Identification of 9 novel FBN1 mutations in German patients with Marfan syndrome

We report 9 new mutations in German patients presenting with classical Marfan syndrome. All mutations occur in exons with calcium‐binding (cb) epidermal growth factor‐like (EGF) domains. Five mutations are missense involving exons 12, 27, 30, 44, and 52 with the resultant substitution of cysteine by phenylalanine (C504F), cysteine by tyrosine (C1129Y), tyrosine by cysteine (Y1261C), cysteine by serine (C1833S), and cysteine by tyrosine (C2142Y), respectively. The other four mutations are single base deletions in exons 39, 43, 48, and 58, at nucleotide A4826, C5311, T6018, and A7291, respectively, each resulting in frameshift with premature termination. Four mutations were detected in sporadic cases and are likely to be de novo. Hum Mutat 14:181, 1999. © 1999 Wiley‐Liss, Inc.     

Fibrillin gene (FBN1) mutations in Japanese patients with Marfan syndrome

Marfan syndrome (MFS; MIM #154700) is a connective tissue disorder characterized by cardiovascular, skeletal, and ocular abnormalities. The fibrillin-1 gene (FBN1; MIM no. 134797) on chromosome 15 was revealed to be the cause of Marfan syndrome. To date over 137 types of FBN1 mutations have been reported. In this study, two novel mutations and a recurrent de-novo mutation were identified in patients with MFS by means of single-strand conformational polymorphism (SSCP) analysis. The two novel mutations are a 4-bp deletion at nucleotide 2820-2823 and a G-to-T transversion at nucleotide 1421 (C474F), located on exon 23 and exon 11, respectively. A previously reported mutation at the splicing donor site of intron 2 (IVS2 G + 1A), which is predicted to cause exon skipping, was identified in a sporadic patient with classical MFS. Received: November 1, 1999 / Accepted: November 9, 1999     

Double heterozygous variants in FBN1 and FBN2 in a Thai woman with Marfan and Beals syndromes

A phenotype of an individual is resulted from an interaction among variants in several genes. Advanced molecular technologies allow us to identify more patients with mutations in more than one genes. Here, we studied a Thai woman with combined clinical features of Marfan (MFS) and Beals (BS) syndromes including frontal bossing, enophthalmos, myopia, the crumpled appearance to the top of the pinnae, midface hypoplasia, high arched palate, dermal stretch marks, aortic enlargement, mitral valve prolapse and regurgitation, aortic root dilatation, and progressive scoliosis. The aortic root enlargement was progressive to a diameter of 7.2 cm requiring an aortic root replacement at the age of 8 years. At her last visit when she was 19 years old, she had moderate aortic regurgitation. Exome sequencing revealed that she carried the c.3159C > G (p.Cys1053Trp) in exon 26 of FBN1 and c.2638G > A (p. Gly880Ser) in exon 20 of FBN2. The variant in FBN1 was de novo, while that in FBN2 was inherited from her unaffected mother. Both genes encode for fibrillins, which are essential for elastic fibers and can form the heterotypic microfibrils. Two defective fibrillins may synergistically worsen cardiovascular manifestations seen in our patient. In this study, we identified the fourth patient with both MFS and BS, carrying mutations in both FBN1 and FBN2.     

FBN1 mutation screening of patients with Marfan syndrome and related disorders: detection of 46 novel FBN1 mutations

Fibrillin-1 gene ( FBN1 ) mutations cause Marfan syndrome (MFS), an inherited connective tissue disorder with autosomal dominant transmission. Major clinical manifestations affect cardiovascular and skeletal apparatuses and ocular and central nervous systems. We analyzed FBN1 gene in 99 patients referred to our Center for Marfan Syndrome and Related Disorders (University of Florence, Florence, Italy): 85 were affected by MFS and 14 by other fibrillinopathies type I. We identified mutations in 80 patients. Among the 77 different mutational events, 46 had not been previously reported. They are represented by 49 missense (61%), 1 silent (1%), 13 nonsense (16%), 6 donor splice site mutations (8%), 8 small deletions (10%), and 3 small duplications (4%). The majority of missense mutations were within the calcium-binding epidermal growth factor-like domains. We found preferential associations between The Cys-missense mutations and ectopia lentis and premature termination codon mutations and skeletal manifestations. In contrast to what reported in literature, the cardiovascular system is severely affected also in patients carrying mutations in exons 1–10 and 59–65. In conclusion, we were able to detect FBN1 mutations in 88% of patients with MFS and in 36% of patients with other fibrillinopathies type I, confirming that FBN1 mutations are good predictors of classic MFS.     

