A novel mutation in FBN1 gene in autosomal dominant Marfan syndrome and macular degeneration in a Chinese consanguineous family

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.     

Recurrent FBN1 mutation (R62C) in a Chinese family with isolated ectopia lentis

PURPOSE: To examine the fibrillin-1 (FBN1) gene for mutations in members of a Chinese family with isolated ectopia lentis. DESIGN: Clinically relevant laboratory investigation. METHODS: Family members underwent clinical examinations. Genomic DNA was extracted from leukocytes of peripheral blood from the available members and 100 controls for mutation analysis. The 65 exons of FBN1 were amplified by polymerase chain reaction and screened for mutations by a combination of denaturing high-performance liquid chromatography analysis and direct DNA sequencing. RESULTS: A mutation, c.184C-->T in exon 2 of FBN1, which results in substitution of arginine by cysteine at position 62 of the fibrillin-1 protein (p.R62C) in all affected family members but in none of the unaffected individuals. CONCLUSIONS: A recurrent mutation of FBN1 gene resulted in an arginine-to-cysteine residue (p.R62C), is responsible for the patients with isolated ectopia lentis in a Chinese family.     

马凡综合征一家系FBN1基因突变筛查

目的 对一个马凡综合征家系进行FBN1基因突变筛查,探讨该家系的分子发病机制.方法 在征得患者知情同意下,采集家系中四名患者及两名正常个体外周静脉血5毫升,提取基因组DNA.采用直接测序法对FBN1基因全部65个外显子,以及外显子内含子拼接部进行序列分析.Polyphen程序分析FBN1基因突变引起的蛋白结构和功能改变.结果 通过基因突变筛查,发现该家系所有患者均携带有c.2261A＞G(p.Y754C)突变体,而患者家中正常个体及100名正常对照无此突变.经Polyphen程序分析,此突变将导致FBN1蛋白结构和功能的改变.结论 FBN1基因突变体p.Y754C是导致该马凡综合征家系的致病原因,此突变首次在中国马凡综合征患者中发现.

Abstract：

Objective To identify FBN1 gene mutations in a Chinese family with Marfan syndrome.Methods Four affected and two unaffected individuals in the family were recruited after informed consent.Five ml blood samples were drawn from each family member and genomic DNA was extracted. Mutations were detected by directly sequencing to the whole coding region and exon-intron boundaries of FBN1 gene.Polyphen program was used to predict the functional and structural changes of the mutant protein. Results We found all four affected individuals carried FBN1gene mutations, c. 2261A ＞ G ( p. Y754C), in exon18 by sequence analysis, while two unaffected family members and 100 normal controls did not have this mutation. A PSIC score of 2. 6 was acquired by Polyphen program analysis. Conclusion Our study supports that FBN1 gene mutation, c. 2261A ＞ G (p. Y754C), is the underlying molecular pathogenesis of this family with Marfan syndrome. This mutation is identified for the first time in Chinese population.     

Ophthalmic findings in a family with early-onset isolated ectopia lentis and the p.Arg62Cys mutation of the fibrillin-1 gene (FBN1)

Purpose: The purpose of this paper is to describe ophthalmic findings in a family with isolated ectopia lentis (EL) caused by a specific FBN1 mutation.

Methods: Detailed family histories and clinical data were recorded for six isolated EL patients of 11 family members. The ophthalmological and systematic examinations were performed on patients and unaffected members of the investigated family. The detailed ocular examinations included visual acuity, anterior chamber depth, pupil size, lens location, optometry, central corneal thickness, keratometry, slitlamp examination, fundus examination, axial length, ocular B-ultrasound, gonioscope checking, ultrasound biomicroscopy (UBM) and intraocular pressure (IOP; Goldmann applanation tonometer). Systematic examinations included the measurement of echocardiogram, height, arm span, skull, face, jaw, tooth, breast bone, spinal column, and skin. Genomic DNA was extracted using the phenol-chloroform extraction method for all subjects, and sequencing was carried out on an ABI Prism 3730 Genetic Analyzer.

Results: A heterozygous mutation, c.184C>T (p.Arg62Cys) in exon 2 of FBN1 was identified in all affected members but was not found in any unaffected member of the family. Our study presented detailed clinical manifestations, including some novel ophthalmic findings, such as pupillary abnormality, different types of glaucoma, and progressive hyperopia.

