先天性无虹膜家系中发现PAX6基因新的致病突变

目的对中国一先天性无虹膜家系进行PAX6基因突变检测,以确定其突变位点。方法实验研究。收集一先天性无虹膜家系,采集该家系患者及健康成员的外周静脉血,收集100名健康人外周血作为正常对照,采用Sanger测序的方法对PAX6基因的11个外显子（外显子4-14）以及外显子-内含子连接区域进行测序,随后进行家系共分离分析以及正常样本的对照分析。结果该家系8名成员经全面眼科检查,3名确诊为先天性无虹膜,且合并有复杂的眼部表型,包括不同程度的角膜病变、不同类型的白内障、黄斑发育不良、轻度上睑下垂和轻度眼球水平震颤等。在该家系患者中发现一个新杂合突变[c.569_570delinsACGG（p.Ile190Asnfs*18）],该突变可致PAX6基因编码的蛋白截短,该突变符合共分离且在100名正常对照者中未检测到。结论PAX6基因第8外显子上一个新的杂合突变[c.569_570delinsACGG（p.Ile190Asnfs*18）]为本研究中先天性无虹膜家系的致病突变,该突变与先天性无虹膜有关,本研究扩大了PAX6基因的突变频谱。     

一先天性无虹膜家系PAX6基因遗传筛查及临床表型

目的探讨我国常染色体显性遗传先天性无虹膜一家系患者的致病基因突变位点及其临床表型。方法实验研究。于南京医科大学第一附属医院眼科收集一先天性无虹膜家系,共8名家庭成员,其中3名患者,2名正常同胞,3名配偶。完善该家系内所有参与者的眼科检查,采集该家系成员的外周静脉血,提取基因组DNA,扩增PAX6基因的全部编码区及外显子-内含子交界区剪切位点附近的序列,直接测序法确定该家系的致病突变。结果遗传学筛查结果证实该家系的致病突变为位于PAX6基因第7号外显子与第7号内含子交接处的杂合突变（c.357+5G>A）。生物信息学分析结果表明该突变可导致正常剪切位点的缺失,产生移码突变,形成截短蛋白p.Ser121Asnfs*30。该家系中3例患者均表现出典型的先天性无虹膜症的临床表型,表现为虹膜发育不全,与此同时,该家系内患者还具有上睑下垂、白内障、眼球震颤、青光眼及玻璃体混浊等眼部异常。结论PAX6 c.357+5G>A杂合突变为该家系的致病突变,是该家系发生先天性无虹膜及上睑下垂、白内障、眼球震颤、青光眼及玻璃体混浊等一系列临床表型的主要致病原因。     

中国一先天性无虹膜家系PAX6基因新致病突变位点的筛查及验证

背景 先天性无虹膜是临床上罕见的先天性遗传性眼病.研究显示,配对盒转录因子6基因(PAX6)与先天性无虹膜症密切相关,但不同患者中PAX6基因的突变位点不同. 目的 对中国一常染色体显性遗传先天性无虹膜家系进行PAX6基因突变位点分析. 方法 于2014年8月在郑州大学第一附属医院收集一汉族先天性无虹膜家系,采集该家系9名成员及同期100名健康体检者的外周静脉血10 ml,采用标准酚-氯仿提取法提取基因组DNA,对PCR扩增产物进行测序、对比及突变分析.采用实时荧光定量PCR法验证和比较该家系中患病者与该家系表型正常者和健康对照者淋巴细胞中PAX6 mRNA的相对含量. 结果 该家系共3代9名成员,遗传方式符合常染色体显性遗传.家系中共5例患病者,成年患病者均表现为虹膜缺失和白内障,儿童患病者表现为无虹膜;其他4名家系成员表型正常.测序结果显示,家系患病者均存在11号染色体PAX6基因10号外显子的移码突变,第796位核糖核苷酸G缺失(c.796 del G),产生提前终止密码子,而家系正常成员及100名对照者均无此突变.实时荧光定量PCR结果显示,家系中患病者淋巴细胞中PAX6 mRNA表达水平比家系中正常成员约低50％,差异有统计学意义(Z=-2.449,P=0.016). 结论 PAX6基因c.796 del G为此先天性无虹膜家系的致病突变位点,扩增了PAX6基因突变谱.     

