一个常染色体显性遗传非综合征性耳聋家系的HBSY-012家系基因检测及遗传学特征分析

目的 研究常染色体显性遗传非综合征性耳聋家系的HBSY-012家系致病基因的突变位点,分析基因型与异常表型的关系。方法 采集一个常染色体显性遗传性非综合征型耳聋HBSY-012家系患者的临床资料,分析耳聋表型、遗传方式,并绘制家系图。提取家系成员外周血DNA,利用耳聋相关基因靶向测序,对家系成员进行全基因组外显子测序,寻找致病基因,采用Sanger测序技术验证突变位点。结果 HBSY-012家系现存四代共19人,9人诊断为感音神经性聋,耳聋表型特点为语后聋,发病早期呈现高频感音神经性耳聋,双耳对称,随着疾病进展出现渐进性听力下降,且快速下降,并转变成全频受累的极重度感音神经性耳聋。该家系的9例患者均在5～7岁开始出现听力下降,患者中年龄最大68岁,最小10岁。HBSY-012家系系谱分析该家系符合常染色体显性遗传特征。遗传性耳聋基因筛查检测显示EVI5基因NM＿005665:c.2399C>T变异、ANKMY2基因NM＿020319:c.822＿826del变异以及CCDC50基因c.363C>T(p.Leu121Phe)杂合突变,其中CCDC50基因c.363C>T...     

一个常染色体显性非综合征型耳聋DFNA15家系的基因检测

目的:探究一个常染色体显性非综合征型语后聋家系的致病基因变异类型,明确可能的遗传学病因。方法:应用高通量测序方法对先证者进行415个遗传性耳聋相关基因的序列检测,应用Sanger测序法对高通量测序结果进行验证并对家系成员进行基因变异位点检测。结果:先证者基因组DNA中检测到一个与非综合征型常染色体显性耳聋15(auto...     

两个中国常染色体显性遗传性多囊肾病家系的表型与基因型分析

目的研究中国人多囊肾病基因1（polycystic kidney disease 1 gene，PKD1）突变的特点，检测基因突变位点。方法25例多囊肾患者，正常对照16名，扩增PKD1基因的第44、45外显子的基因片段，变性梯度凝胶电泳突变检测系统进行初筛，然后测序。结果发现1个移码突变（12431delCT）、1个无义突变（C12217T）、1个多态性（A50747C），突变检测率为8％（2／25）。结论检测到2个新的可能的致病突变：1个移码突变（12431delCT）、1个无义突变（C12217T）。     

常染色体显性高度近视一家系连锁定位分析

目的 通过连锁定位分析,探讨一个中国原发性高度近视家系的致病基因与已报道高度近视相关连锁位点的关系.方法 选择一个连续3代发病的常染色体显性高度近视家系,选取位于18p11.31,12q21-23,7q36,17q21-23,4q22-27,2q,37.1,7p15.3,15q12-13,10q21.1这9个已报道的常染色体显性高度近视致病基因连锁位点的18个多态性微卫星标记物进行STR基因分型,采用两点法进行连锁分析.结果 本家系受累者皆为高度近视,屈光度从-6.00D到-20.00D不等,符合常染色体显性遗传特征.分析显示此9个遗传标记位点与该家系致病基因均不连锁,比值比均<-1.结论 该家系存在一个新的致病基因连锁位点,需进一步实施全基因组多态性微卫星标记连锁分析以确定该家系致病基因的染色体定位.     

珊瑚状常染色体显性遗传白内障家系相关基因的定位和筛选

目的　明确一个延续 4代具有珊瑚状表型的常染色体显性遗传性白内障家系的基因缺陷。方法　家系成员的基因组 DNA进行全基因组扫描和连锁分析 ;利用 L INKAGE5 .1软件计算两点 L OD值 ;用直接测序法对候选基因进行突变检测。结果　 38个家系成员中有 13个患有遗传性白内障。基因组扫描发现 ,D2 S32 5引物在最大重组率为 0 .1时 ,其两点最大 L OD值 >3,提示与该家系连锁。对人类γ-晶状体蛋白基因簇的 4个基因进行突变检测发现 ,此家系患者 γ- D晶状体蛋白 (γ- D crystallin,CRYGD)基因第 2外显子有 1个 C→A突变 ,此突变导致蛋白第 2 3位的脯氨酸被苏氨酸取代 (P2 3T)。结论　珊瑚状白内障表型与C→ A错义突变的 CRYGD基因密切相关 ,且此突变完全相同于最近报道的与一层状白内障表型共分离的突变。发现相同的基因缺陷引起的白内障浑浊可位于晶状体截然不同的部位 ,其病理机理还需进一步的研究。     

