显性遗传视网膜色素变性一家系的遗传分析

目的 对一个视网膜色素变性(retinitis pigmentosa,RP)家系进行基因诊断.方法 选取已知基因附近及覆盖X染色体的微卫星标记,对该家系进行了连锁分析.PCR扩增了包括ORF15在内的GTP酶调节因子基因(retinitis pigmentosa GTPase regulator,RPGR)所有外显子及外显子内含子交界区,对家系先证者进行了序列分析,找到突变之后,直接对家系成员及101个正常对照进行测序分析,以确定该突变是否和RP共分离.结果 连锁分析排除了已知的常染色体显性RP位点,对X染色体的连锁分析发现RP和胆GR所在位置的DXS993和DXS1068连锁,直接对RPGR测序发现缺失突变,g.ORF15+1166delA(c.2919delA).该缺失造成移码突变及提前终止.该突变为de novo,并和该家系所有患者共分离,而在家系正常个体及101个对照中不存在该突变.结论 RPGR新突变g.ORF15+1166delA引起X连锁视网膜色素变性.这一研究结果揭示RPGR突变的可以引起不同的临床表型.     

一个视网膜色素变性家系致病基因定位和CA4基因突变分析

目的通过对一个常染色体显性视网膜色素变性(autosomal dominant retinitis pigmentosa,adRP)家系致病基因的定位和基因突变分析,以确定该家系的致病基因及其突变形式。方法对15个已知的常染色体显性视网膜色素变性致病基因所在染色体位点进行连锁分析,以确定该家系与疾病连锁的染色体区域,对该区域附近候选基因进行直接序列分析。结果连锁分析提示在D17S701和D17S1604为正的连锁值(logofodds,LOD),分别为Zmax=2.107和Zmax=1.806。其余14个adRP染色体位点的微卫星标记两点LOD值均为负数。单倍型分析进一步将该家系致病基因定位于微卫星标记D17S916和D17S794之间的RP17位点,该位点adRP候选基因碳酸酐酶Ⅳ(carbonic anhydrase4,CA4)直接序列分析在其编码区未发现基因突变。结论将一个中国人常染色体显性视网膜色素变性家系的致病基因定位于RP17位点,但未发现该位点内的CA4基因突变,该家系是否存在CA4基因复杂突变或RP17位点是否存在新的视网膜色素变性致病基因有待于进一步研究。     

晶体蛋白βA1 基因缺失突变导致常染色体显性遗传核性先天性白内障

目的 对一个中国人的常染色体显性遗传核性先天性白内障家系的致病基因进行定位克隆研究。方法 选取候选基因附近的短串联重复序列多态性标记进行连锁分析，对提示连锁的染色体区域内的候选基因测序，寻找突变。结果 该家系致病基因定位在17q11．1-12约11．78cM的范围内，并在候选基因晶体蛋白βA1基因(CRYBA1)的外显子4发现一个密码子缺失(△G91)与家系患者共分离，在正常人群中没有检测到。结论 该家系的核性先天性白内障系由CRYBA基因外显子4的缺失突变△G91引起．这是首次报道由CRYBA1基因突变导致先天性核性自内障表型的发生。     

两个有血缘关系的常染色体显性非综合性耳聋家系基因突变分析

目的 对两个有血缘关系的常染色体显性非综合性耳聋家系进行基因定位及突变分析,确定其致病基因.方法 通过家系调查和临床检查,鉴定了两个有血缘关系的常染色体显性非综合性耳聋大家系.并对已知位点及基因进行连锁分析,对致病基因在染色体上进行定位.PCR扩增候选基因MYH14基因的所有外显子和外显子-内含子交界区,直接测序法进行突变检测.结果 将这两个家系的致病基因定位于DFNA4位点,最大连锁值为4.94.具有统计学意义.突变检测发现MYH14基因的杂合突变c.359T>C(p.S120L),DNA直接测序确证两家系的所有患者均携带该突变,而家系中正常人则均不携带该突变.结论 第1次在中国非综合性耳聋家系中发现MYH14基因的突变,表明MYH14基因突变也是导致中国人非综合性耳聋的原因.     

