Recent progress in genetics of Marfan syndrome and Marfan-associated disorders

Directed differentiation of human iPSCs into mesenchymal lineages by optogenetic control of TGF-β signaling

In tissue development and homeostasis, transforming growth factor (TGF)-β signaling is finely coordinated by latent forms and matrix sequestration. Optogenetics can offer precise and dynamic control of cell signaling. We report the development of an optogenetic human induced pluripotent stem cell system for TGF-β signaling and demonstrate its utility in directing differentiation into the smooth muscle, tenogenic, and chondrogenic lineages. Light-activated TGF-β signaling resulted in expression of differentiation markers at levels close to those in soluble factor-treated cultures, with minimal phototoxicity. In a cartilage-bone model, light-patterned TGF-β gradients allowed the establishment of hyaline-like layer of cartilage tissue at the articular surface while attenuating with depth to enable hypertrophic induction at the osteochondral interface. By selectively activating TGF-β signaling in co-cultures of light-responsive and non-responsive cells, undifferentiated and differentiated cells were simultaneously maintained in a single culture with shared medium. This platform can enable patient-specific and spatiotemporally precise studies of cellular decision making.

Bilateral Anteriorly Displaced Microspherophakia in a Female Child With Marfanoid Habitus

Microspherophakia is a rare congenital anomaly characterized by an abnormally small and spherical crystalline lens, which can be associated with several systemic syndromes. We present an extremely rare case of bilateral anteriorly displaced microspherophakia in a female child with Marfanoid habitus. The patient displayed phenotypic features resembling Marfan syndrome, including tall stature, muscle hypotonia, dolichostenomelia, and increased arm span than body length. However, unlike Marfan syndrome, Marfanoid habitus is not associated with mutations in the fibrillin-1 gene. The association between microspherophakia and Marfanoid habitus is a unique presentation that has not been reported in the literature. This case report aims to increase awareness of microspherophakia as a possible ocular association of Marfanoid habitus.

ROLE OF THE TRANSFORMING GROWTH FACTOR β1 IN THE GENESIS OF ARTERIAL HYPERTENSION AND ITS COMPLICATIONS

Transforming growth factor beta 1 (TGFβ1) is an actively studied cytokine with rather contradictory effects. The article systematizes and summarizes the scientific data on TGFβ1 and its role in the development and progression of arterial hypertension, with an emphasis on arterial stiffness.

Intraoperative absent bilateral medial recti in syndromic craniosynostosis

Patients with syndromic craniosynostosis are usually associated with the complexity of the malformation complex. We describe here detailed oculo-motility disorder and a remarkable finding of hypoplastic bilateral media recti on imaging and its intraoperative absence in patients with phenotypic features resembling Shprintzen-Goldberg syndrome (SGS). SGS is a rare congenital disorder with craniosynostosis affecting multiple systems including mentation and having a considerable overlap of its phenotypic features with Marfan syndrome. Large A-pattern exotropia found in these patients may be related to the craniofacial features and their bearing on extraocular muscle development and function. In this paper, we aimed to sensitise ophthalmologists and strabismologists concerning the necessity to recognise syndromic associations of patients with craniosynostosis presenting with a large squint, be aware of the intraoperative surprises and consider the challenges in its management.

5,10-methylenetetrahydrofolate reductase C677T gene polymorphism and peripheral arterial disease: A meta-analysis

INTRODUCTION

Peripheral arterial disease is one common vascular disease most caused by atherosclerosis. As with stroke and coronary heart disease, peripheral arterial disease is one clinical type of atherosclerotic cardiovascular disease with many unmeasured environmental and genetic components. MTHFR C677T polymorphism is associated with the increased risk of ischemic stroke and coronary heart disease. MTHFR C677T polymorphism is associated with decreasing enzyme activity and increasing homocysteine levels. Meta-analysis of studies had demonstrated an association between elevated plasma homocysteine levels and peripheral arterial disease. Elevated plasma homocysteine level is closely related to MTHFR C677T polymorphism. Recent studies had clarified the relationship of MTHFR C677T polymorphism and peripheral arterial disease. So we performed a meta-analysis to investigate the association between MTHFR C677T polymorphism and peripheral arterial disease.

MATERIALS AND METHODS

We searched the database PubMed, Embase, and Cochrane Library for all English-language articles related to peripheral arterial disease and MTHFR C677T through 30 June 2020. Analysis results were shown by forest plot. Publication bias was estimated using funnel plot.

RESULTS

A total of 15 studies comprising 1929 patients with peripheral arterial disease and 2952 healthy controls were included in the meta-analysis. Significant associations between MTHFR C677T genetic polymorphism and peripheral arterial disease were found (OR = 1.31, 95% CI: 1.09-1.58, P <0.01). But there was no significant association (poor OR = 1.11, 95% CI: 0.98-1.26, P =0.11) between the T allele carrier and peripheral arterial disease.

CONCLUSION

Our meta-analysis suggested that MTHFR C677T genetic polymorphism TT genotype may be associated with increased peripheral arterial disease risk. But further studies with large sample sizes are needed to confirm our findings.

Tall stature in children and adolescents

Tall stature is usually defined as a height beyond 97^th percentile or more than 2 SD above the mean height for age and sex in a defined population. Familiar tall stature, also known as constitutional tall stature, is the most common cause of tall stature. Overnutrition, obesity, also usually causes overgrowth. Tall stature by itself is not a pathological condition, however, there are a number of disorders associated with tall stature. Some genetic disorders and syndromes may be associated with mental retardation and various complications. Therefore, recognition of tall stature and revealing the underlying pathogenic causes and making the diagnosis are important not to miss the serious conditions and to provide adequate medical care and genetic counseling. Pathological causes for tall statute include endocrine disorders, such as excessive growth hormone secretion, hyperthyroidism, precocious puberty and lipodystrophy, chromosome disorders, such as Trisomy X (47, XXX female), Klinefelter Syndrome (47, XXY), XYY syndrome (47, XYY male) and fragile X syndrome, and syndromes and metabolic disorders, such as Marfan Syndrome, Beckwith-Wiedemann Syndrome, Simpson-Golabi-Behmel Syndrome, Sotos Syndrome and homocystinuria. Children may require growth-reductive treatment if the predicted adult height would be excessive and unacceptable. Some hormonal, high doses of sex steroids, or surgical, bilateral percutaneous epiphysiodesis of the distal femur and proximal tibia and fibula, treatment is currently available to reduce adult height.

