Marfan syndrome: from gene to therapy

In Search of Mouse Models for Exfoliation Syndrome

PURPOSE

Exfoliation syndrome (XFS) is a systemic connective tissue disorder with elusive pathophysiology. We hypothesize that a mouse model with elastic fiber defects caused by lack of lysyl oxidase like 1 (LOXL1 encoded by Loxl1), combined with microfibril deficiency due to Fbn1 mutation (encoding fibrillin-1, Fbn1C1041G/+) will display ocular and systemic phenotypes of XFS.

METHODS

Loxl1-/- was crossed with Fbn1C1041G/+ to create double mutant (dbm) mice. Intraocular pressure (IOP), visual acuity (VA), electroretinogram (ERG), and biometry were characterized in 4 genotypes (wt, Fbn1C1041G/+, Loxl1-/-, dbm) at 16 weeks of age. Optic nerve (ON) area was measured by ImageJ, and axon counting was achieved by AxonJ. Deep whole-body phenotyping was performed in wt and dbm mice. Two-tailed Student t test was used for statistical analysis.

RESULTS

There was no difference in IOP between the 4 genotypes. VA was significantly reduced only in dbm mice. The majority of biometric parameters showed significant differences in all 3 mutant genotypes compared with wt, and dbm had exacerbated anomalies compared with single mutants. Dbm mice showed reduced retinal function and significantly enlarged ON area compared with wt. Dbm mice exhibited severe systemic phenotypes related to abnormal elastic fibers, such as pelvic organ prolapse and cardiovascular and pulmonary abnormalities.

CONCLUSIONS

Ocular and systemic findings in dbm mice support functional overlap between fibrillin-1 and LOXL1, 2 prominent components of exfoliation material. Although no elevated IOP or reduction of axon numbers was detected in dbm mice at 16 weeks of age, their reduced retinal function and enlarged ON area indicate early retinal ganglion cell dysfunction. Dbm mice also provide insight on the link between XFS and systemic diseases in humans. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Dysregulation of the immune response in TGF-β signalopathies

The transforming growth factor-β (TGF-β) family of cytokines exerts pleiotropic functions during embryonic development, tissue homeostasis and repair as well as within the immune system. Single gene defects in individual component of this signaling machinery cause defined Mendelian diseases associated with aberrant activation of TGF-β signaling, ultimately leading to impaired development, immune responses or both. Gene defects that affect members of the TGF-β cytokine family result in more restricted phenotypes, while those affecting downstream components of the signaling machinery induce broader defects. These rare disorders, also known as TGF-β signalopathies, provide the unique opportunity to improve our understanding of the role and the relevance of the TGF-β signaling in the human immune system. Here, we summarize this elaborate signaling pathway, review the diverse clinical presentations and immunological phenotypes observed in these patients and discuss the phenotypic overlap between humans and mice genetically deficient for individual components of the TGF-β signaling cascade.

Femtosecond Laser Combined with Double-Flange Polypropylene Suture Capsular Tension Ring Suspension for the Treatment of Subluxation of Lens in Marfan Syndrome

Purpose

To evaluate the use of femtosecond laser combined with double-flange polypropylene suture capsular tension ring (CTR) suspension to treat subluxation of lens in Marfan syndrome. The objective is to provide safer and more effective surgical procedures for patients. Setting. Eye Hospital, Aier Eye Hospital of Wuhan University, Wuhan, China

Methods

In this retrospective study, we observed sixteen patients (16 eyes) with Marfan syndrome who had undergone this operation. Femtosecond laser incision was performed on the anterior capsule with the lens as the center. The suspending CTR was clipped to anterior capsule to support it, which was secured to the sclera with a double-flange polypropylene suture. Uncorrected visual acuity (UCVA), intraocular pressure (IOP), tilt, and decentration of the intraocular lens (IOL) and postoperative complications were evaluated.

Results

All 16 patients were successfully implanted with suspended CTR and IOL after femtosecond laser assisted surgery. Visual acuity improved significantly after surgery (p < 0.01). At 1 month, 3 months and 6 months postoperatively, the tilt of the IOL was 2.70 ± 0.934, 2.65 ± 0.897, and 2.66 ± 0.781, and the decentration of the IOL was 0.30 ± 0.770, 0.30 ± 0.682, and 0.29 ± 0.737; both had no statistically significant difference between the three groups. After the operation, 4 patients had hyphema and 2 patients experienced a temporary postoperative IOP increase. Only one flange was exposed one month after operation and recovered right after secondary adjustment.

Conclusion

Femtosecond laser combined with double-flange polypropylene suture CTR suspension was effective in fixing the lens capsule to the scleral wall in cases of subluxation of lens seen in Marfan syndrome during our short-term observation. The long-term efficacy of this operation needs further observation and follow-up.

