Nonsense mutations in the PAX3 gene cause Waardenburg syndrome type I in two Chinese patients

Background Waardenburg syndrome type I （WS1） is an autosomal dominant disorder characterized by sensorineural hearing loss, pigmental abnormalities of the eye, hair and skin, and dystopia canthorum. The gene mainly responsible for WS1 is PAX3 which is involved in melanocytic development and survival. Mutations of PAX3 have been reported in familiar or sporadic patients with WS1 in several populations of the world except Chinese. In order to explore the genetic background of Chinese WS1 patients, a mutation screening of PAX3 gene was carried out in four WS1 pedigrees. Methods A questionnaire survey and comprehensive clinical examination were conducted in four Chinese pedigrees of WSI. Genomic DNA from each patient and their family members was extracted and exons of PAX3 were amplified by PCR. PCR fragments were ethanol-purified and sequenced in both directions on an ABl_Prism 3100 DNA sequencer with the BigDye Terminator Cycle Sequencing Ready Reaction Kit. The sequences were obtained and aligned to the wild type sequence of PAX3 with the GeneTool program. Results Two nonsense PAX3 mutations have been found in the study population. One is heterozygous for a novel nonsense mutation S209X. The other is heterozygous for a previously reported mutation in European population R223X. Both mutations create stop codons leading to truncation of the PAX3 protein. Conclusions This is the first demonstration of PAX3 mutations in Chinese WS1 patients and one of the few examples of an identical mutation of PAX3 occurred in different populations.     

Deafness genes for nonsyndromic hearing loss and current studies in China

Objectives To review the identified deafness genes related to nonsyndromic hearing loss (NSHL) and summarize their expressions and functions in the cochlea and to introduce the current studies of molecular genetics on NSHL in China.Methods The presented data are based on a review of the literature as well as the author’s experience with NSHL and communications with other researchers in China over the past 3 years.Results Currently, 23 deafness genes related to NSHL have been cloned and identified.Some genes are associated with both NSHL and syndromic hearing loss (SHL), in both dominant and recessive deafness.Deafness genes have a highly specific expression pattern in the inner ear.Some functional categories are starting to emerge from a characterization of deafness genes.There are interacting genes in the genetic background that influence the extent of hearing impairment.The GJB3 gene, which is associated with high-frequency hearing impairment, was cloned in a Chinese laboratory.Mutations in some genes, such as GJB2 and mitochondrial 12S rRNA, have been screened in Chinese patients with NSHL.Mapping new deafness gene loci as well as identifying new genes and their functions is an active area of study in China.Conclusions It is challenging for us to continue identifying new deafness genes and analyze gene functions.By identifying genes responsible for monogenic hearing impairment, more insight may be gained into the molecular process of hearing and the pathology of hearing loss.     

Molecular genetic analysis of autosomal dominant late-onset cataract in a Chinese Family

Congenital cataract is a highly heterogeneous disorder at both the genetic and the clinical-phenotypic levels.A unique cataract was observed in a 4-generation Chinese family,which was characterized by autosomal dominant inheritance and late-onset.Mutations in the 13 known genes (CRYAA,CRYAB,CRYBB1,CRYBB2,CRYGC,CRYBA1/A3,CRYGD,Connexin50,Connexin46,intrinsic membrane protein LIM2,cytoskeletal protein BFSP2,the major intrinsic protein-MIP and the heat shock factor HSF4) have previously been demonstrated to be the frequent reason for isolated congenital cataracts,but the exact molecular basis and underlying mechanisms of congenital cataract still remain unclear.This study was designed to find whether these 13 genes developed any mutation in the family members and to identify the disease-causing gene.Polymerase chain reaction (PCR) and direct DNA sequence analysis were carried out to detect the 13 genes.The results showed that no mutation causing amino acid alternations was found in these potential candidate genes among all patients in the family,and only several single-nucleotide polymorphisms (SNPs) were identified.A transitional mutation in the fourth intron of CRYBB2 and some silent mutations in the first exon of BFSP2 and CRYGD were found in the cataract family,but further study showed that these mutations could also be found in normal controls.It was concluded that some unidentified genes may underlie the occurrence of late-onset cataract in this family.A genome-wide screening will be carried out in the next study.     