先天性无虹膜合并先天性白内障家系致病基因突变分析

目的：对先天性无虹膜合并先天性白内障家系进行PAX6基因突变位点筛查,丰富该致病基因的突变谱。

方法：选取就诊于北京同仁医院眼科门诊的1个先天性无虹膜合并先天性白内障家系和100名健康志愿者,采集外周静脉血,提取基因组DNA,采用直接测序法进行PAX6基因突变位点的筛查。

结果：该家系中先证者和其他患者均表现为无虹膜合并白内障,PAX6基因测序结果显示,该致病基因第11外显子无义突变c.991 C>T,造成PAX6基因编码的蛋白截短(R331X),从而使该蛋白失去功能,且该突变在家系内与疾病表型共分离,不存在于家系内及家系外健康样本的基因中。

结论：PAX6 R331X突变与先天性无虹膜合并先天性白内障的发生有关。     

应用外显子结合目标区域捕获测序芯片对一回族先天性白内障家系致病基因的检测

背景 先天性白内障是造成儿童盲和弱视的重要原因,其中约50％的先天性白内障具有遗传性.目的 应用眼遗传病外显子结合目标区域捕获测序芯片检测一常染色体显性遗传先天性白内障家系的致病基因.方法 于2011年在宁夏眼科医院收集一回族常染色体显性遗传先天性白内障家系,采集家系中患者及表型正常成员的临床资料.对家系成员进行眼科检查,抽取患者、表型正常家系成员及300名正常对照者的外周静脉血各5 ml,提取DNA,利用眼遗传病外显子结合目标区域捕获测序芯片筛查和检测候选致病突变位点.采用PCR和直接测序法对家系成员和正常对照者进行突变位点验证,最终确定致病突变位点.结果 该家系共6代61名成员,均为回族,先天性白内障患者18例,为5代遗传,符合常染色体显性遗传特征.患者中合并眼球震颤和斜视者7例,合并高度近视者4例,来诊前均已实施白内障摘出术.利用眼遗传病外显子结合目标区域捕获测序芯片检测结合生物信息学方法筛查后共得到8个候选致病突变位点,其中5个在非编码区,3个在编码区,通过PCR和直接测序法验证确定CRYGD基因上的P24T突变是该家系的致病突变位点.该突变与家系内所有患者表型共分离,在家系表型正常者及300名正常对照者均未发现此突变.结论 外显子结合目标区域捕获测序技术快速检测CRYGD基因P24T突变为该先天性白内障家系致病突变,该技术为临床表型多样、致病基因众多的先天性白内障的致病基因检测提供新的手段.     

三个先天性无虹膜症家系中PAX6基因的突变分析

背景 人类配对盒基因(PAX6)编码一个转录调节子,对眼和大脑形态的形成起关键作用.PAX6突变可导致许多先天性眼部发育异常,如先天性无虹膜症,通常为常染色体显性遗传方式. 目的 对三个先天性无虹膜症家系成员进行PAX6基因分析,探索这些家系发病的遗传基础. 方法 收集三个先天性无虹膜症家系的5例患病者和正常成员13名的外周血标本提取DNA,根据PAX6基因的序列设计4～ 13外显子序列,通过聚合酶链反应(PCR)扩增引物并测序,将目标序列与已发表的PAX6基因序列进行对比分析.结果 三个家系中共有5例患病者,在家系A中2例患者发现一个杂合突变(c.718 C＞T),导致第240位氨基酸由精氨酸突变为终止密码子(p.A rg240X),而其他正常表型者未发现此突变.家系B中的患病者和正常成员均未检测到PAX6基因的突变.家系C中1例患病者发现c.331 delG(p.Val111SerfsX13)的缺失突变,此单个碱基的缺失造成了移码突变,使PAX6蛋白羧基端的299个氨基酸缺失,而此家系的其他正常表型成员未发现此突变. 结论 家系A和家系C先天性无虹膜症的致病与PAX6基因的突变有关.     