Exome Sequencing Identifies Genetic Variants Associated with Extreme Manifestations of the Cardiovascular Phenotype in Marfan Syndrome

Marfan Syndrome (MFS) is an autosomal dominant condition caused by variants in the fibrillin-1 (FBN1) gene. Cardinal features of MFS include ectopia lentis (EL), musculoskeletal features and aortic root aneurysm and dissection. Although dissection of the ascending aorta is the main cause of mortality in MFS, the clinical course differs considerably in age of onset and severity, even among individuals who share the same causative variant, suggesting the existence of additional genetic variants that modify the severity of the cardiovascular phenotype in MFS. We recruited MFS patients and classified them into severe (n = 8) or mild aortic phenotype (n = 14) according to age of presentation of the first aorta-related incident. We used Exome Sequencing to identify the genetic variants associated with the severity of aortic manifestations and we performed linkage analysis where suitable. We found five genes associated with severe aortic phenotype and three genes that could be protective for this phenotype in MFS. These genes regulate components of the extracellular matrix, TGFβ pathway and other signaling pathways that are involved in the maintenance of the ECM or angiogenesis. Further studies will be required to understand the functional effect of these variants and explore novel, personalized risk management and, potentially, therapies for these patients.

Update on the molecular landscape of thoracic aortic aneurysmal disease

PURPOSE OF THE REVIEW

Thoracic aortic aneurysms and dissections (TAADs) are a major health problem in the Western population. This review summarises recent discoveries in the genetic landscape of TAAD disease, discusses current challenges in clinical practice, and describes the molecular road ahead in TAAD research. Disorders, in which aneurysmal disease is not observed in the thoracic aorta, are not discussed.

RECENT FINDINGS

Current gene discovery studies have pinpointed about 40 genes associated with TAAD risk, accounting for about 30% of the patients. Importantly, novel genes, and their subsequent functional characterisation, have expanded the knowledge on disease-related pathways providing crucial information on key elements in this disease, and it pinpoints new therapeutic targets. Moreover, current molecular evidence also suggests the existence of less monogenic nature of TAAD disease, in which the presentation of a diseased patient is most likely influenced by a multitude of genetic and environmental factors.

SUMMARY CLINICAL PRACTICE/RELEVANCE

Ongoing molecular genetic research continues to expand our understanding on the pathomechanisms underlying TAAD disease in order to improve molecular diagnosis, optimise risk stratification, advance therapeutic strategies and facilitate counselling of TAAD patients and their families.

Outcomes of endovascular therapy for Stanford type B aortic dissection in patients with Marfan syndrome

OBJECTIVE

To evaluate the mid-term outcomes of thoracic endovascular aorta repair (TEVAR) for Stanford type B aortic dissection (TBAD) in patients with Marfan syndrome (MFS).

METHODS

Between January 2009 and December 2019, patients with MFS who underwent TEVAR for TBAD were enrolled. Demographic data, preoperative and perioperative clinical profiles, and follow-up data were collected and analyzed. The cumulative survival and freedom from reintervention rates were calculated with Kaplan-Meier analysis.

RESULTS

A total of 26 patients were enrolled. The mean age was 38.5 ± 10.7 (range, 24-64 years). The in-hospital mortality was 0. The cumulative survival rate was 88.1% (95% confidence interval [CI], 67.5%-98.5%) at 5 years and 82.9% (95% CI, 60.2%-93.3%) at 10 years. Patients with a thrombosed false lumen (FL) along the length of the stent had a significantly higher cumulative survival rate (P < .05) and freedom from reintervention (P = .01) than patients with patent FL. The freedom from reintervention was 83.4% (95% CI, 61.4% to 93.4%) at 5 years and 50.3% (95% CI, 21.4%-97.3%) at 10 years. There was no significant difference freedom from reintervention in freedom from reintervention between patients with and those without a previous aortic root procedure (P = .46).

CONCLUSIONS

TEVAR can be performed safely and effectively for TBAD in patients with MFS. Perioperative mortality and morbidity were low; however, lifelong close follow-up in the clinic and imaging are mandatory to prevent aortic rupture. Patients with a patent FL were at high risk of late death.

