表皮松解性掌跖角化症遗传学研究进展

表皮松解性掌跖角化症是一种以掌跖表皮过度角化为主要特征的先天性遗传病.本文阐述了角蛋白分子的结构、分类以及由角蛋白突变所引起的一些遗传性角蛋白病,总结了迄今所发现的导致表皮松解性掌跖角化症的21种不同的角蛋白9基因突变类型及蛋白改变,在各个种族或民族中开展的有关角蛋白基因突变的研究情况.     

056 在一例日本表皮松解性掌跖角化病患儿中检出角蛋白9基因突变

表皮松解性掌跖角化病(EPPK)是一种常染色体显性遗传性皮肤病,皮损局限于手掌和足跖部以皮肤弥漫性角化过度为特征,典型者边缘呈红斑,组织学上显示掌跖表皮角化过度,伴中上部空泡变性。角蛋白9(K9)属于Ⅰ型角蛋白,仅表达于掌跖部表     

一个有独特组织学表现的常染色体显性遗传性掌跖角皮病家族中角蛋白9的R162W突变

掌跖角皮病 (ＰＰＫ)是一组异源性遗传性皮肤病 ,其特征为弥漫性掌跖角化。其中表皮松解性掌跖角皮病 (ＥＰＰＫ)是常染色体显性遗传性皮肤病 ,组织学特征为表皮棘层中部和颗粒层细胞空泡样变 (表皮松解性角化过度症 ,ＥＨＫ)。最近报告了许多该病患者中有角蛋白9的 1Ａ区突变 ,提示在角蛋白 9的α螺旋杆状结构域起始段存在一个高度保守的序列 ,后者为掌跖表皮内角蛋白丝的装配所必须。作者最近观察到一个常染色体显性遗传性ＰＰＫ家族 ,其角质形成细胞缺乏或极少空泡样变 (不完全型ＥＨＫ)。 3 6岁的父亲掌跖弥漫性角化 ,有境界清楚的红斑…     

一例表皮松解性掌跖角化病家系的角蛋白9基因突变检测研究

表皮松解性掌跖角化病(epidermolytic palmoplantar keratoderma)是一种常染色体显性遗传性皮肤病,其临床特征为掌跖表皮弥漫性过度角化,病变部位周边有明显的红斑边缘.     

掌跖角化病致病基因研究进展

掌跖角化病是一组以掌跖表皮角化过度为特征的遗传性皮肤病,包含多种表现亚型.近来,掌跖角化病遗传学发病机制的研究取得很大进展,已确定一些不同临床表现型掌跖角化病的致病基因,目前认为,角蛋白1、角蛋白9、角蛋白16、桥粒芯糖蛋白、桥斑蛋白、连接蛋白26、组织蛋白酶C、ARS等基因突变均能导致掌跖角化病的产生,且越来越多新的突变基因位点被发现,推动遗传性掌跖角化病致病基因的研究进程.     

角化性皮肤病

20090162 β-Catenin在角化性皮肤病与非黑素细胞性皮肤肿瘤中的表达;20090163点状掌跖角化病一家系;20090164一例表皮松解性掌跖角化病家系的角蛋白9基因突变检测研究;20090165副肿瘤性肢端角化病误诊1例     

表皮松解性掌跖角化病1例

报告1例表皮松解性掌跖角化病。患者女,26岁。双侧掌跖角化20余年。皮肤科检查见双侧掌跖对称性角化性斑块。皮损组织病理检查示表皮角化过度,颗粒层增厚,棘层及颗粒层中有较多裂隙,裂隙处细胞界限不清,由淡染物质或透明角质颗粒组成。组织病理改变符合表皮松解性掌跖角化病诊断。采用阿维A治疗后皮损明显改善。     

KRT9基因突变所致表皮松解性掌跖角化病1例

报告KRT9基因突变所致表皮松解性掌跖角化病1例.患者男,中国籍,32岁,手足角化性斑块30余年.皮肤科检查:双侧掌跖面可见对称性弥漫性角化斑块,皮肤粗糙增厚,呈灰黄色.皮损组织病理:表皮明显角化过度,颗粒层棘层增厚,皮突延长,颗粒细胞变性,考虑掌跖角化病.基因全外显子组测序结果:KRT9基因外显子检测出c.487C＞...     

点状掌跖角化病遗传学研究进展

点状掌跖角化病是一种以掌跖部不规则分布、进行性加重的角化性丘疹为特征的常染色体显性遗传性皮肤病.目前已报道AAGAB基因和COL14A1基因是点状掌跖角化病致病基因,除此之外,可能还存在其他致病基因.迄今为止,在多个种族或民族点状掌跖角化病家系中已发现39种AAGAB基因突变和1个COL14A1基因突变位点.AAGAB基因突变导致其编码的p34蛋白功能缺失或不足,使表皮生长因子受体再循环发生障碍,角质形成细胞发生过度增殖,导致点状掌跖角化病发生.COL14A1基因突变的致病性有待于蛋白质功能学研究、体外细胞实验以及该基因突变在其他点状掌跖角化病家系内重复性验证等进一步证实.     

