucoma (POAG) representing a disease biomarker of unclear status and function. Tsk mice display a POAG phenotype and harbor a mutation of fibrillin-1, an important regulator of TGFß bioavailability. AH TGFß2 was higher in Tsk than wild-type (WT) mice (by 34%; p = 0.002; ELISA); similarly, AH TGFß2 was higher in human POAG than controls (2.7-fold; p = 0.00005). As in POAG, TGFß1 was elevated in Tsk serum (p = 0.01). Fibrillin-1 was detected in AH from POAG subjects and Tsk mice where both had similar levels relative to controls (p = 0.45). 350 kDa immunoblot bands representing WT full-length fibrillin-1 were present in human and mouse AH. A 418 kDa band representing mutant full-length fibrillin-1 was present only in Tsk mice. Lower molecular weight fibrillin-1 antibody-reactive bands were present in similar patterns in humans and mice. Certain bands (130 and 32 kDa) were elevated only in human POAG and Tsk mice (p ≤ 0.04 relative to controls) indicating discrete isoforms relevant to disease. In addition to sharing a phenotype, Tsk mice and human POAG subjects had common TGFß and fibrillin-1 features in AH and also blood that are pertinent to understanding glaucoma pathogenesis.

Identification of two novel large deletions in FBN1 gene by next-generation sequencing and multiplex ligation-dependent probe amplification.

BACKGROUND: Mutations in fibrillin-1 (FBN1) are known to be associated with Marfan syndrome (MFS), an autosomal dominant connective tissue disorder. Most FBN1 mutations are missense or nonsense mutations. Traditional molecular genetic testing for the FBN1 gene, like Sanger sequencing, may miss disease-causing mutations in the gene's regulatory regions or non-coding sequences, as well as partial or complete gene deletions and duplications. METHODS: Next-generation sequencing, multiplex ligation-dependent probe amplification and gap PCR were conducted on two MFS patients to screen for disease-causing mutations. RESULTS: We identified two large deletions in FBN1 from two MFS patients. One patient had a 0.23 Mb deletion (NC_000015.9:g.48550506_48779360del) including 5'UTR-exon6 of FBN1. The other patient harbored a 1416 bp deletion (NC_000015.9:g.48410869_48412284del) affecting the last exon, exon 66, of the FBN1 gene. CONCLUSION: Our results expanded the number of large FBN1 deletions and highlighted the importance of screening for large deletions in FBN1 in clinical genetic testing, especially for those with the classic MFS phenotype.

Curcumin Promotes Diabetic Foot Ulcer Wound Healing by Inhibiting miR-152-3p and Activating the FBN1/TGF-ß Pathway.

The objective of this study was to investigate the mechanism of curcumin in diabetic foot ulcer (DFU) wound healing. A DFU rat model was established, and fibroblasts were cultured in a high-glucose (HG) environment to create a cell model. Various techniques, including Western blot, RT‒qPCR, flow cytometry, Transwell, cell scratch test and H&E staining, were employed to measure the levels of relevant genes and proteins, as well as to assess cell proliferation, apoptosis, migration, and pathological changes. The results showed that miR-152-3p was overexpressed in DFU patients, while FBN1 was underexpressed. Curcumin was found to inhibit fibroblast apoptosis, promote proliferation, migration, and angiogenesis in DFU rats, and accelerate wound healing in DFU rats. In addition, overexpression of miR-152-3p weakened the therapeutic effect of curcumin, while overexpression of FBN1 reversed the effects of the miR-152-3p mimic. Further investigations into the underlying mechanisms revealed that curcumin expedited wound healing in DFU rats by restoring the FBN1/TGF-ß pathway through the inhibition of miR-152-3p. In conclusion, curcumin can suppress the activity of miR-152-3p, which, in turn, leads to the rejuvenation of the FBN1/TGF-ß pathway and accelerates DFU wound healing.

Dynamic changes in mitral valve extracellular matrix, tissue mechanics and function in a mouse model of Marfan syndrome.

