中国汉族两个马凡综合征家系FBN1基因的一个新突变

目的 对两个常染色体显性遗传的马凡综合征家系进行基因诊断,并探讨其临床特点。方法 完成家系调查和系谱分析,通过聚合酶链式反应和直接测序的方法对收集到的两个家系中的成员进行原纤维蛋白1(fibrillin 1,FBN1)基因的突变检测。结果 两个家系均呈常染色体显性遗传模式。对两个家系成员进行FBN1基因突变检测发现,在两个家系的患者中发现一个相同的突变位点,即FBN1第27号外显子3463位碱基由G变为A( 3463G＞A),导致原纤维蛋白1第1 155位氨基酸由天冬氨酸变为天冬酰胺(Asp 1155Asn),而两个家系的正常成员及选取的100名健康对照中均未发现该突变位点。结论 先证者均符合Ghent标准诊断为马凡综合征,基因诊断发现两家系中相同的突变位点3463G＞A为中国汉族马凡综合征患者中首次报道。     

FBN1新生突变引起的马凡综合征及其基因型-表型的关联研究

 目的: 本研究对2个不同马凡综合征(Marfan syndrome)的小家系进行致病基因FBN1的编码区和剪切位点突变检测,以寻找致病的突变,并初步探索马凡综合征基因型-表型的关联。方法: 通过临床检查、实验室检查及心脏超声检查确诊2个无血缘关系的家庭中原疑似为马凡综合征的3例患者。运用新一代测序对家系1的疑似患者行FBN1基因的全外显子组测序,并对检出的致病性遗传变异进行Sanger验证及在所有家系成员中验证;对于家系2的存活成员,本研究直接进行PCR扩增FBN1基因的所有编码区及剪切位点,对产物进行直接Sanger测序。另外在50个正常对照中对新发现的突变位点进行基于PCR产物的测序分析,以排除多态性;并对实验结果行生物信息学分析。结果: 所有存活的疑似患者均确诊为马凡综合征。在家系1中,我们检测到了一个FBN1基因数据库中尚未报道的新突变c.4685G>A(p.Cys1562Tyr),并且患者父母和同胞姐姐均未检测到此变异,故此突变为一个新生突变。该错义突变使第1562位上极性中性的含硫的半胱氨酸被极性中性的含羟苯基的酪氨酸所替代,影响了fibrillin-1蛋白一个TGF-β结合结构域,导致蛋白质的二级结构发生改变。家系2含父母及一对同卵双胎患者,其中一患者已去世。我们在存活患者检测到1个FBN1基因的已报道致病突变c.3706T>C(p.Cys1236Arg),该突变在患者父母中不存在,故也为新生突变。结论: 本文报道了一例FBN1基因的新突变及另一例由FBN1基因已知突变引起的马凡综合征,二者皆为新生突变,并在家系中进行了基因型-表型的比较,表明家系1的新突变可能与经典马凡综合征的表型相关,而家系2的已知突变确和新生儿重症马凡综合征表型相关。     

马凡综合征微纤维蛋白1基因突变检测及单倍型连锁分析

目的：检测中国人马凡综合征（Marfan syndrome,MFS)患者微纤维蛋白1（fibillin-1,FBN1)基因的突变及对马凡综合征患者的家系成员进行症状前诊断。方法：应用聚合酶链反应－单链构象多态性技术和测序方法，对汉族9个家系中共17个MFS患者进行基因突变检测；运用FBN1基因内4个内含子中的可变串联重复序列构建染色体单倍型，进行家系单倍型连锁分析和基因诊断。结果：发现MFS（A）家系Ⅱ1患者有单链构象改变，测序证实为位于FBN1基因第25号外显子3243－3256核苷酸之间有I个13bp的小片段缺失，为新位点基因移码突变，其序列为gcctctgcaccca;单倍型连锁分析发现MFS（B）家系Ⅲ1是1个无症状期患者。结论：中国人FBN1基因突变可以引起马凡综合征，应用突变检测与单倍型连锁分析方法能为马凡综合征基因诊断提供依据。     