Conclusions: Ophthalmic findings and the p.Arg62Cys mutation of FBN1 gene were reported in a family with early-onset isolated ectopia lentis.     

FBN1基因新突变导致常染色体显性遗传眼病晶状体脱位一家系三例分析

目的 通过对一汉族晶状体脱位家系3名患病成员的原纤维蛋白-1（FBN1）基因突变分析,追踪观察眼睛、心血管及全身临床表现,分析FBN1基因突变与临床表型关系。方法 系列病例研究。收集该家系所有成员的眼与心血管系统等全身临床资料。采用聚合酶链式反应和直接测序法对该家系所有成员进行FBN1基因的突变检测。结果 研究发现3名晶状体脱位患者均携带FBN1基因一个新的错义突变（c.1999T>C;p.Cys 515Arg）,而家系中正常个体无此变异。SIFT和PolyPhen-2生物信息学分析数据高度支持该变异为致病性突变。家系中3名患者均存在不同程度的晶状体脱位,1名年长患者还伴有主动脉瘤样扩张。结论 FBN1基因c.1999T>C的突变可导致常染色体显性遗传眼病晶状体脱位。家系患者的的临床表现存在异质性,年轻患者是否可确诊为马凡综合征还需长期追踪观察。     

Identification of two novel compound heterozygous mutations of ADGRV1 in a Chinese family with Usher syndrome type IIC

Background:To describe the clinical and genetic findings in a Chinese family with three sibs diagnosed with Usher syndrome type IIC.

Materials and Methods: Four members received ophthalmic and otologic tests to ascertain the clinical characteristics. According to the clinical phenotype, we focused attention on a total of 658 genes associated with them. We screened the possible pathogenic mutation sites, used Sanger to exclude the false positive and verified whether there were co-segregated among the family members. Results:Typical fundus features found in the proband supported the diagnosis of retinitis pigmentosa (RP). Audiometric test indicated moderate to severe sensorineural hearing impairment while the vestibular function was normal. Whole-exome sequencing identified the presence of two novel compound heterozygous mutations in ADGRV1, a known gene responsible for Usher syndrome type IIC. Mutationc.15008delG/p.Gly5003AlafsTer13 was inherited from the mother while c.18383_18386dupACAG/p.His6130GlnfsTer84 was inherited from the father, and they were co-segregated with the disease phenotype in the family. Conclusions: The mutations found in our study not only broaden the mutation spectrum of ADGRV1, but also provide assistances for future genetic diagnosis and treatment for Usher syndrome patients.     

Mutation analysis of FBN1 gene in two Chinese families with congenital ectopia lentis in northern China

AIM: To summarize the phenotypes and identify the underlying genetic cause of the fibrillin-1 (FBN1) gene responsible for congenital ectopia lentis (EL) in two Chinese families in northern China. METHODS: A detailed family history and clinical data from all participants were collected by clinical examination. The candidate genes were captured and sequenced by targeted next-generation sequencing, and the results were confirmed by Sanger sequencing. Haplotyping was used to confirm the mutation sequence. Real-time PCR was used to determine the FBN1 messenger ribonucleic acid (mRNA) levels in patients with EL and in unaffected family members. RESULTS: The probands and other patients in the two families were affected with congenital isolated EL. A heterozygous FBN1 mutation in exon 21 (c.2420_IVS20-8 delTCTGAAACAinsCGAAAG) was identified in FAMILY-1. A heterozygous FBN1 mutation in exon 14 (c.1633C>T, p.R545C) was identified in FAMILY-2. Each mutation co-segregated with the affected individuals in the family and did not exist in unaffected family members and 200 unrelated normal controls. CONCLUSION: The insertion-deletion mutation (c.2420 IVS20-8delTCTGAAACA insCGAAAG) in the FBN1 gene is first identified in isolated EL. The mutation (c.1633C>T) in the FBN1 gene was a known mutation in EL patient. The variable phenotypes among the patients expand the phenotypic spectrum of EL in a different ethnic background.     

