Marfan syndrome in the third Millennium

An integration into the diagnostic workflow in a pediatric patient suspected of having Marfan syndrome

Background

The genetic approach to Marfan syndrome (MFS) has evolved over the last few decades, as has our understanding of the variants’ potential structural and functional consequences. It has been proposed that next-generation sequencing be used to improve genetic diagnosis and patient management. To this end, we used a targeted NGS custom panel to perform genetic analysis in a patient with MFS and his or her family members.

Case presentation

Here, we describe a novel germ-line heterozygous missense variant (transversion c.5371 T > A) found in exon 43 of the FBN1 gene of a patient (proband) with MFS. FBN1 (ENSG0000166147) and TGFB2 (ENSG0000166147) were included in a targeted sequencing panel for MFS (ENSG0000163513). This new variant c.5371 T > A was identified only in the proband, not in unaffected family members or healthy controls.

Conclusions

Given the massive amount of data generated by gene panel analysis, clinical interpretation of genetic variants may become more difficult. As a result, 3D modeling and multidisciplinary approaches should be used in the analysis and annotation of observed variants. The analysis of the protein’s conformational structure in relation to the identified variant could provide useful information. These data can be used to classify observed variants (pathogenic vs non-pathogenic) linked to the MFS phenotype, as well as to track disease progression and potential target treatments.

Classification and Interpretation for 11 FBN1 Variants Responsible for Marfan Syndrome and Pre-implantation Genetic Testing (PGT) for Two Families Successfully Blocked Transmission of the Pathogenic Mutations

Background: The lifespan of Marfan Syndrome (MFS) patients is shortened, especially in patients without early diagnostics, preventive treatment, and elective surgery. Clinically, MFS diagnosis is mainly dependent on phenotypes, but for children, sporadic cases, or suspicious MFS patients, molecular genetic testing, and mainly FBN1 mutation screening, plays a significant role in the diagnosis of MFS. PGT-M gives couples that had a family history of monogenic disorders the opportunity to avoid the occurrence of MFS.

Methods: In this study, 11 families with MFS were recruited and complete clinical features were collected. Variants were classified and interpreted through pedigree analysis according to guidelines. Two families chose to undergo PGT-M; 16 blastocysts were biopsied and amplified. Haplotype analysis was performed to deduce the embryo’s genotype by using single nucleotide polymorphisms (SNPs) identified in each sample.

Results: We identified 11 potential disease-causing FBN1 variants, six of which are novel. All variants were assessed with prediction tools to assess mutation pathogenicity, population databases to evaluate population allele frequency, literature databases to identify whether the variant had been reported in MFS patients, and multiple sequence alignment to carry out conservative analysis. Finally, nine variants were classified as likely pathogenic/pathogenic variants. Among 11 variants, eight variants were missense, and seven of them were located in the Ca-binding EGF-like motifs, moreover, half of them substituted conserved Cysteine residues. We also identified a splice site variant, a frameshift variant, and a synonymous variant. There are two variants that are de novo variants. PGT-M helped two MFS families give birth to a healthy baby not carrying the FBN1 mutation.

Conclusions: In the present study, the FBN1 mutation spectrum was enriched, and may help further elucidate the pathogenesis, benefiting clinical diagnosis and management of MFS. We make use of a reliable PGT-M method for the successful birth of healthy babies to two MFS families.

Proof-of-Concept: Antisense Oligonucleotide Mediated Skipping of Fibrillin-1 Exon 52

Marfan syndrome is one of the most common dominantly inherited connective tissue disorders, affecting 2–3 in 10,000 individuals, and is caused by one of over 2800 unique FBN1 mutations. Mutations in FBN1 result in reduced fibrillin-1 expression, or the production of two different fibrillin-1 monomers unable to interact to form functional microfibrils. Here, we describe in vitro evaluation of antisense oligonucleotides designed to mediate exclusion of FBN1 exon 52 during pre-mRNA splicing to restore monomer homology. Antisense oligonucleotide sequences were screened in healthy control fibroblasts. The most effective sequence was synthesised as a phosphorodiamidate morpholino oligomer, a chemistry shown to be safe and effective clinically. We show that exon 52 can be excluded in up to 100% of FBN1 transcripts in healthy control fibroblasts transfected with PMO52. Immunofluorescent staining revealed the loss of fibrillin 1 fibres with ~50% skipping and the subsequent re-appearance of fibres with >80% skipping. However, the effect of exon skipping on the function of the induced fibrillin-1 isoform remains to be explored. Therefore, these findings demonstrate proof-of-concept that exclusion of an exon from FBN1 pre-mRNA can result in internally truncated but identical monomers capable of forming fibres and lay a foundation for further investigation to determine the effect of exon skipping on fibrillin-1 function.

Elastic fibers during aging and disease

Elastic fibers are essential constituents of the extracellular matrix of higher vertebrates and endow several tissues and organs including lungs, skin and blood vessels with elasticity and resilience. During the human lifespan, elastic fibers are exposed to a variety of enzymatic, chemical and biophysical influences, and accumulate damage due to their low turnover. Aging of elastin and elastic fibers involves enzymatic degradation, oxidative damage, glycation, calcification, aspartic acid racemization, binding of lipids and lipid peroxidation products, carbamylation and mechanical fatigue. These processes can trigger an impairment or loss of elastic fiber function and are associated with severe pathologies. There are different inherited or acquired pathological conditions, which influence the structure and function of elastic fibers and microfibrils predominantly in the cardiorespiratory system and skin. Inherited elastic-fiber pathologies have a direct or indirect impact on elastic-fiber formation due to mutations in the fibrillin genes (fibrillinopathies), in the elastin gene (elastinopathies) or in genes encoding proteins that are associated with microfibrils or elastic fibers. Acquired elastic-fiber pathologies appear age-related or as a result of multiple factors impairing tissue homeostasis. This review gives an overview on the fate of elastic fibers over the human lifespan in health and disease.

A nonsense variant in FBN1 caused autosomal dominant Marfan syndrome in a Chinese family: a case report

Background

Marfan syndrome (MFS) is a common autosomal dominant inherited disease, and the occurrence rate is around 0.1–0.2‰. The causative variant of FNB1 gene accounts for approximately 70–80% of all MFS cases. In this study, we found a heterozygous c.3217G > T (p.Glu1073*) nonsense variant in the FBN1 gene. This finding extended the variant spectrum of the FBN1 gene and will provide a solution for patients to bear healthy offspring by preimplantation genetic testing or prenatal diagnosis.