OBJECTIVE: Mouse models of Marfan syndrome (MFS) with Fibrillin 1 (Fbn1) variant C1041G exhibit cardiovascular abnormalities, including myxomatous valve disease (MVD) and aortic aneurism, with structural extracellular matrix (ECM) dysregulation. In this study, we examine the structure-function-mechanics relations of the mitral valve related to specific transitions in ECM composition and organization in progressive MVD in MFS mice from Postnatal day (P)7 to 1 year-of-age. APPROACH AND RESULTS: Mechanistic links between mechanical forces and biological changes in MVD progression were examined in Fbn1C1041G/+ MFS mice. By echocardiography, mitral valve dysfunction is prevalent at 2 months with a decrease in cardiac function at 6 months, followed by a preserved cardiac function at 12 months. Mitral valve (MV) regurgitation occurs in a subset of mice at 2-6 months, while progressive dilatation of the aorta occurs from 2 to 12 months. Mitral valve tissue mechanical assessments using a uniaxial Permeabilizable Fiber System demonstrate decreased stiffness of MFS MVs at all stages. Histological and microscopic analysis of ECM content, structure, and fiber orientation demonstrate that alterations in ECM mechanics, composition, and organization precede functional abnormalities in Fbn1C1041G/+MFS MVs. At 2 months, ECM abnormalities are detected with an increase in proteoglycans and decreased stiffness of the mitral valve. By 6-12 months, collagen fiber remodeling is increased with abnormal fiber organization in MFS mitral valve leaflets. At the same time, matrifibrocyte gene expression characteristic of collagen-rich connective tissue is increased, as detected by RNA in situ hybridization and qPCR. Together, these studies demonstrate early prevalence of proteoglycans at 2 months followed by upregulation of collagen structure and organization with age in MVs of MFS mice. CONCLUSIONS: Altogether, our data indicate dynamic regulation of mitral valve structure, tissue mechanics, and function that reflect changes in ECM composition, organization, and gene expression in progressive MVD. Notably, increased collagen fiber organization and orientation, potentially dependent on increased matrifibrocyte cell activity, is apparent with altered mitral valve mechanics and function in aging MFS mice.

Three-dimensional co-culturing of stem cell-derived cardiomyocytes and cardiac fibroblasts reveals a role for both cell types in Marfan-related cardiomyopathy.

Pathogenic variants in the FBN1 gene, which encodes the extracellular matrix protein fibrillin-1, cause Marfan syndrome (MFS), which affects multiple organ systems, including the cardiovascular system. Myocardial dysfunction has been observed in a subset of patients with MFS and in several MFS mouse models. However, there is limited understanding of the intrinsic consequences of FBN1 variants on cardiomyocytes (CMs). To elucidate the CM-specific contribution in Marfan's cardiomyopathy, cardiosphere cultures of CMs and cardiac fibroblasts (CFs) are used. CMs and CFs were derived by human induced pluripotent stem cell (iPSC) differentiation from MFS iPSCs with a pathogenic variant in FBN1 (c.3725G>A; p.Cys1242Tyr) and the corresponding CRISPR-corrected iPSC line (Cor). Cardiospheres containing MFS CMs show decreased FBN1, COL1A2 and GJA1 expression. MFS CMs cultured in cardiospheres have fewer binucleated CMs in comparison with Cor CMs. 13% of MFS CMs in cardiospheres are binucleated and 15% and 16% in cardiospheres that contain co-cultures with respectively MFS CFs and Cor CFs, compared to Cor CMs, that revealed up to 23% binucleation when co-cultured with CFs. The sarcomere length of CMs, as a marker of development, is significantly increased in MFS CMs interacting with Cor CF or MFS CF, as compared to monocultured MFS CMs. Nuclear blebbing was significantly more frequent in MFS CFs, which correlated with increased stiffness of the nuclear area compared to Cor CFs. Our cardiosphere model for Marfan-related cardiomyopathy identified a contribution of CFs in Marfan-related cardiomyopathy and suggests that abnormal early development of CMs may play a role in the disease mechanism.

Overcoming challenges associated with identifying FBN1 deep intronic variants through whole-genome sequencing.

