X连锁无汗性外胚叶发育不良家系的基因突变检测

目的 鉴定X连锁无汗性外胚叶发育不良(EDA)家系的基因突变及其突变类型,为建立对该病的基因诊断与遗传咨询提供依据。方法 应用聚合酶链反应-单链构象多态性(PCR-SSCP)分析法,结合DNA测序,检测了汉族人X连锁EDA一家系的基因突变位点与突变方式。结果 EDA致病基因(EDA1基因)外显子1的PCR产物经SSCP分析显示,患者及其携带者母亲出现异常单链条带。DNA测序表明,先证者该基因外显子1的第404位碱基胞嘧啶C被鸟嘌呤G颠换,致使EDA蛋白跨膜区第54位组氨酸突变成谷胺酰胺(H54Q),其母亲同一位置碱基呈现C～G杂合双峰。结论 本EDA家系中患者EDA1基因外显子1存在错义突变(404C→G),这可能是导致EDA发病的分子机制之一。     

板层状鱼鳞病患者转谷氨酰胺酶1活性缺失及其基因突变

目的 检测一板层状鱼鳞病家系中患者转谷氨酰胺酶1的活性及其编码基因的突变。方法 以免疫组化法检测患者转谷氨酰胺酶1的活性,PCR扩增该基因的全部编码序列,并行DNA测序。结果 患者皮肤转谷氨酰胺酶1的活性完全缺失。PCR结合DNA测序发现患者该基因第4外显子存在异常:第604位碱基由胞嘧啶突变为胸腺嘧啶,使第202位氨基酸由谷氨酰胺(Q)变为终止密码(R202X),导致其编码的蛋白缺失了C端的615个氨基酸。其父母皆为杂合子。结论 板层状鱼鳞病患者转谷氨酰胺酶1的活性完全缺失,是其转谷氨酰胺酶1基因的无义突变,引起编码的蛋白缺陷。     

A型着色性干皮病中XPAC基因的无义突变

目的 检测国内一A型着色性干皮病家系中XPAC基因的突变。方法 PCR扩增XPAC基因的全部外显子,并行DNA测序。针对所发现的突变以DdeⅠ内切酶行限制性片段长度多态性(RFLP)分析。结果 PCR结合DNA测序发现患者XPAC基因第5外显子存在异常:第631位碱基由胞嘧啶突变为胸腺嘧啶,使第211位氨基酸由精氨酸变为终止密码(R211X),导致其编码的XPA蛋白缺失了C端的63个氨基酸。其父母皆为杂合子。RFLP结果证实了此突变的存在。结论 本A型着色性干皮病家系中存在XPAC基因突变,突变致使XPA蛋白功能缺陷,DNA损伤的修复功能受损,导致临床上出现皮肤老化和癌变。     

板层状鱼鳞病TGM1基因突变研究

目的 探讨一个板层状鱼鳞病家系转谷氨酰胺酶1基因(TGM1)的突变.方法 提取板层状鱼鳞病患者及家族成员的基因组DNA,采用PCR扩增TGM1基因所有的外显子及其邻近的剪切点并进行双向直接测序,并对TGM1基因的同源性进行分析.结果 板层状鱼鳞病患者TGM1基因存在异常:外显子3的第504位碱基由胞嘧啶突变为胸腺嘧啶,使第142位氨基酸由精氨酸(R)转变为半胱氨酸(C),即R142C错义突变;外显子7的第1122位碱基由胞嘧啶突变为胸腺嘧啶,使348位氨基酸由精氨酸(R)突变为终止密码(R348X),导致其编码的蛋白缺失了C端的470个氨基酸.其父亲为R142C杂合子,母亲为R348X突变杂合子;R142C错义突变位于TGM1基因保守区域.结论 该板层状鱼鳞病患者存在转谷氨酰胺酶1基因的R142C错义突变和R348X无义突变.     