常染色体显性遗传视网膜色素变性家系的基因筛查

目的：确定一个常染色体显性遗传视网膜色素变性(autosomal dominant retinitis pigmentosa,ADRP）家系的致病基因及其突变位点和类型。方法：应用聚合酶链反应－单链构象多态性结合DNA测序技术，对来自同一家系的4例RP患者及4名正常人外周血DNA进行分子遗传学分析，筛查3个候选基因共8个外显子。结果：来自同一家系的4例RP患者均发现有视紫红质基因（rhodopsin,RHO)第1外显子第52密码子存在TTC→TAC的点突变（Phe52Tyr），而4名正常人未发现这种突变。结论：在这个中国ADRP大家系中，发现RHO基因的致病突变，表明ADRP存在明显遗传异质性。     

两个X连锁少汗性外胚层发育不良家系的基因突变分析

目的 对两个X连锁隐性遗传少汗性外胚层发育不良(X-linked hypohidrotic ectodermal dysplasia,XLHED)家系进行ED1基因突变分析,为罹患家庭提供遗传咨询及产前诊断.方法 综合应用序列分析及多重连接依赖性探针扩增方法,对两个家系的先证者进行ED1基因突变分析,并针对检测到的突变位点对女性成员进行检测.采集家系1胎儿的羊水细胞进行产前诊断,包括致病突变位点的分析、ED1基因内4个短串联重复序列(short tandem repeat,STR)位点的单倍型连锁分析、性别鉴定及核型分析.结果 家系1先证者缺失ED1基因第1外显子及下游2个STR位点DXS8269,DXS1422区域,其余外显子序列分析未见异常,其女儿为该缺失突变的携带者;结合连锁分析、性别鉴定及核型分析结果,家系1胎儿为男性非ED1基因缺失突变携带者,胎儿足月分娩后随访,为健康个体.家系2先证者经序列分析检测到ED1基因第3外显子c.463C＞T(R155C)错义突变,母亲为c.463C＞T(R155C)杂合突变携带者.结论 ED1基因第1外显子区域缺失和错义突变R155C是导致2个少汗性外胚层发育不全家系患者临床表型的主要原因,ED1基因的突变检测结合单倍型分析,能准确地对该类家系提供产前诊断.     

一个先天性无虹膜家系PAX6基因的新突变

目的 通过分子遗传学分析,确定中国东北地区一个先天性无虹膜家系PAX6基因的突变位点.方法 采集一个家系3例先天性虹膜患者及5名健康成员和100名正常对照者的外周静脉血,应用聚合酶链反应,直接测序法,单链构象多态性技术以及T载体克隆测序等方法确定其突变位点.结果 患者为第5外显子从483位点开始9个碱基缺失的框内缺失突变:其密码子位置为41～43,即缺失门冬氨酸、异亮氨酸和苏氨酸3个氨基酸(c.483del9).结论 PAX6基因是先天性无虹膜的致病基因,发现了PAX6基因一个新的突变位点.     

一成人型多囊肾家系的遗传检测及产前诊断

目的 对一常染色体显性遗传性多囊肾病(ADPKD)家系进行致病基因突变鉴定,并对先证者妻子首次妊娠进行产前诊断.方法 用聚合酶链式反应,通过微卫星标记进行基因定位、DNA序列测定,确定基因突变;用AS-PCR对家系其他患者成员进行突变点检测和筛查;联合应用突变检测和连锁分析进行产前诊断.结果 该家系中多囊肾疾病的致病基因为PKD2,突变为外显子5中c.1249C>T(p.R417X);胎儿产前诊断结果显示未获得致病突变.结论 该家系的致病突变为c-12A9C>>(p.R417X),成功进行了产前诊断.     