Marfan氏综合征的临床基础及遗传分析

目的通过对马凡综合征患者的临床特征、病因及病理变化的分析,提高其治疗预后水平。方法对患者进行症状、体征、实验室等项检查,得到患者的眼、骨骼、心血管等系统的临床资料,收集完整的家系资料进行遗传分析,判断发病情况并评估再发风险。结果得到一马凡综合征患者的家系,并进一步确定其常染色体显性的遗传方式,明确了患者的表型特征,总结了目前的诊治方法,给与家系中相关人员以必要的遗传指导。结论马凡综合征是编码原纤维蛋白-1(原纤蛋白-1,FIBRILLIN-1)的基因FBN1的突变所致,对该病的诊断治疗已经取得了一定的进展。早期诊断,预防心血管并发症,是降低死亡率的关键。     

马凡综合征两种新的原纤维蛋白-1基因突变

目的对9例马凡综合征(Marfansyndrome,MFS)患者的原纤维蛋白-1(fibrillin-1,FBN1)基因进行突变筛查,以发现新的FBN1基因突变。方法应用变性高效液相色谱法对MFS患者FBN1基因65个外显子中的35个进行突变筛查,对变性高效液相色谱图形异常的PCR扩增片段用DNA测序鉴定突变位置及性质,并用等位基因特异性PCR以及限制性片段长度多态性分析等方法进一步证实突变。结果在两例MFS患者中发现两种新的FBN1基因突变。其中一种为第34外显子4307～4308位4个碱基TCGT的插入突变(4307insTCGT),另一种为第43外显子5309位的点突变5309G>A。结论FBN1基因移码突变(4307insTCGT)与点突变(5309G>A)分别是这两例MFS患者的发病原因。     

Crouzon综合征基因突变检测

目的 研究1个Crouzon综合征家系及1例散发的Crouzon综合征患者的成纤维生长因子受体2(fibroblast growth factors receptor 2,FGFR2)基因突变情况.方法 在1个Crouzon综合征家系的10名成员,和另一例散发者的外周血提取基因组DNA,PCR扩增FGFR2基因的第8和10外显子(部分家族成员仅扩增第8外显子),产物纯化后直接进行DNA测序检测突变.结果 家系中3名成员及另1例散发者FGFR2基因第8外显子的833位核苷酸发生G→T的转换突变,该突变为错义突变,使该位点所编码的氨基酸由半胱氨酸变为苯丙氨酸(C278F).该突变为杂合子突变.结论 FGFR2基因突变是Crouzon综合征致病原因.     

1例新生儿Marfan综合征患者双重突变的原纤蛋白-1等位基因

Marfan综合征是一种常染色体显性遗传的结缔组织疾病，表现为骨骼、眼及心血管异常。该病是因原纤蛋白-1（FBN1）缺陷所致。新生儿Marfan综合征（nMFS）是MFS表型表达最严重的结果，患者除具有在典型MFS中所见的许多骨骼特征外，并且二尖瓣、三尖瓣受累、主动脉根扩张，常在出生后一年内死于先天性心衰。现已知道，编码原纤蛋白-1的基因缺陷，可引起广泛的原纤蛋白病，包括MFS、nMFS及伴有相对轻的骨骼异常、晶状体异位和晚发的主动脉瘤的家系。有意义的是，在nMFS患者中所有报道的突变均集中在外显子24和34之间。本文首次报道1例…     

一个遗传性出血性毛细血管扩张症家系患者的ACVRL1基因突变分析

目的 确定一个遗传性出血性毛细血管扩张症家系患者ACVRL1基因突变位置及分析临床表型.方法 对该家系先证者ACVRL1基因常见突变位置第3、7、8外显子进行PCR和变性高效液相色谱方法筛查,随后DNA测序证实,确定突变位点后,扩增其家系另5名成员的相应区域筛查,并行DNA序列分析.结果 先证者胃黏膜见出血和毛细血管扩张,彩超显示右肾小动静脉瘘;4例患者ACVRL1基因第3外显子145delG,形成移码突变,导致第53密码子为UAG终止密码子,另2名无临床表现者未见此突变.结论 ACVRL1基因145delG突变是这个家系致病遗传基础.     