Genotype FBN1/phenotype relationship in a cohort of patients with Marfan syndrome

Marfan syndrome (MFS) is a systemic connective tissue disorder caused by mutations in the fibrillin-1 (FBN1) gene, and cardiovascular involvement is the leading cause of mortality. We sought to examine the genotype/phenotype realtionship in 61 consecutive patients with a phenotype and genotype compatible with MFS. The FBN1 gene was analyzed by massive sequencing using a hybridization capture-based target enrichment custom panel. Forty-three different variants of FBN1 were identified, of which 17 have not been previously reported. The causal variants of MFS were grouped into mutations resulting in haploinsufficiency (HI group; 23 patients) and mutations producing a dominant-negative effect (DN group; 38 patients). Patient information was collected from electronic medical records and clinical evaluation. While no significant differences were found between the two groups, the HI group included more cases with aortic dissection and occurring at a younger age that the DN group (34.7% vs. 15.8%; p = 0.160). Irrespective of the mutation group, males presented with a higher probability of aortic involvement (4-fold higher risk than females) and aortic dissections events occurred at younger ages. Patients with DN variants carrying a cysteine substitution had a higher incidence of ectopia lentis.

A synonymous mutation in exon 39 of FBN1 causes exon skipping leading to Marfan syndrome

Marfan syndrome is a heritable autosomal-dominant connective tissue disorder and it was typically caused by mutations in FBN1. However, the synonymous mutation was seldom recorded to be related to Marfan syndrome. Hereon, Multiplex ligation-dependent probe amplification failed to detect a copy number variant involving FBN1 but a synonymous mutation c.4773A > G (p.Gly1591Gly) was identified by NGS in exon 39. RNA was extracted from patient's aortic tissue and reverse polymerase chain reaction demonstrated the presence of a shortened mRNA transcript. Results of minigene models indicated that c.4773A > G was bona fide responsibility for the aberrant splicing pattern, and artificial mutations of c.4773A > C and c.4773A > T also gave rise to fragments with exon 39 entire skipped. Together, the novel synonymous mutations in c.4773 position (A > G, C, T), middle of exon 39 of FBN1 gene, was found to be associated with Marfan syndrome by altering the splicing pattern of pre-mRNA.

Multiset sparse partial least squares path modeling for high dimensional omics data analysis

BACKGROUND

Recent technological developments have enabled the measurement of a plethora of biomolecular data from various omics domains, and research is ongoing on statistical methods to leverage these omics data to better model and understand biological pathways and genetic architectures of complex phenotypes. Current reviews report that the simultaneous analysis of multiple (i.e. three or more) high dimensional omics data sources is still challenging and suitable statistical methods are unavailable. Often mentioned challenges are the lack of accounting for the hierarchical structure between omics domains and the difficulty of interpretation of genomewide results. This study is motivated to address these challenges. We propose multiset sparse Partial Least Squares path modeling (msPLS), a generalized penalized form of Partial Least Squares path modeling, for the simultaneous modeling of biological pathways across multiple omics domains. msPLS simultaneously models the effect of multiple molecular markers, from multiple omics domains, on the variation of multiple phenotypic variables, while accounting for the relationships between data sources, and provides sparse results. The sparsity in the model helps to provide interpretable results from analyses of hundreds of thousands of biomolecular variables.

RESULTS

With simulation studies, we quantified the ability of msPLS to discover associated variables among high dimensional data sources. Furthermore, we analysed high dimensional omics datasets to explore biological pathways associated with Marfan syndrome and with Chronic Lymphocytic Leukaemia. Additionally, we compared the results of msPLS to the results of Multi-Omics Factor Analysis (MOFA), which is an alternative method to analyse this type of data.

CONCLUSIONS

msPLS is an multiset multivariate method for the integrative analysis of multiple high dimensional omics data sources. It accounts for the relationship between multiple high dimensional data sources while it provides interpretable results through its sparse solutions. The biomarkers found by msPLS in the omics datasets can be interpreted in terms of biological pathways associated with the pathophysiology of Marfan syndrome and of Chronic Lymphocytic Leukaemia. Additionally, msPLS outperforms MOFA in terms of variation explained in the chronic lymphocytic leukaemia dataset while it identifies the two most important clinical markers for Chronic Lymphocytic Leukaemia AVAILABILITY: http://uva.csala.me/mspls.https://github.com/acsala/2018_msPLS.

Pseudoacromegaly

Individuals with acromegaloid physical appearance or tall stature may be referred to endocrinologists to exclude growth hormone (GH) excess. While some of these subjects could be healthy individuals with normal variants of growth or physical traits, others will have acromegaly or pituitary gigantism, which are, in general, straightforward diagnoses upon assessment of the GH/IGF-1 axis. However, some patients with physical features resembling acromegaly - usually affecting the face and extremities -, or gigantism - accelerated growth/tall stature - will have no abnormalities in the GH axis. This scenario is termed pseudoacromegaly, and its correct diagnosis can be challenging due to the rarity and variability of these conditions, as well as due to significant overlap in their characteristics. In this review we aim to provide a comprehensive overview of pseudoacromegaly conditions, highlighting their similarities and differences with acromegaly and pituitary gigantism, to aid physicians with the diagnosis of patients with pseudoacromegaly.

