C596G mutation in FBN1 causes Marfan syndrome with exotropia in a Chinese family.
ABSTRACT: To screen mutations in the fibrillin-1 (FBN1) gene in a Chinese family with autosomal dominant Marfan syndrome (MFS).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.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.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.
Project description:AIM:To report a novel mutation in FBN1 gene in a Chinese consanguineous family with common Marfan syndrome (MFS) phenotype and an unusual bilateral macular degeneration. METHODS:Ophthalmic, cardiovascular and systemic examinations were performed, and genomic DNA extracted from all living family members. The 24-32 exon mutations of FBN1 gene were screened by Sanger Sequencing in all family members and 100 unrelated healthy Chinese individuals. RESULTS:In the four-generation family, classic MFS phenotypes were observed in all 5 patients, 2 of them had peculiar phenotype of bilateral macular degeneration. Mutation screening in FBN1 identified a heterozygous missense mutation (c.3932A>G, p.Y1311C) with co-segregation. This mutation was found with the MFS phenotypes in all 5 patients but not in unaffected members or unrelated controls. CONCLUSION:A Chinese consanguineous MFS family with uncommon bilateral macular degeneration and an unreported c.3932A>G mutation in FBN1 was identified. Our finding expands the FBN1 mutation spectrum and its possible role in the pathogenesis of Marfan syndrome.
Project description:BACKGROUND:Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutations in the FBN1 gene. Approximately 90% of classic MFS patients have a FBN1 mutation that can be identified by single-gene sequencing or gene-panel sequencing targeting FBN1. However, a small proportion of MFS patients carry a large genomic deletion in FBN1, which cannot be detected by routine sequencing. Here, we performed an MLPA (multiplex ligation-dependent probe amplification) test to detect large deletions and/or duplications in FBN1 and TGFBR2 in 115 unrelated Chinese patients with suspected MFS or early-onset aneurysm/dissection. RESULTS:Five novel large deletions encompassing a single exon or multiple exons in the FBN1 gene were characterized in five unrelated patients, of which four were proven by Sanger sequencing, and the breakpoints were identified. Three of them met the revised Ghent criteria when genetic results were not available, and the other two patients were highly suspected and diagnosed with MFS until the FBN1 deletions were identified. CONCLUSIONS:Our finding expands the mutation spectrum of large FBN1 deletions and emphasizes the importance of screening for large FBN1 deletions in clinical genetic testing, especially for those with classic Marfan phenotype.
Project description:To identify the mutation in the fibrillin-1 gene (FBN1) in a Chinese family with Marfan syndrome (MFS).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.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.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.
Project description:Screening of mutations in the fibrillin-1 (FBN1) gene in a Chinese family with autosomal dominant Marfan syndrome (MFS).It has been reported that FBN1 mutations account for approximately 90% of Autosomal Dominant MFS. FBN1 mutations were analyzed in a Chinese family of 36 members including 13 MFS patients. The genomic DNAs from blood leukocytes of the patients and their relatives were isolated and the entire coding region of FBN1 was amplified by PCR. The sequence of FBN1 was dertermined with an ABI 3100 Genetic Analyzer.A previously unreported the missense mutation G214S (caused by a 640 A?G heterozygous change) in FBN1 was identified in the Chinese family. The mutation was associated with the disease phenotype in patients, but not detected in their relatives or in the 100 normal controls.This is the first report of molecular characterization of FBN1 in the MFS family of Chinese origin. Our results expand the spectrum of FBN1 mutations causing MFS and further confirm the role of FBN1 in the pathogenesis of MFS. Direct sequencing of the mutation in FBN1 may be used for diagnosis of MFS.
Project description:BACKGROUND:Previous studies showed that the fibrillin-1 gene (FBN1) is responsible for Marfan sydrome (MFS) pathogenesis. This study is conducted to screen for mutations in the FBN1 gene in Chinese families with MFS. METHODS:Eight families with MFS and related disorder were recruited in this study. All available family members underwent complete physical, ophthalmic, and cardiovascular examination. Mutation screening was performed using targeted next-generation sequencing. Candidate variants were amplified by polymerase chain reaction and verified by direct Sanger sequencing. RESULTS:Four novel heterozygous mutations in FBN1, including c.2861G>T (p.R954L), c.4087G>A (p.D1363N), c.4987T>G (p.C1663G), and c.5032T>G (p.Y1678D), as well as four known mutations, c.3617G>A (p.G1206D), c.4460A>G (p.D1487G), c.4588C>T (p.R1530C), and c.718C>T (p.R240C) were identified. Affected patients from each family were found to carry one of the mutations, whereas the unaffected members and 1,086 normal controls were not. Each mutation was found to be cosegregated with MFS phenotype and related disorder in each family. Multiple sequence alignment of the human fibrillin-1 protein showed that these mutations occurred in a highly conserved region among different species. CONCLUSIONS:Eight FBN1 mutations were identified in Chinese families with MFS and related disorder. These data expands FBN1 mutation spectrum and further emphasizes the role of FBN1 in the pathogenesis of MFS.
Project description:Marfan syndrome (MFS) is an autosomal dominant inheritary disorder of the connective tissue. We report clinical features of a Chinese family with MFS and identify mutations in fibrillin-1 gene (FBN1). In this study, all three members of this family underwent complete ophthalmologic examinations. Two of the three members were diagnosed with MFS. Molecular genetic analysis was performed on the three members. All coding exons of FBN1 were amplified by polymerase chain reaction (PCR). The amplified products were sequenced and compared with a reference sequence in the database. Possible structural and functional changes of the protein induced by amino acids variance were predicted by bioinformatic analysis. A novel heterozygous mutation c.4504 T>A (p.C1502S) in exon 36 was identified in the two affected members, but not in the unaffected member. To our knowledge, this FBN1 mutation has not been reported beforein MFS or other patients.