PAX6基因在一先天性无虹膜家系中的突变筛查

目的研究PAX6基因突变是否是导致一先天性无虹膜家系致病的原因。方法收集一先天性无虹膜家系,制备外周血基因组DNA,PCR扩增PAX6基因的外显子及其邻近的内含子,应用单链构象多态性（SSCP）法检测,如果发现变异条带,将相应的扩增产物回收并纯化后进行PAX6基因测序。测序结果与GenBank公布的PAX6基因正常序列比对,寻找有无突变。结果本家系43名成员中有8例患病,遗传方式符合常染色体显性遗传特点,40岁以上的4例患者眼压高于35mmHg。所有患者中未发现全身并发症。在家系所有患者中均未发现异常条带。结论 PAX6基因与该先天性无虹膜家系无关。该家系的致病基因有待进一步通过全基因组扫描的方法来确定。     

先天性无虹膜症一家系PAX6基因Q310X突变的致病研究

目的 探讨先天性无虹膜症一家系的致病基因突变情况与发病机制.方法 采用病例对照研究方法.对该家系所有成员21人进行全面的眼科检查,同时进行家系调查并采集外周血样本,分离单个核细胞;用基因组DNA纯化试剂盒提取基因组DNA,以先证者DNA为模板聚合酶链反应法扩增转录因子PAX6基因全部14个外显子,用双脱氧末端终止法进行测序分析.结果 测序结果发现先证者Ⅲ2的PAX6基因在第11外显子上有Q310X(c.1378C>T)无义突变.它导致了第301位氨基酸密码子由CAA改变为TAX(Q301X),编码的谷氨酰胺突变为强终止密码子.对该家系中所有21名成员PAX6基因测序,结果发现所有10例患者都携带这一突变,而11名正常人则未检测到这一改变.结论 PAX6基因Q310X的无义突变所致PAX6蛋白翻译提前终止是此先天性无虹膜症家系的致病原因.     

中国一先天性无虹膜家系的遗传分析及PAX6基因突变位点的检测

背景 先天性无虹膜是双眼发病的遗传性疾病,目前的研究表明先天性无虹膜患者配对盒转录因子6(PAX6)基因突变位点具有多样性. 目的 通过目标序列捕获测序结合一代测序验证技术对1个中国先天性无虹膜家系进行基因突变位点的筛查和遗传分析.方法 采用横断面研究方法,本研究组于2016年3月纳入在郑州大学第一附属医院确诊的1个中国汉族先天性无虹膜家系,并对该家系成员进行致病突变基因检测.该家系全体成员均接受神经系统、口服葡萄糖耐量试验等全身体格检查以及眼科相关检查.采集现存家系所有成员前臂静脉血10 ml以提取基因组DNA,以先证者基因组DNA为模板行前房角发育异常致病基因的目标基因定点捕获测序分析,经与各基因库比对筛选出候选致病基因位点,采用PCR法对该家系成员行致病基因位点DNA片段扩增,采用Sanger测序技术在该家系除先证者以外的2例患病者和表型正常成员中进行候选致病基因验证. 结果 该家系共3代9名成员,Ⅰ1去世,现存8位成员,包括患病者3例(Ⅱ2及其子代Ⅲ1、Ⅲ2)和表型正常者5人,符合常染色体显性遗传模式.所有家系成员未发现神经系统异常,口服葡萄糖耐量试验结果均呈阴性.3例患病者视力均明显下降且不能矫正,眼压平均值为21 mmHg(1 mmHg=0.133 kPa),患者均存在虹膜完全缺如、角膜基质层混浊、眼球水平震颤、黄斑中心凹发育不良症状.此外,Ⅱ2患者存在左眼上睑下垂、右眼先天性白内障表现,Ⅲ2同时存在双眼先天性白内障、双侧晶状体不全脱位.先证者目标序列捕获测序分析及数据库比对显示,所有患病者PAX6基因第6号外显子上碱基替换c.183C＞A,经Sanger测序验证后证实突变基因与表型共分离. 结论 PAX6基因c.183C＞A突变是该先天性无虹膜家系的致病突变位点.     