Eight novel mutations of the FBN1 gene found in Japanese patients with Marfan syndrome

Marfan syndrome (MFS), an autosomal dominant connective tissue disorder, is caused by mutations in the gene encoding fibrillin 1 (FBN1). The clinical spectrum and severity of MFS disorder varies greatly both between and within families. Since there have been only a few reports on the relationship between FBN1 genotypes and clinical phenotypes in Japanese patients, the FBN1 gene was analyzed in 27 Japanese patients diagnosed with MFS. The nucleotide sequence of the 65 exons of the FBN1 gene was analyzed by PCR and direct sequencing. We have identified six polymorphisms and nine mutations including: four missense mutations (C1652Y, Q2054P, D2127Y, C2221R) in six patients, three nonsense mutations (R215X, S813X, R2220X) in three patients, and two frameshift mutations (2567insT, 7790insT) in three patients. Six of these nine mutations were in the calcium-binding epidermal growth factor-like domains all causative mutations detected except for C2221R were novel. It has been reported that the severe phenotypes of infantile MFS correlate with mutations in the mid region of FBN1, however, mutations were not detected in this region in the population analyzed in this study. Our results suggest that the location of the mutation is not the sole determinant of phenotypic severity; rather there is some difference in the genetic basis of MFS between Japanese and Caucasian populations.     

Multi-exon deletions of the FBN1 gene in Marfan syndrome

Background  

Mutations in the fibrillin -1 gene (FBN1) cause Marfan syndrome (MFS), an autosomal dominant multi-system connective tissue disorder. The 200 different mutations reported in the 235 kb, 65 exon-containing gene include only one family with a genomic multi-exon deletion.     

Severe Marfan syndrome due to FBN1 exon deletions

Marfan syndrome is an autosomal dominant condition, with manifestations mainly in the skeletal, ocular, and cardiovascular systems. The disorder is caused by mutations in fibrillin-1 gene (FBN1). The majority of these are family-specific point mutations, with a small number being predicted to cause exon-skipping. To date, there have only been five reports of in-frame exon deletions in FBN1, with the largest of these spanning three exons. Mosaicism is rarely recorded and has only been reported in the unaffected, or mildly affected, parents of probands. Here, we report on the clinical histories of two children with exon deletions in FBN1. Both have severe Marfan syndrome with significant signs in infancy. One patient has a deletion of exon 33, which has not previously been reported. The other has the largest reported deletion, which spans 37 exons, and also represents the first reported case of mosaicism in a patient with Marfan syndrome.     

Mutation spectrum of the fibrillin-1 (FBN1) gene in Taiwanese patients with Marfan syndrome

The aim of this study was to establish a national database of mutations in the fibrillin-1 ( FBN1 ) gene that cause Marfan syndrome (MFS) in the Taiwanese population. In this study, we screened 294 patients from 157 families for the presence of FBN1 mutations using polymerase chain reaction/ denaturing high performance liquid chromatography (PCR/DHPLC). We identified 56 mutations in 62 of the 157 (40%) families including 49 single-base substitutions (36 missense mutations, seven nonsense mutations, and six splicing sites), one small insertion, four small deletions, one small indel (insertion and deletion), and one exonic deletion (Exon 36). When family history was taken into consideration, the mutation detection rate rose to 91% (29 of 32). We further investigated the phenotypic data and found that one third (47 of 157) of the families fit the Ghent criteria for MFS. Based on that data, the mutation rate was 98% (46/47). That finding implies that family history and the Ghent criteria play a more important role than clinical manifestations in establishing a clinical diagnosis of Marfan syndrome. Among the 56 mutations found in this study, 40 (71%) have not been registered in the Human Gene Mutation Database (HGMD) or in the Universal Mutation Database (UMD). This is the first study of the mutation spectrum of MFS in a cohort of patients in Taiwan. The database is expected to considerably improve genetic counseling for and medical care of MFS families.     