Case presentation

The patient was treated due to tachycardia during excitement in a hospital. Echocardiography showed dilatation of the ascending aorta and main pulmonary artery, mitral regurgitation (mild), tricuspid regurgitation (mild), and abnormal left ventricular filling. Electrocardiograph showed sinus rhythm. In addition, flutters of shadows in front of his eyes and vitreous opacity were present in the patient. Genomic DNA was extracted from peripheral blood samples from members of the family and 100 unrelated controls. Potential variants were screened out by next-generation sequencing and confirmed by MLPA & Sanger sequencing. Real-time fluorescence quantitative PCR (RT-qPCR) was performed to detect the relative mRNA quantitation in the patient. A heterozygous nonsense variant c.3217G > T of the FBN1 gene, which resulted in p. Glu1073Term, was identified in both patients. Only wild type bases were found in the cDNA sequence of the patient. Real-time fluorogenic quantitative PCR results showed that the relative expression level of FBN1 cDNA in the patient was only about 21% compared to that of normal individuals. This variant c.3217G > T of the FBN1 gene introduces a Stop codon in the cb-EGF12 domain. We speculated that a premature translational-termination codon (PTC) was located in the mRNA and the target mRNA was disintegrated through a process known as nonsense-mediated mRNA decay (NMD), which led to a significant decrease of the fibrillin-1 protein, eventually causing clinical symptoms in the patient.

Conclusions

In this study, we found a heterozygous c.3217G > T (p.Glu1073*) nonsense variant in the FBN1 gene, which eventually led to Marfan syndrome in a Chinese family.

Missed diagnoses: Clinically relevant lessons learned through medical mysteries solved by the Undiagnosed Diseases Network

BACKGROUND

Resources within the Undiagnosed Diseases Network (UDN), such as genome sequencing (GS) and model organisms aid in diagnosis and identification of new disease genes, but are currently difficult to access by clinical providers. While these resources do contribute to diagnoses in many cases, they are not always necessary to reach diagnostic resolution. The UDN experience has been that participants can also receive diagnoses through the thoughtful and customized application of approaches and resources that are readily available in clinical settings.

METHODS

The UDN Genetic Counseling and Testing Working Group collected case vignettes that illustrated how clinically available methods resulted in diagnoses. The case vignettes were classified into three themes; phenotypic considerations, selection of genetic testing, and evaluating exome/GS variants and data.

RESULTS

We present 12 participants that illustrate how clinical practices such as phenotype-driven genomic investigations, consideration of variable expressivity, selecting the relevant tissue of interest for testing, utilizing updated testing platforms, and recognition of alternate transcript nomenclature resulted in diagnoses.

CONCLUSION

These examples demonstrate that when a diagnosis is elusive, an iterative patient-specific approach utilizing assessment options available to clinical providers may solve a portion of cases. However, this does require increased provider time commitment, a particular challenge in the current practice of genomics.

<p>Ocular Manifestations and Biometrics in Marfan’s Syndrome from Eastern Nepal</p>

Purpose

To evaluate the ocular characteristics of Marfan’s syndrome (MFS) fulfilling the revised Ghent-2 nosology in Eastern Nepal.

Materials and Methods

A hospital-based observational and cross-sectional study was conducted. Ocular manifestations and biometrics were incorporated. Patients were subdivided into adults (16 years or older) and children (5–15 years). Ocular biometric parameters consisted of values of refractive error, keratometry readings, anterior chamber depth (ACD), central corneal thickness (CCT), lens thickness (LT) and axial length (AL).

Results

A total of 34 eyes of 17 patients with MFS were included, where 32 eyes were phakic. Mean age of the study participants was 14.5 ± 9.1 years. The mean best corrected visual acuity (BCVA) of phakic eyes was 0.99 ± 0.82 LogMAR. Myopia greater than −3 diopters (D) was present in 28/34 (82.35%) eyes. The average spherical equivalent was −12.34 ± 8.85 D. Ectopia lentis (EL) was present in 24/32 (75%) eyes where superonasal was the most common subluxation in 10/24 (41.7%) eyes. AL was longer in adults 26.54 ± 4.42 mm compared to 25.21 ± 1.93 mm in children. Likewise, LT in adults was 4.9 ± 0.70 mm and 4.40 ± 0.59 mm in pediatric participants. Flat corneas were noted in both the groups with an average of 41.53 ± 2.21 D. The mean CCT and ACD were 524.62 ± 21.74 μm and 3.64 ± 0.80 mm, respectively. There was a negative association between the AL and the average corneal curvature (K_med, correlation coefficient −0.11, p=0.54).

Conclusion

Myopia is the foremost ocular involvement with significant visual disability in MFS. Though, AL and corneal curvature are not included in the revised Ghent-2 nosology, we strongly recommend these parameters to be considered during ophthalmic evaluation in suspected and diagnosed cases of MFS in the absence of genetic testing.

Marfan syndrome revisited: From genetics to the clinic

Marfan syndrome is an autosomal dominant connective tissue disease with an estimated incidence of 1 in 5000 individuals. In 90% of cases it is caused by mutations in the gene for fibrillin-1, the main constituent of extracellular microfibrils. Studies on animal models of Marfan syndrome have revealed that fibrillin-1 mutations interfere with local TGF-β signaling, in addition to impairing tissue integrity. The cardinal features involve the cardiovascular, ocular and skeletal systems. The diagnosis of Marfan syndrome is made according to the revised Ghent nosology. Early identification and appropriate management are critical for patients with Marfan syndrome, who are prone to the life-threatening cardiovascular complications of aortic aneurysms and aortic dissection. The standard treatment includes prophylactic beta-blockers in order to slow down dilation of the ascending aorta, and prophylactic aortic surgery. The success of current medical and surgical treatment of aortic disease in Marfan syndrome has substantially improved mean life expectancy, extending it above 72 years. This review aims to provide an overview of this hereditary disorder.

Identification of a novel mutation in FBN1 in a Chinese family with inherited ectopia lentis by targeted NGS

AIMS

To diagnose a Chinese family with inherited ectopia lentis in a genetic method and analyze the genotype-phenotype correlation.

METHODS

The phenotype of each family member was identified by detailed clinical examination. We used targeted next generation sequencing (NGS) to identify mutations in FBN1 in an efficient and accurate way. The mutation in FBN1 was confirmed in all affected family members by Sanger sequencing.

RESULTS

A novel mutation c.385T>C (p.C129R) in FBN1 was identified in the proband by targeted NGS. The mutation was segregated in all affected family members and contributes to specific disease phenotypes. The same mutation was not found in other unaffected relatives and a 100 normal random population by Sanger sequencing.

CONCLUSIONS

Our study reports a novel mutation in FBN1 in a Chinese family and to diagnose this family as Marfan syndrome, we also expand the genotype-phenotype correlation of this disease.