珊瑚状先天性白内障一家系致病基因筛查与鉴定

目的：对一个珊瑚状先天性白内障家系进行致病基因的筛查。方法：采集家系中2例患者和1例正常对照者的外周静脉血,提取基因组DNA。选择与珊瑚状白内障相关的候选基因GJA3、GJA8、CRYGC及CRYGD设计引物,进行聚合酶链反应（ PCR）扩增候选基因,并对扩增片段进行Sanger测序。结果：该家系疾病表型为珊瑚状白内障,呈常染色体显性遗传。通过对扩增产物测序,发现家系内患者CRYGD第2个外显子第70位有1个C＞A碱基的杂合突变（ c．70C＞A）,正常对照未见该点突变。结论：CRYGD基因的错义突变c．70C＞A是该珊瑚状白内障家系的致病原因。     

PAX6 Analysis of Two Unrelated Families from the Arabian Peninsula with Classic Hereditary Aniridia

Introduction: Reports from around the world confirm that heterozygous PAX6 mutation is the major cause of hereditary aniridia (with a classic phenotype of iris hypoplasia, keratopathy, lens opacity, and foveal hypoplasia). However, genotype/phenotype reports are lacking from the Arabian Peninsula, a historically isolated region with a relatively high incidence of recessive disease and thus a potential for phenocopy and pseudodominance. The purpose of this study to assess for PAX6 mutation in two unrelated families with classic hereditary aniridia from the Arabian Peninsula. Methods: Interventional cases series of two unrelated affected Saudi Arabian families. Available family members underwent ophthalmic examination and venous blood sampling for PAX6 sequencing. Results: The pedigrees of both families suggested dominant (or pseudodominant) inheritance of the classic aniridia phenotype. Affected individuals in Family #1 were heterozygous for a novel frameshift PAX6 mutation (c.delA1294). Affected individuals in Family #2 had heterozygosity for a commonly-reported PAX6 nonsense mutation (p.Arg240X). Conclusions: PAX6 haploinsufficiency, the major cause of classic hereditary aniridia worldwide, is also associated with the phenotype in two different families from the Arabian Peninsula. Homozygosity by descent is not expected to affect genotype/phenotype correlation for the classic phenotype.     

A novel PAX6 gene mutation (P118R) in a family with congenital nystagmus associated with a variant form of aniridia

Background: A variety of PAX6 gene mutations were identified in patients with aniridia and/or allied ocular dysgenesis such as keratopathy, Peters’ anomaly, foveal hypoplasia, and nystagmus. To scrutinize the etiology of a four-generation Japanese family with autosomal dominant nystagmus associated with anterior and posterior segment anomalies, the PAX6 gene was examined. Patients and methods: A Japanese family showed a variant aniridia phenotype in four successive generations. Affected individuals had congenital nystagmus, microcornea with shortened axial length, superficial peripheral corneal opacification with pannus formation, dislocated pupil, and foveal hypoplasia. Analysis of the PAX6 gene mutation was performed in affected and unaffected individuals. Results: A novel missense mutation in the PAX6 gene was found in all affected individuals examined, but neither in unaffected individuals nor in unrelated healthy individuals. This mutation predicted a proline to arginine change at codon 118 (P118R) in the paired domain of PAX6 protein. Conclusion: The reported family illustrates that mutations in the PAX6 gene, in particular missense mutations, may manifest atypical clinical expression or forme fruste of aniridia. Received: 24 June 1999 Revised: 22 November 1999 Accepted: 23 November 1999     