TGF-β Signaling in Control of Cardiovascular Function

Genetic studies in animals and humans indicate that gene mutations that functionally perturb transforming growth factor β (TGF-β) signaling are linked to specific hereditary vascular syndromes, including Osler-Rendu-Weber disease or hereditary hemorrhagic telangiectasia and Marfan syndrome. Disturbed TGF-β signaling can also cause nonhereditary disorders like atherosclerosis and cardiac fibrosis. Accordingly, cell culture studies using endothelial cells or smooth muscle cells (SMCs), cultured alone or together in two- or three-dimensional cell culture assays, on plastic or embedded in matrix, have shown that TGF-β has a pivotal effect on endothelial and SMC proliferation, differentiation, migration, tube formation, and sprouting. Moreover, TGF-β can stimulate endothelial-to-mesenchymal transition, a process shown to be of key importance in heart valve cushion formation and in various pathological vascular processes. Here, we discuss the roles of TGF-β in vasculogenesis, angiogenesis, and lymphangiogenesis and the deregulation of TGF-β signaling in cardiovascular diseases.

Management of Eosinophilic Esophagitis Based on Pathophysiological Evidence

Over the past decades eosinophilic esophagitis (EoE) has been increasingly diagnosed, and significant progress has been made in our understanding of its pathophysiology. As EoE cannot be cured yet, treatment goals are suppression of disease activity and symptoms as well as the prevention of progression to a more severe disease phenotype. Disease-modifying treatment options can be divided into dietary therapy and immunosuppressive medications, of which topical steroids have been most investigated, yet are still prescribed off-label. In this review, we will summarize recent advances in our understanding of EoE and discuss the mechanisms of action of current treatment options, with emphasis on the role of the esophageal epithelial barrier and the effects of proton-pump inhibitors in the management of patients with EoE.

How Doctors Think: Common Diagnostic Errors in Clinical Judgment-Lessons from an Undiagnosed and Rare Disease Program

The scientific process of analysis and deduction is frequently, often subconsciously, used by physicians to develop a differential diagnosis based on patients' symptoms. Common disorders are most frequently diagnosed in general practice. Rare diseases are uncommon and frequently remain undiagnosed for many years. Cognitive errors in clinical judgment delay definitive diagnosis. Whole-exome sequencing has helped identify the cause of undiagnosed or rare diseases in up to 40% of children. This article provides experiences with an undiagnosed or rare disease program, where detailed data accumulation and a multifaceted analytical approach assisted in diagnosing atypical presentations of common disorders.

Aetiology and management of hereditary aortopathy

Aortic aneurysms are a major health problem because they account for 1-2% of all deaths in the Western population. Although abdominal aortic aneurysms (AAAs) are more prevalent than thoracic aortic aneurysms (TAAs), TAAs have been more exhaustively studied over the past 2 decades because they have a higher heritability and affect younger individuals. Gene identification in both syndromic and nonsyndromic TAA is proceeding at a rapid pace and has already pinpointed >20 genes associated with familial TAA risk. Whereas these genes explain <30% of all cases of familial TAA, their functional characterization has substantially improved our knowledge of the underlying pathological mechanisms. As such, perturbed extracellular matrix homeostasis, transforming growth factor-β signalling, and vascular smooth muscle cell contractility have been proposed as important processes in TAA pathogenesis. These new insights enable novel treatment options that are currently being investigated in large clinical trials. Moreover, together with the advent of next-generation sequencing approaches, these genetic findings are promoting a shift in the management of patients with TAA by enabling gene-tailored interventions. In this Review, we comprehensively describe the molecular landscape of familial TAA, and we discuss whether familial TAA, from a biological point of view, can serve as a paradigm for the genetically more complex forms of the condition, such as sporadic TAA or AAA.