Comparison of Evolution of Aortic Root Dilation and Ghent Criteria in Preadolescents and Adolescents with and without Marfan Syndrome

OBJECTIVE

To determine whether the Ghent Criteria (2010) can be reliably used in evaluating preadolescents and adolescents for Marfan syndrome by comparing aortic growth, systemic scores, and anthropometric features in individuals with and without Marfan syndrome.

STUDY DESIGN

A retrospective chart review was completed for patients less than 15 years of age referred for Marfan syndrome. Comparisons were made between the first and last visit. Paired t tests were used to compare Ghent systemic scores. Wilcoxon rank-sum test were used to compare age, aortic root z scores, height z scores, and body mass index z scores. Recursive partitioning was used to identify combinations of factors to distinguish Marfan syndrome.

RESULTS

In total, 53 individuals met inclusion criteria (29 Marfan syndrome and 24 non-Marfan syndrome). Ghent systemic score increased in the Marfan syndrome group and declined in the non-Marfan syndrome. The non-Marfan syndrome group did not develop progressive aortic root dilation with age. Individuals with Marfan syndrome had higher median height z scores than non-Marfan syndrome, with no difference in median body mass index z score between groups. A combination of aortic root z score above 0.95 and Ghent systemic score above 3 was highly indicative of a Marfan syndrome diagnosis in children less than 15 years of age.

CONCLUSION

The Ghent criteria (2010) can be used to reliably exclude a diagnosis of Marfan syndrome in individuals less than 15 years of age. Genetic testing should be used as an aide in confirming or excluding the diagnosis of Marfan syndrome in individuals with an aortic root z score above 0.95 in combination with a Ghent systemic score above 3 at initial visit.

Extracellular matrix, regional heterogeneity of the aorta, and aortic aneurysm

Aortic aneurysm is an asymptomatic disease with dire outcomes if undiagnosed. Aortic aneurysm rupture is a significant cause of death worldwide. To date, surgical repair or endovascular repair (EVAR) is the only effective treatment for aortic aneurysm, as no pharmacological treatment has been found effective. Aortic aneurysm, a focal dilation of the aorta, can be formed in the thoracic (TAA) or the abdominal (AAA) region; however, our understanding as to what determines the site of aneurysm formation remains quite limited. The extracellular matrix (ECM) is the noncellular component of the aortic wall, that in addition to providing structural support, regulates bioavailability of an array of growth factors and cytokines, thereby influencing cell function and behavior that ultimately determine physiological or pathological remodeling of the aortic wall. Here, we provide an overview of the ECM proteins that have been reported to be involved in aortic aneurysm formation in humans or animal models, and the experimental models for TAA and AAA and the link to ECM manipulations. We also provide a comparative analysis, where data available, between TAA and AAA, and how aberrant ECM proteolysis versus disrupted synthesis may determine the site of aneurysm formation.

A review of aneurysm formation, swelling in blood vessel, in the aorta, examines distinctions between two forms of the condition and the role of proteins in the extracellular matrix which surrounds cells of the arterial wall. Rupture of aneurysms in the aorta, the body’s main artery, is a major cause of death. Researchers led by Zamaneh Kassiri at the University of Alberta, Edmonton, Canada, emphasize that aneurysms in the thoracic and abdominal regions of the aorta are distinct conditions with crucial differences in their causes. Disrupted production and assembly of the extracellular matrix and its proteins may underlie thoracic aneurysm formation. Factors triggering the degradation of extracellular matrix proteins may be more significant in abdominal aneurysms. Understanding the differing molecular mechanisms involved could help address the current lack of effective drug treatments for these dangerous conditions.

Identification of novel FBN1 variations implicated in congenital scoliosis

Congenital scoliosis (CS) is a form of scoliosis caused by congenital vertebral malformations. Genetic predisposition has been demonstrated in CS. We previously reported that TBX6 loss-of-function causes CS in a compound heterozygous model; however, this model can explain only 10% of CS. Many monogenic and polygenic CS genes remain to be elucidated. In this study, we analyzed exome sequencing (ES) data of 615 Chinese CS from the Deciphering Disorders Involving Scoliosis and COmorbidities (DISCO) project. Cosegregation studies for 103 familial CS identified a novel heterozygous nonsense variant, c.2649G>A (p.Trp883Ter) in FBN1. The association between FBN1 and CS was then analyzed by extracting FBN1 variants from ES data of 574 sporadic CS and 828 controls; 30 novel variants were identified and prioritized for further analyses. A mutational burden test showed that the deleterious FBN1 variants were significantly enriched in CS subjects (OR = 3.9, P = 0.03 by Fisher’s exact test). One missense variant, c.2613A>C (p.Leu871Phe) was recurrent in two unrelated CS subjects, and in vitro functional experiments for the variant suggest that FBN1 may contribute to CS by upregulating the transforming growth factor beta (TGF-β) signaling. Our study expanded the phenotypic spectrum of FBN1, and provided nove insights into the genetic etiology of CS.