A Novel PAX6 Mutation in Chinese Patients with Severe Congenital Aniridia

Purpose: We identified a novel mutation in Paired Box gene 6 (PAX6) and characterized its associated clinical features of severe ocular malformation in a Chinese family with congenital aniridia. Methods: We studied two patients with aniridia from a Chinese family. All patients and noncarriers in this family underwent full ophthalmologic, general and urinary examinations. Total genomic DNA was isolated from peripheral blood of two aniridia patients. PAX6 levels were determined by PCR and its mutational status was determined by sequencing. Direct sequencing detected variations in PAX6. Results: Patients had bilateral congenital nystagmus, anterior polar cataract, absence of iris tissue, and foveal hypoplasia with severely reduced visual acuity. A novel heterozygous PAX6 mutation in exon 6 c.662G>A (p.W100X) was identified which created a premature termination codon. This observed sequence alteration was not found in 100 normal controls and has not been previously reported. Conclusions: We identified a novel PAX6 mutation in a family with severe ocular malformation. Our study expands the mutational spectrum of PAX6 and enriches our knowledge of the relationship between genotype and phenotype due to these mutations.     

A novel deletion downstream of the PAX6 gene identified in a Chinese family with congenital aniridia

Purpose: Congenital aniridia, a severe bilateral panocular visual disorder, is an autosomal dominantly inherited eye anomaly. Mutations in the paired box 6 gene (PAX6) have been shown to be responsible for congenital aniridia in most patients. The purpose of the present study was to report clinical features of a Chinese family with congenital aniridia and to screen novel genetic mutations for congenital aniridia.

Methods: All members of a three-generation family underwent comprehensive ophthalmic examination, and 8 of its 25 members were diagnosed with congenital aniridia. The proband was analyzed by exome sequencing and whole genome sequencing, and linkage analysis was performed for the family. The mutation was confirmed by direct DNA sequencing.

Results: Using Illumina’s Human Linkage-12 beadchip microarray (including 6090 SNPs) whole genome scan, the LOD score value showed that the interval on chromosome 11 between rs1389423 to rs910090 exhibited a strong linkage. A novel heterozygous 469 kb deletion mutation within the downstream region of PAX6 (chr11:31189937–31659379) was identified in all affected family members, but not in unaffected family members or 2000 ethnically matched controls.

Conclusion: A novel deletion mutation was identified within the PAX6 downstream region that results in congenital aniridia.     

Microphthalmia,late onset keratitis,and iris coloboma/aniridia in a family with a novel PAX6 mutation

Autosomal dominant microphthalmia with late-onset keratitis and iris coloboma/aniridia has not been reported before. Here we report a Chinese family with these phenotypes and a novel PAX6 mutation. Microphthalmia, late-onset keratitis, iris coloboma, and nystagmus were present in the proband. His son had microphthalmia, aniridia, foveal hypoplasia, and nystagmus. A novel c.649C>T (p.Arg217X) mutation in PAX6 was detected in the proband and his affected son. This study expands the phenotypic spectrum of PAX6 mutation and enriched our knowledge of the genetic cause for microphthalmia and late-onset keratitis.     

Microphthalmia, late onset keratitis, and iris coloboma/aniridia in a family with a novel PAX6 mutation

Autosomal dominant microphthalmia with late-onset keratitis and iris coloboma/aniridia has not been reported before. Here we report a Chinese family with these phenotypes and a novel PAX6 mutation. Microphthalmia, late-onset keratitis, iris coloboma, and nystagmus were present in the proband. His son had microphthalmia, aniridia, foveal hypoplasia, and nystagmus. A novel c.649C>T (p.Arg217X) mutation in PAX6 was detected in the proband and his affected son. This study expands the phenotypic spectrum of PAX6 mutation and enriched our knowledge of the genetic cause for microphthalmia and late-onset keratitis.