Panlobular Emphysema: Enhancing Visibility with Quantitative Computed Tomography

Rationale: Several chronic obstructive pulmonary disease (COPD) studies have evaluated risk factors for emergency department (ED) visits or hospitalizations, and found insufficient data available about social and demographic factors that drive these behaviors. This U.S. study was designed to describe the characteristics of COPD patients with ED visits or a hospitalization and to investigate how often common COPD comorbidities are present in these individuals. Methods: Data for 7180 COPD patients regarding demographic factors, comorbidities, smoking status, and ED visits or hospitalization was obtained from the 2012 Behavioral Risk Factor Surveillance System (BRFSS) survey. Logistic regression analysis was used to adjust demographic factors and smoking status to model the correlation between patients with ED visits or hospitalizations and morbidities generating odds ratios (OR) and confidence intervals (CI). Results: Among diagnosed COPD patients in the BRFSS, 16.5% had ED visits or hospitalization in the previous year. These individuals were younger, had a lower socio-economic status (lower education, lower income, and more often unemployed) and 23.4% of the individuals could not visit a doctor because of the financial difficulties compared to 16.7% who had no visit (p<0.0001 for all comparisons). The prevalence of comorbidities was higher in those with ED visits or hospitalization compared to those without. Conclusion: In a population representative of COPD patients, lower socio-economic status and higher comorbidities are associated with ED visits or hospitalization. Studies are needed to further elucidate the complex relationship between COPD, comorbidities, and ED visits or hospitalization.

Neonatal Marfan Syndrome: Report of a Case with an Inherited Splicing Mutation outside the Neonatal Domain

We report a child and her mother affected by Marfan syndrome. The child presented with a phenotype of neonatal Marfan syndrome, revealed by acute and refractory heart failure, finally leading to death within the first 4 months of life. Her mother had a common clinical presentation. Genetic analysis revealed an inherited FBN1 mutation. This intronic mutation (c.6163+3_6163+6del), undescribed to date, leads to exon 49 skipping, corresponding to in-frame deletion of 42 amino acids (p.Ile2014_Asp2055del). FBN1 next-generation sequencing did not show any argument for mosaicism. Association in the same family of severe neonatal and classical Marfan syndrome illustrates the intrafamilial phenotype variability.

The genetics and pathogenesis of thoracic aortic aneurysm disorder and dissections

Major advances have been made over the last 20 years to better elucidate the molecular basis of aortic aneurysmal diseases. Thoracic aortic aneurysm disorder and dissections (TAADs) have a high mortality rate, and one-fifth of TAADs patients have a high familial prevalence of the disease. Clinical presentations of TAADs are different, from no symptom to aortic insufficiency that may result in sudden death. The identification of the genetic factors associated with familial TAADs is beneficial for screening and early intervention of TAADs and provides a paradigm for the study of inherited blood vessel disorders. Defects in multiple genes have been identified as causing TAADs. Many genes/alleles are associated with clinical presentations of TAADs; however, the roles of these gene defects in the pathogenesis of TAADs remain unclear. Genetic studies are now beginning to shed light on the key molecules that regulate the extracellular matrix and cytoskeleton in smooth muscle cells and transforming growth factor-beta signaling pathways involved in TAADs pathogenesis. Deciphering the molecular basis of TAADs will improve our understanding of the basic physiology of aortic function and will provide knowledge of the causative genes/alleles and typical manifestations, which will benefit clinical decision-making going forward.

Ocular manifestations of genetic skin disorders

Genetic skin diseases, or genodermatoses, often have extracutaneous manifestations. Ocular manifestations in particular can have significant clinical implications, like blindness. Other manifestations, such as the corneal opacities that occur in X-linked ichthyosis, are asymptomatic but characteristic of a particular genodermatosis. Ophthalmologic examination can aid in diagnosis when characteristic findings are seen. The genodermatoses with ocular manifestations will be reviewed, but neurocutaneous, syndromes, genetic pigmentary disorders, and genetic metabolic diseases are not included because they are covered elsewhere in this issue.

Endovascular Repair of Aortic Dissection in Marfan Syndrome: Current Status and Future Perspectives

Over the last decades, improvement of medical and surgical therapy has increased life expectancy in Marfan patients. Consequently, the number of such patients requiring secondary interventions on the descending thoracic aorta due to new or residual dissections, and distal aneurysm formation has substantially enlarged. Surgical and endovascular procedures represent two valuable options of treatment, both associated with advantages and drawbacks. The aim of the present manuscript was to review endovascular outcomes in Marfan syndrome and to assess the potential role of Thoracic Endovascular Aortic Repair (TEVAR) in this subset of patients.

Divergent Roles of Matrix Metalloproteinase 2 in Pathogenesis of Thoracic Aortic Aneurysm

Objective—

Aortic aneurysm, focal dilation of the aorta, results from impaired integrity of aortic extracellular matrix (ECM). Matrix metalloproteinases (MMPs) are traditionally known as ECM-degrading enzymes. MMP2 has been associated with aneurysm in patients and in animal models. We investigated the role of MMP2 in thoracic aortic aneurysm using 2 models of aortic remodeling and aneurysm.

