眼皮肤白化病分型及TYR基因新突变的鉴定

目的 了解我国眼皮肤白化病(oculocutaneous albinism,OCA)的分型和相关基因突变类型,探讨新突变可能的分子致病机制.方法 应用PCR方法扩增TYR基因,经DNA序列测定检出突变,采用错配引物PCR进行新突变的群体筛查,结合生物信息学方法探讨一种新突变的致病性和可能的分子致病机制.结果 10名患者中有5人存在2个突变TYR等位基因,共计8种突变类型,其中c.71G＞A(C24Y)和c.841G＞T (E281X)是OCA1A致病性新突变;C24极可能参与二硫键形成,C24Y将导致酪氨酸酶肽链内此二硫键消失,进而引起蛋白空间构象变化和功能异常而致病.结论 从基因水平初步了解了我国OCA1所占的比例,探讨了TYR基因C24Y的致病性并初步阐明了其致病的分子机制.本结果丰富了人类TYR基因突变类型,为我国OCA分型诊断、产前基因诊断和遗传咨询等积累了有价值的数据资料.     

一个眼皮肤白化病家系的 TYR基因变异研究

目的:分析1个眼皮肤白化病(oculocutaneous albinism,OCA)患者家系的基因变异情况。方法:采用芯片捕获高通量测序与Sanger测序技术对先证者及其父母进行基因测序,应用PolyPhen-2、SIFT、MutationTaster和FATHMM软件对新变异进行功能预测,同时对该家系的4例白化病患者...     

眼皮肤白化病研究的新途径及 TYR基因2种新突变的分析

目的: 探讨自眼皮肤白化病(OCA)患者毛发提取DNA对OCA分型研究的可行性及TYR基因2种新突变的致病性。方法: 应用毛发压片镜检,PCR扩增毛发DNA中OCA相关基因各外显子、外显子-内含子交界区及启动子区,直接以序列测定技术分析患者基因突变,明确患者的基因型。对于发现的新突变,采用突变等位基因频率等方法对其进行深入研究。结果: 3个家系的先证者均为1型OCA。家系1的先证者为c.715C>T (p.R239W)和c.929insC (p.P310PfsX7)突变的复合杂合子;家系2的先证者为c.896G>A (p.R299H)的纯合子;家系3的先证者为c.1362+3A>T和c.650G>C (p.R217P)突变的复合杂合子。其中,c.1362+3A>T和c.650G>C (p.R217P)突变为至今尚未报道的新突变,通过对新突变进行分析,推测其极可能为病理性新突变。结论: 本实验成功证实从毛发中提取DNA的方法对OCA分型研究的可行性,同时确定了2种致病性新突变,为今后OCA研究开拓了新的思路和途径。     

眼皮肤白化病Ⅰ型患者TYR基因突变研究

目的对1例眼皮肤白化病患儿及其父母进行TYR基因分析,确定其分型和基因型。方法PCR扩增外周血gDNA的TYR基因外显子和外显子-内含子交界区,以DNA序列测定技术检测先证者的TYR基因突变,应用错配PCR/限制性内切酶分析法进行突变的致病性研究。结果在先证者TYR基因内检测到C24Y和R299S两个突变等位基因,其中C24Y突变是国际上尚未见报道的OCA1致病突变。结论对1例中国大陆眼皮肤白化病Ⅰ型患者进行基因突变研究,发现并鉴定了一种OCA1致病性新突变—TYR基因C24Y。     

眼皮肤白化病常见亚型的基因与基因突变

白化病(albinism)是一组由黑素合成相关的基因突变导致眼或眼、皮肤、毛发黑色素缺乏引起的遗传性疾病.受累个体相应部位颜色浅淡或缺如,发育过程中眼部黑色素的缺乏又可导致视网膜中央小凹发育不良、视神经通路异常,出现眼球震颤、斜视、视力低下等.皮肤缺乏色素的保护,对紫外线敏感,易于患皮肤癌.     