GJB2 (Cx26) gene mutations in Chinese patients with congenital sensorineural deafness and a report of one novel mutation

Background Mutations in GJB2 gene are a major cause of autosomal recessive congenital hearing loss and the cause in some rare cases of the autosomal dominant form. The purpose of this study was to investigate the frequency and the features of GJB2 mutations in the Chinese patients with congenital sensorineural deafness.Methods Using PCR amplifying the entire coding region of GJB2 gene and direct DNA sequencing to analyze mutations in this gene among unrelated 69 cases with autosomal recessive congenital nonsyndromic deafness and 27 cases of dominant congenital deafness and 35 sporadic cases. We also detected mutations in GJB2 in 100 control subjects with normal hearing.Results 17. 4% (12/69) of the probands in the autosomal recessive, 7. 4% (2/27) of dominant families and 5.7% ( 2/35 ) of the sporadic congenital deafness patients had deafness-causing mutations in GJB2, respectively. Nine types of the mutations in GJB2 were detected in the recessive and sporadic group. They consisted of five types of polymorphism, and four types of deafness-causing mutation with homozygous 35delG in 1 sporadic (1/35), and 235delC frameshift mutation in 1 sporadic (homozygotes) and 10 recessive patients (2 heterozygotes and 8 homozygotes), and homozygous 442G→A missense mutation and homozygous 465T→A nonsense mutation in 1 different recessive proband, respectively. The 465T→A that related to recessive deafness was a novel mutation found by this study. The homozygous (10/69, 14. 5%) and the heterozygous (2/69,2.9%) GJB2 mutation in the recessive patients (12/69, 17.4%) and the homozygotes in the sporadic patient (2/35, 5. 7%) all had congenital severe to profound sensorineural hearing loss.511G→A missense mutation and 299 -300delAT frameshift mutation were found in two autosomal dominant congenital deafness families (2/27, 7.4%). The total mutation frequency of GJB2 was 12.2% (16/131) in the Chinese patients with congenital sensorineural deafness and 235delC was the most common deafness-causing mutation. Six types of mutation-5 types of polymorphism and 1 type of heterozygous deletion (235delC) mutation were found in the 100 control subjects. The carry rate of the most frequent type of mutation 235delC was 0. 5% in the controls(1/200 alleles). 109G→A was the most frequent (15/100, 15%) and 79G→A was the second common (8/100, 8%) polymorphism in this population.Conclusions The general mutation rate of GJB2 is 12.2% (16/131) and the 235delC is the most common type of deafness-causing mutation in Chinese patients with congenital hearing loss. 465T→A nonsense mutation that is associated to autosomal recessive deafness is a novel mutation found by this screening. 511G→A and 299-300delAT mutations contribute to autosomal dominant hearing loss. The study further supports the view that the common types of mutation in GJB2 according to different ethnic background and that the mutation prevalence in the East Asian deafness population is lower than that in the white population.     

Molecular analysis for diagnosis of Marfan syndrome and Marfan-associated disorders

Marfan syndrome is a systemic disorder of connective tissue, caused by mutations in the FBN1, TGFBR1 or TGFBR2 genes. This syndrome is characterized by involvement of three major systems, skeletal, ocular, and cardiovascular. The continuing improvements in molecular biology and increasing availability of molecular diagnosis in clinical practice allow recognition of Marfan syndrome in patients with incomplete phenotypes. Additionally, molecular analyses could also be used for preimplantation genetic diagnosis. The identification of a mutation allows for early diagnosis, prognosis, genetic counseling, preventive management of carriers and reassurance for unaffected relatives. The importance of knowing in advance the location of the putative family mutation is highlighted by its straightforward application to prenatal and postnatal screening.