Approach and Results—

Male 10-week-old MMP2-deficient (MMP2 −/− ) and wild-type mice received angiotensin II (Ang II, 1.5 mg/kg/day) or saline (Alzet pump) for 4 weeks. Although both genotypes exhibited dilation of the ascending aorta after Ang II infusion, MMP2 −/− mice showed more severe dilation of the thoracic aorta and thoracic aortic aneurysm. The Ang II–induced increase in elastin and collagen (mRNA and protein) was markedly suppressed in MMP2 −/− thoracic aorta and smooth muscle cells, whereas only mRNA levels were reduced in MMP2 −/− -Ang II abdominal aorta. Consistent with the absence of MMP2, proteolytic activities were lower in MMP2 −/− -Ang II compared with wild-type-Ang II thoracic and abdominal aorta. MMP2-deficiency suppressed the activation of latent transforming growth factor-β and the Smad2/3 pathway in vivo and in vitro. Intriguingly, MMP2 −/− mice were protected against CaCl 2 -induced thoracic aortic aneurysm, which triggered ECM degradation but not synthesis.

Conclusions—

This study reveals the dual role of MMP2 in ECM degradation, as well as ECM synthesis. Moreover, the greater susceptibility of the thoracic aorta to impaired ECM synthesis, compared with vulnerability of the abdominal aorta to aberrant ECM degradation, provides an insight into the regional susceptibility of the aorta to aneurysm development.

Correlation between Fibrillin-1 Degradation and mRNA Downregulation and Myofibroblast Differentiation in Cultured Human Dental Pulp Tissue

Myofibroblasts and extracellular matrix are important components in wound healing. Alpha-smooth muscle actin (α-SMA) is a marker of myofibroblasts. Fibrillin-1 is a major constituent of microfibrils and an extracellular-regulator of TGF-β1, an important cytokine in the transdifferentiation of resident fibroblasts into myofibroblasts. To study the correlation between changes in fibrillin-1 expression and myofibroblast differentiation, we examined alterations in fibrillin-1 and α-SMA expression in organotypic cultures of dental pulp in vitro. Extracted healthy human teeth were cut to 1-mm-thick slices and cultured for 7 days. In intact dental pulp, fibrillin-1 was broadly distributed, and α-SMA was observed in pericytes and vascular smooth muscle cells. After 7 days of culture, immunostaining for fibrillin-1 became faint concomitant with a downregulation in its mRNA levels. Furthermore, fibroblasts, odontoblasts and Schwann cells were immunoreactive for α-SMA with a significant increase in α-SMA mRNA expression. Double immunofluorescence staining was positive for pSmad2/3, central mediators of TGF-β signaling, and α-SMA. The administration of inhibitors for extracellular matrix proteases recovered fibrillin-1 immunostaining; moreover, fibroblasts lost their immunoreactivity for α-SMA along with a downregulation in α-SMA mRNA. These findings suggest that the expression of α-SMA is TGF-β1 dependent, and fibrillin-1 degradation and downregulation might be implicated in the differentiation of myofibroblasts in dental pulp wound healing.

Congenital Contractural Arachnodactyly without FBN1 or FBN2 Gene Mutations Complicated by Dilated Cardiomyopathy

Congenital contractural arachnodactyly (CCA) is a rare connective tissue disorder characterized by marfanoid habitus with camptodactyly. However, cardiac features have rarely been documented in adults. We herein report a sporadic case of CCA in a 20-year-old woman who developed decompensated dilated cardiomyopathy. The patient did not have any mutations in the FBN1 or FBN2 genes, which are most commonly associated with Marfan syndrome and CCA, respectively. Although whether these two diseases are caused by a mutation(s) in the same gene or two different genes remains unknown, this case provides new clinical insight into the cardiovascular management of CCA.

Pathophysiology and Japanese clinical characteristics in Marfan syndrome

Marfan syndrome is an autosomal dominant heritable disorder of the connective tissue, caused by mutations of the gene FBN1, which encodes fibrillin-1, a major component of the microfibrils of the extracellular matrix. Fibrillin-1 interacts with transforming growth factor-β (TGF-β), and dysregulated TGF-β signaling plays a major role in the development of connective tissue disease and familial aortic aneurysm and dissection, including Marfan syndrome. Losartan, an angiotensin II blocker, has the potential to reduce TGF-β signaling and is expected to be an additional therapeutic option. Clinical diagnosis is made using the Ghent nosology, which requires comprehensive patient assessment and has been proven to work well, but evaluation of some of the diagnostic criteria by a single physician is difficult and time-consuming. A Marfan clinic was established at the University of Tokyo Hospital in 2005, together with cardiologists, cardiac surgeons, pediatricians, orthopedists, and ophthalmologists in one place, for the purpose of speedy and accurate evaluation and diagnosis of Marfan syndrome. In this review, we discuss the recent progress in diagnosis and treatment of Marfan syndrome, and the characteristics of Japanese patients with Marfan syndrome.