Detection of six novel FBN1 mutations in British patients affected by Marfan syndrome

Marfan syndrome (MFS), an autosomal dominant disorder of the extracellular matrix, is due to mutations in fibrillin-1 (FBN1) gene. Investigations carried out in the last decade, unveiled the unpredictability of the site of the mutation, which could be anywhere in the gene. FBN1 mutations have been reported in a spectrum of diseases related to MFS, with no clear evidence for a phenotype-genotype correlation. In this paper we analysed 10 British patients affected by MFS and we were able to characterise five novel missense mutations (C474W, C1402Y, G1987R, C2153Y, G2536R), one novel frameshift mutation (7926delC), one already described mutation (P1424A) and one FBN1 variant (P1148A) classified as a polymorphism in the Asian population. Four out of the five novel missense mutations involved either cysteines or an amino acid conserved in the domain structure. The mutation yield in this study is calculated at 80.0% (8/10), thus indicating that SSCA is a reliable and cost-effective technique for the screening of such a large gene. Our results suggest that this method is reliable to search for FBN1 mutations and that FBN1 screening could be a helpful tool to confirm and possibly anticipate the clinical diagnosis in familial cases. Hum Mutat 18:251, 2001.     

Difficulties in diagnosing Marfan syndrome using current FBN1 databases

PurposeThe diagnostic criteria of Marfan syndrome (MFS) highlight the importance of a FBN1 mutation test in diagnosing MFS. As genetic sequencing becomes better, cheaper, and more accessible, the expected increase in the number of genetic tests will become evident, resulting in numerous genetic variants that need to be evaluated for disease-causing effects based on database information. The aim of this study was to evaluate genetic variants in four databases and review the relevant literature.MethodsWe assessed background data on 23 common variants registered in ESP6500 and classified as causing MFS in the Human Gene Mutation Database (HGMD). We evaluated data in four variant databases (HGMD, UMD-FBN1, ClinVar, and UniProt) according to the diagnostic criteria for MFS and compared the results with the classification of each variant in the four databases.ResultsNone of the 23 variants was clearly associated with MFS, even though all classifications in the databases stated otherwise.ConclusionA genetic diagnosis of MFS cannot reliably be based on current variant databases because they contain incorrectly interpreted conclusions on variants. Variants must be evaluated by time-consuming review of the background material in the databases and by combining these data with expert knowledge on MFS. This is a major problem because we expect even more genetic test results in the near future as a result of the reduced cost and process time for next-generation sequencing.     

Detection of thirty novel FBN1 mutations in patients with Marfan syndrome or a related fibrillinopathy

Marfan syndrome (MFS) is a disorder of the extracellular matrix caused by mutations in the gene encoding fibrillin-1 (FBN1). Recent studies have illustrated the variability in disease severity and clinical manifestations of MFS. Useful genotype-phenotype correlations have been slow to emerge. We screened 57 unrelated patients with MFS or a Marfan-like phenotype using a combination of SSCP and/or DHPLC. We detected 49 different FBN1 mutations, 30 (62%) of which were novel. The mutations comprised 38 substitutions (78%), 10 deletions (20%), and one duplication (2%). There were 28 missense (57%), nine frameshift (18%), eight splice site (16%), and four nonsense mutations (8 %). Genotype-phenotype analysis revealed that patients with an identified FBN1 mutation were more likely to have ectopia lentis and cardiovascular complications compared to those without an identifiable mutation (relative risks of 4.6 and 1.9, respectively). Ectopia lentis was also found to be more prevalent in patients whose mutations involved a cysteine substitution (relative risk 1.6) and less prevalent in those with premature termination mutations (relative risk 0.4). In our hands, we achieved 93% mutation detection for DHPLC analysis of patients who fulfilled the Ghent criteria. Further analysis of detailed clinical information and mutation data may help to anticipate the clinical consequences of specific FBN1 mutations.     