一个脂蛋白肾小球病家系中apoE基因的九个碱基缺失

目的 分析1个脂蛋白肾小球病家系的载脂蛋白E(apolipoprotein E,apoE)基因突变.方法 用盐析法提取该家系4名成员和2名正常人的外周血基因组DNA,PCR扩增apoE基因第4外显子、第3外显子以及多态性片段,扩增产物纯化后分别构建到pTA2载体中,克隆载体转化至大肠杆菌DH5α感受态中,经蓝白斑和抗菌素筛选后集菌,提取重组子质粒,EcoRⅠ酶切鉴定是否转化成功,鉴定正确的菌液行双向测序.PCR-限制性片段长度多态性检测apoE基因多态性.结果 家系中先证者及其母亲和姐姐apoE基因第4外显子第484～492位9个碱基(CAAGCTGCG)缺失,为杂合缺失,其导致apoE氨基酸序列第143～145位KLR的3个氨基酸缺失.第3外显子测序未发现异常.apoE基因多态性分析结果与测序结果一致.结论 该家系的脂蛋白肾小球病因可能为apoE基因第484～492位9个碱基(CAAGCTGCG)缺失.     

新疆3个HCM家系MYH7基因突变DHPLC检测和DNA测序结果分析

目的 研究家族性肥厚型心肌病(HCM)的主要致病基因β肌球蛋白重链,MYH7突变情况.方法 用变性高效液相色谱DHPLC检测和DNA测序方法对3个HCM家系成员的MYH7基因8、14外显子及附近上下游序列进行检测分析.结果 3个家系其中1个家系发现MYH7基因14外显子中存在Thr441Met突变,该突变在中国人中是首次发现,此外外显子8也存在1个点突变.另外两个家系也发现有不同位点的突变.结论 运用变性高效液相色谱技术和DNA直接测序技术能实现对家族性肥厚型心肌病MYH7基因突变的筛查,有利于早期诊断、患病风险预测.     

Neanthes japonica (Iznka) fibrinolytic enzyme reduced cerebral infarction, cerebral edema and increased antioxidation in rat models of focal cerebral ischemia

X-linked retinitis pigmentosa (XLRP) is the most severe type of retinitis pigmentosa (RP), with patients consistently showing early onset and rapid deterioration. Obtaining a genetic diagnosis for a family with XLRP is important for counseling purposes. In this study, we aimed to identify disease-causing mutations in two unrelated XLRP families. Genetic analysis was performed on two unrelated XLRP families. Genomic DNA was extracted from peripheral blood or amniotic fluid samples. The coding regions and intron/exon boundaries of the Retinitis Pigmentosa GTPase Regulator (RPGR) and RP2 genes were amplified by PCR and then sequenced directly. A clinically unaffected pregnant female and the four month old fetus were found to have a hemizygous 2 base pair deletion (g.ORF15+484_485delAA) in the exon ORF15 of RPGR gene. In another XLRP family, a nonsense mutation (g.ORF15+810G>T) was identified. Neither mutation has been reported previously. Both are predicted to cause premature termination of the protein. In conclusion, we identified a micro-deletion through prenatal genetic diagnosis and another novel nonsense mutation in RPGR-ORF15. Identifying a disease-causing mutation facilitated early diagnosis and genetic counseling for the patients. Discovery of novel mutations also broadens knowledge of XLRP and the spectrum of its pathogenic genotypes.     

Five novel RPGR mutations in families with X-linked retinitis pigmentosa

X-linked forms of retinitis pigmentosa (XLRP) are among the most severe because of their early onset, often leading to significant visual impairment before the fourth decade. RP3, genetically localized at Xp21.1, accounts for 70% of XLRP in different populations. The RPGR (Retinitis Pigmentosa GTPase Regulator) gene that was isolated from the RP3 region is mutated in 20% of North American families with XLRP. From mutation analysis of 27 independent XLRP families, we have identified five novel RPGR mutations in 5 of the families (160delA, 789 A>T, IVS8+1 G>C, 1147insT and 1366 G>A). One of these mutations was detected in a family from Chile. Hum Mutat 17:151, 2001.     

