Detection of RB Germline Mutations Using Exon-by-exon Heteroduplex Analysis Compared with SSCP

Purpose: To compare heteroduplex analysis with SSCP and to develop a simple and effective method for mutational screening of RB gene.Materials and Methods: Leukocyte DNA was prepared from 12 unrelated Japanese patients with hereditary retinoblstoma. PCR combined with simultaneous nonisotopic heteroduplex and SSCP analysis was used to screen leukocyte DNA for such mutations, exon-by-exon, without the use of restriction endonu-clease digestion. PCR was conducted using 28 pairs of primers flanking all 27 ex-ons and the promoter region of the RB gene, with PCR products ranging from 159bp to 326bp. Mutations were identified by sequencing.Results: Heterozygous germline mutations were detected in 8 of 12 Japanese patients. The mutations were identified by sequencing as follows; G→C/acceptor of exon 11, T insertion/codon 389, C→T/codon 455, 33bp insertion/codon 455 (C GA), G→T/codon 533, C→T/codon 579, C deletion/codon 674, and C→T/ codon 787.Conclusion: Our results suggest that small RB gene mutations are     

Complete mitochondrial DNA sequence analysis in two southern Chinese pedigrees with Leber hereditary optic neuropathy revealed secondary mutations along with the primary mutation

AIM: To investigate mitochondrial factors associated with Leber hereditary optic neuropathy (LHON) through complete sequencing and analysis of the mitochondrial genome of Chinese patients with this disease. METHODS: Two unrelated southern Chinese families with LHON and 10 matched healthy controls were recruited, and their entire mitochondrial DNA (mtDNA) was amplified and sequenced with the universal M13 primer. Then DNA sequence analysis and variation identification were perfomed by DNAssist and Chromas 2 software and compared with authoritative databases such as Mitomap. RESULTS: Mutational analysis of mtDNA in these two Chinese pedigrees revealed one common LHON-associated mutation, G11778A (Arg→His), in the MT-ND4 gene. In addition, there were two secondary mutations in Pedigree 1: C3497T (Ala→Val), and C3571T (Leu→Phe) in the MT-ND1 gene, which have not been reported; and two secondary mutations occurred in Pedigree 2: A10398G (Thr→Ala) in the MT-ND3 gene, and T14502C (Ile→Val) in the MT-ND6 gene. Three polymorphisms, A73G, G94A and A263G in the mtDNA control region, were also found. CONCLUSION: Our study confirmed that the known MT-ND4*G11778A mutation is the most significant cause of LHON. The C3497T and C3571T mutations in Pedigree 1 were also both at hot-spots of MT-ND1; they may affect the respiratory chain in coordination with the primary mutation G11778A. In Pedigree 2, the two secondary mutations A10398G of MT-ND3 and T14502C of MT-ND6 may influence mitochondrial respiratory complex I, leading to the mitochondrial respiratory chain dysfunction which results in optic atrophy together with G11778A. Therefore, not only the common primary LHON mutation is responsible for the visual atrophy, but other secondary mtDNA mutations should also be considered when giving genetic counseling.     

TGFBI and CHST6 gene analysis in Chinese stromal corneal dystrophies

AIM: To investigate whether mutations in TGFBI gene or CHST6 gene correlated with stromal corneal dystrophies (CD) in 8 Chinese probands. METHODS: Eight unrelated patients with stromal corneal dystrophies were recruited in this study; all affected members were assessed by completely ophthalmologic examinations. Genomic DNA was extracted from peripheral leukocytes, 17 exons of TGFBI gene and the exon of CHST6 gene were amplified by polymerase chain reaction (PCR), sequenced directly and compared with the reference database. RESULTS: Three heterozygous mutations in TGFBI gene were identified in six patients: c. 370C>T (p.Arg124Cys) was found in exon 4 of TGFBI gene in three members, c. 371G>A (p.Arg124His) was found in one patient; c. 1663C>T (p.Arg555Trp) was found in exon 12 in other two members. In addition,four polymorphisms with the nucleotide changes rs1442, rs1054124, rs4669, and rs35151677 were found in TGFBI gene. Mutations were not identified in the rest of 2 affected individuals in TGFBI gene or CHST6 gene. CONCLUSION: Within these patients, R124C, R124H and R555W mutations were co-segregated with the disease phenotypes and were specific mutations for lattice corneal dystrophy type I (LCD I), Avellino corneal dystrophy (ACD, GCDⅡ), granular corneal dystrophy type I (GCD I), respectively. Our study highlights the prevalence of codon 124 and codon 555 mutations in the TGFBI gene among the Chinese stromal corneal dystrophies patients.     

