四个遗传性耳聋家系的TMC1基因变异分析及产前诊断

目的对4个耳聋家系进行遗传性耳聋基因变异的筛查,为家系遗传咨询与产前诊断提供依据。方法应用二代测序技术对家系先证者进行耳聋基因检测,并对可疑基因变异采用Sanger双向测序对先证者及家系成员进行验证,确定可疑致病变异后,对3个家系高危胎儿进行产前诊断。结果家系1先证者检测到TMC1基因c.100C>T(p.R34X)和c.642+4A>C复合杂合变异,家系2先证者检测到TMC1基因c.582G>A(p.W194X)和c.589G>A(p.G197R)复合杂合变异,家系3先证者检测到TMC1基因c.1396_1398delAAC和c.1571T>C(p.F524S)复合杂合变异,家系4先证者检测到TMC1基因c.2050G>C(p.D684H)纯合变异,4个家系先证者父母均为携带者,其中c.642+4A>C、c.1571T>C(p.F524S)变异位点既往未见报道;产前诊断结果显示3个家系胎儿均不是患者,出生后随访至2019年9月,听力未见异常。结论TMC1基因变异是4个耳聋家系的可能致病原因,分子生物学的发现增加了对TMC1基因功能的认识并丰富了人类基因变异数据库,为家系遗传咨询和产前诊断提供了依据。     

两个Joubert综合征家系的致病基因变异分析与产前诊断

目的明确两个小脑蚓部发育不全、怀疑为Joubert综合征家系的遗传学病因并帮助确诊及生育指导。方法收集来郑州大学第一附属医院就诊的两个家系先证者和正常表型父母的临床资料,取组织或外周血样提取基因组DNA。通过高通量测序法筛查、Sanger测序法验证AHI1和CPLANE1基因变异位点,判断变异的致病性。这两个家系中母亲再次怀孕时进行产前诊断。结果家系1先证者AHI1基因存在c.2072delT(p.F691S*fs19)纯合变异,该导致其编码的Abelson辅助集成站点1蛋白在第691位氨基酸发生移码,使翻译提前终止。家系2先证者CPLANE1基因存在c.7243dupA(p.T2415Nfs*7)和c.8001delG(p.K2667Nfs*31)复合杂合变异,分别导致其编码的纤毛发生和平面极性效应因子1蛋白在第2415和第2667位氨基酸处发生移码,使翻译提前终止。这3个变异在公共数据库中均未见报道及频率记录。综合分析认为上述3个新变异具致病性。结论AHI1基因c.2072delT变异和CPLANE1基因c.7243dupA及c.8001delG变异分别是导致家系1 Joubert综合征3型和家系2 Joubert综合征17型的原因,据此变异位点可进行产前诊断。     

一例由 SCN9A基因复合杂合变异所致的先天性无痛症

目的:对一个先天性无痛症(congenital insensitivity to pain,CIP)家系进行基因变异分析,以明确其病因。方法:应用二代测序对先证者进行基因变异分析,对候选变异位点进行Sanger测序验证。结果:先证者携带 SCN9A基因c.1598delA(p.N533Ifs*31)、c．2...     

一个复合杂合变异致遗传性凝血因子Ⅺ缺陷症家系分析

目的探讨一个遗传性凝血因子XI(coagulation factor Ⅺ, FⅪ)缺陷症家系成员的分子致病机制。方法提取外周血基因组DNA, 并采用Sanger测序法检测先证者的15个外显子、侧翼序列及家系成员的相应变异外显子区域, 并用反向测序予以验证;ClustalX-2.1-win软件分析变异氨基酸位点的保守性;用Mutation Taster、PolyPhen2、PROVEAN三个在线生物信息学软件分析变异的致病性;用Swiss-pdbViewer软件分析变异氨基酸对蛋白质结构的影响。结果基因分析显示先证者第10外显子存在c.1107C>A(p.Tyr369stop)杂合无义变异以及第13外显子存在c.1562A>G(p.Tyr521Cys)杂合错义变异;其父亲携带c.1107C>A杂合无义变异, 其母亲和女儿均携带c.1562A>G杂合错义变异, 丈夫为野生型。保守性分析表明Tyr521在进化过程中为高度保守位点。变异碱基致病性预测发现c.1107C>A和c.1562A>G均为致病性变异。蛋白质模型分析显示在野生型FⅪ蛋白结构中, Tyr5...     