FBN1基因新变异所致马凡综合征患儿1例的分析

目的探讨1例马凡综合征(MFS)患儿的遗传学病因, 并分析其临床表型与基因型的相关性。方法选取2021年3月30日于中南大学湘雅三医院就诊的1例MFS患儿为研究对象。收集患儿及其家系成员的外周血样, 提取基因组DNA, 进行家系全外显子组测序, 对候选致病变异进行Sanger测序家系验证, 并用生物信息学软件分析变异的致病性。结果患儿为13岁男性, MFS体型包括身材瘦长、臂展大于身高、手指及足趾细长、漏斗胸、脊柱侧弯, 但未见主动脉扩张或胸腹主动脉瘤、二尖瓣脱垂等典型病变, 晶状体未见脱位。全外显子组测序显示其FBN1基因存在c.7383₇413del(p.N2461Kfs*211)杂合变异, 其父母、弟弟均未发现相同的变异。该变异既往未见文献报道, 被判断为致病性。结论本研究发现了FBN1基因的一个新变异, 进一步拓展了MFS的变异谱及表型谱。     

表皮松解性掌跖角化症一家系KRT9基因突变研究

目的研究表皮松解性掌跖角化症一家系角蛋白9(keratin 9,KRT9)基因突变情况。方法用聚合酶链反应技术扩增家系成员及家系外5O名正常人KRT9基因外显子1,DNA序列分析寻找突变位点。结果家系中患者KRT9基因外显子1第488位碱基C→T,导致162位的精氨酸被谷氨酸取代(R162Q),家系内正常成员及家系外5O名正常人均不存在此突变。结论 KRT9基因外显子1第488位密码子发生C→T突变导致该家系患者发生表皮松解性掌跖角化症。     

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.     

Compound-heterozygous Marfan syndrome

We report two families in which the probands have compound-heterozygous Marfan syndrome (MFS). The proband of family 1 has the R2726W FBN1 mutation associated with isolated skeletal features on one allele and a pathogenic FBN1 mutation on the other allele. The phenotype of the compound-heterozygous probands appears to be more severe than that of their heterozygous family members which underlines the possibility that certain trans-located FBN1 mutations might act as modifiers of phenotype explaining some of the intrafamilial variability in Marfan syndrome.     

Novel approach to the molecular diagnosis of Marfan syndrome: application to sporadic cases and in prenatal diagnosis

Marfan syndrome is an autosomal dominant disorder affecting the skeletal, ocular, and cardiovascular systems. Defects in the gene that encodes fibrillin-1 (FBN1), the main structural component of the elastin-associated microfibrils, are responsible for the disorder. Molecular diagnosis in families with Marfan syndrome can be undertaken by using intragenic FBN1 gene markers to identify and track the disease allele. However, in sporadic cases, which constitute up to 30% of the total, DNA-based diagnosis cannot be performed using linked markers but rather requires the identification of the specific FBN1 gene mutation. Due to the size and complexity of the FBN1 gene, identification of a causative Marfan syndrome mutation is not a trivial undertaking. Herein, we describe a comprehensive approach to the molecular diagnosis of Marfan syndrome that relies on the direct analysis of the FBN1 gene at the cDNA level and detects both coding sequence mutations and those leading to exon-skipping, which are often missed by analysis at the genomic DNA level. The ability to consistently determine the specific FBN1 gene mutation responsible for a particular case of Marfan syndrome allows both prenatal and pre-implantation diagnosis, even in sporadic instances of the disease.     

Homozygosity for a FBN1 missense mutation: clinical and molecular evidence for recessive Marfan syndrome

Marfan syndrome (MFS) is known as an autosomal-dominant connective tissue disorder (MIM 154,700), involving primarily the skeletal, ocular and cardiovascular systems, and caused by mutations in the gene for fibrillin1 (FBN1). Here, we report on two cousins from a consanguineous family with a homozygous c.1,453C>T FBN1 mutation (p.Arg485Cys) and MFS. All four healthy parents were heterozygous for the c.1,453C>T FBN1 mutation and none fulfilled the Ghent criteria for MFS. This family is the first molecularly confirmed recessive MFS. The demonstration of recessive cases of MFS has obvious implications for genetic counselling as well as for molecular diagnosis.     