     

Birth of healthy children after preimplantation diagnosis of β-thalassemia

Background Clinical programs for preventing β-thalassemia are presently based on prospective carrier screening and prenatal diagnosis. This paper report an achievement of a pregnancy with unaffected embryos using in vitro fertilization and embryo transfer (IVF-ET), in combination with preimplantation genetic diagnosis (PGD), for a couple at risk of having children with β-thalassemia.Methods A couple carrying different thalassemia mutations, both a codon 41-42 mutation and the IVS Ⅱ 654 mutation, received standard IVF treatment, with intracytoplasmic sperm injection, embryo biopsiy, single cell polymerase chain reaction (PCR) and DNA analysis. Only unaffected or carrier embryos were transferred to the uterine cavity. After confirmation of pregnancy, a prenatal diagnosis was performed.Results Of a total of 13 embryos analyzed for β-globin mutations, PGD indicated that 2 were normal,3 were affected, and 6 were carriers. Diagnosis could not be made in the other 2 embryos. Three embryos were transferred to the uterus on the third day after oocyte retrieval. Ultrasonography revealed a twin pregnancy with one blighted ovum. The prenatal genetic diagnosis revealed that both fetuses were unaffected, and two healthy boys were born, confirming the results of PGD.Conclusions We developed a single-cell based primer extension preamplification (PEP)-PCR assay for the detection of β-thalassemia mutations. The assays were efficient and accurate at all stages of the procedure, and resulted in the birth of PGD-confirmed β-thalassemia free children in China. PEP was used here in PGD for β-thalassemia.     

Screening of pathogenic genes in Chinese patients with arrhythmogenic right ventricular cardiomyopathy

Background Arrhythmogenic right ventricular cardiomyopathy （ARVC） is a heritable cardiac disease predominantly caused by mutations in desmosomal protein genes. Previous genetic analyses of the Chinese ARVC population are limited to small size and restriction to a single gene. This study was aimed to investigate the genotype in a large series of Chinese patients with ARVC through comprehensively screening nine ARVC-causing genes. Methods A total of 100 unrelated ARVC patients and 300 age, gender and ethnicity matched healthy controls were genetically tested with multiplexing targeted resequencing for nine previously reported ARVC-causing genes, including plakophilin-2, desmoplakin, desmoglein-2, desmocollin-2, plakoglobin, transforming growth factor beta-3, transmembrane protein 43, desmin and Lamin A/C. Results Fifty-nine mutations were identified in 64% of the patients, among which, 93% were located in desmosomal protein genes. Plakophilin-2 mutations accounted for 54% of the total and 58% of the desmosomal mutations, with a truncating mutation type making up about 2/3 of the plakophilin-2 mutations. Only four mutations were found in nondesmosomal genes; two in transmembrane protein 43 and two in transforming growth factor beta-3. Two of them （one of each gene） appeared as single missense mutations. No mutation was identified in desmin or Lamin A/C. Multiple mutations were found in 23% of the patients, with plakophilin-2 being found in 57% of the multi-mutation carriers. Conclusions Plakophilin-2 was the most common gene mutation that was identified in Chinese ARVC patients. Nondesmosomal genes should be added to desmosomal protein genes when performing molecular genetic screening in patients with suspected ARVC.     

A COMPLETE SCREEN FOR MUTATIONS OF THE RHODOPSIN GENE IN A PANEL OF CHINESE PATIENTS WITH AUTOSOMAL DOMINANT RETINITIS PIGMENTOSA