Mitral valve prolapse and Marfan syndrome

Marfan syndrome is a multisystemic genetic condition affecting connective tissue. It carries a reduced life expectancy, largely dependent on cardiovascular complications. More common cardiac manifestations such as aortic dissection and aortic valve incompetence have been widely documented in the literature. Mitral valve prolapse (MVP), however, has remained poorly documented. This article aims at exploring the existing literature on the pathophysiology and diagnosis of MVP in patients with Marfan syndrome, defining its current management and outlining the future developments surrounding it.

Genome-wide association analysis for chronic venous disease identifies EFEMP1 and KCNH8 as susceptibility loci

Chronic venous disease (CVD) is a multifactorial condition representing one of the most common disorders among populations of Western countries. The heritability of about 17% suggests genetic risk factors in CVD etiology. However, so far the genetic causes are unknown. We undertook the hitherto first genome-wide association study (GWAS) for CVD, analyzing more than 1.93 M SNPs in 4,942 German individuals, followed by replication in two independent German data sets. The combined analysis of discovery and replication stages (2,269 cases and 7,765 controls) yielded robust associations within the two genes EFEMP1 and KCNH8 (rs17278665, rs727139 with P < 5 × 10⁻⁸), and suggestive association within gene SKAP2 (rs2030136 with P < 5 × 10⁻⁷). Association signals of rs17278665 and rs727139 reside in regions of low linkage disequilibrium containing no other genes. Data from the ENCODE and Roadmap Epigenomics projects show that tissue specific marks overlap with the variants. SNPs rs17278665 and rs2030136 are known eQTLs. Our study demonstrates that GWAS are a valuable tool to study the genetic component of CVD. With our approach, we identified two novel genome-wide significant susceptibility loci for this common disease. Particularly, the extracellular matrix glycoprotein EFEMP1 is promising for future functional studies due to its antagonistic role in vessel development and angiogenesis.

A novel FBN1 missense mutation (p.C102Y) associated with ectopia lentis syndrome in a Chinese family

AIM

To characterize the disease-causing mutations in a Chinese family with ectopia lentis syndrome (ELS).

METHODS

Patients and their family members were given complete physical, ophthalmic, and cardiovascular examinations. Genomic DNA samples were extracted from the peripheral blood of the pedigree members and 100 healthy controls. Mutation screening was performed in the fibrillin-1 (FBN1) gene by bi-directional sequencing of the amplified products. The mutation was analyzed using two bioinformatics methods.

RESULTS

A novel heterozygous c.305G>A mutation in exon 3 of FBN1 was detected. As a result of this change, a highly conserved cysteine residue was replaced by a tyrosine residue (p.C102Y). Another mutation was found in the same exon (c.303T>C), which did not change the amino acid sequence. Both mutations were discovered in each affected individual, but not in the unaffected family members, or in 100 ethnically matched controls. A bioinformatics analysis predicted that mutation p.C102Y would affect protein function.

CONCLUSION

In the first epidermal growth factor-like module, we identified a novel FBN1 mutation (p.C102Y), which caused ELS in the family. Our study presented a unique phenotype, including some distinct ophthalmic findings, such as hypoplasia of the iris and anisometropia. Our results expanded the mutation spectrum of FBN1 and enriched the overall knowledge of genotype-phenotype correlations due to FBN1 mutations.

Two novel mutations of FBN1 in Jordanian patients with Marfan syndrome

Marfan syndrome is an autosomal dominant inheritance disorder with a 1/5000-live-birth prevalence. More than 3000 mutations have been characterized thus far in the FBN1 gene. The goal of this study is to facilitate Marfan syndrome diagnosis in Jordanian patients using a molecular genetic testing. All of the 65 coding exons and flanking intronic sequences of the FBN1 gene were amplified using polymerase chain reaction and were subjected to sequencing in five unrelated Jordanian patients suspected of having Marfan syndrome. Four different mutations were identified, including two novel mutations: the c.1553dupG frame-shift (p.Tyr519Ilefs*14) and the c.6650G>A (p.Cys2217Tyr) missense mutations. Two other missense mutations, c.2243G>A (p.Cys748Tyr) and c.2432G>A (p.Cys811Tyr), have been previously detected. Patient number five was heterozygous for the synonymous substitution variant c.1875T>C (p.Asn625Asn; rs#25458). Additionally, eight variants in the intronic sequence of the FBN1 gene were identified, of which the c.2168-46A>G mutation was a new variant. The data provide molecular-based evidence linking Marfan syndrome to pathogenic mutations in the FBN1 gene among Jordanians for the first time. Thus, our results will contribute to the better management of the disease using molecular tools and will help in genetic counseling of the patients' families.

C596G mutation in FBN1 causes Marfan syndrome with exotropia in a Chinese family

PURPOSE

To screen mutations in the fibrillin-1 (FBN1) gene in a Chinese family with autosomal dominant Marfan syndrome (MFS).

METHODS

Patients and unaffected family members were given ophthalmic, cardiovascular, and physical examinations with a 5-year follow-up. Genomic DNA was extracted from the leukocytes of venous blood from all patients and their relatives. The entire coding region of the FBN1gene was screened with an ABI 9700 GeneAmp PCR System. The mutation identified was screened in 100 healthy and ethnically unrelated Chinese individuals.

RESULTS

Mutation screening in FBN1 identified a T>G transition at position c.1786 in exon 14, leading to substitution of cysteine for glycine at codon 596 (C596G) in this four-generation Chinese family. The C596G mutation was associated with the disease phenotypes in all six patients but not found in 14 unaffected family members or the 100 ethnically unrelated and healthy controls.

CONCLUSIONS

A C596G mutation in FBN1 was identified in a Chinese family with MFS. Our results expand the spectrum of FBN1 mutations and contribute to the understanding of the role of FBN1 in the pathogenesis of Marfan syndrome.

Novel mutation in FBN1 causes ectopia lentis and varicose great saphenous vein in one Chinese autosomal dominant family

PURPOSE

To identify genetic defects in a Chinese family with ectopia lentis (EL) and varicose great saphenous vein (GSV) and to analyze the correlations between phenotype and genotype.

METHODS

Twenty-two (12 affected subjects and ten unaffected subjects) among 53 members of a Chinese family underwent complete physical, ophthalmic, and cardiovascular examinations. Genomic DNA was extracted from the leukocytes in the subjects' peripheral blood. A minimum interval was achieved with linkage study and haplotype analysis. All 65 exons and the flanking intronic regions of fibrillin-1 (FBN1) were amplified with PCR and screened for mutations with direct Sanger sequencing. Molecular modeling was analyzed in an in silico study.