BACKGROUND: Marfan syndrome (MFS), caused by pathogenic variants of FBN1 (fibrillin-1), is a systemic connective tissue disorder with variable phenotypes and treatment responsiveness depending on the variant. However, a significant number of individuals with MFS remain genetically unexplained. In this study, we report novel pathogenic intronic variants in FBN1 in two unrelated families with MFS. METHODS: We evaluated subjects with suspected MFS from two unrelated families using Sanger sequencing or multiplex ligation-dependent probe amplification of FBN1 and/or panel-based next-generation sequencing. As no pathogenic variants were identified, whole-genome sequencing was performed. Identified variants were analyzed by reverse transcription-PCR and targeted sequencing of FBN1 mRNA harvested from peripheral blood or skin fibroblasts obtained from affected probands. RESULTS: We found causative deep intronic variants, c.6163+1484A>T and c.5788+36C>A, in FBN1. The splicing analysis revealed an insertion of in-frame or out-of-frame intronic sequences of the FBN1 transcript predicted to alter function of calcium-binding epidermal growth factor protein domain. Family members carrying c.6163+1484A>T had high systemic scores including prominent skeletal features and aortic dissection with lesser aortic dilatation. Family members carrying c.5788+36C>A had more severe aortic root dilatation without aortic dissection. Both families had ectopia lentis. CONCLUSION: Variable penetrance of the phenotype and negative genetic testing in MFS families should raise the possibility of deep intronic FBN1 variants and the need for additional molecular studies. This study expands the mutation spectrum of FBN1 and points out the importance of intronic sequence analysis and the need for integrative functional studies in MFS diagnosis.

Re-evaluation of a Fibrillin-1 Gene Variant of Uncertain Significance Using the ClinGen Guidelines.

Background: Marfan syndrome (MFS) is caused by fibrillin-1 gene (FBN1) variants. Mutational hotspots and/or well-established critical functional domains of FBN1 include cysteine residues, calcium-binding consensus sequences, and amino acids related to interdomain packaging. Previous guidelines for variant interpretation do not reflect the features of genes or related diseases. Using the Clinical Genome Resource (ClinGen) FBN1 variant curation expert panel (VCEP), we re-evaluated FBN1 germline variants reported as variants of uncertain significance (VUSs). Methods: We re-evaluated 26 VUSs in FBN1 reported in 161 patients with MFS. We checked the variants in the Human Genome Mutation Database, ClinVar, and VarSome databases and assessed their allele frequencies using the gnomAD database. Patients' clinical information was reviewed. Results: Four missense variants affecting cysteines (c.460T>C, c.1006T>C, c.5330G>C, and c.8020T>C) were reclassified as likely pathogenic and were assigned PM1_strong or PM1. Two intronic variants were reclassified as benign by granting BA1 (stand-alone). Four missense variants were reclassified as likely benign. BP5 criteria were applied in cases with an alternate molecular basis for disease, one of which (c.7231G>A) was discovered alongside a pathogenic de novo COL3A1 variant (c.1988G>T, p.Gly633Val). Conclusions: Considering the high penetrance of FBN1 variants and clinical variability of MFS, the detection of pathogenic variants is important. The ClinGen FBN1 VCEP encompasses mutational hotspots and/or well-established critical functional domains and adjusts the criteria specifically for MFS; therefore, it is beneficial not only for identifying pathogenic FBN1 variants but also for distinguishing these variants from those that cause other connective tissue disorders with overlapping clinical features.

A novel de novo intragenic duplication in FBN1 associated with early-onset Marfan syndrome in a 16-month-old: A case report and review of the literature.

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder due to pathogenic variants in Fibrillin-1 (FBN1) affecting nearly one in every 10,000 individuals. We report a 16-month-old female with early-onset MFS heterozygous for an 11.2 kb de novo duplication within the FBN1 gene. Tandem location of the duplication was further confirmed by optical genome mapping in addition to genetic sequencing and chromosomal microarray. This is the third reported case of a large multi-exon duplication in FBN1, and the only one confirmed to be in tandem. As the vast majority of pathogenic variants associated with MFS are point mutations, this expands the landscape of known FBN1 pathogenic variants and supports consistent use of genetic testing strategies that can detect large, indel-type variants.

A population-based survey of FBN1 variants in Iceland reveals underdiagnosis of Marfan syndrome.