Objective To evaluate the prevalence of rhodopsin (RHO) mutations and the genotype-phenotype relationships in Chinese patients with autosomal dominant retinitis pigmentosa (ADRP) by conformation sensitive gel electrophoresis (CSGE) and direct DNA sequencing. Methods We have screened the five coding exons and splice sites of RHO gene in 27 probands who had no relativity from Chinese ADRP families and 100 normal controls to identify disease-associated mutations, using CSGE and direct DNA sequencing. Family members of some probands with disease-associated mutations were also genotyped to determine whether the RHO mutations segregated with retinitis pigmentosa (RP) in their families. Two RHO mutations, Pro347Leu and Pro327 (l-bp del), were identified separately in two families, thus the frequency of RHO mutations among this set of Chinese ADRP families is about 7.4% (2/27). Pro347Leu mutation was found in one ADRP proband as well as three her children who also had RP. She had relatively early onset at about 17 years.The only one child without this mutation had no symptom or sign of RP at age of 34. Pro327 (l-bp del) was identified in a late-onset ADRP patient, who appeared night blindness around 30 years old and in her fifties electroretinogram (ERG) has been fiat in both scotopic and photopic phases. Family analysis showed that this mutation also existed in her younger daughter and her elder sister, both of them also had RP. Three other family members were genotypically and phenotypically normal. Neither of the two mutations was detected in 100 normal controls. Conclusions The frequency of RHO mutations in Chinese patients was lower than that in Europe and North America.The phenotype of the patients with Pro347Leu corresponded to type 1 ADRP, with severe rod degeneration and some cone preservation later, while the phenotype of the patients carrying Pro327 (l-bp del) corresponded to type 2 ADRP, with a concomitant loss of rod and cone visual function. CSGE was found to be a sensitive, simple, and practical method for the screening of a large number of samples under highly reproducible conditions, and could be utilized in routine molecular diagnostic laboratories.     

Mutation of plakophilin-2 gene in arrhythmogenic right ventricular cardiomyopathy

Background Arrhythmogenic right ventricular cardiomyopathy （ARVC） is one of the leading causes of sudden cardiac death. Recent studies have shown that ARVC, which is an inheritable genetic change, results from mutations in genes encoding desmosomal proteins. Plakophilin-2 is an important component of the desmosome. Because the full range of genetic variations related to ARVC is unknown and no related studies of the Chinese population have been reported, we aimed to investigate the genetic variation of plakophilin-2 in ARVC patients from the Southern Region of China.
Methods Genomic DNA was isolated from peripheral blood samples of all 34 ARVC patients, who were screened through a clinical evaluation. They were used to detect variations in the sequences of the plakophilin-2 genes by polymerase chain reaction amplification in combination with direct sequencing.
Results In exon-1 of the plakophilin-2 gene, a deletion mutation （c.145_148 del GACA） was found in one family pedigree. The mutation was also found in exon-2, 4, and 11 of the plakophilin-2 gene. The QT interval dispersion of the ECG was considerably longer in the mutation group than in the non-mutation group of ARVC patients, and this result was statistically significant （P 〈0.05）.
Conclusion We discovered a plakophilin-2 mutation that prolongs the QT interval dispersion in the southern Chinese ARVC population.     

Original article ：Identification of seven novel mutations in the factor Ⅷ gene in 18 unrelated Chinese patients with hemophilia A

Background Hemophilia A （HA） is an X-linked inherited bleeding disorder caused by decreased activity of factor Ⅷ（FⅧ） due to heterogenous mutations in the FⅧ coding gene （F8）. The type of mutation plays an important role in the FVIII inhibitor formation. To date, several studies on the spectra of F8 defects have been performed in Western populations, but similar studies in Asian races are scarce. Here, we reported the distribution of the F8 gene mutations in 18 unrelated Chinese patients with HA. Methods Intron 22 and intron 1 inversions in the F8 gene were screened in 158 unrelated patients with HA using a long-distance PCR and multiplex PCR method. Direct sequencing of the coding region of the F8 gene was used to identify the mutations responsible for HA in 18 unrelated Chinese HA patients who were negative for intron 22 and intron 1 inversions; sequences were compared with the HAMSTERS database. A clotting method was used to assay the FⅧ activity level and the Bethesda assay was used to detect the FⅧ inhibitor. Results A total of 18 different HA F8 mutations were identified, seven of which were described for the first time. These novel mutations included five small deletions, one point mutation and one small insertion. One novel mutation （4382-3 AC deletion） was associated with inhibitor development. Conclusion These data extend our insight into the mechanisms by which novel amino acid mutations may lead to HA and how the HA patient genotypes influence the risk of FⅧ inhibitor.     