一个先天性挛缩蜘蛛指畸形综合征家系的FBN2基因变异分析及产前诊断

目的对1个中国先天性挛缩蜘蛛指畸形综合征(congenital contractural arachnodactyly,CCA)家系进行致病基因分析,明确其致病变异,为家系遗传咨询和产前诊断提供依据。方法应用二代测序技术(骨骼疾病Panel)对先证者进行变异筛查,发现FBN2基因可疑致病位点后,用Sanger测序技术对该家系成员和100名正常对照进行新变异验证,确定该家系的致病位点,并对家系中孕23周胎儿抽取羊水标本进行产前诊断。结果先证者及家系中所有患者均携带FBN2基因c.3528C>A(p.Asn1176Lys)杂合变异,而家系正常成员和100名正常对照中均未检测到该变异。产前诊断结果显示胎儿也携带FBN2基因c.3528C>A(p.Asn1176Lys)杂合变异。结论FBN2基因c.3528C>A(p.Asn1176Lys)变异是该家系的致病原因,新变异的检出丰富了FBN2基因变异谱。     

NDP基因c.361C>T错义变异致诺里病一家系

目的分析1个诺里病家系的致病基因变异,确定其遗传学病因。方法对先证者核心家系4名成员的DNA样本进行全外显子组检测,筛选变异位点,确定致病基因。通过Sanger测序对核心家系及7名其他家系成员进行验证。结果全外显子组检测及Sanger测序结果显示先证者及另外3例男性患者的NDP基因均存在c.361C>T(p.Arg121Trp)半合子错义变异,先证者母亲、外祖母和2个表妹均为c.361C>T杂合变异携带者,正常表型男性家系成员均未检测到该变异,符合X连锁隐性遗传病的特点。结论NDP基因c.361C>T错义变异是该诺里病家系的遗传学病因。     

一个淋巴水肿-双行睫综合征家系的FOXC2基因变异分析

目的对1个淋巴水肿-双行睫综合征(lymphedema-distichiasis syndrome,LDS)家系患者的FOXC2基因进行变异分析,明确患者的致病原因。方法采集家系成员血液样本并提取DNA和蛋白,对先证者进行全外显子组测序及生物信息学分析,确定可疑致病变异后应用Sanger测序进行家系验证、Western印迹技术检测蛋白表达量的变化。结果测序结果显示先证者和患病母亲均携带FOXC2基因c.177C>G(p.Tyr59X)杂合无义变异,该变异目前尚未被报道过,Western印迹检测显示FOXC2蛋白表达下降。其母在早孕期B超提示胎儿NT增厚,孕21+1周行羊水穿刺对胎儿进行产前诊断,产前基因诊断结果提示胎儿也携带c.177C>G变异。结论FOXC2基因c.177C>G无义变异是患儿的致病原因,并导致Foxc2蛋白表达下降,胎儿NT增厚可能和Foxc2表达量下降有关。本研究结果扩大了FOXC2基因变异谱。     

MCCC2基因变异致3-甲基巴豆酰辅酶A羧化酶缺乏症患儿的家系分析

目的对1例临床疑诊3-甲基巴豆酰辅酶A羧化酶缺乏症(3-methylcrotonyl-coenzyme A carboxylase deficiency,MCCD)患儿及其父母进行基因变异分析,寻找该家系的致病变异,为临床诊断提供分子遗传学依据。方法抽提先证者及其父母的外周血基因组DNA,应用全外显子组基因测序技术对疑似为MCCD疾病的先证者进行致病基因筛查。根据高通量测序结果,对先证者及其父母进行变异位点的Sanger测序验证分析。应用计算机软件预测变异位点氨基酸进化保守性和变异可能导致的蛋白质结构和功能变化,分析变异位点的性质。结果Sanger测序结果显示先证者为MCCC2基因c.1342G>A(p.Gly448Ala)纯合错义变异,为未报道过的新变异。先证者母亲为c.1342G>A(p.Gly448Ala)杂合变异携带者,父亲未检测到该变异。用PolyPhen-2和Mutation Taster软件预测该变异为致病性,变异区域序列在不同物种间高度保守。根据美国医学遗传学与基因组学学会遗传变异分类标准与指南,MCCC2基因c.1342G>A(p.Gly448Ala)变异判定为可能致病性变异(PM2+PP2~PP5)。结论先证者MCCC2基因c.1342G>A(p.Gly448Ala)纯合错义变异是其分子发病机制,基因变异分析有助于明确临床诊断。     