RESULTS

The linkage study showed a strong cosegregation signal on chromosome 15. The non-parametric linkage analysis yielded a maximum score of 29.1(p<0.00001), and the parametric logarithm of the odds (LOD) score was 3.6. The minimum interval of the shared haplotype was rs1565863-rs877228. The best candidate gene in this region was FBN1. A novel mutation, c.3928G>A, p.1310G>S in exon 31, was identified in FBN1 and cosegregated well in the family. We applied molecular modeling to show the effect of this mutation on the fibrillin-1 structure. The mutation significantly distorts the calcium coordination, decreases the binding of the calcium ion in that motif, and affects the local calcium-binding epidermal growth factor (cbEGF) interface that depends on Ca binding.

CONCLUSIONS

FBN1-associated fibrillinopathies are a group of diseases with dynamic phenotype changes. Novel mutation p.1310G>S was first reported to cause Marfan syndrome (MFS). Our results expand the mutation spectrum in FBN1 and enhance our knowledge of genotype-phenotype correlations underlying FBN1 mutations.

Trigeminal neuralgia in a patient with Marfan syndrome: case report

Marfan syndrome can demonstrate tortuous and elongated intracranial arteries. However, these arteries rarely cause neurovascular compression resulting in hemifacial spasm or trigeminal neuralgia. The authors report a 33-year-old woman who was diagnosed as Marfan syndrome, suffered from trigeminal neuralgia. Magnetic resonance (MR) angiography showed tortuous and elongated left vertebral artery (VA). The coronal section of three dimensional (3D) MR cisternography with contrast enhancement showed that the left trigeminal nerve was compressed from underneath by the tortuous and elongated left VA. After successful surgery of microvascular decompression, the patient’s symptom resolved and no recurrence was encountered. Neurosurgeons should not only be aware of hemifacial spasm but also of trigeminal neuralgia caused by elongated vessels in a patient with Marfan syndrome, although it is an extremely rare condition. In addition, offending vessel is not atherosclerotic in younger patients unlike usual cases of trigeminal neuralgia. Thus, microvascular decompression can be easier than usual cases. Care should be taken to prevent arterial dissection during transposition by using some technical tips.

Identification of a novel FBN1 gene mutation in a large Pakistani family with Marfan syndrome

PURPOSE

To describe a novel mutation in the fibrillin-1 (FBN1) gene in a large Pakistani family with autosomal dominant Marfan syndrome (MFS).

METHODS

Blood samples were collected of 11 family members affected with Marfan syndrome, and DNA was isolated by phenol-extraction. The coding exons of FBN1 were analyzed by polymerase chain reaction (PCR) and direct sequencing. One hundred-thirty controls were screened for a mutation in the FBN1 gene that was identified in this family by restriction fragment length polymorphism (RFLP) analysis.

RESULTS

A novel heterozygous missense mutation c.2368T>A; p.Cys790Ser was observed in exon 19. This mutation substitutes a highly conserved cysteine residue by serine in a calcium binding epidermal growth factor-like domain (cbEGF) of FBN1. This mutation was present in all affected members and absent from unaffected individuals of the family in addition to 130 healthy Pakistani controls. Interestingly all affected family members presented with ectopia lentis, myopia and glaucoma, but lacked the cardinal cardiovascular features of MFS.

CONCLUSIONS

This is a first report of a mutation in FBN1 in MFS patients of Pakistani origin. The identification of a FBN1 mutation in this family confirms the diagnosis of MFS patients and expands the worldwide spectrum of FBN1 mutations.

Identification and study of a FBN1 gene mutation in a Chinese family with ectopia lentis

PURPOSE

To identify the mutation in the fibrillin-1 gene (FBN1) in a Chinese family with ectopia lentis (EL) and to predict the structural and functional consequences of the mutation.

METHODS

Patients and family members were given complete physical, ophthalmic, and cardiovascular examinations. Genomic DNA was extracted from leukocytes of venous blood of three affected and three unaffected individuals in the family, and 100 healthy controls. All 65 coding exons and their flanking intronic boundaries of FBN1 were amplified in the proband by polymerase chain reaction, followed by direct sequencing. The mutation identified in the proband was screened for in other family members and 100 healthy controls by direct sequencing. Protein conservation analysis was performed in seven species using an online ClustalW tool. Protein structure was modeled based on the Protein data bank and mutated in PyMOL 1.1r1 to predict the structural and functional consequences of the mutation.

RESULTS

A heterozygous c.2262A>G change in exon 18 of FBN1 was detected in the proband, which resulted in the substitution of tyrosine by cysteine at codon 754 (p.Y754C). This mutation was also present in the affected family members, but absent in other unaffected family members and 100 healthy controls. The mutant residue, located in the calcium binding epidermal growth factor-like7 domain, was highly conserved among mammalian species. The mutation could probably affect the disulfide bond formation of the domain and calcium binding of the adjacent domain, which would induce a critical functional change of the domain itself and neighboring domains.

CONCLUSIONS

We indentified a p.Y754C mutation in FBN1, which is the causative mutation for EL in this family. This missense mutation introduced an additional cysteine residue by substitution of a highly conserved tyrosine residue within the cbEGF-like7 module.

Identification of a novel FBN1 mutation in a Chinese family with isolated ectopia lentis

PURPOSE

To identify the genetic defect in a Chinese family with autosomal dominant inherited ectopia lentis.

METHODS

twenty-one family members, including seven patients underwent general physical and fully ophthalmic examinations. Genomic DNA was extracted from leukocytes of venous blood of these individuals in the family. Polymerase chain reaction (PCR) amplification and direct sequencing of all 65 coding exons of the fibrillin-1 gene (FBN1) were analyzed.

RESULTS

Mutation screening in FBN1 identified a T>C transition at nucleotide position c,1759 leading to substitution of Cysteine for Arginine at codon 587 (C587R). This nucleotide substitution was not seen in any unaffected member of the family.

CONCLUSIONS

We detected a novel mutation in FBN1. Our result expands the mutation spectrum of FBN1 and help in the study of the molecular pathogenesis of Marfan syndrome and Marfan-related diseases.

Pulmonary histologic changes in Marfan syndrome: a case series and literature review

Marfan syndrome is one of the most common connective tissue diseases and may manifest with a range of symptoms and pathologic changes. We present a retrospective series of 5 cases of patients with Marfan syndrome and pulmonary pathology. Patients were young to middle-aged adults with absent or minimal smoking histories and absent to severe clinical pulmonary symptoms. Tissue specimens were obtained from the surgical pathology and autopsy services. Histologic examination revealed a consistent pattern of distal acinar emphysema in all patients. Comparisons are made with other cystic-type diseases of the lung that may histologically mimic this pattern. This is the largest contemporary series of histologic pulmonary involvement of Marfan syndrome and the first to describe this pattern of pulmonary changes in this patient population.