Project description:Marfan syndrome (MFS) is an autosomal dominant heterogeneous disorder of connective tissue characterized by the early development of thoracic aneurysms/dissections, together with defects of the ocular and skeletal systems. Loss-of-function mutations in fibrillin-1 (FBN1) encoded by the gene, FBN1 (MFS?1), and in the transforming growth factor ? receptor 2 (TGFBR2) gene, TGFBR2 (MFS?2), are major causes of this disorder. In the present study, a rapid and cost?effective method for genetically diagnosing MFS was described and used to identify disease?causing mutations in two unrelated pedigrees with MFS in mainland China. Using targeted semiconductor sequencing, two pathogenic mutations in four MFS patients of the two pedigrees were identified, including a novel frameshift insertion, p.G2120fsX2160, and a reported nonsense mutation, p.Arg529X (rs137854476), in the FBN1 gene. In addition, a rare, probably benign Chinese?specific polymorphism in the FBN1 gene was also revealed.
Project description:Marfan syndrome (MFS) is a heritable disorder of connective tissue resulting from pathogenic variants of the fibrillin-1 gene (FBN1). Neonatal Marfan syndrome (nMFS) is rare and the most severe form of MFS, involving rapidly progressive cardiovascular dysfunction leading to death during early childhood. The constant enrichment of the nMFS mutation spectrum is helpful to improve our understanding of genotype-phenotype correlations in the disease. Herein, we report a novel dominant mutation in exon 26 of FBN1 (c.3331 T > C) in a sporadic case with nMFS.An 8-month-old Han Chinese girl presented with the classic nMFS phenotype, including prominent manifestations of bone overgrowth, aortic root dilatation, and multiple cardiac valve dysfunctions. Genetic analysis revealed that she was heterozygous for a de novo FBN1 missense mutation (c.3331 T > C). The mutation leads to the substitution of a highly conserved FBN1 cysteine residue (p.Cys1111Arg), which is likely to severely perturb the FBN1 structure because of an alteration of the disulfide bond pattern in the calcium-binding epidermal growth factor-like (cbEGF) 12 domain. This variant was absent in 208 ethnically matched controls, providing further evidence that it may be causative of nMFS. An analysis of nMFS-associated mutations from the UMD-FBN1 database indicates that those de novo mutations altering disulfide bonds or Ca(2+) binding sites of the cbEGF domains encoded by exons 25-33, and a lack of phenotypic heterogeneity may be associated with an increased risk for nMFS.We diagnosed an infant with rare nMFS showing rapidly progressive cardiovascular dysfunction and widely systemic features. As the only causal FBN1 mutation identified in the patient, the missense mutation c.3331 T > C (p.Cys1111Arg) was associated with the severe phenotype of MFS. However, the pathogenicity of the novel mutation needs further confirmation in other patients with nMFS. Our review of the prominent characteristics of nMFS mutations relative to classic or incomplete MFS-related mutations will be helpful for the recognition of novel nMFS-associated variants.
Project description:Congenital contractural arachnodactyly (CCA, OMIM: 121050) is an autosomal dominant condition that shares skeletal features with Marfan syndrome (MFS, OMIM: 154700), including contractures, arachnodactyly, dolichostenomelia, scoliosis, crumpled ears and pectus deformities but excluding the ocular and cardiovascular complications that characterize MFS. These two similar syndromes result from mutations in two genes belonging to the fibrillin family, FBN1 and FBN2, respectively. We successfully identified a novel FBN2 mutation (C1406R) in a Chinese family with CCA for over five generations. This mutation was detected in the patients of this family but not in the seven unaffected family members or 100 normal individuals. SIFT and PolyPhen analyses suggested that the mutation was pathogenic. We identified a missense mutation in the calcium binding-epidermal growth factor (cbEGF)-like domain. Our study extends the mutation spectrum of CCA and confirms a relationship between mutations in the FBN2 gene and the clinical findings of CCA.
Project description:Background:Marfan syndrome (MFS) is an inherited connective tissue disorder affecting the ocular, skeletal and cardiovascular systems. Previous studies of MFS have demonstrated the association between genetic defects and clinical manifestations. Our purpose was to investigate the role of novel genetic variants in determining MFS clinical phenotypes. Methods:We sequenced the whole exome of 19 individuals derived from three Han Chinese families. The sequencing data were analyzed by a standard pipeline. Variants were further filtered against the public database and an in-house database. Then, we performed pedigree analysis under different inheritance patterns according to American College of Medical Genetics guidelines. Results were confirmed by Sanger sequencing. Results:Two novel loss-of-function indels (c.5027_5028insTGTCCTCC, p.D1677Vfs*8; c.5856delG, p.S1953Lfs*27) and one nonsense variant (c.8034C>A, p.Y2678*) of FBN1 were identified in Family 1, Family 2 and Family 3, respectively. All affected members carried pathogenic mutations, whereas other unaffected family members or control individuals did not. These different kinds of loss of function (LOF) variants of FBN1 were located in the cbEGF region and a conserved domain across species and were not reported previously. Conclusions:Our study extended and strengthened the vital role of FBN1 LOF mutations in the pathogenesis of MFS with an autosomal dominant inheritance pattern. We confirm that genetic testing by next-generation sequencing of blood DNA can be fundamental in helping clinicians conduct mutation-based pre- and postnatal screening, genetic diagnosis and clinical management for MFS.