一个常染色体显性智力低下1型家系的MBD5基因新变异

目的对1例智力、运动发育落后、语言发育严重受损、面部畸形合并癫痫的患儿及其家系成员进行基因变异分析。方法应用全外显子分析技术对先证者进行致病变异筛查,结合先证者的表型确定候选致病位点,应用Sanger测序对先证者、父母及其他家系成员进行变异位点验证。结果先证者携带MBD5基因c.2217delT(p.F739Lfs*6)框移变异,文献未见报道,来源于母亲,经家系验证,其兄携带相同变异且具有相似的表型,其母年幼时语言表达能力差,学习成绩差,可做家务,无抽搐病史。结论发现一个MBD5基因新的致病变异,丰富了MBD5基因变异谱,家系研究发现该基因变异存在表现度差异。本研究结果为该家系的病因诊断和产前诊断提供了依据。     

一个先天性小眼畸形家系的全外显子组测序分析及产前诊断

目的分析1个先天性小眼畸形家系的临床表型及遗传学病因。方法应用高通量测序技术对先证者及其父母进行全外显子组测序,筛选候选致病位点,对其家系进行Sanger测序验证,并通过羊水穿刺和Sanger测序为先证者母亲提供产前诊断。结果全外显子组测序和Sanger测序发现家系中的3例患者均携带OTX2基因c.289C>T(p.R97*)杂合变异,先证者母亲亦携带该变异,但无小眼畸形。先证者的父亲、舅母和胎儿未携带上述变异。结论OTX2基因c.289C>T(p.R97*)杂合变异很可能是该家系的发病原因。上述诊断将有助于该家系的遗传咨询和产前诊断。     

SACS基因复合杂合突变导致Charlevoix-Saguenay型痉挛性共济失调一家系两例CSCD

目的对1个常染色体隐性遗传痉挛性共济失调Charlevoix-Saguenay型（autosomal recessive spastic ataxia of Charlevoix-Saguenay, ARSACS）家系进行SACS基因突变分析,探讨其遗传学病因。方法应用目标区捕获高通量靶向测序对SACS基因进行突变筛查,用Sanger测序对突变位点进行验证。结果测序结果显示先证者和弟弟存在SACS基因C．13085T〉G（P．14362R）和C．5236dupA（P．T1746fs）复合杂合突变,父亲携带SACS基因c．5236dupA（P．T1746fs）杂合突变,母亲携带SACS基因C．13085T〉G（p．14362R）杂合突变,因此患者的C．5236dupA（P．T1746fs）和C．13085T〉G（P．14362R）突变分别来自父母。经检索人类基因突变数据库这两个变异均为未报道过的新突变,根据美国医学遗传学及基因组学会遗传变异解读指南,提示均为可能的致病性突变。结论C．5236dupA（P．T1746fs）和C．13085T〉G（P．14362R）突变为该ARSACS家系患者的遗传学病因,新突变的检出丰富了SACS基因突变谱。     

Autosomal dominant polycystic kidney disease caused by somatic and germline mosaicism

Autosomal dominant polycystic kidney disease (ADPKD) is a heterogeneous genetic disorder caused by loss of function mutations of PKD1 or PKD2 genes. Although PKD1 is highly polymorphic and the new mutation rate is relatively high, the role of mosaicism is incompletely defined. Herein, we describe the molecular analysis of ADPKD in a 19‐year‐old female proband and her father. The proband had a PKD1 truncation mutation c.10745dupC (p.Val3584ArgfsX43), which was absent in paternal peripheral blood lymphocytes (PBL). However, very low quantities of this mutation were detected in the father's sperm DNA, but not in DNA from his buccal cells or urine sediment. Next generation sequencing (NGS) analysis determined the level of this mutation in the father's PBL, buccal cells and sperm to be ～3%, 4.5% and 10%, respectively, consistent with somatic and germline mosaicism. The PKD1 mutation in ～10% of her father's sperm indicates that it probably occurred early in embryogenesis. In ADPKD cases where a de novo mutation is suspected because of negative PKD gene testing of PBL, additional evaluation with more sensitive methods (e.g. NGS) of the proband PBL and paternal sperm can enhance detection of mosaicism and facilitate genetic counseling.     