山东省5 664例听力障碍患者听力检测联合失聪基因检测结果分析

背景失聪是影响人类健康和造成人类残疾的常见疾病,其发病率一直在各类残疾中高居首位。引起失聪的原因很多,其中遗传因素约占60%,通过失聪基因筛查和家系分析明确是否为遗传性失聪,为失聪患者提供相应的遗传咨询服务,以阻断失聪的代代相传。目的了解山东省听力障碍患者听力损失情况和失聪基因突变频率,明确听力障碍致病原因。方法对2016—2020年参加山东省听力障碍人士失聪基因检测项目的5 664例持听力残疾证或持听力诊断证明的听力障碍患者进行遗传性失聪基因筛查检测,通过纯音测听检测听力障碍患者听力损失情况,应用常见的4个基因15位点遗传性失聪基因芯片进行基因检测。结果5 664例听力障碍患者中,听力残疾一级3 891例,听力残疾二级1 463例,听力残疾三级188例,听力残疾四级73例,其余49例（小耳畸形38例,外耳道封闭11例）。5 664例听力障碍患者检测出失聪基因突变者2 503例,其中GJB2基因突变1 227例（携带率为21.66%）,SLC26A4基因突变975例（携带率为17.21%）,线粒体12SrRNA基因突变97例（携带率为1.71%）;GJB3基因突变158例（携带率为2.79%）;双基因杂合突变46例（携带率为0.81%）。GJB2、SLC26A4基因突变在听力等级中比较一致,属于热点突变。携带GJB2基因、SLC26A4基因突变患者听力一级比例高于听力二级（P<0.05）。结论山东省听力障碍患者中常见的4个遗传性失聪基因热点突变主要集中在GJB2基因和SLC26A4基因上;失聪相关基因尚存有许多未知的领域,有待于进一步研究。通过对不同基因型个体进行婚育指导,可以降低聋-聋婚配中聋病的垂直传递,减少本地区新生听力障碍儿童的出生。     

非综合征性耳聋人工耳蜗植入者基因分析

目的研究连接蛋白26（Connexin26）基因（GJB2）突变和线粒体12S rRNA基因突变在人工耳蜗植入的非综合征性耳聋患者中发生的几率及特性。方法选取100例接受人工耳蜗植入患者,语前聋为96例,语后聋为4例。自外周静脉血中提取总DNA,进行GJB2基因和线粒体12S rRNA基因核苷酸PCR,对扩增的基因片段进行测序,检测GJB2基因突变和线粒体12S rRNA基因突变。结果接受人工耳蜗植入的非综合征性耳聋病例中发现GJB2基因突变率最高,为34％（34／100）。其突变类型主要为235delC,占27％;同时有氨基糖甙类药物使用史的16例病例中发现2例有线粒体12S rRNA基因A1555G突变,1例有线粒体12S rRNA基因突变delT961Cn。结论GJB2基因突变在人工耳蜗植入的患者中发生率最高,235delC是主要突变类型,有氨基糖甙类药物应用史的语后聋患者中线粒体12S rRNA基因突变A1555G为常见突变形式。     

240例耳聋患者常见耳聋基因筛查分析

目的 分析非综合征型耳聋患者常见耳聋基因突变情况,探讨遗传性耳聋基因芯片检测的临床意义。方法 2013年3-8月来自沈阳市和平区残联的非综合征型耳聋患者240例,患者或监护人签署知情同意后提取被检者外周静脉血基因组DNA,采用晶芯？遗传性耳聋基因检测试剂盒对常见的4个耳聋基因（GJB2、GJB3、SLC26A4以及线粒体12S rRNA）的9个突变位点进行检测。结果 240例受检者中,102例存在被检测基因突变,其中GJB2基因突变44例（18.33%,44/240）,SLC26A4基因突变38例（15.83%,38/240）,线粒体12S rRNA基因突变17例（7.08%,17/240）,GJB3 538 C〉T 1例（0.39%,1/240）。明确诊断为遗传性耳聋60例,提示遗传性耳聋42例,占全部耳聋患者的42.5%（102/240）。结论 非综合征型耳聋患者耳聋基因携带率较高,对高危人群进行耳聋基因突变的筛查和遗传咨询是防止和控制遗传性耳聋、优生优育的重要步骤。     