Identification of a novel FBN1 gene mutation in a Chinese family with Marfan syndrome

PURPOSE

To identify the mutation in the fibrillin-1 gene (FBN1) in a Chinese family with Marfan syndrome (MFS).

METHODS

Patients and family members were given complete physical, ophthalmic, and cardiovascular examinations. Genomic DNA was extracted from leukocytes of venous blood of six individuals in the family and 170 healthy Chinese individuals. All of the 65 coding exons and their flanking intronic boundaries of FBN1 were amplified in the proband by polymerase chain reaction and followed by direct sequencing. The mutation identified in the proband was screened in the other family members and the 170 healthy Chinese individuals by direct sequencing. Protein conservation analysis was performed in six species using an online ClustalW tool. Protein structure was modeled based on the Protein data bank and mutated in DeepView v4.0.1 to predict the functional consequences of the mutation.

RESULTS

A novel heterozygous c.3703T>C change in exon 29 of FBN1 was detected in the proband, which resulted in the substitution of serine by proline at codon 1235 (p.S1235P). This mutation was also present in two family members but absent in the other, unaffected family members and the 170 healthy Chinese individuals. The mutant residue located in the calcium binding epidermal growth factor-like#15 domain is highly conserved among mammalian species and could probably induce conformation change of the domain.

CONCLUSIONS

We indentified a novel p.S1235P mutation in FBN1, which is the causative mutation for MFS in this family. Our result expands the mutation spectrum of FBN1 and contributes to the study of the molecular pathogenesis of Marfan syndrome.

Two novel FBN1 mutations associated with ectopia lentis and marfanoid habitus in two Chinese families

PURPOSE

To identify the molecular defects in the fibrillin-1 gene (FBN1) in two Chinese families with ectopia lentis (EL) and marfanoid habitus.

METHODS

Five patients and eight non-carriers in the two families underwent complete physical, ophthalmic, and cardiovascular examinations. Genomic DNA was extracted from leukocytes of venous blood of these individuals in the families as well as 100 healthy normal controls. Polymerase chain reaction (PCR) amplification and direct sequencing of all 65 coding exons of FBN1 were analyzed. The functional consequences of the mutations were analyzed with various genomic resources.

RESULTS

Two novel mutations of FBN1 were identified in our study. One is a splice defect in intron 17 (IVS 17-1G>T) adjacent to exon 18. The other is c.6182G>T in exon 50, which results in the substitution of cysteine by phenylalanine at codon 2,061 (p. C2061F). We provided strong evidences that the splice mutation would potentially lead to the skipping of exons after intron 17 and that the missense mutation at codon 2,061 (p. C2061F) would destroy a disulfide bond.

CONCLUSIONS

We detected two novel mutations in FBN1. Our results expand the mutation spectrum of FBN1 and help in the study of the molecular pathogenesis of Marfan syndrome and Marfan-related disorders.

Prevalence data on all Ghent features in a cross-sectional study of 87 adults with proven Marfan syndrome

The prevalence of each single feature in the Ghent criteria in patients with Marfan syndrome (MFS) is not known. To elucidate this, a cross-sectional study of 105 adults with presumed MFS was carried out. All patients were examined by the same group of investigators with standardized and complete assessment of all features in the Ghent criteria. Eighty-seven (83%) fulfilled the criteria in 56 different variants. The most prevalent major criterion in Ghent-positive persons was dural ectasia (91%), followed by major genetic criterion (89%) and ectopic lenses (62 %). In 14 persons (16%), the diagnosis was dependent on the dural findings. In all, 79% fulfilled both major dural and major genetic (positive family history and/or FBN1 mutation) criteria, suggesting that most patients with MFS might be identified by investigating these criteria. A history or finding of ascending aortic disease was present in 46 patients (53%). This low prevalence might partly reflect a high number of diagnosed patients encompassing the whole spectrum of the syndrome. The study confirms the need to examine for the complete set of features in the Ghent criteria to identify all patients with MFS. The majority of persons with MFS might be identified by the combined assessment of dura mater and family history, supplemented with DNA analysis in family-negative cases. The low prevalence of ascending aortic disease might indicate better future prospects in an adult population than those traditionally considered.

ADAMTSL2 mutations in geleophysic dysplasia demonstrate a role for ADAMTS-like proteins in TGF-beta bioavailability regulation

Geleophysic dysplasia is an autosomal recessive disorder characterized by short stature, brachydactyly, thick skin and cardiac valvular anomalies often responsible for an early death. Studying six geleophysic dysplasia families, we first mapped the underlying gene to chromosome 9q34.2 and identified five distinct nonsense and missense mutations in ADAMTSL2 (a disintegrin and metalloproteinase with thrombospondin repeats-like 2), which encodes a secreted glycoprotein of unknown function. Functional studies in HEK293 cells showed that ADAMTSL2 mutations lead to reduced secretion of the mutated proteins, possibly owing to the misfolding of ADAMTSL2. A yeast two-hybrid screen showed that ADAMTSL2 interacts with latent TGF-beta-binding protein 1. In addition, we observed a significant increase in total and active TGF-beta in the culture medium as well as nuclear localization of phosphorylated SMAD2 in fibroblasts from individuals with geleophysic dysplasia. These data suggest that ADAMTSL2 mutations may lead to a dysregulation of TGF-beta signaling and may be the underlying mechanism of geleophysic dysplasia.

[Spontaneous pneumothorax - a clue to another diagnosis]

Marfan syndrome is an autosomal dominant illness of the connective tissue, with typical skeletal, ocular and cardiovascular manifestations. Less frequently, pulmonary involvement occurs, namely spontaneous pneumothorax, which generally is recurrent and occurs in 4 -11% of cases. The authors describe a 14 -year -old boy, previously healthy, admitted with a unilateral spontaneous pneumothorax, and clinical phenotype of Marfan syndrome. The subsequent investigation led to the diagnosis of mitral valve prolapse and dilatation of the root of aorta. Pneumothorax resolved through active drainage and a computerised tomography scan excluded subpleural blebs. The patient was readmitted two months later with a new spontaneous pneumothorax, with an identical localization. Surgical resection of a newly identified enfisematous bleb and pleurodesis were performed. Two years later he is asymptomatic. We highlight the importance of an early diagnosis of and a multidisciplinary approach to these patients. Monitoring illness progression and prevention of serious complications, namely cardiovascular, are essential.