TGFBI and CHST6 gene analysis in Chinese stromal corneal dystrophies

AIM: To investigate whether mutations in TGFBI gene or CHST6 gene correlated with stromal corneal dystrophies (CD) in 8 Chinese probands. METHODS: Eight unrelated patients with stromal corneal dystrophies were recruited in this study; all affected members were assessed by completely ophthalmologic examinations. Genomic DNA was extracted from peripheral leukocytes, 17 exons of TGFBI gene and the exon of CHST6 gene were amplified by polymerase chain reaction (PCR), sequenced directly and compared with the reference database. RESULTS: Three heterozygous mutations in TGFBI gene were identified in six patients: c. 370C>T (p.Arg124Cys) was found in exon 4 of TGFBI gene in three members, c. 371G>A (p.Arg124His) was found in one patient; c. 1663C>T (p.Arg555Trp) was found in exon 12 in other two members. In addition,four polymorphisms with the nucleotide changes rs1442, rs1054124, rs4669, and rs35151677 were found in TGFBI gene. Mutations were not identified in the rest of 2 affected individuals in TGFBI gene or CHST6 gene. CONCLUSION: Within these patients, R124C, R124H and R555W mutations were co-segregated with the disease phenotypes and were specific mutations for lattice corneal dystrophy type I (LCD I), Avellino corneal dystrophy (ACD, GCDⅡ), granular corneal dystrophy type I (GCD I), respectively. Our study highlights the prevalence of codon 124 and codon 555 mutations in the TGFBI gene among the Chinese stromal corneal dystrophies patients.     

Compound heterozygous mutations of CRB1 gene in a Chinese family with Leber congenital amaurosis by whole exome sequencing北大核心CSCD

Objective: To investigate the disease-causing mutation in a family with Leber congenital amaurosis (LCA). Methods: A Chinese Han pedigree with LCA from Chaoshan area was recruited in Shantou International Eye Center in August 2011.The clinical features of the families were evaluated, including medical history, best corrected visual acuity, intraocular pressure and fundus photography. The peripheral blood sample of 5 ml was collected from each of the family members for the extraction of genomic DNA.DNA of the proband was investigated by whole exome sequencing (WES) and was filtered for function of variants and inheritance pattern. Then, Sanger sequencing was performed to confirm the WES result on all the participating subjects in the pedigree. Results: There were 11 families of 3 generations in this pedigree, and 2 female LCA patients were found (Ⅱ2 and Ⅱ4) who were sisters. The parents (Ⅰ-1 and Ⅰ-2) and children (Ⅲ-1, Ⅲ-2, Ⅲ-3 and Ⅲ-4) of the patients showed normal phenotype, suggesting an autosomal recessive pattern. The patients appeared severe visual impairment during early childhood. Ophthalmic examination showed diffuse pigmentation on the retina and attenuation of retinal artery in both patients.WES of proband revealed two compound heterozygous mutations (c.2234C>T, p.T745M; c. 3488G>T, p.C1163F) of the CRB1 gene. Sanger sequencing confirmed the mutations in both patients (Ⅱ-2 and Ⅲ-4), and the parents of the patients were found to carry one mutations respectively and the other subjects with normal phenotype had neither none or only one mutation. Conclusions: The compound heterozygous mutation of c. 2234C>T, p.T745M and c. 3488G>T, p.C1163F in CRB1 is responsible for LCA pathogenesis this Chinese Han pedigree. Copyright © 2018 by the Chinese Medical Association.     