一遗传性对称性色素异常症家系ADAR基因突变检测

目的 探讨遗传性对称性色素异常症(DSH)一家系ADAR基因突变情况。方法 收集1个遗传性对称性色素异常症家系的外周血标本,采取PCR结合DNA直接测序的方法,检测了该家系中4例患者及3例表型正常者和150例无亲缘关系健康个体的ADAR基因突变情况。结果 该家系中患者存在ADAR基因上第2879位碱基腺嘌呤(A)转换成鸟嘌呤(G),使得ADAR基因的第10号外显子960位密码子由TAT突变成TGT,导致正常的酪氨酸(Tyr)被半胱氨酸(Cys)替代,而该家系的正常人对照及无关健康个体不存在此突变。结论 DSH家系中患者ADAR基因存在错义突变(2879 A→G),这可能是导致DSH发病的分子机制之一。     

一毛囊角化病家系ATP2A2基因突变的检测

目的 检测一毛囊角化病家系中ATP2A2基因的突变。方法 1例经组织病理结合临床诊断为毛囊角化病,采用聚合酶链反应和DNA测序方法对此家系进行基因突变情况检测。结果 家系中患者在ATP2A2上第1541位腺嘌呤A变为鸟嘌呤G,使编码ATP酶结合域第514位氨基酸由赖氨酸变为精氨酸,家系中未患病者及对照的健康人均不存在此突变。结论 K514R是引起该家系临床病变的一个新的特异突变,不是多态性变化。     

一例伴丘疹性损害的先天性无毛症患者的基因突变研究

目的 研究1例伴丘疹性损害的先天性无毛症患者基因突变情况.方法 采用PCR和DNA直接测序法检测伴丘疹性损害的先天性无毛症HR基因的突变.同时对2个与秃发相关的基因GJB6和CDSN基因进行突变检测.结果 在HR基因、GJB6基因和CDSN基因所检测的区域中均未检测到突变.在HR基因和CDSN基因上发现了数处单核苷酸多态性(SNP).结论 在该伴丘疹性损害的先天性无毛症家庭中未检测到HR、GJB6和CDSN基因的突变.     

角膜炎、鱼鳞病、耳聋综合征的GJB2基因突变研究

目的 检测国内首例先天性角膜炎、鱼鳞病、耳聋综合征(KID)患者的GJB2基因和GJB6基因突变.方法 提取KID综合征患者及家族成员的基因组DNA,采用聚合酶链反应扩增GJB2基因和GJB6基因所有的外显子及其邻近的剪切点,并进行双向直接测序.结果 KID综合征患者的GJB6基因未见变化,GJB2基因核苷酸序列exon2第148位碱基由G突变成A,导致蛋白第50位的天冬氨酸转换成天冬酰胺(D50N).结论 GJB2基因突变可能是本例角膜炎、鱼鳞病、耳聋综合征的致病基因.     

遗传性对称性色素异常症一家系致病基因的定位和突变研究

目的 探讨遗传性对称性色素异常症家系的致病基因。方法 明确先证者的临床诊断后,收集该家系成员的血样抽提基因组DNA,应用基因分型和连锁分析的方法进行基因定位,并对该定位区域内DSRAD基因直接测序,分析其突变位点。结果 基因分型和连锁分析将该家系的致病基因定位于1号染色体,和已知报道的区域一致。突变研究发现该家系所有患者的DSRAD基因2号外显子均携带CAA→TAA的突变,使得517位氨基酸由谷氨酰胺变成中止密码子。结论 该遗传性对称性色素异常症家系中的患者存在DSRAD基因的无义突变。     

先天性角化不良的一个新的基因突变

目的 检测一例先天性角化不良(DKC)患者DKC1基因的突变情况。方法 采用PCR技术扩增DKC1基因的15个外显子,然后采用变性高效液相色谱(DHPLC)技术进行基因突变筛查,对筛查结果异常的外显子进行DNA测序:基因突变的验证在100例无相关遗传性疾病的无关男性中进行。结果 患者DKC1基因的第12号外显子呈异常的DHPLC洗脱峰,家庭其他成员及正常群体对照未见此异常洗脱峰。测序结果显示患者DKC1基因第12外显子的1236位碱基由G→T,导致W412C突变,家庭其他成员及正常群体对照均未见此突变。结论 我们检测到的患者DKC1基因W412C是一个新的散发性突变,它可能导致患者先天性角化不良。     