The economic impact of Marfan syndrome: a non-experimental, retrospective, population-based matched cohort study

Background

Marfan syndrome is a rare disease of the connective tissues, affecting multiple organ systems. Elevated morbidity and mortality in these patients raises the issue of costs for sickness funds and society. To date, there has been no study analysing the costs of Marfan syndrome from a sickness fund and societal perspective.

Objective

To estimate excess health resource utilisation, direct (non-)medical and indirect costs attributable to Marfan syndrome from a healthcare payer and a societal perspective in Germany in 2008.

Methods

A retrospective matched cohort study design is applied, using claims data. For isolating the causal effect of Marfan syndrome on excess costs, a genetic matching algorithm was used to reduce differences in observable characteristics between Marfan syndrome patients and the control group. 892 patients diagnosed with Marfan syndrome (ICD-10 Q87.4) were matched from a pool of 26,645 control individuals. After matching, we compared health resource utilisation and costs.

Results

From the sickness fund perspective, an average Marfan syndrome patient generates excess annual costs of €2496 compared with a control individual. From the societal perspective, excess annual costs amount to €15,728. For the sickness fund, the strongest cost drivers are inpatient treatment and care by non-physicians. From the sickness fund perspective, the third (25–41 years) and first (0–16 years) age quartiles reveal the greatest surplus in total costs. Marfan syndrome patients have 39% more physician contacts, a 153% longer average length of hospital stay, 119% more inpatient stays, 33% more prescriptions, 236% more medical imaging and 20% higher average prescription costs than control individuals. Depending on the prevalence, the economic impact from the sickness fund perspective ranges between €24.0 million and €61.4 million, whereas the societal economic impact extends from €151.3 million to €386.9 million.

Conclusions

Relative to its low frequency, Marfan syndrome requires high healthcare expenditure. Not only the high costs of Marfan syndrome but also its burden on patients’ lives call for more awareness from policy-makers, physicians and clinical researchers. Consequently, the diagnosis and treatment of Marfan syndrome should begin as soon as possible in order to prevent disease complications, early mortality and substantial healthcare expenditure.

An FBN1 deep intronic mutation in a familial case of Marfan syndrome: an explanation for genetically unsolved cases?

Marfan syndrome (MFS) is caused by mutations in the FBN1 (fibrillin-1) gene, but approximately 10% of MFS cases remain genetically unsolved. Here, we report a new FBN1 mutation in an MFS family that had remained negative after extensive molecular genomic DNA FBN1 testing, including denaturing high-performance liquid chromatography, Sanger sequencing, and multiplex ligation-dependent probe amplification. Linkage analysis in the family and cDNA sequencing of the proband revealed a deep intronic point mutation in intron 56 generating a new splice donor site. This mutation results in the integration of a 90-bp pseudo-exon between exons 56 and 57 containing a stop codon, causing nonsense-mediated mRNA decay. Although more than 90% of FBN1 mutations can be identified with regular molecular testing at the genomic level, deep intronic mutations will be missed and require cDNA sequencing or whole-genome sequencing.

Marfan Syndrome

Marfan syndrome is a multisystem connective tissue disorder, with primary involvement of the cardiovascular, ocular, and skeletal systems. This autosomal heritable disease is mainly attributable to a defect in the FBN1 gene. Clinical diagnosis of Marfan syndrome has been based on the Ghent criteria since 1996. In 2010, these criteria were updated, and the revised guidelines place more emphasis on aortic root dilation, ectopia lentis, and FBN1 mutation testing in the diagnostic assessment of Marfan syndrome. Among its many different clinical manifestations, cardiovascular involvement deserves special consideration, owing to its impact on prognosis. Recent molecular, surgical, and clinical research has yielded profound new insights into the pathological mechanisms that ultimately lead to tissue degradation and weakening of the aortic wall, which has led to exciting new treatment strategies. Furthermore, with the increasing life expectancy of patients with Marfan syndrome, there has been a subtle shift in the spectrum of medical problems. Consequently, this article focuses on recent advances to highlight their potential impact on future concepts of patient care from a clinical, surgical, and anesthetic perspective.

Marfan syndrome: a review of the literature and case report

Marfan syndrome (MFS) is a connective tissue disorder of variable inheritance that affects multiple organ systems. Cardiovascular, ocular, and skeletal abnormalities are cardinal features of the syndrome. Orofacially, MFS patients typically exhibit skeletal class II malocclusion, dolichofacial growth pattern, mandibular retrognathia, malar hypoplasia, high arched palate, dental crowding, and root anomalies. The purpose of this paper is to provide a review of the literature, as well as describe an 11-year-old female with MFS diagnosed at the age of 10.5 years. This report emphasizes the orofacial findings in MFS and highlights particularities of dental treatment when social deficits and intellectual disabilities are also implicated.