Functional role of periostin in development and wound repair: implications for connective tissue disease

Integrity of the extracellular matrix (ECM) is essential for maintaining the normal structure and function of connective tissues. ECM is secreted locally by cells and organized into a complex meshwork providing physical support to cells, tissues, and organs. Initially thought to act only as a scaffold, the ECM is now known to provide a myriad of signals to cells regulating all aspects of their phenotype from morphology to differentiation. Matricellular proteins are a class of ECM related molecules defined through their ability to modulate cell-matrix interactions. Matricellular proteins are expressed at high levels during development, but typically only appear in postnatal tissue in wound repair or disease, where their levels increase substantially. Members of the CCN family, tenascin-C, osteopontin, secreted protein acidic rich in cysteine (SPARC), bone sialoprotein, thrombospondins, and galectins have all been classed as matricellular proteins. Periostin, a 90 kDa secreted homophilic cell adhesion protein, was recently added to matricellular class of proteins based on its expression pattern and function during development as well as in wound repair. Periostin is expressed in connective tissues including the periodontal ligament, tendons, skin and bone, and is also prominent in neoplastic tissues, cardiovascular disease, as well as in connective tissue wound repair. This review will focus on the functional role of periostin in tissue physiology. Fundamentally, it appears that periostin influences cell behaviour as well as collagen fibrillogenesis, and therefore exerts control over the structural and functional properties of connective tissues in both health and disease. Periostin is a novel matricellular protein with close homology to Drosophila fasciclin 1. In this review, the functional role of periostin is discussed in the context of connective tissue physiology, in development, disease, and wound repair.

Late-onset bilateral lens dislocation and glaucoma associated with a novel mutation in FBN1

PURPOSE

To describe the clinical and genetic findings in one Chinese family with late-onset bilateral lens dislocation and secondary glaucoma.

METHODS

One family including three affected members and 16 unaffected family members was examined clinically. After informed consent was obtained, genomic DNA was extracted from venous blood of all participants. Linkage analysis was performed with two microsatellite markers around the fibrillin-1 (FBN1) gene (D15S992 and D15S126). Mutation screening was performed using direct DNA sequence analysis and single strand conformation polymorphism (SSCP).

RESULTS

Clinical examination and pedigree analysis revealed that four members in three generations were affected by late-onset lens dislocation and secondary glaucoma but had no signs of cardiovascular abnormality or abnormal skeletal features. By genotyping, the family showed the linkage to FBN1 on 15q21.1. After mutation screening analysis on 65 exons of FBN1, a novel heterozygous missense mutation, c.2860C>T (R954C), was detected. This mutation cosegregated with the disease phenotype in the family and was not found in 100 normal controls.

CONCLUSIONS

Late-onset isolated ectopia lentis with secondary glaucoma is consistent with a novel mutation in FBN1. Our finding expands the spectrum of FBN1 mutations and is useful for further genetic consultation and genetic diagnosis.

Fibrillin-1 in incisional hernias: an immunohistochemical study in scar and non-scar regions of human skin and muscle fasciae

Incisional hernias represent one of the most common complications after laparotomy. Specific pre-operative risk factors have not yet been identified. Recent studies indicate that changes in extracellular matrix components such as collagen I and collagen III may be involved in hernia development. In the present study we have evaluated the significance of fibrillin-1 in hernia development as one of the main components of the extracellular matrix. Tissue samples from non-scar skin and muscle fascia of 12 patients with incisional hernias as well as from the respective scar tissues were obtained. Corresponding tissue samples of 10 patients with normal postoperative wound healing served as controls. Distribution of fibrillin-1 was evaluated immunohistochemically. Differences in fibrillin-1 distribution in the non-scar tissues of muscle fascia have been found in patients with incisional hernia, compared to those without hernia. In scar regions of both patient groups, slight differences in the pattern of fibrillin-1 were observed. A tendency to a differential deposition of fibrillin-1 in skin samples, although hardly quantifiable, was observed as well. Our results suggest that fibrillin-1 is a relevant factor contributing to tissue stability. Disturbances in its deposition, even before scar formation, may be an important factor to the development of incisional hernias.

Aberrant fibrillin-1 expression in early emphysematous human lung: a proposed predisposition for emphysema

Parenchymal destruction, airspace enlargement, and loss of elasticity are hallmarks of pulmonary emphysema. Although the basic mechanism is unknown, there is a consensus that malfunctioning of the extracellular matrix is a major contributor to the pathogenesis of emphysema. In this study, we analyzed the expression of the elastic fiber protein fibrillin-1 in a large number (n=69) of human lung specimens with early-onset emphysema. Specimens were morphologically characterized by the Destructive Index, the Mean Linear Intercept, and the Panel Grading. We observed a strong correlation (P<0.001) of aberrant fibrillin-1 staining with the degree of destruction of lung parenchyma (r=0.71), airspace enlargement (r=0.47), and emphysema-related morphological abnormalities (r=0.69). There were no obvious correlations with age and smoking behavior. Staining for three other extracellular matrix components (type I collagen, type IV collagen, and laminin) was not affected. The aberrant fibrillin-1 staining observed in this study is similar to that observed in Marfan syndrome, a syndrome caused by mutations in the gene encoding fibrillin-1. Strikingly, emphysema is noticed in a number of Marfan patients. This, together with the notion that disruption of the fibrillin-1 gene in mice results in emphysematous lesions, makes fibrillin-1 a strong candidate to be involved in the etiology and pathogenesis of emphysema.

Association between semicarbazide-sensitive amine oxidase, a regulator of the glucose transporter, and elastic lamellae thinning during experimental cerebral aneurysm development

Object

Amine oxidases play a key role in the polymerization and cross-linking of the collagens and elastic lamellae of the arterial wall. The loss of elastic lamellae integrity is one of the first steps in the genesis of a cerebral aneurysm. The authors investigated the relation between semicarbazide-sensitive amine oxidase (SSAO) and the organization of the cerebral arterial wall during aneurysm development.

Methods

Intracranial aneurysms were induced in rats via unilateral carotid artery ligation and renovascular hypertension. This modified Hashimoto model was used to create elevated blood pressure associated with shear stress in cerebral arteries. The authors immunohistologically investigated some markers of the extracellular matrix (Types I, III, and IV collagen and elastin), vascular smooth muscle cell differentiation (smooth muscle myosin heavy chain [sm-MHC], α–smooth muscle actin, and desmin), and amine oxidases (SSAO and lysyl oxidase [LOX]) in the cerebral arterial wall in control and treated rats 1, 2, 3, 4, and 6 months after the surgical procedure.