Novel Hairless mutations in two kindreds with autosomal recessive papular atrichia

Papular atrichia is an autosomal recessive disorder characterized clinically by the occurrence of universal congenital alopecia and disseminated papular lesions. Recently, mutations in the human hairless (HR) gene have been reported in Irish and Arab Palestinian families with papular atrichia. We have studied two further kindreds with this clinical phenotype from other ethnic backgrounds. For mutation detection the complete coding region as well as exon-intron boundaries of the HR gene were sequenced. The first family is a Mexican family with clinically typical papular atrichia. Sequencing identified a homozygous deletion of 4 bp in exon 7 (2001delCCAG) leading to a premature stop codon in exon 8. The second family is a South Tyrolian family with affected individuals showing papular atrichia and retardation of bone age during childhood. All affected individuals were identified as homozygous for an A-->G transition at nucleotide position 2909 (exon 14) leading to an amino acid change of asparagine to serine in codon 970 (Asn970Ser). These data provide further evidence for the involvement of hairless mutations in papular atrichia. In addition, these findings suggest that the hairless protein is not only involved in hair development but also in the process of ossification during development.     

Evidence for pseudodominant inheritance of atrichia with papular lesions

Atrichia with papular lesions is a rare form of total alopecia, in which mutations in the hairless gene have been shown to underlie the phenotype. In the literature to date, atrichia with papular lesions has generally been reported to be inherited in an autosomal recessive manner. A few rare cases exist, however, in which parent-to-child transmission of atrichia with papular lesions has been documented. In this study, further investigations were carried out into the molecular basis of atrichia with papular lesions in a family with mother-to-son transmission by searching for mutations in the human hairless gene. Specific ally, we wanted to determine whether this case truly represented an example of dominantly inherited atrichia with papular lesions, or whether another mode of inheritance might be responsible for the disorder in this kindred. Pseudodominant inheritance, for example, occurs when an individual with a known recessive disorder has a clinically unaffected partner, but then unexpectedly gives birth to children who are affected with the same recessive disorder as the affected parent, and can easily be distinguished from classical dominant inheritance with molecular diagnosis and haplotype analysis. In the family reported here, we have determined that both the mother and son are, in fact, homozygous for a novel mutation in the hairless gene, R33X. We provide the first evidence for pseudodominant inheritance in atrichia with papular lesions, and at the same time extend our knowledge of pathogenetic mutations in the human hairless gene. Importantly, this information allows revisions in genetic counseling for risk of transmission for individuals in the family, previously impossible in the absence of knowing the genetic basis of atrichia with papular lesions in this unusual kindred.     

Nonsense mutations in the hairless gene underlie APL in five families of Pakistani origin

BACKGROUND: Atrichia with papular lesions (APL) is a rare autosomal recessive form of inherited alopecia. Affected individuals present with a distinct pattern of total hair loss on the scalp, axilla and body shortly after birth and are essentially devoid of eyelashes and eyebrows. This form of hair loss is irreversible and the histology is consistent with an absence of mature hair follicles. In addition to total atrichia, APL patients also present with papules and follicular cysts filled with cornified material. Mutations in the Hairless (HR) gene have been shown to underlie APL. OBJECTIVE: Here, we studied five unrelated large Pakistani families with clinical manifestations of APL. METHODS: Based on previous reports of HR mutations in APL, we performed direct DNA sequencing analysis. RESULTS: DNA sequencing of the HR gene in APL patients revealed three novel nonsense mutations in five unrelated families. All affected individuals were homozygous for a nonsense mutation due to C-to-T transitions at different positions in the amino acid sequence. Two families carry the mutation Q323X (CAG-TAG) in exon 3, two families harbor the mutation Q502X (CAG-TAG) in exon 6, and one family had a mutation at R940X (CGA-TGA) in exon 14. Haplotype analysis revealed that all affected individuals of both APL1 and APL16 families were homozygous for the same haplotype, and likewise, the mutation in families APL2 and APL19 was on the same haplotype. CONCLUSIONS: We report three novel nonsense mutations in the HR gene in APL. Two of the newly identified mutations, Q323X and Q502X, were found to be shared between unrelated families and marker analysis confirmed an identical homozygous haplotype for APL1 and APL16, and for APL2 and APL19. These findings suggest that Q323X and Q502X did not arise independently, but instead appear to have been propagated in the population. Collectively, these findings contribute further evidence for the involvement of hairless mutations in papular atrichia.     