眼皮肤白化病Ⅲ型研究进展

眼皮肤白化病Ⅲ型(OCA3)由酪氨酸酶相关蛋白1基因(TYRPl)突变所致,该基因与酪氨酸酶基因(TYR)结构相似.有研究显示,TYRPl在黑色素的合成过程中发挥重要作用,但具体机制尚未完全明了.较早前已确定了TYRPl基因S166X和1104delA两种病理性突变,最近在巴基斯坦和德国先后发现3种TYRPl基因新突变R373X、R356E、L36X,但它们与OCA3的关系有待进一步确定.以前曾认为OCA3只发生在黑色人种,最近在巴基斯坦和德国发现的这两例极可能是OCA3的病例却为高加索人种,这可能会更新人们对OCA3表型与亚型的认识.     

一个近亲婚配家系中的一种P基因新突变

目的在DNA水平上对1个有2例患者的姨表兄妹近亲婚配家系中的眼皮肤白化病患者进行分型诊断。方法用PCR扩增先证者P基因及TYR基因各外显子、外显子-内含子交界区及3＇端和5＇端非翻译区，以DNA序列测定技术检测基因突变，以DNA测序技术和限制性内切酶酶切法检测该家系其他成员及群体中正常人的相应基因位点。结果先证者和其白化病妹妹为P基因A787T突变纯合子，其父母和表型正常的弟弟均为A787T突变杂合子。先证者TYR基因未见突变。群体中102名表型正常者中无A787T突变等位基因。结论在基因水平确定我国存在眼皮肤白化病Ⅱ型，同时发现了一种P基因病理性新突变。     

眼皮肤白化病Ⅳ型产前基因诊断及一种MATP基因新突变

目的 对3例眼皮肤白化病(oculocutaneous albinism,OCA)患儿进行分型诊断,并在此基础上开展OCA4产前基因诊断研究,为临床OCA遗传咨询和产前诊断提供指导.方法 应用聚合酶链反应及DNA序列测定技术,确定先证者及其父母的基因型后,取绒毛或羊水进行产前基因诊断.结果 3例患儿均为OCA4.家系1患儿母亲后来两次怀孕,第1次诊断为患儿,已选择流产,再次怀孕时诊断为父源G349R致病基因携带者.家系2产前诊断结果显示胎儿既未获得父源突变,也未获得母源突变.家系3产前诊断结果显示胎儿仅获得父源G349R突变.结论 检出MATP基因3种已报道的OCA4致病性突变G349R、D160H和P419L,发现1种致病性新突变c,870delC.

Abstract：

Objective To provide guidance for clinical genetic counseling and prenatal diagnosis of oculocutaneous albinism (OCA) in China. Methods PCR and automatic DNA sequencing were applied to obtain the genotypes of the patients and their parents in three Chinese albinism families. Prenatal gene diagnoses were performed at early pregnancy by chorionic villus sampling (CVS) or by amniocentesis at midpregnancy. Results The three patients were all OCA4, whose genotypes were G349R/c. 870delC, G349R/P419L, G349R/D160H, respectively. The three couples had been diagnosed as carriers. In family 1, the first fetus was diagnosed as affected. Termination of pregnancy was opted following genetic counseling. The second fetus (monozygotic twin) was heterozygous only with the paternal G349R mutation. The fetus in family 2 did not get either one of the two mutations. The fetus in family 3 was heterozygous only with the paternal G349R mutation. Conclusion This study detected three reported pathogenic mutations of the membrane associated transporter protein gene (MATP), including G349R, D160H and P419L, and identified a novel pathogenic mutation c. 870delC. The prenatal gene diagnosis of OCA4 will be important to prevent the birth of affected child.     

眼皮肤白化病Ⅲ型研究进展

眼皮肤白化病Ⅲ型(OCA3)由TYRP1基因突变所致，该基因与TYR基因结构相似。有研究显示，TYRP1在黑色素的合成过程中发挥重要作用，但具体机制尚未完全明了。较早前已确定了TYRP1基因S166X和1104delA两种病理性突变，最近在巴基斯坦和德国先后发现3种新突变R373X、R356E、L36X，但它们与OCA3的关系有待进一步确定。以前曾认为OCA3只发生在黑色人种，最近在巴基斯坦和德国发现的这两例极可能是OCA3的病例却为高加索人种，这可能会更新人们对OCA3表型与分型的认识。     