CRISPR Diagnosis and Therapeutics with Single Base Pair Precision

Clustered regularly interspaced short palindromic repeats, or CRISPR, has been widely accepted as a versatile genome editing tool with significant potential for medical application. Reliable allele specificity is one of the most critical elements for successful application of this technology to develop high-precision therapeutics and diagnostics. CRISPR-based genome editing tools achieve high-fidelity distinction of single-base differences in target genomic loci by structural identification of CRISPR-associated (Cas) proteins and sequences of the guide RNAs. In this review, we describe the structural features of ribonucleoprotein complex formation by CRISPR proteins and guide RNAs that eventually recognize target DNA sequences. This structural understanding provides the basis for the recent applications of enhanced single-base precision genome editing technologies for effective distinction of specific alleles.

Atypical Neonatal Marfan Syndrome with p.Glu1073Lys Mutation of FBN1: the First Case in Korea

Neonatal Marfan syndrome (nMFS) is considered to be on the most severe end of the spectrum of type I fibrillinopathies. The common features of nMFS include ascending aortic dilatation, severe mitral and/or tricuspid valve insufficiency, ectopia lentis, arachnodactyly, joint contractures, crumpled ear, loose skin, and pulmonary emphysema.We describe a newborn male diagnosed with nMFS. He presented several atypical features, such as diaphragmatic eventration, severe hydronephrosis with hydroureter, and dilated cisterna magna. Molecular analysis revealed a missense mutation at nucleotide 3217 (c.3217G>A) in exon 26 of the fibrillin-1 (FBN1) gene, resulting in the substitution of a glutamate for a lysine at codon 1073 (E1073K) in the 12th calcium binding epidermal growth factor-like domain of the FBN1 protein. Here we report a rare case of Nmfs with several combined atypical features, such as diaphragmatic eventration, severe hydronephrosis with hydroureter, and dilated cisterna magna. Our report is the first atypical nMFS case with p.Glu1073Lys mutation of FBN1 in Korea and may help clinicians with the diagnosis and follow-up of atypical nMFS.

Marfan syndrome associated aortic disease in neonates and children: a clinical-morphologic review

BACKGROUND

Marfan syndrome (MFS) is a multisystem connective tissue disorder that can lead to aortic dilation requiring aortic root replacement. Neonatal MFS (nMFS) is a rare and severe form of MFS compared to classic MFS (cMFS). Aortic root histology in MFS is thought to demonstrate predominantly medial degeneration (MD) of a translamellar mucoid extracellular matrix accumulation (MEMA-T) vs. the intralamellar mucoid extracellular matrix accumulation (MEMA-I) seen in other aortopathies. The objective of this study was to describe the clinical and histopathologic features of nMFS and cMFS patients undergoing aortic root replacement.

METHODS

Children with MFS who underwent aortic root replacement between 2000 and 2012 at a single institution were included. Medical records including clinical details, aortic dimensions (Z scores), and histology including MD type were obtained. Statistics were descriptive with univariate analysis of age at surgery and type of MD.

RESULTS

Eleven patients, 3 (27%) with nMFS, were included. Root dilation at time of surgery was greater in nMFS compared to cMFS (Z=12.8 vs. 7.6, P=.005), and nMFS patients were younger at time of surgery (7.3 vs. 18.8 years, P=.002). Histology in the nMFS group demonstrated MEMA-I in one and no MD in two. In the cMFS group, there were three with MEMA-T, four with MEMA-I, and one with both types.

CONCLUSION

In summary, nMFS has earlier root dilation often in the absence of MD. Both forms of MD were present in our cohort, and there was no correlation between age at surgery and type of MD.

A FBN1 mutation association with different phenotypes of Marfan syndrome in a Chinese family

BACKGROUND

Previous studies demonstrated that patients with different FBN1 mutations often present more considerable phenotypic variation compared to different members of the related family carrying a same mutation. The purpose of our study was to identify pathogenic mutation and provide more information about genotype-phenotypic correlations in a large Chinese family with Marfan syndrome.

METHODS

15 related family members from a Chinese 4-generation pedigree with Marfan syndrome underwent physical, ophthalmologic, radiological and cardiovascular examinations. The propositus has De Bakey III aortic dissection and didn't fulfill the revised Ghent criteria for Marfan syndrome. Nine family members have ectopia lentis and their echocardiogram was normal. Five other family members have no evidence of Marfan syndrome. Genomic DNA was isolated from blood leukocytes. The exome sequencing was employed on the propositus, then the Sanger sequencing was conducted for mutation verification in other 14 participants of this family.

RESULTS

The causative mutation in FBN1 discovered in the propositus was a known heterozygous missense mutation, c.1633T>G (p.R545C), in exon 14 (NM 000138). This same mutation was also identified in all 9 ectopia lentis patients and one unaffected 8-year-old girl. However, the same mutation was not discovered in other 4 unaffected family members.

CONCLUSIONS

Our data enhance the information of genotype-phenotype correlation owing to FBN1 mutations. To our current knowledge, we firstly reported that the same FBN1 mutation, c. 1633C>T (Arg545Cys), was detected simultaneously in three different cardinal phenotypes (ectopia lentis, aortic dissection and unaffected) within one family. The unaffected girl with FBN1 mutation may presumably represent a rare case of nonpenetrance.

Periosteal osteosarcoma and Marfan's syndrome: A case report and literature review

Periosteal osteosarcoma (POS) is a rare primary malignant bone tumor arising from the surface of long bones. In addition, Marfan's syndrome (MFS) is an infrequent hereditary autosomal dominant connective tissue disorder with high penetrance and variable phenotypes, which primarily affects the ocular, skeletal and cardiovascular systems. The present study reported a case of POS and MFS co-occurring in a child. A 6-year-old girl with MFS presented with pain, swelling and deformity in the right thigh following a fall. The patient was diagnosed with a right femoral shaft fracture and underwent open internal fixation surgery at a local hospital. At 2 weeks following surgery, the patient's parents observed increased swelling in the right thigh and thus, revisited the clinic. X-ray examination revealed extensive osteotylus around the fracture site and the clinician decided to remove the internal fixation. Following removal of the implant, aggravated swelling and superficial venous engorgement were observed. The patient was then admitted to Nanfang Hospital, where magnetic resonance imaging was performed, which identified symptoms of an abnormal periosteal reaction with bone erosion, indicating POS. The patient underwent a wide resection of the tumor and the histopathological examination confirmed the diagnosis of POS. No recurrence was identified at 9 months postoperatively. In conclusion, the present case report may result in increased awareness of the possibility of malignant bone tumors in a hereditary patient with osteotylus overgrowth following fracture surgery; in addition, the present case indicated a possible correlation between POS and MFS.