Results

The authors found severe disorganization and thinning of the elastic lamellae and a dramatic reduction in SSAO activity and immunostaining during cerebral aneurysm development. In contrast, LOX markers were slightly increased. Elastic lamellae thinning was highly correlated with decreases in SSAO (r = 0.76, p < 0.0001). There was also a correlation between sm-MHC and SSAO levels.

Conclusions

The data suggested that cerebral hemodynamic modifications induce decreases in SSAO activity resulting in cell dedifferentiation and inducing dysregulation of glucose transport.

The role of shear stress on ET-1, KLF2, and NOS-3 expression in the developing cardiovascular system of chicken embryos in a venous ligation model

In this review, the role of wall shear stress in the chicken embryonic heart is analyzed to determine its effect on cardiac development through regulating gene expression. Therefore, background information is provided for fluid dynamics, normal chicken and human heart development, cardiac malformations, cardiac and vitelline blood flow, and a chicken model to induce cardiovascular anomalies. A set of endothelial shear stress-responsive genes coding for endothelin-1 (ET-1), lung Krüppel-like factor (LKLF/KLF2), and endothelial nitric oxide synthase (eNOS/NOS-3) are active in development and are specifically addressed.

In Vivo Corneal Confocal Microscopy in Marfan Syndrome

PURPOSE

To examine the cornea of patients with Marfan syndrome in comparison with a control group by using the in vivo confocal microscope.

METHODS

Twenty-four eyes of 12 patients with Marfan syndrome had their corneas examined using the in vivo confocal microscope Heidelberg Retina Tomograph (HRT) II/Rostock Cornea Module. The control group included 24 eyes of 12 subjects who had their corneas examined by the same in vivo confocal microscope.

RESULTS

Epithelium and neural plexus examination did not show any difference between the 2 groups. Examination of the stroma showed no significant differences concerning the morphology and density of keratocytes. The extracellular matrix of 16 of the 24 eyes of the Marfan group was clearly visible and showed thin highly reflective interconnected lines between keratocytes. In the healthy eye group, reflective lines were observed in only 5 of the 24 eyes. The endothelium of 14 corneas of the Marfan group showed brightly reflective particles. In no cornea of the control group were such particles observed.

CONCLUSIONS

Highly reflective extracellular matrix of the stroma and brightly reflective particles among the endothelial cells were the 2 main corneal findings observed by using in vivo corneal confocal microscopy in patients with Marfan syndrome compared with a control group. Further studies need to be made to confirm these findings and eventually find new criteria for Marfan syndrome from the examination of in vivo corneal confocal microscopy.

Knockout mice: is it just genetics? Effect of enriched housing on fibulin-4(+/-) mice

BACKGROUND

Fibulin-4 is an extracellular matrix protein expressed by vascular smooth muscle cells that is essential for maintaining arterial integrity. Fibulin-4(-/-) mice die just before birth due to arterial hemorrhage, but fibulin-4(+/-) mice appear to be outwardly normal. Experiments were therefore performed to determine whether fibulin-4(+/-) mice display arterial pathologies on a microscopic scale. After preliminary experiments were performed, a second purpose developed, which was to test the hypothesis that any observed pathologies would be ameliorated by housing the animals in enriched cages.

METHODOLOGY

Fibulin-4(+/-) and wild-type mice were housed either four/cage in standard cages or two per cage in larger cages, each cage containing a tunnel and a wheel. After three weeks the mice were sacrificed, and the aortas perfusion-fixed and excised for light and electron microscopy.

PRINCIPLE FINDINGS

When the mice were in standard cages, localized regions of disorganized extracellular matrix and collagen fibers consistently appeared between some of the medial smooth muscle cells in the fibulin-4(+/-) mice. In the wild-type mice, the smooth muscle cells were closely connected to each other and the media was more compact. The number of disorganized regions per square mm was significantly greater for fibulin-4(+/-) mice (172+/-43 (SEM)) than for wild-type mice (15+/-8) (p<0.01, n = 8). When the mice were in enriched cages, the fibulin-4(+/-) mice showed significantly fewer disorganized regions than those in standard cages (35+/-12) (p<0.05, n = 8). The wild type mice also showed fewer disorganized regions (3+/-2), but this difference was not significant.

CONCLUSIONS

These results indicate that arterial pathologies manifested in fibulin-4(+/-) mice can be reduced by enriching the housing conditions, and imply that appropriate environments may counteract the effects of some genetic deficiencies.

The molecular genetics of Marfan syndrome and related disorders

Marfan syndrome (MFS), a relatively common autosomal dominant hereditary disorder of connective tissue with prominent manifestations in the skeletal, ocular, and cardiovascular systems, is caused by mutations in the gene for fibrillin-1 (FBN1). The leading cause of premature death in untreated individuals with MFS is acute aortic dissection, which often follows a period of progressive dilatation of the ascending aorta. Recent research on the molecular physiology of fibrillin and the pathophysiology of MFS and related disorders has changed our understanding of this disorder by demonstrating changes in growth factor signalling and in matrix-cell interactions. The purpose of this review is to provide a comprehensive overview of recent advances in the molecular biology of fibrillin and fibrillin-rich microfibrils. Mutations in FBN1 and other genes found in MFS and related disorders will be discussed, and novel concepts concerning the complex and multiple mechanisms of the pathogenesis of MFS will be explained.

Functional analysis of zebrafish microfibril-associated glycoprotein-1 (Magp1) in vivo reveals roles for microfibrils in vascular development and function

Mutations in fibrillin-1 (FBN1) result in Marfan syndrome, demonstrating a critical requirement for microfibrils in vessel structure and function. However, the identity and function of many microfibril-associated molecules essential for vascular development and function have yet to be characterized. In our morpholino-based screen for members of the secretome required for vascular development, we identified a key player in microfibril formation in zebrafish embryogenesis. Microfibril-associated glycoprotein-1 (MAGP1) is a conserved protein found in mammalian and zebrafish microfibrils. Expression of magp1 mRNA is detected in microfibril-producing cells. Analysis of a functional Magp1-mRFP fusion protein reveals localization along the midline and in the vasculature during embryogenesis. Underexpression and overexpression analyses demonstrate that specific Magp1 protein levels are critical for vascular development. Integrin function is compromised in magp1 morphant embryos, suggesting that reduced integrin-matrix interaction is the main mechanism for the vascular defects in magp1 morphants. We further show that Magp1 and fibrillin-1 interact in vivo. This study implicates MAGP1 as a key player in microfibril formation and integrity during development. The essential role for MAGP1 in vascular morphogenesis and function also supports a wide range of clinical applications, including therapeutic targets in vascular disease and cardiovascular tissue engineering.