γ-crystallin gene screen in a congenital nuclear cataract family

Objects To screen the γ-crystallin genes in a Chinese autosomal dominant congenital nu-clear cataract (ADCC) family. Methods Tile genes CRYGA,CRYGB,CRYGC,CRYGD were screened by direct sequencing in the ADCC family. Family analysis was used to analyze the correlation of the mutations and tile disease. Results Nine sequence variants were found: 198G→A and 196T→C (LI48P) in CRYGA,2218-2219 in C,2437C→T and 5391C→A (L111I) in CRYGB, 18782T→G in CRYGC,2861T→C, 517T→C and 570C→T in CRYGD. Two mutations lead to amino acid changes. However,no mutation could be identi-fled as co-segregating with tile disease. L148P in CRYGA and L111I in CRYGB were supposed to be nu-cleotide polymorphisms. Conclusion Nine sequence variations have been found in the ADCC Family. But they seem not to be responsible for the disease.     

γ-crystallin gene screen in a congenital nuclear cataract family

Objects To screen the γ-crystallin genes in a Chinese autosomal dominant congenital nu-clear cataract (ADCC) family. Methods Tile genes CRYGA,CRYGB,CRYGC,CRYGD were screened by direct sequencing in the ADCC family. Family analysis was used to analyze the correlation of the mutations and tile disease. Results Nine sequence variants were found: 198G→A and 196T→C (LI48P) in CRYGA,2218-2219 in C,2437C→T and 5391C→A (L111I) in CRYGB, 18782T→G in CRYGC,2861T→C, 517T→C and 570C→T in CRYGD. Two mutations lead to amino acid changes. However,no mutation could be identi-fled as co-segregating with tile disease. L148P in CRYGA and L111I in CRYGB were supposed to be nu-cleotide polymorphisms. Conclusion Nine sequence variations have been found in the ADCC Family. But they seem not to be responsible for the disease.     

γ-crystallin gene screen in a congenital nuclear cataract family

Objects To screen the γ-crystallin genes in a Chinese autosomal dominant congenital nu-clear cataract (ADCC) family. Methods Tile genes CRYGA,CRYGB,CRYGC,CRYGD were screened by direct sequencing in the ADCC family. Family analysis was used to analyze the correlation of the mutations and tile disease. Results Nine sequence variants were found: 198G→A and 196T→C (LI48P) in CRYGA,2218-2219 in C,2437C→T and 5391C→A (L111I) in CRYGB, 18782T→G in CRYGC,2861T→C, 517T→C and 570C→T in CRYGD. Two mutations lead to amino acid changes. However,no mutation could be identi-fled as co-segregating with tile disease. L148P in CRYGA and L111I in CRYGB were supposed to be nu-cleotide polymorphisms. Conclusion Nine sequence variations have been found in the ADCC Family. But they seem not to be responsible for the disease.     

γ-crystallin gene screen in a congenital nuclear cataract family

Objects To screen the γ-crystallin genes in a Chinese autosomal dominant congenital nu-clear cataract (ADCC) family. Methods Tile genes CRYGA,CRYGB,CRYGC,CRYGD were screened by direct sequencing in the ADCC family. Family analysis was used to analyze the correlation of the mutations and tile disease. Results Nine sequence variants were found: 198G→A and 196T→C (LI48P) in CRYGA,2218-2219 in C,2437C→T and 5391C→A (L111I) in CRYGB, 18782T→G in CRYGC,2861T→C, 517T→C and 570C→T in CRYGD. Two mutations lead to amino acid changes. However,no mutation could be identi-fled as co-segregating with tile disease. L148P in CRYGA and L111I in CRYGB were supposed to be nu-cleotide polymorphisms. Conclusion Nine sequence variations have been found in the ADCC Family. But they seem not to be responsible for the disease.     

γ-crystallin gene screen in a congenital nuclear cataract family

Objects To screen the γ-crystallin genes in a Chinese autosomal dominant congenital nu-clear cataract (ADCC) family. Methods Tile genes CRYGA,CRYGB,CRYGC,CRYGD were screened by direct sequencing in the ADCC family. Family analysis was used to analyze the correlation of the mutations and tile disease. Results Nine sequence variants were found: 198G→A and 196T→C (LI48P) in CRYGA,2218-2219 in C,2437C→T and 5391C→A (L111I) in CRYGB, 18782T→G in CRYGC,2861T→C, 517T→C and 570C→T in CRYGD. Two mutations lead to amino acid changes. However,no mutation could be identi-fled as co-segregating with tile disease. L148P in CRYGA and L111I in CRYGB were supposed to be nu-cleotide polymorphisms. Conclusion Nine sequence variations have been found in the ADCC Family. But they seem not to be responsible for the disease.     