MicroRNAs in congenital heart disease

Congenital heart disease (CHD) is a broad term which encompasses a spectrum of pathology, the most common phenotypes include atrial septal defects (ASDs), ventricular septal defects (VSDs), patent ductus arteriosus (PAD) and tetralogy of Fallot (TOF). The impact of CHD is profound and it is estimated to be responsible for over 40% of prenatal deaths. MicroRNAs (miRs) are small, highly conserved, non-coding RNAs which have complex roles in a variety of pathophysiological states. miRs are post-transcriptional negative regulators of gene expression. Individual miRs are known to exert effects in multiple target genes, therefore the altered expression of a single miR could influence an entire gene network resulting in complex pathological states. Recent evidences suggest a role in the dysregulation of miRs in CHD. Mouse knock out models have contributed to our knowledge base revealing specific patterns of miR expression in cardiovascular physiology and pathological states. Specific miRs necessary for embryonic cardiac development have been revealed. Dysregulation of these miRs has been shown to cause structural abnormalities in the heart and vasculature, thus furthering our understanding of the processes which result in CHD. These advances have provided new insight into the signalling pathways responsible for CHD. Furthermore, this new appreciation for miRs in the development of CHD has uncovered their potential for new therapeutic targets where modulated miR activity may reduce the burden of disease. Here, we summarize current knowledge of the cause-effect relationships of miRs in CHD and consider their potential as a therapeutic targets and biomarkers in this clinical setting.

Cardiac remodeling in the mouse model of Marfan syndrome develops into two distinctive phenotypes

Marfan syndrome (MFS) is a systemic disorder of connective tissue caused by mutations in fibrillin-1. Cardiac dysfunction in MFS has not been characterized halting the development of therapies of cardiac complication in MFS. We aimed to study the age-dependent cardiac remodeling in the mouse model of MFS FbnC1039G+/- mouse [Marfan heterozygous (HT) mouse] and its association with valvular regurgitation. Marfan HT mice of 2-4 mo demonstrated a mild hypertrophic cardiac remodeling with predominant decline of diastolic function and increased transforming growth factor-β canonical (p-SMAD2/3) and noncanonical (p-ERK1/2 and p-p38 MAPK) signaling and upregulation of hypertrophic markers natriuretic peptides atrium natriuretic peptide and brain natriuretic peptide. Among older HT mice (6-14 mo), cardiac remodeling was associated with two distinct phenotypes, manifesting either dilated or constricted left ventricular chamber. Dilatation of left ventricular chamber was accompanied by biochemical evidence of greater mechanical stress, including elevated ERK1/2 and p38 MAPK phosphorylation and higher brain natriuretic peptide expression. The aortic valve regurgitation was registered in 20% of the constricted group and 60% of the dilated group, whereas mitral insufficiency was observed in 40% of the constricted group and 100% of the dilated group. Cardiac dysfunction was not associated with the increase of interstitial fibrosis and nonmyocyte proliferation. In the mouse model fibrillin-1, haploinsufficiency results in the early onset of nonfibrotic hypertrophic cardiac remodeling and dysfunction, independently from valvular abnormalities. MFS heart is vulnerable to stress-induced cardiac dilatation in the face of valvular regurgitation, and stress-activated MAPK signals represent a potential target for cardiac management in MFS.

Inherited neurovascular diseases affecting cerebral blood vessels and smooth muscle

Neurovascular diseases are among the leading causes of mortality and permanent disability due to stroke, aneurysm, and other cardiovascular complications. Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and Marfan syndrome are two neurovascular disorders that affect smooth muscle cells through accumulation of granule and osmiophilic materials and defective elastic fiber formations respectively. Moyamoya disease, hereditary hemorrhagic telangiectasia (HHT), microcephalic osteodysplastic primordial dwarfism type II (MOPD II), and Fabry's disease are disorders that affect the endothelium cells of blood vessels through occlusion or abnormal development. While much research has been done on mapping out mutations in these diseases, the exact mechanisms are still largely unknown. This paper briefly introduces the pathogenesis, genetics, clinical symptoms, and current methods of treatment of the diseases in the hope that it can help us better understand the mechanism of these diseases and work on ways to develop better diagnosis and treatment.

Transforming growth factor-beta (TGF- β) signaling in paravertebral muscles in juvenile and adolescent idiopathic scoliosis

Most researchers agree that idiopathic scoliosis (IS) is a multifactorial disease influenced by complex genetic and environmental factors. The onset of the spinal deformity that determines the natural course of the disease, usually occurs in the juvenile or adolescent period. Transforming growth factors β (TGF-βs) and their receptors, TGFBRs, may be considered as candidate genes related to IS susceptibility and natural history. This study explores the transcriptional profile of TGF-βs, TGFBRs, and TGF-β responsive genes in the paravertebral muscles of patients with juvenile and adolescent idiopathic scoliosis (JIS and AIS, resp.). Muscle specimens were harvested intraoperatively and grouped according to the side of the curve and the age of scoliosis onset. The results of microarray and qRT-PCR analysis confirmed significantly higher transcript abundances of TGF-β2, TGF-β3, and TGFBR2 in samples from the curve concavity of AIS patients, suggesting a difference in TGF-β signaling in the pathogenesis of juvenile and adolescent curves. Analysis of TGF-β responsive genes in the transcriptomes of patients with AIS suggested overrepresentation of the genes localized in the extracellular region of curve concavity: LTBP3, LTBP4, ITGB4, and ITGB5. This finding suggests the extracellular region of paravertebral muscles as an interesting target for future molecular research into AIS pathogenesis.