七个眼皮肤白化病Ⅰ型家系的早期产前诊断

目的 探讨酪氨酸酶基因( tyrosinase,TYR)检测用于眼皮肤白化病Ⅰ型(oculocutaneous albinism type Ⅰ,OCA1)产前诊断的可行性.方法 采用聚合酶链反应扩增与DNA直接测序技术对7个OCA1家系的先证者及其父母的TYR基因进行序列分析.在确定先证者或携带者的基因型后,对高危胎儿取胎盘绒毛进行产前诊断.结果 7个家系中均检出了TYR基因的复合杂合突变,包括R76Q、c.232insGGG、R116X、R278X、R299H、c.929-930insC、IVS2-11delTT、Q399X和W400L共9种,其中R76Q和Q399X为尚未报道的突变.对7个家庭的胎儿行产前诊断,1名胎儿携带与先证者相同的双突变,行引产术;2名胎儿未携带TYR基因突变,4名为突变携带者.6个家庭均选择继续妊娠,随访至出生后新生儿表型均无异常.结论 应用基因测序技术对TYR基因行突变分析可有效减少生育OCA1患儿的风险.     

Mutations of the human P gene associated with type II oculocutaneous albinism (OCA2)

Mutations in the human P gene lead to oculocutaneous albinism type 2 (OCA2, MIM #203200), the most common type of albinism in humans. The P gene encodes a 110 kDa protein that is associated with melanosomal membranes and contains 12 potential membrane spanning domains. The specific function of the P protein is currently unknown. We report 7 new mutations in the P gene associated with OCA2. This includes 6 missense mutations (S86R, C112F, A368V, T592I, A724P and A787V) and one frameshift mutation (1047del7). We also report 8 polymorphisms including one amino acid substitution, D/A257. We and others have found many polymorphisms of the P gene in the coding region, several of which result in amino acid substitutions, making molecular diagnosis problematic. In contrast to this is the tyrosinase gene associated with OCA1, with a limited number of polymorphic variations in the coding region. There is also no apparent clustering of P gene missense mutations in contrast to the clustering observed by the tyrosinase gene missense mutations that define functional domains of the protein. Further mutational analysis is needed to help define the critical functional domains of the P protein and to allow a definitive diagnosis of OCA2. © 1998 Wiley-Liss, Inc.     

13个白化病家系的遗传学分析及产前基因诊断

目的:对13个眼皮肤白化病(oculocutaneous albinism, OCA)家系进行致病基因变异鉴定,并以此为基础为患者家庭提供遗传咨询和产前基因诊断。方法:收集13例临床确诊的无亲缘关系的白化病患者,并根据患者皮肤和眼睛的临床表现确定疾病分型;采集先证者及其家系成员的外周血样各3~5 mL;用常规酚-氯仿法...     

Mutations of theTyrosinase gene in three Korean patients with Type I oculocutaneous albinism

Summary Oculocutaneous albinism (OCA) is an inherited disorder of the melanin pigmentary system, characterized by a decrease or an absence of melanin in the skin, hair, and eyes. Type I (tyrosinase-deficient) OCA results from mutations of thetyrosinase (TYR) gene encoding tyrosinase, the enzyme that catalyzes at least the first two steps of melanin biosynthesis. We have analyzed theTYR gene in three Korean patients with severe type I OCA. Two patients were compound heterozygotes for the Arg (CGG) to Gln (CAG) mutation at position 77 and a C insertion mutation at position 310. The other was a compound heterozygote for a C insertion mutation at position 310 and the Asp (GAT) to Asn (AAT) mutation at position 383. These mutations were easily detected by restriction enzyme digestion or by SSCP analysis. Such methods of mutation analysis thus provide a basis for a screening system for theTYR gene mutations in Korean patients with type I OCA.     

Detection of 53 novel DNA variations within the tyrosinase gene and accumulation of mutations in 17 patients with albinism

Oculocutaneous albinism (OCA) in man may be caused by mutations within the tyrosinase gene (TYR) resulting in OCA1. Analysing patients with recessively inherited albinism we found DNA variations in 82 unrelated individuals. 53 out of 78 mutations and polymorphisms revealed by this study are not published previously. The changes include 68 nucleotide substitutions resulting in amino acid changes, stop mutations and polymorphisms as well as four nucleotide insertions and six deletions. Furthermore, we found an accumulation of three to five mutations in 17 patients with OCA1.     