微阵列基因芯片在新生儿遗传性耳聋筛查中的应用研究

背景　新生儿听力筛查在世界范围内广泛开展,在早期发现、诊断和干预方面发挥了重要作用。2012年1月北京市启动了新生儿听力和基因筛查同步工作,同时进行新生儿听力和基因筛查,将发挥重要作用。目的　应用微阵列基因芯片对新生儿进行遗传性耳聋筛查,评估新生儿中4个常见遗传性耳聋基因突变的频率、突变类型以及其与遗传性耳聋的相关性,为推广新生儿遗传性耳聋基因筛查提供临床研究证据。方法　选取2017年度北京大学第三医院妇产科生殖医学中心检测的17 824例新生儿,采集出生3 d后的足跟血,使用微阵列基因芯片进行4个常见遗传性耳聋基因9个突变位点的筛查,对阳性结果进行测序验证。结果　新生儿遗传性耳聋基因筛查17 824例,检出阳性890例,阳性率为4.99%。其中GJB2基因杂合突变型501例（2.81%）,SLC26A4基因杂合突变型290例（1.63%）,SLC26A4基因纯合突变型1例（0.01%）,线粒体DNA 12S rRNA突变型41例（0.23%）,GJB3基因杂合突变型41例（0.23%）,双杂合突变型16例（0.09%）。结论　新生儿常见遗传性耳聋基因突变以GJB2基因突变、SLC26A4基因突变为主,微阵列基因芯片可以及早有效地检出先天性耳聋、迟发性耳聋及药物性耳聋基因的携带情况。微阵列基因芯片筛查,快速、高效,对遗传性耳聋的早期诊断、早期干预及遗传咨询具有重要意义,提倡推广新生儿听力筛查联合基因筛查。     

耳聋分子病因学检测与临床应用研究

目的:探讨基因检测在耳聋病因学诊断中的应用前景?方法:收集原因不明的门诊非综合征型耳聋患者200例,采用耳聋基因芯片结合DNA序列测定方法,对中国人中4个常见耳聋相关基因的9个热点突变进行分子检测?9个突变位点分别是:GJB2基因的35delG?176del16bp?235delC和299delAT,GJB3基因的C538T,SLC26A4基因的IVS7-2A>G和A2168G,以及线粒体DNA 12S rRNA基因的A1555G和C1494T?结果:芯片筛查发现携带上述耳聋基因突变者78例(39.0%),其中GJB2突变37例(18.5%),SLC26A4突变28例(14.0%),GJB3突变2例(1.0%),mtDNA 12S rRNA突变11例(5.5%)?59例(29.5%)患者可确诊为遗传性耳聋?结论:约30%的原因不明的门诊非综合征型耳聋患者与遗传因素有关,耳聋基因诊断具有广阔的应用前景?     

遗传性耳聋基因诊断技术的建立和初步临床应用

目的 :建立一种能实用于临床应用的检测技术 ,以解决遗传性耳聋基因诊断这一难题。方法 :首先依照临床表现对遗传性耳聋病人进行分类 ,然后确定与各类遗传性耳聋可能相关的致病基因 ,再根据这些基因的突变频率确定检测顺序 ,针对不同的基因结构采用不同的突变检测方法 ;最后对有突变家系的其他成员进行突变检测以最后确立诊断。结果 :通过对 4 0个常染色体隐性非综合征型耳聋家系、2 4个常染色体显性非综合征型耳聋家系进行检测 ,我们发现了CX2 6基因的 2种致病性突变和 6种多态、POU4F3基因的一种同义突变、CX31基因的三种多态。结论 :本诊断技术体系对于遗传性耳聋的基因诊断是一种较为有效的方法 ,具有一定的实用价值。     