Cardiovascular genomics: implications for acute and critical care nurses

As genomic health care becomes commonplace, nurses will be asked to provide genomic care in all health care settings including acute care and critical care. Three common cardiac conditions are reviewed, Marfan syndrome, bicuspid aortic valve, and hypertrophic cardiomyopathy, to provide acute care and critical care nurses with an overview of these pathologies through the lens of genomics and relevant case studies. This information will help critical care nursing leaders become familiar with genetics related to common cardiac conditions and prepare acute care and critical care nurses for a new phase in patient diagnostics, with greater emphasis on early diagnosis and recognition of conditions before sudden cardiac death.

Critical roles of miRNA-mediated regulation of TGFβ signalling during mouse cardiogenesis

AIMS

MicroRNAs (miRNAs) play critical roles during the development of the cardiovascular system. Blocking miRNA biosynthesis in embryonic hearts through a conditional gene inactivation approach led to differential cardiac defects depending on the Cre drivers used in different studies. The goal of this study is to reveal the cardiogenic pathway that is regulated by the miRNA mechanism at midgestation, a stage that has not been evaluated in previous publications.

METHODS AND RESULTS

We specifically inactivated Dicer1, which is essential for generation of functional mature miRNAs, in the myocardium by crossing cTnt-Cre mice with Dicer1(loxP) mice. cTnt-Cre efficiently inactivates target genes in cardiomyocytes at midgestation. All mutants died between E14.5 and E16.5 with severe myocardial wall defects, including reduced cell proliferation, increased cell death, and spongy myocardial wall. Expression of TGFβ type I receptor (Tgfbr1), which encodes the Type I receptor of TGFβ ligands, was up-regulated in mutant hearts. As expected, TGFβ activity was increased in Dicer1-inactivated hearts. Our further molecular analysis suggested that Tgfbr1 is a direct target of three miRNAs. Reducing TGFβ activities using a pharmacological inhibitor on in vitro cultured hearts, or through an in vivo genetic approach, partially rescued the cardiac defects caused by Dicer1 inactivation.

CONCLUSIONS

We show for the first time that TGFβ signalling is directly regulated by the miRNA mechanism during myocardial wall morphogenesis. Increased TGFβ activity plays a major role in the cardiac defects caused by myocardial deletion of Dicer1. Thus, miRNA-mediated regulation of TGFβ signalling is indispensable for normal cardiogenesis.

Role of TGF-β pathway polymorphisms in sporadic thoracic aortic aneurysm: rs900 TGF-β2 is a marker of differential gender susceptibility

Thoracic aortic aneurysm (TAA) is a progressive disorder involving gradual dilation of ascending and/or descending thoracic aorta with dissection or rupture as complications. It occurs as sporadic or defined syndromes/familial forms.Genetic, molecular and cellular mechanims of sporadic TAA forms are poorly characterized and known. Thus, our interest has been focused on investigating the role of genetic variants of transforming growth factor-β (TGF-β) pathways in TAA risk. On the other hand, no data on the role of genetic variants of TGF-β pathway in sporadic TAA exist until now. In addition, other cytokines, including IL-10, orchestrate TAA pathophysiology. Their balance determines the ultimate fate of the aortic wall as healing atherosclerosis or aneurysm formation. Thus, in this paper it was analyzed the role of ten polymorphisms of genes encoding TGF-β isoforms and receptors, and IL-10 in sporadic TAA. Our study included cases affected by sporadic TAA and two control groups. The most relevant finding obtained allows us to propose that rs900 TGF-β2 SNP is associated with sporadic TAA in women. This might open new perspectives for the analysis of sporadic TAA susceptibility factors and prevention.

A prospective, randomized, placebo-controlled, double-blind, multicenter study of the effects of irbesartan on aortic dilatation in Marfan syndrome (AIMS trial): study protocol

BACKGROUND

Cardiovascular complications are the leading cause of mortality and morbidity in Marfan syndrome (MFS), a dominantly inherited disorder caused by mutations in the gene that encodes fibrillin-1. There are approximately 18,000 patients in the UK with MFS. Current treatment includes careful follow-up, beta blockers, and prophylactic surgical intervention; however, there is no known treatment which effectively prevents the rate of aortic dilatation in MFS. Preclinical, neonatal, and pediatric studies have indicated that angiotensin receptor blockers (ARBs) may reduce the rate of aortic dilatation. This trial will investigate the effects of irbesartan on aortic dilatation in Marfan syndrome.

METHODS/DESIGN

The Aortic Irbesartan Marfan Study (AIMS) is an investigator-led, prospective, randomized, placebo-controlled, double-blind, phase III, multicenter trial. Currently, 26 centers in the UK will recruit 490 clinically confirmed MFS patients (aged ≥6 to ≤40 years) using the revised Ghent diagnostic criteria. Patients will be randomized to irbesartan or placebo. Aortic root dilatation will be measured by transthoracic echocardiography at baseline and annually thereafter. The primary outcome is the absolute change in aortic root diameter per year measured by echocardiography. The follow-up period will be a minimum of 36 months with an expected mean follow-up period of 48 months.

DISCUSSION

This is the first clinical trial to evaluate the ARB irbesartan versus placebo in reducing the rate of aortic root dilatation in MFS. Not only will this provide useful information on the safety and efficacy of ARBs in MFS, it will also provide a rationale basis for potentially lifesaving therapy for MFS patients.

TRIAL REGISTRATION

ISRCTN, 90011794.