一个Waardenburg综合征Ⅱ型家系SOX10基因的突变分析CSCD

目的对1例Waardenburg综合征Ⅱ型先证者及其家系成员进行SOX10基因的突变分析,探讨其可能的分子生物学致病原因。方法抽提先证者及其家系成员的外周血基因组DNA,芯片捕获高通量测序方法对MITF、PAX3、SOX10、SNA12、END3和ENDRB基因的全部外显子及其侧翼序列进行检测。根据高通量测序结果,对先证者及其父母进行突变位点的Sanger测序验证分析。结果Sanger测序结果显示先证者存在SOX10C．127c〉T（P．R43X）杂合突变,导致SOX10基因第43位编码精氨酸的密码子（CGA）突变为终止密码子（UGA）,产生截短蛋白,影响蛋白质功能的正常发挥。经检索人类基因突变数据库,该突变为未报道过的新突变。患儿父母未检测到该突变。结论先证者SOX10基因C．127c〉T（P．R43X）杂合突变可能是其分子生物学致病原因。     

Analysis of NFU1 gene mutation in a Chinese family affected with multiple mitochondrial dysfunction syndrome北大核心CSCD

Objective To detect potential mutation of NFU1 gene in a Chinese family affected with multiple mitochondrial dysfunction syndrome (MMDS). Methods For a mother with two children died of MMDS, next-generation sequencing (NGS) was used to scan her exome. Suspected mutation was validated with PCR and Sanger sequencing. Potential mutation of exons 1 to 8 and flanking regions of the NFU1 gene was also detected in the father by PCR and Sanger sequencing. Results A novel deletional mutation c. 90delC(p. Tyr30Ter) of the NFU1 gene was found in the mother, while the father was found to have carried a heterozygous c. 572A>T (p. Aspl91Val) mutation. The same mutations were not found among 100 healthy controls. Conclusion The novel mutations c. 90delC (p. Tyr30Ter) and c. 572A > T (p. Aspl91Val) of the NFU1 gene probably underlie the pathogenesis of MMDS in our case. Combined NGS and Sanger sequencing may provide efficient and accurate diagnosis for this disease.     

Analysis of DSPP gene mutation in a Chinese pedigree affected with hereditary dentinogenesis imperfectaCSCD

Objective: To analyze the clinical phenotype of a Chinese pedigree affected with hereditary dentinogenesis imperfecta and mutation of dentin sialophosphoprotein (DSPP) gene. Methods: Affected members underwent intraoral photography, dental film and panoramic radiography. Genomic DNA was extracted from peripheral venous blood samples. Coding regions of the DSPP gene were subjected to PCR amplification and Sanger sequencing. Functional effect of the mutation was predicted with SIFT and PolyPhen-2. The tertiary structure of wild type and mutant proteins were predicted by Swiss-Port. Results: A heterozygous c. 50C>T (p. P17L) mutation was identified in exon 2 of the DSPP gene in the proband and her father. The same mutation was not found among 200 unrelated healthy controls. The Pro-17 residues and its surrounding positions in DSPP are highly conserved across various species. The mutation was predicted to be damaging to the structure of DSPP protein. Conclusion: The c. 50C>T (p. P17L) mutation of the DSPP gene probably underlies the disease in this pedigree. Above finding has expanded the spectrum of DSPP gene mutations and provided a basis for genetic counseling and prenatal diagnosis for this family. © 2018 MeDitorial Ltd. All rights reserved.     