Marfan syndrome (MFS) is an autosomal dominant condition characterized by aortic aneurysm, skeletal abnormalities, and lens dislocation, and is caused by variants in the FBN1 gene. To explore causes of MFS and the prevalence of the disease in Iceland we collected information from all living individuals with a clinical diagnosis of MFS in Iceland (n = 32) and performed whole-genome sequencing of those who did not have a confirmed genetic diagnosis (27/32). Moreover, to assess a potential underdiagnosis of MFS in Iceland we attempted a genotype-based approach to identify individuals with MFS. We interrogated deCODE genetics' database of 35,712 whole-genome sequenced individuals to search for rare sequence variants in FBN1. Overall, we identified 15 pathogenic or likely pathogenic variants in FBN1 in 44 individuals, only 22 of whom were previously diagnosed with MFS. The most common of these variants, NM_000138.4:c.8038 C > T p.(Arg2680Cys), is present in a multi-generational pedigree, and was found to stem from a single forefather born around 1840. The p.(Arg2680Cys) variant associates with a form of MFS that seems to have an enrichment of abdominal aortic aneurysm, suggesting that this may be a particularly common feature of p.(Arg2680Cys)-associated MFS. Based on these combined genetic and clinical data, we show that MFS prevalence in Iceland could be as high as 1/6,600 in Iceland, compared to 1/10,000 based on clinical diagnosis alone, which indicates underdiagnosis of this actionable genetic disorder.

Weill-Marchesani syndrome: natural history and genotype-phenotype correlations from 18 news cases and review of literature.

BACKGROUND: Weill-Marchesani syndrome (WMS) belongs to the group of acromelic dysplasias, defined by short stature, brachydactyly and joint limitations. WMS is characterised by specific ophthalmological abnormalities, although cardiovascular defects have also been reported. Monoallelic variations in FBN1 are associated with a dominant form of WMS, while biallelic variations in ADAMTS10, ADAMTS17 and LTBP2 are responsible for a recessive form of WMS. OBJECTIVE: Natural history description of WMS and genotype-phenotype correlation establishment. MATERIALS AND METHODS: Retrospective multicentre study and literature review. INCLUSION CRITERIA: clinical diagnosis of WMS with identified pathogenic variants. RESULTS: 61 patients were included: 18 individuals from our cohort and 43 patients from literature. 21 had variants in ADAMTS17, 19 in FBN1, 19 in ADAMTS10 and 2 in LTBP2. All individuals presented with eye anomalies, mainly spherophakia (42/61) and ectopia lentis (39/61). Short stature was present in 73% (from -2.2 to -5.5 SD), 10/61 individuals had valvulopathy. Regarding FBN1 variants, patients with a variant located in transforming growth factor (TGF)-ß-binding protein-like domain 5 (TB5) domain were significantly smaller than patients with FBN1 variant outside TB5 domain (p=0.0040). CONCLUSION: Apart from the ophthalmological findings, which are mandatory for the diagnosis, the phenotype of WMS seems to be more variable than initially described, partially explained by genotype-phenotype correlation.

The usefulness of the genetic panel in the classification and refinement of diagnostic accuracy of Mexican patients with Marfan syndrome and other connective tissue disorders.

Marfan syndrome (MFS) is a multisystem genetic disorder with over 3000 mutations described in the fibrillin 1 (FBN1) gene. Like MFS, other connective tissue disorders also require a deeper understanding of the phenotype-genotype relationship due to the complexity of the clinical presentation, where diagnostic criteria often overlap. Our objective was to identify mutations in patients with connective tissue disorders using a genetic multipanel and to analyze the genotype-phenotype associations in a cohort of Mexican patients. We recruited 136 patients with MFS and related syndromes from the National Institute of Cardiology. Mutations were identified using next-generation sequencing (NGS). To examine the correlation between mutation severity and severe cardiovascular conditions, we focused on patients who had undergone Bentall-de Bono surgery or aortic valve repair. The genetic data obtained allowed us to reclassify the initial clinical diagnosis across various types of connective tissue disorders. The transforming growth factor beta receptor 2 (TGFBR2) rs79375991 mutation was found in 10 out of 16 (63%) Loeys-Dietz patients. We observed a high prevalence (65%) of more severe mutations, such as frameshift indels and stop codons, among patients requiring invasive treatments like aortic valve-sparing surgery, Bentall and de Bono procedures, or aortic valve replacement due to severe cardiovascular injury. Although our study did not achieve precise phenotype-genotype correlations, it underscores the importance of a multigenetic panel evaluation. This could pave the way for a more comprehensive diagnostic approach and inform medical and surgical treatment decision-making.