Immunolocalisation of fibrillin microfibrils in the calf metacarpal and vertebral growth plate

Overgrowth of limbs and spinal deformities are typical clinical manifestations of Marfan syndrome (MFS) and congenital contractural arachnodactyly (CCA), caused by mutations of the genes encoding fibrillin-1 (FBN1) and fibrillin-2 (FBN2), respectively. FBN1 mutations are also associated with acromicric (AD) and geleophysic dysplasias (GD), and with Weill-Marchesani syndrome (WMS), which is characterised by short stature. The mechanisms leading to such abnormal skeletal growth and the involvement of the fibrillins are not understood. Postnatal longitudinal bone growth mainly occurs in the epiphyseal growth plate. Here we investigated the organisation of fibrillin microfibrils in the growth plate of the long bone and vertebra immunohistochemically. Fibrillin-1 was dual-immunostained with elastin, with fibrillin-2 or with collagen X. We report that fibrillin microfibrils are distributed throughout all regions of the growth plate, and that fibrillin-1 and fibrillin-2 were differentially organised. Fibrillin-1 was more abundant in the extracellular matrix of the resting and proliferative zones of the growth plate than in the hypertrophic zone. More fibrillin-2 was found in the calcified region than in the other regions. No elastin fibres were observed in either the proliferative or hypertrophic zones. This study indicates that, as fibrillin microfibrils are involved in growth factor binding and may play a mechanical role, they could be directly involved in regulating bone growth. Hence, mutations of the fibrillins could affect their functional role in growth and lead to the growth disorders seen in patients with MFS, CCA, AD, GD and WMS.

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.

Mutations in LRPAP1 are associated with severe myopia in humans

Myopia is an extremely common eye disorder but the pathogenesis of its isolated form, which accounts for the overwhelming majority of cases, remains poorly understood. There is strong evidence for genetic predisposition to myopia, but determining myopia genetic risk factors has been difficult to achieve. We have identified Mendelian forms of myopia in four consanguineous families and implemented exome/autozygome analysis to identify homozygous truncating variants in LRPAP1 and CTSH as the likely causal mutations. LRPAP1 encodes a chaperone of LRP1, which is known to influence TGF-β activity. Interestingly, we observed marked deficiency of LRP1 and upregulation of TGF-β in cells from affected individuals, the latter being consistent with available data on the role of TGF-β in the remodeling of the sclera in myopia and the high frequency of myopia in individuals with Marfan syndrome who characteristically have upregulation of TGF-β signaling. CTSH, on the other hand, encodes a protease and we show that deficiency of the murine ortholog results in markedly abnormal globes consistent with the observed human phenotype. Our data highlight a role for LRPAP1 and CTSH in myopia genetics and demonstrate the power of Mendelian forms in illuminating new molecular mechanisms that may be relevant to common phenotypes.

Villous papillary thyroid carcinoma: a variant associated with marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant hereditary disorder of connective tissue associated with perturbations in transforming growth factor β (TGF-β) biology, most often due to mutations in FBN1 gene that encodes fibrillin-1. To our knowledge, there is no known association of MFS with thyroid carcinoma. We report a 46-year-old man with known history of MFS who developed an unusual histological variant of papillary thyroid carcinoma. The tumor exhibited a widely invasive florid papillary growth pattern with prominent long villous fronds. Immunohistochemical and molecular analysis revealed a BRAF(V600E) mutation, evidence of aggressive biomarker expression (positivity for HBME-1, cytokeratin 19, galectin-3 and cyclin D1, and loss of p27), and changes associated with TGF-β-related epithelial-to-mesenchymal transition with active phospho-SMAD signaling. We introduce a unique histological pattern of papillary thyroid carcinoma that is associated with MFS. The combination of BRAF(V600E) mutation in the setting of altered TGF-β signaling and weak connective tissue integrity associated with MFS may cooperate and possibly be responsible to form this unique villous morphology with epithelial-to-mesenchymal transition and invasive growth.

Exon 47 skipping of fibrillin-1 leads preferentially to cardiovascular defects in patients with thoracic aortic aneurysms and dissections

Excessive activation of the transforming growth factor beta signaling pathway and disorganized cellular skeleton caused by genetic mutations are known to be responsible for the inherited thoracic aortic aneurysms and dissections (TAAD), a life-threatening vascular disease. To investigate the genotype-phenotype correlation, we screened genetic mutations of fibrillin-1 (FBN1), transforming growth factor-β receptor-1 (TGFBR1) and transforming growth factor-β receptor-2 (TGFBR2) for TAAD in 7 affected families and 22 sporadic patients. Of 19 potential mutations identified in FBN1, 11 appeared novel while the others were recurrent. Two mutations were detected in TGFBR2. Eight patients carried no mutation in either of these genes. Characterization of FBN1 c.5917+6T>C in transfected HEK293 cells demonstrated that it caused skipping of exon 47, leading to the loss of the 33th calcium binding epidermal growth factor-like domain associated with Marfan syndrome. Compared with exon 46, skipping of 47 did not cause patients ectopia lentis in all carriers. To correlate genotypes with phenotypes in different human ancestries, we reviewed the published mutational studies on FBN1 and found that the probability of cardiovascular defects were significantly increased in Chinese patients with premature termination codon or splicing mutations than those with missense mutations (91.7 % vs 54.2 %, P = 0.0307) or with noncysteine-involved point mutations than those with cysteine-involved mutations (88.9 % vs 33.3 %, P = 0.0131). Thus, we conclude that exon 47 skipping of FBN1 leads preferentially to cardiovascular defects and human ancestries influence genotype-phenotype correlation in TAAD.

Combination of familial Barlow's disease with bilateral axillary artery aneurysms in two brothers

We encountered two brothers with a combination of Barlow's disease and bilateral axillary artery aneurysms who were operated on during their third decade of life. A symmetrical form of true bilateral axillary artery aneurysms is uncommon. Recurrent mitral regurgitation was presented in the older brother with an endocardial defect in the left atrium, suggesting connective tissue fragility. A hereditary connective tissue disorder was strongly suspected because of the similar presentation and an unusual cluster of pathologies in siblings. Careful follow-up is required to detect recurrence of mitral regurgitation or aneurysm formation in other vessels.