常染色体显性成人多囊肾病两家系PKD1、PKD2基因的突变鉴定

目的 鉴定两个常染色体显性成人多囊肾病家系的致病突变.方法 采用酚氯仿法提取家系成员及无亲缘关系的100名健康对照个体的外周血白细胞DNA,PCR扩增先证者致病基因PKD1、PKD2的所有外显子序列及其侧翼内含子剪切区域,直接测序确定DNA序列的变异.通过家系和正常对照的比较分析,对检测到的变异是否与疾病相关进行了初步探讨.结果 在两个家系中共检测到5个序列变异:PKD1:c.2469G＞A,PKD1:c.5014_5015 delAG,PKD1:c.10529C＞T,PKD2:c.568G＞A和PKD2:c.2020-1_2020 delAG.其中PKD1:c.2469G＞A和PKD2:c.2020-1_2020 delAG为新发现的变异.此外,检测到的移码突变和剪切突变未见于家系中健康成员及无亲缘关系的正常对照.结论 PKD1:c.5014_5015 delAG和PKD2:c.2020-1_2020 delAG分别为家系A和B的致病突变,且PKD2:c.2020-1_2020 delAG为先证者新发生的突变.     

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。     

一个常染色体显性遗传先天性皮肤淀粉样变家系

摘 要：为寻找疾病相关基因,通过调查、体检、病理检查等手段,发现了一皮肤淀粉样变家系,到目前4代中有12人患有皮肤淀粉样变病,主要表现斑状淀粉样变的特征,其特点是由点状色素斑点聚集成波纹状或网状褐色色素斑,对称分布于背部肩胛区、小腿、臂部、乳房和臀部,中等度瘙痒.遗传分析表明,该疾病属常染色体显性遗传.该家系可作为寻找眼外肌纤维化疾病相关基因的宝贵资源。     

常染色体不完全显性遗传癫痫两家系

家系1 先证者（Ⅲ8）女，15岁，半年前无明显诱因突然发作四肢抽搐，跌倒，两眼上翻，口吐白沫，发作持续10分钟左右，发作时意识丧失，醒后不能回忆发作经过，但倒地时颜面擦伤感觉疼痛，同时口述心里难受。一个月后再发，症状类似。检查：智力、发育正常，体格检查未发现明显异常，脑电图显示a节律失调，过度换气出现2．5—3．5C／S高波幅尖、棘慢波，以额、颞为甚，持续20s左右。     

常染色体显性遗传性多囊肾病临床及基因突变分析

目的 分析常染色体显性遗传性多囊肾病（ADPKD）患者临床特征及基因突变特点。方法 入选ADPKD患者23例,收集临床数据,并进行家系调查;抽取外周血经高通量测序方法进行多囊肾基因检测。结果 23例ADPKD患者主要临床表现为腰腹痛、血尿、感染,肾功能不全;与女性患者相比,男性ADPKD患者血尿酸水平明显增高;基因检测PKD1基因突变19例;PKD2基因突变4例。同处于慢性肾脏病（CKD）5期的ADPKD患者,PKD1基因突变患者血红蛋白明显低于PKD2基因突变患者（65.89±13.59 vs 97.5±17.02,P<0.01）。结论 ADPKD可进展至肾功能衰竭,基因检测有助于早期诊断和预后评估,终末期ADPKD患者,PKD1基因突变患者预后更差。     

A gene for autosomal dominant hearing impairment (DFNA14) maps to a region on chromosome 4p16.3 that does not overlap the DFNA6 locus

Non-syndromic hearing impairment is one of the most heterogeneous hereditary conditions, with more than 40 reported gene localisations. We have identified a large Dutch family with autosomal dominant non-syndromic sensorineural hearing impairment. In most patients, the onset of hearing impairment is in the first or second decade of life, with a slow decline in the following decades, which stops short of profound deafness. The hearing loss is bilateral, symmetrical, and only affects low and mid frequencies up to 2000 Hz. In view of the phenotypic similarities of this family with an American family that has been linked to chromosome 4p16.3 (DFNA6), we investigated linkage to the DFNA6 region. Lod score calculations confirmed linkage to this region with two point lod scores above 6. However, as haplotype analysis indicated that the genetic defect in this family is located in a 5.6 cM candidate region that does not overlap the DFNA6 region, the new locus has been named DFNA14.     