Life-Threatening Aortic Dissection during Pregnancy: A Case Report of Undiagnosed FBN1-Related Marfan Syndrome at 39 Weeks Gestation.

BACKGROUND Inherited deficiencies in the FBN1 gene, which encodes fibrillin-1, result in Marfan syndrome, an autosomal dominant connective tissue disorder that is associated with aortic root dilatation and predisposes to aortic dissection. This report is of a 37-year-old woman presenting at 39 weeks of pregnancy with acute thoracic aortic dissection due to previously undiagnosed FBN1-related Marfan syndrome. This case report aims to illustrate the challenges in the diagnosis and in the peri-operative management of acute aortic dissection during pregnancy. CASE REPORT A healthy 37-year-old woman at 39 weeks of gestation presented to our hospital with dyspnea and chest pain. Initial evaluation for pulmonary embolism with chest computed tomography was unrevealing. The patient was admitted to the intensive care unit for further management. Overnight, her clinical conditions deteriorated, and a transthoracic echocardiography was obtained, demonstrating an acute ascending aortic dissection. She emergently underwent a successful combined cesarean section and ascending aortic dissection repair, with no immediate complications. On postoperative day 4 she developed cardiac tamponade, for which she underwent emergent mediastinal exploration. She was discharged home on postoperative day 10. A month later she completed genetic testing, which revealed a pathogenic mutation in the FBN1 gene, consistent with a molecular diagnosis of Marfan syndrome. CONCLUSIONS This report has shown that FBN1-related Marfan's syndrome has a variable clinical presentation that can include life-threatening aortic dissection during pregnancy. Successful diagnosis and management of these patients is challenging and requires multidisciplinary expertise, including confirmation of the diagnosis by a clinical geneticist.

Unraveling the role of TGFß signaling in thoracic aortic aneurysm and dissection using Fbn1 mutant mouse models.

Although abnormal TGFß signaling is observed in several heritable forms of thoracic aortic aneurysms and dissections including Marfan syndrome, its precise role in aortic disease progression is still disputed. Using a mouse genetic approach and quantitative isobaric labeling proteomics, we sought to elucidate the role of TGFß signaling in three Fbn1 mutant mouse models representing a range of aortic disease from microdissection (without aneurysm) to aneurysm (without rupture) to aneurysm and rupture. Results indicated that reduced TGFß signaling and increased mast cell proteases were associated with microdissection. In contrast, increased abundance of extracellular matrix proteins, which could be reporters for positive TGFß signaling, were associated with aneurysm. Marked reductions in collagens and fibrillins, and increased TGFß signaling, were associated with aortic rupture. Our data indicate that TGFß signaling performs context-dependent roles in the pathogenesis of thoracic aortic disease.

FBN1 knockout promotes cervical artery dissection by inducing N-glycosylation alternation of extracellular matrix proteins in rat VSMCs.

FBN1 mutation promotes the degeneration of microfibril structures and extracellular matrix (ECM) integrity in the tunica media of the aorta in Marfan syndrome. However, whether FBN1 modulates cervical artery dissection (CAD) development and the potential molecular mechanisms of abnormal FBN1 in CAD remains elusive. In this study, FBN1 deficiency participated in the development of CAD and influenced the proliferation, apoptosis, and migration of vascular smooth muscle cells. FBN1 knockout induced alternations in mRNA levels of the transcriptome, protein expression of the proteome, and abundance of N-glycosylation of the N-glycoproteome. Comprehensive analysis of multiple omics showed up-regulation in mRNA levels of ECM proteins; yet, both the ECM protein levels and relative abundance of N-glycosylation were decreased. Moreover, we performed in vivo experiments to confirm the altered glycosylation of proteins in vascular smooth muscle cells. In conclusion, FBN1 deletion in vascular smooth muscle cells can result in altered N-glycosylation of ECM protein, which were critical for the stability of ECM and the process of CAD. This may open the way for a novel therapeutic strategy to treat people with CAD.