TGFβ signaling and cardiovascular diseases

Transforming growth factor β (TGFβ) family members are involved in a wide range of diverse functions and play key roles in embryogenesis, development and tissue homeostasis. Perturbation of TGFβ signaling may lead to vascular and other diseases. In vitro studies have provided evidence that TGFβ family members have a wide range of diverse effects on vascular cells, which are highly dependent on cellular context. Consistent with these observations genetic studies in mice and humans showed that TGFβ family members have ambiguous effects on the function of the cardiovascular system. In this review we discuss the recent advances on TGFβ signaling in (cardio)vascular diseases, and describe the value of TGFβ signaling as both a disease marker and therapeutic target for (cardio)vascular diseases.

Loeys-Dietz syndrome: cardiovascular, neuroradiological and musculoskeletal imaging findings

Loeys-Dietz syndrome (LDS) is an increasingly recognized autosomal-dominant connective tissue disorder with distinctive radiological manifestations, including arterial tortuosity/aneurysms, craniofacial malformations and skeletal abnormalities. LDS exhibits a more aggressive course than similar disorders, such as Marfan or the vascular subtype of Ehlers-Danlos syndrome, with morbidity and mortality typically resulting from complications of aortic/arterial dissections. Early diagnosis, short-interval follow-up imaging and prophylactic surgical intervention are essential in preventing catastrophic cardiovascular complications. This review focuses on the cardiovascular, neuroradiological and musculoskeletal imaging findings in this disorder and recommendations for follow-up imaging.

[Overgrowth with and without obesity: clinical and molecular principles]

Somatic overgrowth is a complex and heterogeneous pathology that is only partially understood, although developments in molecular biology have allowed the discovery of the aetiological basis of some of these conditions. The differential diagnosis of a patient with a possible variant of normality, a chromosomopathy, a dysmorphic syndrome, a metabolic or an endocrine disease is essential. The initial clinical evaluation should include a correct anamnesis and physical examination, as well as complementary laboratory and image analyses that will help to orient the diagnosis. This should include a full blood counts and complete biochemical analysis, determinations of IGF-I, IGFBP-3, free T4, TSH and homocystinuria, as well as a karyotype and an X-ray of the left hand and wrist. These results should be very beneficial in orienting the diagnosis. Additional molecular studies should be performed when a monogenic disease is suspected. Cardiological, ophthalmological, skeletal, psychological and psychiatric studies should be performed if the clinical information and previously mentioned complementary studies so indicate. In this review, the aetiological basis and the diagnostic-therapeutic principles in the most common causes of overgrowth, will be analysed.

[Genotypic characterization of a Portuguese population of Marfan syndrome patients]

INTRODUCTION

The diagnosis of Marfan syndrome (MFS) depends on a multidisciplinary clinical evaluation. Molecular study to identify mutations in the FBN1 gene can establish a definitive diagnosis even with atypical or «incomplete» phenotypes and enable earlier diagnosis in asymptomatic patients.

OBJECTIVES

The aim of the present work was to evaluate the frequency and type of FBN1 gene mutations in a population of Marfan syndrome patients referred to a tertiary care center with cardiothoracic surgery.

METHODS

Our sample included 30 individuals with MFS (from 14 families), evaluated in cardiology, rheumatology and ophthalmology consultations. In all patients, DNA was extracted from a peripheral blood sample and mutation screening of the entire coding sequence of the FBN1 gene was then performed, using the polymerase chain reaction.

RESULTS

We identified 12 different mutations in the 14 families studied. Of these, only two had been previously described in the literature, while the other 10 were found to be new mutations; 36% of patients carried a missense mutation and 50% carried a mutation leading to a premature termination codon.

CONCLUSIONS

To the best of our knowledge this is the first genotypic description of Portuguese patients with MFS. In this study, we highlight the need for comprehensive clinical evaluation of these patients and the value of FBN1 mutation analysis in selected cases. By describing 10 new mutations, we have also helped broaden the spectrum of known FBN1 mutations associated with MFS.

The pathogenesis of aortopathy in Marfan syndrome and related diseases

Marfan syndrome is a systemic connective tissue disorder that is inherited in an autosomal-dominant pattern with variable penetrance. Although there are many clinical manifestations of this disease, the most life threatening are cardiovascular complications, including mitral valve prolapse and aortic root aneurysm. When the primary defect was discovered in the fibrillin-1 gene, it was hypothesized that mutations in fibrillin-1 resulted in a weakened and disordered elastic architecture. However, recent evidence has suggested that the Marfan syndrome is caused by more than just a disordered microfibril matrix. Interest was stimulated when it was discovered that fibrillin-1 mutations enhanced the release of sequestered latent transforming growth factor-beta, a well-described mediator of vascular remodeling. This article focuses on the pathophysiology of aortopathy in the Marfan syndrome and related diseases, with special emphasis on the role of transforming growth factor-beta in mediating the pathogenesis of this disease.

Critical appraisal of the revised Ghent criteria for diagnosis of Marfan syndrome

Marfan syndrome (MFS) is a connective tissue disorder with major features in cardiovascular, ocular and skeletal systems. Recently, diagnostic criteria were revised where more weight was given to the aortic root dilatation. We applied the revised Marfan nosology in an established adult Marfan population to define practical repercussions of novel criteria for clinical practice and individual patients. Out of 180 MFS patients, in 91% (n = 164) the diagnosis of MFS remained. Out of 16 patients with rejected diagnosis, four patients were diagnosed as MASS (myopia, mitral valve prolapse, borderline non-progressive aortic root dilatation, skeletal findings and striae) phenotype, three as ectopia lentis syndrome and in nine patients no alternative diagnosis was established. In 13 patients, the diagnosis was rejected because the Z-score of the aortic root was <2, although the aortic diameter was larger than 40 mm in six of them. In three other patients, the diagnosis of MFS was rejected because dural ectasia was given less weight in the revised nosology. Following the revised Marfan nosology, the diagnosis of MFS was rejected in 9% of patients, mostly because of the absence of aortic root dilatation defined as Z-score ≥2. Currently used Z-scores seem to underestimate aortic root dilatation, especially in patients with large body surface area (BSA). We recommend re-evaluation of criteria for aortic root involvement in adult patients with a suspected diagnosis of MFS.