广州地区非综合征性耳聋患者耳聋相关基因突变分析

目的分析广州地区非综合性耳聋患者相关耳聋基因突变,初步了解广州地区耳聋患者发病的分子机制。方法详细询问病史和临床检查后,收集广州地区52例非综合性耳聋患者的外周血,提取基因组DNA,用遗传性耳聋基因芯片对4个常见耳聋相关基因(GJB2、SLC26A4、线粒体12SrRNA及GJB3基因)的9个位点进行检测。结果 52例耳聋患者中共检出18例带有耳聋基因突变,检出阳性率为34.6%,其中GJB2基因235delC纯合突变6例,杂合突变2例,299delAT纯合突变1例;SLC26A4基因IVS7-2A>G纯合突变4例,杂合突变1例;线粒体12SrRNA A1555G均质突变4例。结论广州地区非综合性耳聋患者的耳聋相关基因检出阳性率、GJB2基因及SLC26A4基因的携带率均低于全国平均水平,而线粒体基因突变的携带率明显高于全国平均水平。     

中国人群迟发性耳聋家系及散发病例凝血因子C同源物基因突变分析

目的分析中国常染色体显性遗传非综合征性耳聋（DFNA）群体凝血因子C同源物（COCH）基因突变发生率及突变谱。方法在我国汉族人群中收集26个DFNA家系、19个遗传方式不明的迟发性耳聋小家系、22例迟发性耳聋散发病例和100例正常对照者的临床资料及外周静脉血并提取DNA,采取PCR扩增后直接测序的方法进行COCH全序列突变分析。结果在1个巨大DFNA家系中发现COCH 1625G〉A杂合突变,使原来542位的半胱氨酸突变成酪氨酸（C542Y）;在1个遗传方式不明的迟发性耳聋小家系中发现COCH 1535 T〉C杂合突变,使512位蛋氨酸突变为苏氨酸（M512T）。进化保守性分析提示C542、M512在小鼠、牛、鸡和斑马鱼中高度保守。2个家系成员的表现型与基因型共分离。100例正常对照未见COCH突变。结论COCH M512T和C542Y突变是这2个迟发性耳聋家系患者致聋的分子病因。     

两个线粒体12S rRNA C1494T突变及药物性耳聋家系的分子遗传学研究

目的:探讨2个氨基糖甙类药物性耳聋及非综合征型耳聋家系的分子遗传学特征?方法:收集家系成员外周血样,常规方法提取基因组DNA?首先,利用基因芯片对中国人4个常见耳聋基因的9个突变热点进行分子筛查,9个位点分别为:GJB2基因的35 delG?176 del16?235 delC和299 delAT;GJB3基因的538 C>T;PDS基因的IVS7-2 A>G和2168 A>G以及mtDNA 12S rRNA基因的1494 C>T和1555 A>G?然后,对两家系的先证者分别进行线粒体DNA全序列及核基因TRMU和MTO1编码区的PCR扩增和测序分析?结果:芯片检测发现两家系的7名母系成员均存在同质性mtDNA 12S rRNA C1494T突变?与修正的剑桥参考序列相比,2名先证者的mtDNA全序列分析共检测到53个碱基变异,但除已知的12S rRNA C1494T突变外,其余52个碱基变异均为已报道的多态性位点;两家系先证者线粒体单体型分别是D4和D5a;TRMU和MTO1基因序列分析无异常发现?结论:线粒体DNA 12S rRNA C1494T突变是两个家系耳聋发生的主要分子基础,而氨基糖甙类抗生素的应用增强了该突变的表型表达;未能证实线粒体单体型以及核基因TRMU和MTO1对家系成员C1494T突变的表型具有修饰作用?