A non-ancestral RPGR missense mutation in families with either recessive or semi-dominant X-linked retinitis pigmentosa

Most X-linked diseases show a recessive pattern of inheritance in which female carriers are unaffected. In X-linked retinitis pigmentosa (XLRP), however, both recessive and semi-dominant inheritance patterns have been reported. We identified an Israeli family with semi-dominant XLRP due to a missense mutation (p.G275S) in the RPGR gene. The mutation was previously reported in two Danish families with recessive XLRP. Obligate carriers from the two Danish families had no visual complaints and normal to slightly reduced retinal function, while those from the Israeli family suffered from high myopia, low visual acuity, constricted visual fields, and severely reduced electroretinogram (ERG) amplitudes. The disease-related RPGR haplotype of the Israeli family was found to be different from the one found in the two Danish families, indicating that the mutation arose twice independently on different X-chromosome backgrounds. A series of genetic analyses excluded skewed X-inactivation pattern, chromosomal abnormalities, distorted RPGR expression level, and mutations in candidate genes as the cause for the differences in disease severity of female carriers. To the best of our knowledge, this is the first detailed analysis of an identical mutation causing either a recessive or a semi-dominant X-linked pattern of disease in different families. Our results indicate that an additional gene (or genes), linked to RPGR, modulate disease expression in severely affected carriers. These may be related to the high myopia concomitantly found in affected carriers from the Israeli family.     

Identification of novel RP2 mutations in a subset of X‐linked retinitis pigmentosa families and prediction of new domains

X‐linked Retinitis Pigmentosa (XLRP) shows a huge genetic heterogeneity with almost five distinct loci on the X chromosome. So far, only two XLRP genes have been identified, RPGR (or RP3) and RP2, being mutated in approximately 70% and 10% of the XLRP patients. Clinically there is no clearly significative difference between RP3 and RP2 phenotypes. In the attempt to assess the degree of involvement of the RP2 gene, we performed a complete mutation analysis in a cohort of patients and we identified five novel mutations in five different XLRP families. These mutations include three missense mutations, a splice site mutation, and a single base insertion, which, because of frameshift, anticipates a stop codon. Four mutations fall in RP2 exon 2 and one in exon 3. Evidence that such mutations are different from the 21 RP2 mutations described thus far suggests that a high mutation rate occurs at the RP2 locus, and that most mutations arise independently, without a founder effect. Our mutation analysis confirms the percentage of RP2 mutations detected so far in populations of different ethnic origin. In addition to novel mutations, we report here that a deeper sequence analysis of the RP2 product predicts, in addition to cofactor C homology domain, further putative functional domains, and that some novel mutations identify RP2 amino acid residues which are evolutionary conserved, hence possibly crucial to the RP2 function. Hum Mutat 18:109–119, 2001. © 2001 Wiley‐Liss, Inc.     

Ten novel ORF15 mutations confirm mutational hot spot in the RPGR gene in European patients with X-linked retinitis pigmentosa

RGPR was the first gene found to be mutated in XLRP, the subtype of RP displaying the most severe form of retinal degeneration with partial or complete blindness in the third or fourth decade of life. Despite the RP3 locus on Xp21.1 accounting for 60-90% of XLRP, only 10-20% of identified RPGR mutations were reported in earlier analyses. This discrepancy appeared to be resolved when Vervoort et al. identified a mutational hot spot in a new purine-rich 3' exon (ORF15) that accounted for 60% of their XLRP patients [Vervoort et al., 2000]. In our mutation screening of 37 unrelated European XLRP patients we identified two recently described deletions and 10 novel mutations in exon ORF15 of RPGR, 4 of which were nonsense and 6 frameshift mutations. The latter included one duplication and 5 deletion mutations, all of which lead to a downstream premature termination. No mutations were detected in the additionally screened new exon ORF14. The data reported here, together with previous findings, document a significant clustering of mutations as well as polymorphisms in ORF15 of RPGR. In our unselected XLRP patient population, ORF15 mutations constitute 32% of cases, a finding that contradicts the results of Vervoort and coworkers [Vervoort et al., 2000] but is in agreement with a more recent study on North American XLRP patients [Breuer et al., 2002]. The observed prevalence is sufficient to justify an initial mutation screening of ORF15 in the genetically heterogeneous group of XLRP.     