Atrichia with papular lesions resulting from a nonsense mutation within the human hairless gene.

Atrichia with papular lesions is a rare autosomal recessive form of alopecia characterized by hair loss soon after birth and the development during childhood of a diffuse papular rash. We have previously shown that this disorder results from a deleterious mutation in the human hairless gene, a gene also involved in the pathogenesis of a related but clinically distinct form of congenital alopecia, termed alopecia universalis congenita. In this report, we describe a novel nonsense mutation in exon 4 of the human hairless gene in a consanguineous kindred affected with atrichia with papular lesions. This report provides additional evidence for phenotypic heterogeneity among inherited atrichias and for an association between the papular rash of atrichia with papular lesions and nonsense mutations in the human hairless gene.     

Atrichia with papular lesions resulting from a novel insertion mutation in the human hairless gene

BACKGROUND: Congenital atrichia with papular lesions is a rare, recessively inherited condition of total alopecia, characterized clinically by complete and irreversible hair loss, which begins shortly after birth with the development of the papular lesions of keratin-filled cysts over an extensive area of the body. Mutations in the human hairless (HR) gene have been implicated in the pathogenesis of this disorder. OBJECTIVE: To search for a mutation in human HR in a family with congenital atrichia. METHODS: Linkage analysis was carried out using genotyping markers closely linked to congenital atrichia locus on chromosome 8p12. Subsequently, human HR was sequenced to identify a disease-causing mutation. RESULTS: A novel 11 bp insertion mutation, G202 (InsCTTCCCCCAGG), in exon 2 of the hairless gene was identified in a Pakistani consanguineous family affected by congenital atrichia. The insertion results in the expansion of 11 bp tandem repeat, which introduces a translational frameshift leading to downstream premature termination codon. CONCLUSIONS: This mutation is the first insertion mutation identified in the coding sequence of human HR. This extends our knowledge of mutations in HR that define the pathogenic basis of this disease.     

Identification of a new mutation in the gene coding for hairless protein responsible for alopecia universalis: The importance of direct gene sequencing

Mutations in the gene HR coding for the hairless protein are associated with atrichia with papular lesions (APL), an autosomal recessive form of alopecia universalis that is characterized by generalized scalp and body atrichia with papular lesions. We here describe a South Italian family of ancient Albanian heritage. The full phenotype with complete atrichia was expressed in 2 siblings, whereas the parents and one sister were unaffected. Direct sequencing of the gene coding for the hairless protein allowed the identification of a new mutation in exon 17. Consistent with the recessive inheritance of the disease, both the siblings were homozygous for the mutation, whereas the parents and the unaffected sister where heterozygous. A relevant discrepancy with a haplotype linkage study is reported, stressing the importance of gene sequencing in genetic diagnosis and counseling because linkage studies can be biased by recombination events.     