Mutations in the MATP gene in five German patients affected by oculocutaneous albinism type 4

Oculocutaneous albinism (OCA) is caused by a deficiency of melanin synthesis and characterized by generalized hypopigmentation of skin, hair, and eyes. Due to the hypopigmentation of the retinal pigment epithelium, OCA is usually associated with congenital visual impairment, in addition to an increased risk of skin cancer. OCA is a genetically heterogeneous disease with distinct types resulting from mutations in different genes involved in the pathway which results in pigmentation. OCA1 is associated with mutations in the TYR gene encoding tyrosinase. OCA2 results from mutations in the P gene encoding the P protein and is the most common form of OCA. OCA3, also known as rufous/red albinism, is caused by mutations in the TYRP1 gene, which encodes the tyrosinase-related protein 1. Recently, OCA4 was described as a new form of OCA in a single patient with a splice site mutation in the MATP gene (or AIM1), the human ortholog of the murine underwhite gene. The similarity of MATP to transporter proteins suggests its involvement in transport functions, although its actual substrate is still unclear. We screened 176 German patients with albinism for mutations within the MATP gene and identified five individuals with OCA4. In this first report on West European patients, we describe 10 so far unpublished mutations, as well as two intronic variations, in addition to two known polymorphisms.     

Mutation analysis of the tyrosinase gene in oculocutaneous albinism

Type I oculocutaneous albinism (OCA) is an autosomal recessive disorder caused by the reduction or the absence of tyrosinase (TYR) activity in melanocytes of the skin, hair and eyes. Here we report an analysis of 45 patients with OCA. We found five novel mutations in the tyrosinase gene involved in the pathogenesis of oculocutaneous albinism type IA or type IB (OCA-1A/B) in five unrelated patients. Three mutations are missense mutations (G109R, P205T and H256Y) and two are nucleotide deletions (336-337delCA and 678-680delAGG). One patient is homozygous for the previously known V275F mutation but has an extremely mild OCA phenotype and has no eye features typical of OCA. In several patients we discovered only one or even no mutation in the coding sequence of the TYR gene. Thus, this disease may also result from mutations in non coding regions of the gene or in another gene involved in the biosynthesis of melanin. Hum Mutat 17:352, 2001.     

Mapping the TYR gene reveals novel and previously reported variants in Eastern Indian patients highlighting preponderance of the same changes in multiple unrelated ethnicities

Oculocutaneous albinism (OCA) is a group of congenital autosomal recessive disorders with seven known subtypes (OCA1–OCA7) characterized by loss or absence of pigmentation in the skin, hair, and eyes. OCA1, caused by pathogenic variations in the tyrosinase (TYR) gene, has been documented to be the most prevalent subtype across the world including India. In the present study, we recruited 53 OCA-affected individuals from 45 unrelated families belonging to 20 different marriage groups/ethnicities of 15 different districts of West Bengal. We took a targeted sequencing-based approach to find the causal variations in the TYR gene. We report here identification of two novel potentially pathogenic variations [NM_000372.4:c.614C>T, NP_000363.1:p.(Pro205Leu), and NM_000372.4:c.1036+1=/G>T], one novel synonymous TYR variant [NM_000372.4:c.204=/A>G, NP_000363.1:p.(Gln68=)], two pathogenic variations documented for the first time in Indian OCA cases [NM_000372.4:c.1147G>A, NP_000363.1:p.(Asp383Asn), and NM_000372.4:c.585G>A, NP_000363.1:p.(Trp195*)], along with nine previously reported pathogenic variants in 36 out of 53 (∼68%) patients recruited. We report common haplotype backgrounds for the two most prevalent variations [NM_000372.4:c.124G>A, NM_000372.4:c.832C>T] in cases belonging to different marriage/ethnic groups, suggesting a possible founder effect. To our knowledge, this is the most comprehensive genetic study on OCA1 from India, firmly establishing OCA1 as the commonest form of albinism in this part of the world.