The genetics and genomics of thoracic aortic disease

Genetic studies over the past several decades have helped to better elucidate the genomics and inheritance of thoracic aortic diseases. Seminal work from various researchers have identified several genetic factors and mutations that predispose to aortic aneurysms, which will aid in better screening and early intervention, resulting in better clinical outcomes. Syndromic aneurysms have been associated with Marfan syndrome, Loeys-Dietz syndrome, aneurysm osteoarthritis syndrome, arterial tortuosity syndrome, Ehlers-Danlos Syndrome, and TGFβ mutation. Mutations in MYH11, TGFβR1, TGFβR2, MYLK, and ACTA2 genes have been linked to familial non-syndromic cases, although linkage analysis is limited by incomplete penetrance and/or locus heterogeneity. This overview presents a summary of key genetic and genomic factors that are associated with thoracic aortic diseases.

Dissecting the genotype in syndromic intellectual disability using whole exome sequencing in addition to genome-wide copy number analysis

When a known microimbalance affecting multiple genes is detected in a patient with syndromic intellectual disability, it is usually presumed causative for all observed features. Whole exome sequencing (WES) allows questioning this assumption. In this study of three families with children affected by unexplained syndromic intellectual disability, genome-wide copy number and subsequent analyses revealed a de novo maternal 1.1 Mb microdeletion in the 14q32 imprinted region causing a paternal UPD(14)-like phenotype, and two inherited 22q11.21 microduplications of 2.5 or 2.8 Mb. In patient 1 carrying the 14q32 microdeletion, tall stature and renal malformation were unexplained by paternal UPD(14), and there was no altered DLK1 expression or unexpected methylation status. By WES and filtering with a mining tool, a novel FBN1 missense variant was found in patient 1 and his mother, who both showed clinical features of Marfan syndrome by thorough anthropometric assessment, and a novel EYA1 missense variant as a probable cause of the renal malformation in the patient. In patient 2 with the 22q11.21 microduplication syndrome, skin hypo- and hyperpigmentation and two malignancies were only partially explained. By WES, compound heterozygous BLM stop founder mutations were detected causing Bloom syndrome. In male patient 3 carrying a 22q11.21 microduplication inherited from his unaffected father, WES identified a novel missense variant in the OPHN1 X-linked intellectual disability gene inherited from the unaffected mother as a possible additional cause for developmental delay. Thus, WES seems warranted in patients carrying microdeletions or microduplications, who have unexplained clinical features or microimbalances inherited from an unaffected parent.

Integration of multiple signaling pathways determines differences in the osteogenic potential and tissue regeneration of neural crest-derived and mesoderm-derived calvarial bones

The mammalian skull vault, a product of a unique and tightly regulated evolutionary process, in which components of disparate embryonic origin are integrated, is an elegant model with which to study osteoblast biology. Our laboratory has demonstrated that this distinct embryonic origin of frontal and parietal bones confer differences in embryonic and postnatal osteogenic potential and skeletal regenerative capacity, with frontal neural crest derived osteoblasts benefitting from greater osteogenic potential. We outline how this model has been used to elucidate some of the molecular mechanisms which underlie these differences and place these findings into the context of our current understanding of the key, highly conserved, pathways which govern the osteoblast lineage including FGF, BMP, Wnt and TGFβ signaling. Furthermore, we explore recent studies which have provided a tantalizing insight into way these pathways interact, with evidence accumulating for certain transcription factors, such as Runx2, acting as a nexus for cross-talk.

Height matters-from monogenic disorders to normal variation

Height is a classic polygenic quantitative trait with a high level of heritability. As it is a simple and stable parameter to measure, height is a model for both common, complex disorders and monogenic, Mendelian disease. In this Review, we examine height from the perspective of monogenic and complex genetics and discuss the lessons learned so far. We explore several examples of rare sequence variants with large effects on height and compare these variants to the common variants identified in genome-wide association studies that have small effects on height. We discuss how copy number changes or genetic interactions might contribute to the unidentified aspects of the heritability of height. We also ask whether information derived from genome-wide association studies on specific loci in the vicinity of genes can be used for further research in clinical paediatric endocrinology. Furthermore, we address key challenges that remain for gene discovery and for the transition of moving from genomic localization to mechanistic insights, with an emphasis on using next-generation sequencing to identify causative variants of people at the extremes of height distribution.