Germinal and somatic mutations in the PKD2 gene of renal cysts in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in one of three genes: PKD1 on chromosome 16 accounts for approximately 85% of cases whereas PKD2 on chromosome 4 accounts for approximately 15%. Mutations in the PKD3 gene are rare. All patients present with similar clinical phenotypes, and the cardinal symptom is the formation of fluid-filled cysts in the kidneys. Previous work has provided data supporting the notion that cysts in ADPKD1 are focal in nature and form after loss of function of polycystin 1. This became evident by demonstrating that the normal PKD1 allele was inactivated somatically by loss of heterozygosity or by mutagenesis in a subset of renal or liver cysts examined. We show in this report, for the first time, multiple novel somatic mutations within the PKD2 gene of epithelial cells, in both kidneys of an ADPKD2 patient. From a total of 21 cysts examined, seven (33%) had the same C insertion within the inherited wild-type allele. In two other cysts, a nonsense mutation and a splice site AG deletion had occurred in a PKD2 allele that could not be identified as the inherited wild-type or mutant. We suggest that the autosomal dominant form of ADPKD2 occurs by a cellular recessive mechanism, supporting a two-hit model for cyst formation.      

Mutation analysis in PKD1 of Japanese autosomal dominant polycystic kidney disease patients

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic renal disorder (incidence, 1:1,000). The mutation of PKD1 is thought to account for 85% of ADPKD. Although a considerable number of studies on PKD1 mutation have been published recently, most of them concern Caucasian ADPKD patients. In the present study, we examined PKD1 mutations in Japanese ADPKD patients. Long-range polymerase chain reaction (LR-PCR) with PKD1-specific primers followed by nested PCR was used to analyze the duplicated region of PKD1. Six novel chain-terminating mutations were detected: three nonsense mutations (Q2014X transition in exon 15, Q2969X in exon 24, and E2810X in exon 23), two deletions (2132del29 in exon10 and 7024delAC in exon 15), and one splicing mutation (IVS21-2delAG). There was also one nonconservative missense mutation (T2083I). Two other potentially pathogenic missense mutations (G2814R and L2816P) were on the downstream site of one nonsense mutation. These three mutations and a following polymorphism (8662C>T) were probably the result of gene conversion from one of the homologous genes to PKD1. Six other polymorphisms were found. Most PKD1 mutations in Japanese ADPKD patients were novel and definitely pathogenic. One pedigree did not link to either PKD1 or PKD2.     

Presymptomatic molecular diagnosis of autosomal dominant polycystic kidney disease using PKD1-and PKD2-linked markers in Cypriot families

Autosomal dominant polycystic kidney disease (ADPKD), is a heterogeneous disorder, primarily characterized by the formation of cysts in the kidneys, and the late development in life of progressive chronic kidney failure. Three genes are implicated in causing ADPKD. One on chromosome 16, PKD1, accounts for 85–90% of all cases, and the PKD2 gene on chromosome 4 accounts for the remainder. A very rare third locus is still of unknown location. We used PKD1-and PKD2-linked polymorphic markers to make the diagnosis of ADPKD in young presymptomatic members in affected families. We showed that in young members of families where clinical diagnosis cannot be definitively established, molecular linkage analysis can assist clinicians in the diagnosis. In one family a 24-year old had one cyst on the right kidney; however, molecular analysis showed clearly that he had inherited the normal haplotype. In another family, in one part of the pedigree there was co-inheritance of the disease with a PKD1-linked haplotype which originated in a non-affected 78-year-old father. Analysis with PKD2-linked markers excluded this locus. The data can be explained in one of two ways. Either this family phenotype is linked to a third locus, or the proband was the first affected person, most probably because of a novel mutation in one of her father's chromosomes. In conclusion, the combined use of markers around the PKD1 and the PKD2 locus provides more definitive answers in cases where presymptomatic diagnosis is requested by concerned families.     

Genetic and prenatal diagnosis of a retinitis pigmentosa pedigreeCSCD

Objective To explore the genetic etiology of a pedigree affected with hereditary retinitis pigmentosa. Methods High-throughput DNA sequencing was used to analyze the sequences of 173 genes associated with hereditary eye diseases in the proband. Suspected mutation was verified with PCR amplification and Sanger sequencing. Results The proband was found to have carried a c. 570-571 ins GAAGATGCTGT insertional mutation in the RP2 gene located on the X chromosome. All female carriers of the pedigree were heterozygous, while all affected males were hemizygous for the same mutation. Conclusion The inheritance pattern of this retinitis pigmentosa pedigree was X-linked recessive. The c. 570-571 ins GAAGATGCTGT insertional mutation of the RP2 gene probably underlies the disease. © 2018 West China University of Medical Sciences. All rights reserved.