Compound heterozygosity for mutations in the hairless gene causes atrichia with papular lesions

BACKGROUND: Congenital atrichias represent a complex and heterogeneous group of genodermatoses, which have been shown in several consanguineous families to result from homozygous mutations in the hairless gene (HR). OBJECTIVES: To identify the molecular basis of congenital atrichia in a non-consanguineous family. METHODS: Genetic analysis was carried out in a two-generation family with two children with congenital atrichia and one healthy child. RESULTS: We established a diagnosis of atrichia with papular lesions based on clinical and histopathological data. We identified a heterozygous 11-bp deletion (189-199del) in the two affected children and their mother. In addition, the two affected children and their father were shown to carry a non sense mutation (Q478X), which has previously been described in a Pakistani family. Haplotype analysis revealed that mutation Q478X occurred independently in the two families. CONCLUSIONS: We have identified the first case of compound heterozygosity for mutations in HR as well as the first instance of a recurrent mutation in this gene. These data further expand our understanding of the molecular pathomechanisms underlying congenital atrichias.     

Clinical and pathologic correlations in genetically distinct forms of atrichia

BACKGROUND: The genetic basis of 2 distinct forms of atrichia with papules has recently been defined at the molecular level. In atrichia with papular lesions (APL; Online Mendelian Inheritance in Man [OMIM] 209500), mutations in the hairless gene on chromosome 8p21 have recently been identified. Atrichia with papules also occurs in the clinical setting of vitamin D-dependent rickets type IIA (VDDR IIA; OMIM 277440), resulting from mutations in the vitamin D receptor gene on chromosome 12q12-q14. Despite the distinct genetic basis for both forms of atrichia, the clinical findings are strikingly similar and exhibit classic pathognomonic features unique to this phenotype. We sought to document the clinical and molecular features of APL and VDDR IIA. OBSERVATIONS: Molecular analysis of the hairless and vitamin D receptor genes was performed on genomic DNA from probands and family members from 3 families with APL and 2 with VDDR IIA. We present a clinical and histologic comparison of atrichia in patients with APL and VDDR IIA and highlight the genetically heterogeneous basis of atrichia by identification of pathogenetic mutations. CONCLUSIONS: Increased awareness of these diseases will allow early diagnosis and potential therapeutic intervention for the rickets in VDDR IIA and avoidance of treatment of the atrichia in both APL and VDDR IIA. Their phenotype similarities suggest the possibility of a functional relationship between HR and VDR.     

Atrichia with papular lesions: a report of three novel human hairless gene mutations and a revision of diagnostic criteria

Atrichia with papular lesions is a rare autosomal recessive condition characterized by complete irreversible hair loss during the first months of life and papules that appear during early childhood. Atrichia with papular lesions is frequently misdiagnosed as alopecia universalis, despite increasing reports of its prevalence and the presence of well-defined diagnostic criteria. Most cases of atrichia with papular lesions have been reported in consanguineous families residing in small geographical regions, but the increasing number of sporadic cases of unrelated individuals suggests that atrichia with papular lesions is more common than previously thought. Mutations in the human hairless gene on chromosome 8p12 have been implicated in this disease. Here, we report two novel heterozygous mutations in an Australian family and a novel homozygous mutation in 2 Arab siblings. We also revise the diagnostic criteria for atrichia with papular lesions in order to clarify its uniqueness and distinguishing features from alopecia universalis.     

Congenital atrichia with papular lesions resulting from novel mutations in human hairless gene in four consanguineous families

Congenital atrichia with papular lesions (APL; Mendelian Inheritance in Man no. 209500) is a rare form of irreversible alopecia that follows an autosomal recessive mode of inheritance. Patients with this form of alopecia show hair loss soon after birth with the development of papular lesions of keratin-filled cysts over the body. Several studies have reported sequence variants in the human hairless (HR) gene as the underlying cause of this disorder. In the present study, we have reported four consanguineous families showing features of APL. Genotyping using microsatellite markers showed mapping of all four families to the hairless (HR) gene on chromosome 8p21.1. Further, DNA sequence analysis of the HR gene revealed three novel mutations including two nonsense (p.Cys690X, p.Arg819X) and a missense (p.Pro1157Arg) in the four families.