Analysis of RPGR in a South African family with X-linked retinitis pigmentosa: research and diagnostic implications

Analysis of exon ORF15 of the RPGR gene has revealed a novel mutation in a South African family with X-linked retinitis pigmentosa (XLRP), which has implications for the rest of the family in terms of pre-symptomatic testing. The ability to test for this mutation will be beneficial for the accurate determination of carrier status in female relatives who may have been unaware of their risk before this study was performed. This work also highlights the need to be aware of the ramifications of mutation testing in what may appear to be small families. This is the first report of an RPGR ORF15 mutation in a South African family of mixed ancestry.     

Comprehensive survey of mutations in RP2 and RPGR in patients affected with distinct retinal dystrophies: genotype-phenotype correlations and impact on genetic counseling

X-linked forms of retinitis pigmentosa (RP) (XLRP) account for 10 to 20% of families with RP and are mainly accounted for by mutations in the RP2 or RP GTPase regulator (RPGR) genes. We report the screening of these genes in a cohort of 127 French family comprising: 1) 93 familial cases of RP suggesting X-linked inheritance, including 48 out of 93 families with expression in females but no male to male transmission; 2) seven male sibships of RP; 3) 25 sporadic male cases of RP; and 4) two cone dystrophies (COD). A total of 5 out of the 93 RP families excluded linkage to the RP2 and RP3 loci and were removed form the cohort. A total of 14 RP2 mutations, 12 of which are novel, were identified in 14 out of 88 familial cases of RP and 1 out of 25 sporadic male case (4%). In 13 out of 14 of the familial cases, no expression of the disease was noted in females, while in 1 out of 14 families one woman developed RP in the third decade. A total of 42 RPGR mutations, 26 of which were novel, were identified in 80 families, including: 69 out of 88 familial cases (78.4%); 2 out of 7 male sibship (28.6%); 8 out of 25 sporadic male cases (32.0%); and 1 out of 2 COD. No expression of the disease was noted in females in 41 out of 69 familial cases (59.4%), while at least one severely affected woman was recognized in 28 out of 69 families (40.6%). The frequency of RP2 and RPGR mutations in familial cases of RP suggestive of X-linked transmission are in accordance to that reported elsewhere (RP2: 15.9% vs. 6-20%; RPGR: 78.4% vs. 55-90%). Interestingly, about 30% of male sporadic cases and 30% of male sibships of RP carried RP2 or RPGR mutations, confirming the pertinence of the genetic screening of XLRP genes in male patients affected with RP commencing in the first decade and leading to profound visual impairment before the age of 30 years.     

Somatic and gonadal mosaicism in X-linked retinitis pigmentosa

The g.ORF15 + 652-653delAG mutation in the RPGR gene is the most frequent mutation in X-linked retinitis pigmentosa (XLRP). The objective of this study was to investigate the possibility of mosaicism in an XLRP family. Eight subjects in the RP family were recruited. Blood samples were collected for DNA extraction. Haplotype analysis and mutational screening on the RPGR gene were performed. Additionally, samples of hair follicles and buccal cells from the mother of the proband were acquired for DNA extraction and molecular analysis. Phenotype was characterized with routine ophthalmic examination, Goldmann perimetry, electroretinography, and color fundus photography. A g.ORF15 + 652-653delAG mutation was identified in second- and third-generation patients/carriers. A first-generation female, who was considered to be an obligate carrier, demonstrated a normal phenotype as well as a normal genotype in lymphocytic DNA, indicating the gonadal mosaicism; however, a heterozygous AG-deletion at nucleotide 652 and 653 was identified in the genomic DNA of hair follicles, hair shaft, and buccal cells, indicating that the mutation is somatic. In conclusion, we reported on a family in which an asymptomatic woman with somatic-gonadal mosaicism for a RPGR gene mutation transmitted the mutation to an asymptomatic daughter and to a son with XLRP. Gonadal mosaicism may be responsible for a proportion of multiplex or simplex RP families, in which more than 50% of all cases of RP are found. (c) 2007 Wiley-Liss, Inc.