国人视网膜母细胞瘤患者RB1基因突变的特性

目的:检测国人RB患者体细胞中RB1基因突变,分析我国RB1基因突变的特性,探讨RB1基因突变的分子生物学机制。方法:应用PCR—SSCP技术筛查28例RB患者及亲属的白细胞基因组DNA,测序分析确定突变。结果:共确定7例RB1基因生殖细胞性突变。结论:本组RB1基因生殖细胞性突变的方式为点突变和小缺失,这些突变改变了RB1基因的遗传信息,致使异常的RB1基因蛋白产生,导致视网膜母细胞瘤的发生。中国RB1基因突变方式主要是以微小突变为主,但复杂突变的比例相对较高。     

RB患者肿瘤及体细胞中Rb基因点突变谱及其特征和意义

目的：研究RB患者肿瘤及体细胞巾Rb基因点突变的频率，特征及其在肿瘤遗传易感性的传递及肿瘤形成机制中所起的作用。 方法：SSCP分析及直接DNA序列分析。 结果：在302例经Southern blotting杂交证实无明显Rb基因缺失或重排的RB患者的肿瘤或外周血白细胞DNA中共发现187个Rb基因点突变。 结沦：Rb基因点突变几乎随机分布在整个编码区，常常导致氨基酸密码突变为终止密码，阅读框架移位或mRNA拼接异常，产生缩短丁的或缺乏某个外显子编码氨基酸的蛋白质。并以半个碱基取代占绝大多数。缺失或插入突变通常是一个或二个碱基的微小病变。 （中华眼底病杂志，1995，11：240-243）     

108例视网膜母细胞瘤Rb基因突变的特征

目的；研究RB患者肿瘤及体细胞内Rb基因的存在状态、细微结构、Rb基因突变的特征、起源与传递。 方法；DNA分子杂交、SSCP分析、DNA序列测定。结果：108例RB肿瘤标本中80例(?4％)存在Rb基因点突变，其中44例为纯合型，20例有二个独立发生的杂合型点突变，16例只检出一个杂合型点突变。通过对比分析RB患者肿瘤与白细胞DNA、RB患者家庭成员白细胞DNARlo基因的结构，揭示了Rb基因点突变的起源与遗传特征。 结论：Rb基因是与RB肿瘤形成关系最为密切的基因。RB肿瘤发生需二次突变事件导致Rb基因的二个等位基因失活，第一次突变事件突出表现为点突变；第二次突变事件主要是LOH，其次是点突变。 （中华眼底病杂志，1997，13：12-16）     

Two nonsense mutations of PAX6 in two Japanese aniridia families: case report and review of the literature

PURPOSE: To identify PAX6 mutations in patients from four Japanese families with aniridia. METHODS: Polymerase chain reaction (PCR)-single stand conformational polymorphism (SSCP) analysis (SSCA) was performed in probands of the families, and restriction analysis using MaeIII or AvaI was carried out in other affected family members. RESULTS: PCR-SSCA demonstrated in the proband from one family an extra-band in the PCR product for PAX6 exon 8. Base sequence analysis revealed that the patient is a heterozygote for a C to T transition mutation at codon 203. DNAs from the patient and another affected member in the same family were cut with MaeIII into two fragments, while non-affected members in the family showed only one MaeIII fragment, the result confirmed the mutation. In another family, PCR-SSCA revealed an extra-band in the PCR product for exon 9. Sequencing detected a C-->T substitution at codon 240 in the patient, the mutation resulted in loss of an AvaI site. AvaI cleavage analysis confirmed the mutation in the patient. The two transition mutations observed in the two families also predict the conversion of arginine to a stop codon (R203X and R240X, respectively) around the homeodomain (HD), leading to the truncation of the PAX6 protein within its glycine-rich region. No abnormal SSCP bands or abnormal restriction fragments were detected in patients from the other two families. CONCLUSIONS: The two mutations sites identified in the two families, one at codon 203 and the other at codon 240, are those most frequently observed among 118 previously reported PAX6 mutations. This indicates that the two mutations are two hot-spots in the gene.     