Hemifacial spasm in a patient with Marfan syndrome and Chiari I malformation

Marfan syndrome, hemifacial spasm, and Chiari malformation are all relatively rare and seemingly separate entities. Marfan syndrome is caused by a defect in the gene that encodes fibrillin and leads to weakness of the artery wall. Hemifacial spasm results from compression of the facial nerve by an abnormal artery. Chiari malformation is characterized by a small posterior fossa. The authors report the case of a patient with Marfan syndrome who presented with hemifacial spasm and was also found to have a Chiari malformation Type I. The patient's Chiari malformation and hemifacial spasm were successfully treated by performing suboccipital and microvascular decompression surgeries, respectively. The pathophysiological characteristics of Marfan syndrome, hemifacial spasm, and Chiari malformation are discussed, and the authors propose a link between these conditions in this patient. The authors hypothesize that the patient's Marfan syndrome contributed to the abnormal shape of his vertebral artery and that, given the lack of space in his crowded posterior fossa due to the Chiari malformation, the artery caused compression of his facial nerve, resulting in hemifacial spasm.

Lysyl oxidase deficiency: a new cause of human arterial dissection

Spontaneous coronary artery dissection is a rare cause of myocardial ischaemia. The underlying mechanism is unknown but some dissections are associated with extracellular matrix disorganisation of genetic origin. A deficiency in extracellular matrix protein cross links has rarely been studied. A single clinical case of spontaneous coronary artery dissection is reported. Lysyl oxidase (LOX) and extracellular matrix organisation were investigated by skin immunohistology and polymerase chain reaction of LOX expression. Both approaches found a dramatic LOX decrease. LOX deficiency has a major role in human arterial wall organisation during development. The suspected mechanism is an elastin or collagen polymer cross linking deficiency.

Postural headache in a child with Marfan syndrome: case report and review of the literature

The case of a 10-year-old female with Marfan syndrome and postural headache secondary to spontaneous intracranial hypotension is described. The patient was found to have multiple dural ectasias and a cerebrospinal fluid leak at the left cervicothoracic junction. Her presentation, diagnostic work-up, and management are reviewed, and the relevant literature is discussed. Spontaneous intracranial hypotension secondary to cerebrospinal fluid leaks from dural ectasia should be recognized as a potential complication in children with Marfan syndrome and other connective tissue diseases.

Stent-Grafts in Patients With Marfan Syndrome

PURPOSE

To explore the safety and feasibility of stent-graft placement in the dissected descending thoracic aorta of patients with Marfan syndrome.

METHODS

Six consecutive patients (4 men; mean age 33+/-15 years, range 24-61) with Marfan syndrome were offered endovascular repair for dissection after previous aortic root repair in 5 and solitary type B dissection in 1.

RESULTS

Transluminal placement of customized Talent stent-grafts was technically successful in all patients, with no 30-day or 1-year intervention-related mortality. Complete abolition of the dissection and reconstruction of the entire dissected aorta was documented in 2 patients. Over a mean 51+/-22-month follow-up (range 12-74), elective conversion to surgical repair was necessary in 2 patients at 22 and 43 months after stent-graft implantation. In a third patient, conversion to surgery is being considered at 74 months after stent-grafting. One patient died suddenly 12 months after endovascular repair.

CONCLUSIONS

Nonsurgical reconstruction of postsurgical distal aortic dissection in patients with Marfan syndrome is feasible and technically successful. Stent-graft placement may either avoid or bridge to repeat surgery of distal aortic dissections after previous aortic root repair. Technical expertise and close postinterventional surveillance appear mandatory and may limit the procedure to centers of competence for aortic diseases.

The FBN1 (R2726W) mutation is not fully penetrant

The R2726W mutation in the fibrillin 1 (FBN1, Marfan syndrome) gene segregates with isolated skeletal features of Marfan syndrome and/or high stature. Here we report a family in which two out of four individuals, an 18-year-old son and his mother, a 41-year-old woman, had the R2726W mutation of FBN1. Both family members carrying the mutation were of average height. The son had a Marfan-like phenotype, but his mother did not. The FBN1 R2776W mutation, which is associated with skeletal features of Marfan syndrome, appears incompletely penetrant. Consequently, genetic counselling in the presence of this mutation is difficult.

Heterozygous TGFBR2 mutations in Marfan syndrome

Marfan syndrome is an extracellular matrix disorder with cardinal manifestations in the eye, skeleton and cardiovascular systems associated with defects in the gene encoding fibrillin (FBN1) at 15q21.1 (ref. 1). A second type of the disorder (Marfan syndrome type 2; OMIM 154705) is associated with a second locus, MFS2, at 3p25-p24.2 in a large French family (family MS1). Identification of a 3p24.1 chromosomal breakpoint disrupting the gene encoding TGF-beta receptor 2 (TGFBR2) in a Japanese individual with Marfan syndrome led us to consider TGFBR2 as the gene underlying association with Marfan syndrome at the MSF2 locus. The mutation 1524G-->A in TGFBR2 (causing the synonymous amino acid substitution Q508Q) resulted in abnormal splicing and segregated with MFS2 in family MS1. We identified three other missense mutations in four unrelated probands, which led to loss of function of TGF-beta signaling activity on extracellular matrix formation. These results show that heterozygous mutations in TGFBR2, a putative tumor-suppressor gene implicated in several malignancies, are also associated with inherited connective-tissue disorders.

Three novel mutations of the fibrillin-1 gene and ten single nucleotide polymorphisms of the fibrillin-3 gene in Marfan syndrome patients

Marfan syndrome (MFS) is an autosomal dominant disorder of the extracellular matrix. Allelic variations in the gene for fibrillin-1 ( FBN1) have been shown to cause MFS. To date, over 550 mutations have been identified in patients with MFS and related connective tissue diseases. However, about a half of MFS cases do not possess mutations in the FBN1 gene. These findings raise the possibility that variants located in other genes cause or modify MFS. To explore this possibility, firstly we analyzed FBN1 allelic variants in 12 Japanese patients with MFS, and secondly we analyzed fibrillin-3 gene ( FBN3) in patients without FBN1 mutations using conformation sensitive gel electrophoresis (CSGE) and direct sequencing analysis. We identified three novel FBN1 mutations and ten FBN3 single nucleotide polymorphisms (SNPs). In this report, we could not detect a responsible mutation of the FBN3 gene for MFS. Although the number of the cases in this report is small, at least these results suggest that disease-causing mutations in exon regions of the FBN3 gene are very rare in MFS.