Utility of molecular analyses in the exploration of extreme intrafamilial variability in the Marfan syndrome

The diagnosis of Marfan syndrome may be hampered by the existence of very mild and atypical cases as well as by marked intrafamilial variability. In these instances, molecular analysis of the fibrillin-1 gene (FBN1) can be helpful to identify individuals at risk. The underlying molecular mechanism for the clinical variability is presently unknown. We performed clinical and molecular studies in 36 subjects from three unrelated families. Expression studies of both FBN1 alleles were performed and related to the clinical severity. In family 1, an overlapping phenotype between Marfan syndrome (MFS) and Weill-Marchesani syndrome is presented. The diagnosis necessitated molecular studies and clinical examination in first-degree relatives. In family 2, the young proband presented with a phenotype overlapping between MFS and the kyphoscoliotic type of Ehlers-Danlos syndrome. Follow-up over time and identification of a FBN1 mutation allowed confirmation of the diagnosis. Mutation analysis enabled us to identify family members with mild expression. Family 3 illustrates the extensive intrafamilial variability in the clinical severity of MFS. Identification of a FBN1 mutation was helpful to identify subjects with mild expression and for the timely diagnosis in a neonate. In families 2 and 3, the relative expression of both FBN1 alleles was not related to clinical severity. We demonstrated that confirmation of the diagnosis of MFS may require detailed and repeated clinical evaluation and thorough family history taking. FBN1 mutation analysis is supportive for the diagnosis in mild and atypical presentations.     

Clinical and linkage study of a large family with simple ectopia lentis linked to FBN1

Simple ectopia lentis (EL) was studied in a large family, by clinical examination and analysis of linkage to markers in the region of FBNl, the gene for fibrillin which causes Marfan syndrome on chromosome 15. No patient had clinical or echocardiographic evidence of Marfan syndrome, although there was a trend towards relatively longer measurements of height; lower segment; arm span; middle finger, hand, and foot length in the affected members of the family, compared with unaffected sibs of the same sex. Analysis of linkage to intragenic FBN1 markers was inconclusive because they were relatively uninformative. Construction of a multipoint background map from the CEPH reference families identified microsatellite markers linked closely to FBN1 which could demonstrate linkage of EL in this family to the FBN1 region. LINKMAP analysis detected a multipoint lod score of 5.68 at D15S119, a marker approximately 6 cM distal to FBN1, and a multipoint lod score of 5.04 at FBN1. The EL gene in this family is likely to be allelic to Marfan syndrome, and molecular characterization of the FBN1 mutation should now be possible. © 1994 Wiley-Liss, Inc.     

TGGE screening of the entire FBN1 coding sequence in 126 individuals with marfan syndrome and related fibrillinopathies

Mutations in the gene for fibrillin-1 (FBN1) cause Marfan syndrome (MFS), an autosomal dominant heritable disorder of connective tissue with prominent manifestations in the skeletal, ocular, and cardiovascular system. FBN1 mutations have also been identified in a series of related disorders of connective tissue collectively termed type-1 fibrillinopathies. We have developed temperature-gradient gel electrophoresis (TGGE) assays for all 65 FBN1 exons, screened 126 individuals with MFS, other type-1 fibrillinopathies, and other potentially related disorders of connective tissue for FBN1 mutations, and identified a total of 53 mutations, of which 33 are described here for the first time. Several mutations were identified in individuals with fibrillinopathies other than classic Marfan syndrome, including aneurysm of the ascending aorta with only minor skeletal anomalies, and several individuals with only skeletal and ocular involvement. The mutation detection rate in this study was 42% overall, but was only 12% in individuals not fulfilling the diagnostic criteria for MFS, suggesting that clinical overdiagnosis is one reason for the low detection rate observed for FBN1 mutation analysis.     

The clinical spectrum of missense mutations of the first aspartic acid of cbEGF-like domains in fibrillin-1 including a recessive family

Marfan syndrome (MFS) is a dominant disorder with a recognizable phenotype. In most patients with the classical phenotype mutations are found in the fibrillin-1 gene (FBN1) on chromosome 15q21. It is thought that most mutations act in a dominant negative way or through haploinsufficiency. In 9 index cases referred for MFS we detected heterozygous missense mutations in FBN1 predicted to substitute the first aspartic acid of different calcium-binding Epidermal Growth Factor-like (cbEGF) fibrillin-1 domains. A similar mutation was found in homozygous state in 3 cases in a large consanguineous family. Heterozygous carriers of this mutation had no major skeletal, cardiovascular or ophthalmological features of MFS. In the literature 14 other heterozygous missense mutations are described leading to the substitution of the first aspartic acid of a cbEGF domain and resulting in a Marfan phenotype. Our data show that the phenotypic effect of aspartic acid substitutions in the first position of a cbEGF domain can range from asymptomatic to a severe neonatal phenotype. The recessive nature with reduced expression of FBN1 in one of the families suggests a threshold model combined with a mild functional defect of this specific mutation.