Molecular analysis of the CYP1B1 gene: identification of novel truncating mutations in patients with primary congenital glaucoma

BACKGROUND: Mutations and polymorphisms have been identified in the CYP1B1 gene; while mutations that affect the conserved core structures of cytochrome P4501B1 result in primary congenital glaucoma (PCG), mutations in other regions hold the potential to define differences in estrogen metabolism. In the present study, we analyzed the CYP1B1 gene in Mexican patients with PCG and described four novel mutations. MATERIALS AND METHODS: The sample included 12 nonrelated cases with PCG. Analysis of coding regions of the CYP1B1 gene was performed through PCR and DNA sequencing analysis from genomic DNA. RESULTS AND DISCUSSION: Molecular analysis of the CYP1B1 gene showed the following molecular defects: (1) a novel single-base pair deletion within codon 370 (1454delC) that produces a substitution of leucine instead of proline and a premature stop codon 57 amino acids after the last original amino acid; this family also harbored a novel polymorphic variant of the cytochrome P4501B1 with six single-nucleotide polymorphisms (142C-->G; 355G-->T; 729G-->C; 4326C-->G; 4360C-->G and 4379C-->T); (2) a novel single-base pair deletion within codon 277 (1176delT) that results in a premature stop codon; (3) a novel single-base pair deletion within codon 179 (880delG) that produces a substitution of arginine instead of alanine and a premature stop codon 17 amino acids downstream from the last original amino acid, and (4) a duplication (or insertion) of ten base pairs within codon 404 (1556dupATGCCACCAC) that results in a premature stop codon 26 amino acids after the last original amino acid. We also observed in 2 nonrelated patients a deletion of 13 bp (1410_1422delGAGTGCAGGCAGA) previously reported for other populations. CONCLUSION: We reported four novel mutations and a novel polymorphic variant in the CYP1B1 gene in PCG in the Mexican population; it has important implications in diagnosis and genetic counseling.     

PCR-SSCP联合序列分析法在RB1基因突变检测中的应用

用聚合酶链反应-单链构象多态(PCR-SSCP)联合序列分析，对视网膜母细胞瘤肿瘤组织RB1基因存在状态进行检测。对RB1基因全部27个外显子分别进行PCR扩增后，选用适当的限制性核酸内切酶将扩增产物切割成200bp左右的片段，加热至双链解离后，6%聚丙烯酰胺凝胶电泳。电泳后对有异常电泳迁移率条带所属标本的同一外显子行PCR扩增、序列分析，进一步证实突变的位置和类型。本研究发现包括点突变、缺失、插入等RBl基因改变，显示PCR-SSCP联合序列分析在已知序列基因突变检测中的敏感性和可靠性。 （中华眼底病杂志，1994，10：17-20）     

Identification of a CRYAB mutation associated with autosomal dominant posterior polar cataract in a Chinese family

PURPOSE: A four-generation Chinese family with 13 members affected with autosomal dominant congenital posterior polar cataract was studied. The purpose of this study was to identify the disease-causing gene in the family and to validate that mutations in CRYAB, the alphaB-crystallin gene, cause the congenital cataract. METHODS: Linkage analysis was performed with a panel of microsatellite markers flanking candidate genetic loci for cataracts, including 14 known autosomal dominant congenital cataract (ADCC) genes. For mutation analysis, the complete coding region and exon-intron boundaries of CRYAB were sequenced with DNA from the proband. Single-strand conformation polymorphism (SSCP) analysis for exon 1 of CRYAB was performed in all family members and 200 normal control subjects. RESULTS: The disease gene in the Chinese family was mapped to chromosome 11 in region q22-22.3 with a maximum lod score of 4.52. Direct DNA sequence of CRYAB revealed a heterozygous C-->T transition at nucleotide 58, resulting in a novel 58 C-->T (Pro20Ser) mutation. The Pro20Ser mutation cosegregated with all affected individuals and was not present in unaffected members in the family or in 200 normal control subjects. The mutation occurs at the evolutionarily conserved residue Pro20 in the N-terminal region of alphaB-crystallin. CONCLUSIONS: To date, only one CRYAB mutation has been associated with congenital isolated cataract. This study identified a second novel mutation in CRYAB in a large Chinese cataract family. Together, these results provide strong evidence that CRYAB is a pathogenic gene for congenital cataract.     