Low prevalence of Connexin 26 (GJB2) variants in Pakistani families with autosomal recessive non-syndromic hearing impairment

The Pakistani population has become an important resource for research on autosomal recessive non-syndromic hearing impairment (ARNSHI) due to the availability of large extended and highly consanguineous pedigrees. Here is presented the first report on the prevalence of gap junction beta-2 (GJB2) variants in Pakistan. One hundred and ninety-six unrelated Pakistani families with ARNSHI were recruited for a study on the genetics of NSHI. DNA sequencing of the GJB2 coding region was done on two affected individuals per family. Evolutionary conservation and predicted effect on the protein product were studied in order to hypothesize whether or not a variant was potentially deleterious. Homozygous putatively functional GJB2 variants were identified in 6.1% of families. None of the putatively functional GJB2 variants were observed in the compound heterozygous state. The six putatively causative variants noted were 231G > A(W77X), 71G > A(W24X), 167delT, 95G > A(R32H), 358-360delGAG(delE120), and 269T > C(L90P), with 231G > A(W77X) and 71G > A(W24X) being the most common. In addition, five benign polymorphisms, 380G > A(R127H), 457G > A(V153I), 493C > T(R165W), 79G > A(V27I), and 341 A > G(E114G), were identified within this population. In a few individuals, benign polymorphisms were observed to occur on the same haplotype, namely [457G > A(V153I); 493C > T(R165W)] and [79G > A(V27I); 341 A > G(E114G)]. The spectrum of GJB2 sequence variants in Pakistan may reflect shared origins of hearing impairment alleles within the Indian subcontinent. The high degree of consanguinity within Pakistan may have maintained the GJB2 prevalence at a much lower rate than within India and other populations.     

A novel locus for autosomal dominant non-syndromic deafness, DFNA53, maps to chromosome 14q11.2-q12

Background

Non‐syndromic hearing loss is among the most genetically heterogeneous traits known in humans. To date, at least 50 loci for autosomal dominant non‐syndromic sensorineural hearing loss (ADNSSHL) have been identified by linkage analysis.

Objective

To report the mapping of a novel autosomal dominant deafness locus on the long arm of chromosome 14 at 14q11.2‐q12, DFNA53, in a large multigenerational Chinese family with post‐lingual, high frequency hearing loss that progresses to involve all frequencies.

Results

A maximum multipoint LOD score of 5.4 was obtained for marker D14S1280. The analysis of recombinant haplotypes mapped DFNA53 to a 9.6 cM region interval between markers D14S581 and D14S1021. Four deafness loci (DFNA9, DFNA23, DFNB5, and DFNB35) have previously been mapped to the long arm of chromosome 14. The critical region for DFNA53 contains the gene for DFNA9 but does not overlap with the regions for DFNB5, DFNA23, or DFNB35. Screening of the COCH gene (DFNA9), BOCT, EFS, and HSPC156 within the DFNA53 interval did not identify the cause for deafness in this family.

Conclusions

Identifying the DFNA53 locus is the first step in isolating the gene responsible for hearing loss in this large multigeneration Chinese family.     

Localization of a novel autosomal recessive non-syndromic hearing impairment locus DFNB55 to chromosome 4q12-q13.2

Hereditary hearing impairment (HI) is the most genetically heterogeneous trait known in humans. So far, 54 autosomal recessive non-syndromic hearing impairment (ARNSHI) loci have been mapped, and 21 ARNSHI genes have been identified. Here is reported the mapping of a novel ARNSHI locus, DFNB55, to chromosome 4q12-q13.2 in a consanguineous Pakistani family. A maximum multipoint LOD score of 3.5 was obtained at marker D4S2638. The region of homozygosity and the 3-unit support interval are flanked by markers D4S2978 and D4S2367. The region spans 8.2 cm on the Rutgers combined linkage-physical map and contains 11.5 Mb. DFNB55 represents the third ARNSHI locus mapped to chromosome 4.     

Identification of p.A684V missense mutation in the WFS1 gene as a frequent cause of autosomal dominant optic atrophy and hearing impairment

Optic atrophy (OA) and sensorineural hearing loss (SNHL) are key abnormalities in several syndromes, including the recessively inherited Wolfram syndrome, caused by mutations in WFS1. In contrast, the association of autosomal dominant OA and SNHL without other phenotypic abnormalities is rare, and almost exclusively attributed to mutations in the Optic Atrophy-1 gene (OPA1), most commonly the p.R445H mutation. We present eight probands and their families from the US, Sweden, and UK with OA and SNHL, whom we analyzed for mutations in OPA1 and WFS1. Among these families, we found three heterozygous missense mutations in WFS1 segregating with OA and SNHL: p.A684V (six families), and two novel mutations, p.G780S and p.D797Y, all involving evolutionarily conserved amino acids and absent from 298 control chromosomes. Importantly, none of these families harbored the OPA1 p.R445H mutation. No mitochondrial DNA deletions were detected in muscle from one p.A684V patient analyzed. Finally, wolframin p.A684V mutant ectopically expressed in HEK cells showed reduced protein levels compared to wild-type wolframin, strongly indicating that the mutation is disease-causing. Our data support OA and SNHL as a phenotype caused by dominant mutations in WFS1 in these additional eight families. Importantly, our data provide the first evidence that a single, recurrent mutation in WFS1, p.A684V, may be a common cause of ADOA and SNHL, similar to the role played by the p.R445H mutation in OPA1. Our findings suggest that patients who are heterozygous for WFS1 missense mutations should be carefully clinically examined for OA and other manifestations of Wolfram syndrome.     