先天性晶状体半脱位一家系FBN1基因突变研究及手术治疗

目的 对一个先天性晶状体半脱位家系进行FBN1基因突变筛查,总结该家系晶状体半脱位的治疗方法。设计 回顾性病例系列。研究对象 2014年5月就诊于北京同仁医院白内障中心一个先天性晶状体半脱位家系人员25例。方法 提取该家系成员外周血全基因组DNA,利用目标基因捕获技术,收集目标基因组DNA,再利用HiSeq2000进行高通量测序,确定突变位点,用Sanger法验证测序结果。晶状体半脱位90°~180°者4例（8眼）行一期囊袋张力环IOL植入术（Phaco+CTR+IOL）,二期晶状体囊袋复合体（IOL-CTR)单点巩膜缝合固定术。晶状体半脱位大于180°者1例（2眼）行晶状体玻璃体切除IOL植入,巩膜缝合固定术（PPL+PPV+IOL）。2例（4眼）行晶状体囊内摘除术（ICCE）,1例（1眼）行玻璃体切除术（PPV）。主要指标 FBN1基因测序结果、术式、最佳矫正视力（BCVA）。结果 该家系所有患者FBN1基因38号外显子mRNA第4588位碱基均出现C→T杂合性错义改变,导致患者均携带c.4588C>T（p.R1530C）突变体,而家系正常个体15人无此突变。行Phaco+CTR+IOL联合二期IOL-CTR术后BCVA 0.5~0.8。行PPL+PPV+IOL术后BCVA 0.3~0.5。结论 FBN1基因c.4588C>T（p.R1530C）突变体是导致该家系的致病原因。采用一期囊袋内张力环IOL植入及二期IOL-CTR单点巩膜缝合固定术矫正IOL偏位效果较好。（眼科, 2018,  27： 85-90）     

Familial retinal detachment associated with COL2A1 exon 2 and FZD4 mutations

Background: To characterize the clinical and genetic abnormalities within two Australian pedigrees with high incidences of retinal detachment and visual disability. Design: Prospective review of two extended Australian pedigrees with high rates of retinal detachment. Participants: Twenty‐two family members from two extended Australian pedigrees with high rates of retinal detachment were examined. Methods: A full ophthalmic history and examination were performed, and DNA was analysed by linkage analysis and mutation screening. Main Outcome Measures: Characterization of a causative hereditary gene mutation in each family. Results: All affected family members of one pedigree carried a C192A COL2A1 exon 2 mutation. None of the affected family members had early‐onset arthritis, hearing abnormalities, abnormal clefting or facial features characteristic of classical Stickler syndrome. All affected members of the familial exudative vitreoretinopathy pedigree carried a 957delG FZD4 mutation. Conclusions: Patients with retinal detachment and a positive family history should be investigated for heritable conditions associated with retinal detachment such as Stickler syndrome and familial exudative vitreoretinopathy. The absence of non‐ocular features of Stickler syndrome should raise the possibility of mutations in exon 2 of COL2A1. Similarly, late‐onset familial exudative vitreoretinopathy may appear more like a rhegmatogenous detachment and not be correctly diagnosed. When a causative gene mutation is identified, cascade genetic screening of the family will facilitate genetic counselling and screening of high‐risk relatives, allowing targeted management of the pre‐detachment changes in affected patients.     

回旋状脉络膜视网膜萎缩一家系的新型突变与临床观察

目的：探讨一个回旋状脉络膜视网膜萎缩(GA)中国家系各家庭成员OAT基因的致病性突变及临床表现。

方法：对该家系中的6名家庭成员均进行详细的眼科检查,通过全外显子组测序、生物信息学分析及Sanger验证明确基因测序结果及致病性突变。

结果：先证者因其临床表现及体征诊断为GA。全外显子组测序结果显示先证者OAT基因分别于第6外显子和第10外显子上发现致病突变c.722C>T(p.P241L)、c.1186C>T(p.R396X),该复合杂合性突变在家系中呈现共分离状态。先证者的父亲和哥哥均检出杂合型p.R396X致病变异,母亲检出杂合型p.P241L致病变异。除先证者外,其他家庭成员均无临床症状。

结论：该家系的先证者为复合杂合性突变,其中p.P241L为首次报道的基因突变类型。这一研究结果扩大了OAT基因变异的范围,有利于在分子基础水平进一步理解GA的致病因素。新型突变类型的发现与证实也将有助于为GA的临床诊断和基因治疗提供新的依据。