Diverging alternative splicing fingerprints in the transforming growth factor-β signaling pathway identified in thoracic aortic aneurysms

Impaired regulation of the transforming growth factor-β (TGFβ) signaling pathway has been linked to thoracic aortic aneurysm (TAA). Previous work has indicated that differential splicing is a common phenomenon, potentially influencing the function of proteins. In the present study we investigated the occurrence of differential splicing in the TGFβ pathway associated with TAA in patients with bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV). Affymetrix human exon arrays were applied to 81 intima/media tissue samples from dilated (n = 51) and nondilated (n = 30) aortas of TAV and BAV patients. To analyze the occurrence of alternative splicing in the TGFβ pathway, multivariate techniques, including principal component analysis and OPLS-DA (orthogonal partial least squares to latent structures discriminant analysis), were applied on all exons (n = 614) of the TGFβ pathway. The scores plot, based on the splice index of individual exons, showed separate clusters of patients with both dilated and nondilated aorta, thereby illustrating the potential importance of alternative splicing in TAA. In total, differential splicing was detected in 187 exons. Furthermore, the pattern of alternative splicing is clearly differs between TAV and BAV patients. Differential splicing was specific for BAV and TAV patients in 40 and 86 exons, respectively, and splicings of 61 exons were shared between the two phenotypes. The occurrence of differential splicing was demonstrated in selected genes by reverse transcription-polymerase chain reaction. In summary, alternative splicing is a common feature of TAA formation. Our results suggest that dilatation in TAV and BAV patients has different alternative splicing fingerprints in the TGFβ pathway.

Multiple self-healing squamous epithelioma is caused by a disease-specific spectrum of mutations in TGFBR1

Multiple self-healing squamous epithelioma (MSSE), also known as Ferguson-Smith disease (FSD), is an autosomal-dominant skin cancer condition characterized by multiple squamous-carcinoma-like locally invasive skin tumors that grow rapidly for a few weeks before spontaneously regressing, leaving scars. High-throughput genomic sequencing of a conservative estimate (24.2 Mb) of the disease locus on chromosome 9 using exon array capture identified independent mutations in TGFBR1 in three unrelated families. Subsequent dideoxy sequencing of TGFBR1 identified 11 distinct monoallelic mutations in 18 affected families, firmly establishing TGFBR1 as the causative gene. The nature of the sequence variants, which include mutations in the extracellular ligand-binding domain and a series of truncating mutations in the kinase domain, indicates a clear genotype-phenotype correlation between loss-of-function TGFBR1 mutations and MSSE. This distinguishes MSSE from the Marfan syndrome-related disorders in which missense mutations in TGFBR1 lead to developmental defects with vascular involvement but no reported predisposition to cancer.

Comparison of the background, needs, and expectations for genetic counseling of adults with experience with Down syndrome, Marfan syndrome, and neurofibromatosis

We describe an analysis of the responses of 605 adults with experience with Down syndrome, Marfan syndrome, or neurofibromatosis (NF) to the BNE Scale, a scale specifically designed to assess the background, needs, and expectations (BNE) of genetic counseling patients. Significant group differences were found. Specifically, the respondents in the Down syndrome group reported more favorable beliefs about the condition and the availability of social support than the respondents in the other groups. Respondents in the NF group reported more unsureness about their condition and a greater need for genetic information than members of the other groups. Notably, having positive feelings about the condition was negatively correlated with support group interest for respondents of the Marfan syndrome group (r = -0.159, P < 0.01). Having an affected child was associated with interest in health provider input (t = -3.4; P = 0.001) and the desire to talk about psychosocial issues (t = -2.9; P = 0.004). However, previous experience with genetic counseling was not found to affect BNE. These results support the usefulness of the BNE Scale to compare the BNE of patient groups, as well as provide important insight into the BNE of individuals seeking counseling about Down syndrome, Marfan syndrome, and NF.

Genetics of obesity and overgrowth syndromes

Childhood overweight and obesity is highly prevalent within society. In the majority of individuals, weight gain is the result of exposure to an 'obesogenic' environment, superimposed on a background of genetic susceptibility brought about by evolutionary adaptation. These individuals tend to be tall in childhood with a normal final adult height, as opposed to those who have an underlying monogenic cause where short stature is more common (although not universal). Identifying genetic causes of weight gain, or tall stature and overgrowth, within this setting can be extremely problematic and yet it is imperative that clinicians remain alert, as identification of a genetic diagnosis has major implications for the individual, family and potential offspring. Alongside this, the recognition of new genetic mutations in this area is furthering our knowledge on the important mechanisms that regulate childhood growth and body composition. This review describes the genetic syndromes associated with obesity and overgrowth.

Hereditary disorders of connective tissue: a guide to the emerging differential diagnosis

PURPOSE

To create a practical desk reference for clinicians focused on the differential diagnosis of individuals presenting with features that suggest an inherited disorder of connective tissue.

METHODS

We searched the medical literature for distinct clinical entities that shared clinical features with Marfan syndrome and other classical inherited disorders of connective tissue.

RESULTS

Thirty-six distinct heritable disorders of connective tissue were identified that have overlapping features. These disorders were organized into two matrices according to clinical characteristics and according to causative genes.

CONCLUSIONS

A broad differential diagnosis is emerging for individuals presenting with features suggestive of altered connective tissue. Recent advances in molecular genetics have aided in the delineation of these disorders.