A novel C202F mutation in the connexin26 gene (GJB2) associated with autosomal dominant isolated hearing loss

Mutations in the GJB2 gene encoding connexin26 (CX26) account for up to 50% of cases of autosomal recessive hearing loss. In contrast, only one GJB2 mutation has been reported to date in an autosomal dominant form of isolated prelingual hearing loss. We report here a novel heterozygous 605G→T mutation in GJB2 in all affected members of a large family with late childhood onset of autosomal dominant isolated hearing loss. The resulting C202F substitution, which lies in the fourth (M4) transmembrane domain of CX26, may impair connexin oligomerisation. Finally, our study suggests that GJB2 should be screened for heterozygous mutations in patients with autosomal dominant isolated hearing impairment, whatever the severity of the disease.


Keywords: C202F mutation; connexin26 gene (GJB2); autosomal dominant hearing loss     

A complex phenotype of peripheral neuropathy, myopathy, hoarseness, and hearing loss is linked to an autosomal dominant mutation in MYH14

Both peripheral neuropathy and distal myopathy are well-established inherited neuromuscular disorders characterized by progressive weakness and atrophy of the distal limb muscles. A complex phenotype of peripheral neuropathy, myopathy, hoarseness, and hearing loss was diagnosed in a large autosomal dominant Korean family. A high density single nucleotide polymorphism (SNP)-based linkage study mapped the underlying gene to a region on chromosome 19q13.3. The maximum multipoint LOD score was 3.794. Sequencing of 34 positional candidate genes in the segregating haplotype revealed a novel c.2822G>T (p.Arg941Leu) mutation in the gene MYH14, which encodes the nonmuscle myosin heavy chain 14. Clinically we observed a sequential pattern of the onset of muscle weakness starting from the anterior to the posterior leg muscle compartments followed by involvement of intrinsic hand and proximal muscles. The hearing loss and hoarseness followed the onset of distal muscle weakness. Histopathologic and electrodiagnostic studies revealed both chronic neuropathic and myopathic features in the affected patients. Although mutations in MYH14 have been shown to cause nonsyndromic autosomal dominant hearing loss (DFNA4), the peripheral neuropathy, myopathy, and hoarseness have not been associated with MYH14. Therefore, we suggest that the identified mutation in MYH14 significantly expands the phenotypic spectrum of this gene.     

The mapping of DFNB62, a new locus for autosomal recessive non-syndromic hearing impairment, to chromosome 12p13.2-p11.23

Autosomal recessive non-syndromic hearing impairment (ARNSHI) is the most common form of prelingual inherited hearing impairment (HI). Here is described the mapping of a novel ARNSHI locus in a consanguineous Pakistani family with profound congenital HI. Two-point and multipoint linkage analyses were performed for the genome scan and fine mapping markers. Haplotypes were constructed to determine the region of homozygosity. At theta = 0, the maximum two-point LOD score of 4.0 was obtained at marker AAC040. A maximum multipoint LOD score of 5.3 was derived at marker D12S320, with the three-unit support interval demarcated by D12S89 and D12S1042. The region of homozygosity is flanked by markers D12S358 and D12S1042, which corresponds to 22.4 cM according to the Rutgers combined linkage-physical map of the human genome and spans 15.0 Mb on the sequence-based physical map. A novel ARNSHI locus DFNB62 was mapped to chromosome 12p13.2-p11.23. DFNB62 represents the second ARNSHI locus to map to chromosome 12.     

Two Iranian families with a novel mutation in GJB2 causing autosomal dominant nonsyndromic hearing loss

Mutations in GJB2, encoding connexin 26 (Cx26), cause both autosomal dominant and autosomal recessive nonsyndromic hearing loss (ARNSHL) at the DFNA3 and DFNB1 loci, respectively. Most of the over 100 described GJB2 mutations cause ARNSHL. Only a minority has been associated with autosomal dominant hearing loss. In this study, we present two families with autosomal dominant nonsyndromic hearing loss caused by a novel mutation in GJB2 (p.Asp46Asn). Both families were ascertained from the same village in northern Iran consistent with a founder effect. This finding implicates the D46N missense mutation in Cx26 as a common cause of deafness in this part of Iran mandating mutation screening of GJB2 for D46N in all persons with hearing loss who originate from this geographic region.