Genotypic and phenotypic spectrum of X-linked retinoschisis in Australia

BACKGROUND: X-linked retinoschisis (XLRS), an X-linked recessive inherited degenerative retinopathy, is characterized by splitting in the nerve fibre layer and is caused by alterations in the RS1 gene. The aim of the present study was to review both the phenotypic features of XLRS and the mutation spectrum of the RS1 gene in an Australian cohort. METHODS: Patients were recruited from ophthalmic and paediatric hospitals as well as private ophthalmic clinics across Australia. A cohort of 18 presumably unrelated families was identified. Twenty-two affected patients underwent clinical examination. Following DNA extraction all six exons of the RS1 gene were sequenced. RESULTS: The median age at diagnosis was 8 years (range 1-43 years); the median age at review was 14 years (range 5-63 years). The median best-corrected visual acuity upon review was 6/24 (range 6/6-1/36). Typical foveal schisis was found in 90.1% eyes examined (39/43) while peripheral schisis was present in 30% of eyes (13/43). The scotopic blue b-wave amplitude ranged between 2% and 82% of the mean normal amplitude. Five novel mutations (61G-->T, Gly21X; 103C-->T, Gln35X; 327-329del, Cys110del; 527T-->C, Phe176Ser; 573Gdel, Pro192fs) and six previously identified missense mutations (304C-->T, Arg102Trp; 305G-->A, Arg102Gln; 336G-->C, Trp112Cys; 418G-->A, Gln140Arg; 598C-->T, Arg200Cys; 625C-->T, Arg209Cys) were found. The mutations present in codons 21 and 102 were each identified in two presumably unrelated pedigrees. One previously described point deletion (416Adel) was identified. Two pedigrees contained affected individuals where exons 2 or 3, respectively, were unable to be amplified, indicating the likely presence of a significant deletion. No mutation was found in the RS1 gene in two affected individuals from different pedigrees. CONCLUSION: Population genetic studies of XLRS have not previously been conducted in Australia. The phenotype associated with these mutations varied. The identification of each pedigree's specific mutation allows future determination of female carrier status for genetic counselling purposes. Further study into the refinement of the XLRS phenotype as well as the degree of intrafamilial phenotypic variation is required.     

Role of genetic testing in retinoblastoma management at a tertiary referral centre

Background: Retinoblastoma (MIM +180 200) is a malignant neoplasm affecting embryonal retina, associated with mutations in the RB1 gene. This paper investigates the results of RB1 testing in retinoblastoma management in a tertiary referral centre. Methods: A retrospective audit of genetic testing for retinoblastoma from 2003 to 2008, to determine epidemiology, rate of mutation detection and spectrum was undertaken. Eligible probands were identified from the department database and hospital records examined. DNA extracted from tumour tissue and/or peripheral blood was analysed. All patients and families underwent genetic counselling. Results: Twenty patients, including one family, were identified. Eight had bilateral tumours, of whom seven presented before 2 years of age, whereas 10 of 12 unilateral cases presented after 2 years of age. Ten patients (50%) were European, four Maori (20%), three Pacific (15%), two Asian (10%), and one of mixed ancestry (5%). Genetic analysis achieved mutation detection on all affected alleles of all the patients, with tumour tissue available for testing in 19 cases. Ten (40%) had germline mutations (eight bilateral and two unilateral), including one mosaic. 75% of affected Maori had germline mutations compared with 40% Europeans. A wide range of mutations was detected with one novel mutation identified in a familial case. Conclusion: Advances in gene testing have enabled a high rate of mutation detection, particularly when tumour tissue is genotyped. Genetic analysis is integral to the management of retinoblastoma patients allowing enhanced follow‐up care, avoidance of unnecessary examinations, family screening, counselling and reproductive planning, with early tumour detection in predisposed individuals.     

10遗传型视网膜母细胞瘤肿瘤Rb基因突变分析

１０例遗传型视网膜母细胞瘤肿瘤组织Ｒｂ基因突变分析张清炯箕田健生曾瑞萍吴中耀遗传性视网膜母细胞瘤（ｒｅｔｎｏｂｌａｓｔｏｍａ，ＲＢ）是由Ｒｂ基因两次突变而失活所致，第一次突变为生殖细胞性突变，第二次突变为体细胞性突变。生殖细胞性突变决定携带者患ＲＢ的...