Alternative splicing of exon 37 of FBN1 deletes part of an 'eight-cysteine' domain resulting in the Marfan syndrome

A child and his father had the skeletal and cardiovascular manifestations of Marfan syndrome due to a heterozygous G+5 --> T transversion in intron 37 of the FBN1 gene. Cultured dermal fibroblasts preferentially used an alternative splice site in exon 37 that resulted in the loss of the 3' 48 nucleotides of this exon. The translational reading frame was maintained with deletion of lysine 1568 to threonine 1582 and splitting of the codons for glycine 1567 and serine 1583 to yield GCC for alanine. The deletion removed two cysteine residues as well as a potential N-linked oligosaccharide attachment site from the '8-cysteine' domain encoded by exons 37 and 38.     

Pathogenic FBN1 variants in familial thoracic aortic aneurysms and dissections

Marfan syndrome (MFS) due to mutations in FBN1 is a known cause of thoracic aortic aneurysms and acute aortic dissections (TAAD) associated with pleiotropic manifestations. Genetic predisposition to TAAD can also be inherited in families in the absence of syndromic features, termed familial TAAD (FTAAD), and several causative genes have been identified to date. FBN1 mutations can also be identified in FTAAD families, but the frequency of these mutations has not been established. We performed exome sequencing of 183 FTAAD families and identified pathogenic FBN1 variants in five (2.7%) of these families. We also identified eight additional FBN1 rare variants that could not be unequivocally classified as disease‐causing in six families. FBN1 sequencing should be considered in individuals with FTAAD even without significant systemic features of MFS.     

Mutations of FBN1 and genotype-phenotype correlations in Marfan syndrome and related fibrillinopathies

The Marfan syndrome (MFS) is a pleiotropic, autosomal dominant disorder of connective tissue with highly variable clinical manifestations including aortic dilatation and dissection, ectopia lentis, and a series of skeletal anomalies. Mutations in the gene for fibrillin-1 (FBN1) cause MFS, and at least 337 mainly unique mutations have been published to date. FBN1 mutations have been found not only in MFS but also in a range of connective tissue disorders collectively termed fibrillinopathies ranging from mild phenotypes, such as isolated ectopia lentis, to severe disorders including neonatal MFS, which generally leads to death within the first two years of life. The present article intends to provide an overview of mutations found in MFS and related disorders and to discuss potential genotype-phenotype correlations in MFS.     

Marfan syndrome caused by a novel FBN1 mutation with associated pigmentary glaucoma

Mutations in fibrillin‐1 (FBN1) cause a wide spectrum of disorders, including Marfan syndrome, which have in common defects in fibrillin‐1 microfibrils. Ectopia lentis and myopia are frequently observed ocular manifestations of Marfan syndrome. Glaucoma is also associated with Marfan syndrome, though the form of glaucoma has not been well‐characterized. In this report, ocular examination of a patient diagnosed with Marfan syndrome based on family history and aortic dilatation was performed, including measurement of facility of aqueous humor outflow by tonography. The patient did not have ectopia lentis at the age of 42 years. Based on optic nerve appearance, reduced outflow facility, elevated IOP with open angles and clear signs of pigment dispersion, the patient was diagnosed with pigmentary glaucoma. The patient was heterozygous for a novel truncating mutation in FBN1, p.Leu72Ter. Histology of normal human eyes revealed abundant expression of elastic fibers and fibrillin‐1 in aqueous humor outflow structures. This is the first report of a patient with Marfan syndrome that is caused by a confirmed FBN1 mutation with associated pigmentary glaucoma. In addition to identifying a novel mutation of FBN1 and broadening the spectrum of associated ocular phenotypes in Marfan syndrome, our findings suggest that pigmentary glaucoma may involve defects in fibrillin‐1 microfibrils. © 2013 Wiley Periodicals, Inc.