遗传性皮肤病

胫前型营养不良性大疱性表皮松解症1例,痒疹样营养不良型大疱性表皮松解症1例,痒疹样营养不良型大疱性表皮松解症1例,表皮松解性角化过度鱼鳞病1例,无严重掌跖角化过度-1型表皮松解性角化过度鱼鳞病1例．     

Atypical epidermolytic palmoplantar keratoderma presentation associated with a mutation in the keratin 1 gene

BACKGROUND: Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant genodermatosis characterized by epidermolytic hyperkeratosis strictly confined to the palms and soles, and usually associated with mutations in the keratin K9 gene (KRT9). Mutations in the keratin K1 gene (KRT1) have been shown to underlie a variety of phenotypes typically involving generalized epidermolytic hyperkeratosis, but in some cases the phenotype can be more regionally restricted. OBJECTIVES: To identify the genetic defect in two unrelated families initially presenting with EPPK but where careful examination revealed hyperkeratosis extending on to the proximal wrist flexure. Methods Linkage analysis and DNA sequencing. RESULTS: We found that this phenotype is caused by a heterozygous missense mutation in the K1 gene, designated I479T. This mutation lies in the highly conserved helix termination motif of K1, previously shown to be important for keratin assembly and filament formation. In general, mutations in this region of keratins are associated with more severe disease phenotypes. However, K1 mutations in this region and the I479T mutation in particular have previously been associated with both severe and mild bullous congenital ichthyosiform erythroderma phenotypes. When further clinical enquiries were made, several affected individuals in the families studied here were found to have had transient flexural peeling and hyperkeratosis in the neonatal period. CONCLUSIONS: K1 mutations may underlie a phenotype closely resembling EPPK. A history of transient flexural peeling and hyperkeratosis in childhood and palmoplantar keratoderma which extends beyond the boundary of the palmoplantar margins may indicate a K1 mutation rather than a K9 defect. As K1 mutations are also associated with severe widespread phenotypes, with important implications for prognostic and genetic counselling, whole body examination is recommended for patients presenting with EPPK.     

Identification of the keratin K9 R162W mutation in patients of Italian origin with epidermolytic palmoplantar keratoderma

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant skin disorder characterized by hyperkeratosis of the palms and soles associated with histologic findings of hyperkeratosis and epidermolysis. Ultrastructurally, there is vacuolization of the cytoplasm and abnormal keratin filament network with tonofilament clumping. EPPK is caused by mutations in the keratin 9 gene (KRT9), which is expressed exclusively in suprabasal keratinocytes of palmoplantar epidermis. The mutation R162W is the most frequent keratin 9 alteration reported in patients from different geographical areas. We present three unrelated Italian families affected by EPPK in which we confirmed the presence of the R162W mutation, by RT-PCR analysis followed by sequencing of the KRT9 gene, in all affected members. The finding of the same mutation in all patients, together with the previous reports of the disease, strongly suggest that position 162 of the KRT9 gene represents a mutation "hot-spot", probably due to the peculiarity of the sequence.     

Analysis of the KRT9 Gene in a Mexican Family with Epidermolytic Palmoplantar Keratoderma

Epidermolytic palmoplantar keratoderma (EPPK), an autosomal‐dominant genodermatosis, is the most frequently occurring hereditary palmoplantar keratoderma. EPPK is characterized by hyperkeratosis of the palms and soles. Approximately 90% of patients present with mutations in the KRT9 gene, which encodes for keratin 9. Many of these mutations are located within the highly conserved coil 1A region of the alpha‐helical rod domain of keratin 9, an important domain for keratin heterodimerization. The objective was to assess the clinical and molecular characteristics of a Mexican family with EPPK. The clinical characteristics of members of this family were analyzed. The KRT9 gene of affected members was polymerase chain reaction amplified from genomic DNA and sequenced. All affected members of the family had hyperkeratosis of the palms and soles with knuckle pads. The R163W mutation in the KRT9 gene was present in all affected individuals who were tested. Although R163W is the most frequent KRT9 mutation in patients with EPPK, only two families have been reported with knuckle pads associated with this mutation. Our findings indicate that knuckle pads can be associated with EPPK and the R163W mutation in a family with a genetic background different from that described here.     

Epidermolytic palmoplantar keratoderma due to a novel type of keratin mutation, a 3-bp insertion in the keratin 9 helix termination motif

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant genodermatosis characterized by diffuse keratoderma, typically with an erythematous border. Histologically, palmoplantar epidermis shows suprabasal cytolysis and ultrastructurally, tonofilament aggregation with overlying epidermolytic hyperkeratosis. Mutations in the KRT9 gene, encoding keratin 9 (K9), a cytoskeletal protein expressed exclusively in suprabasal keratinocytes of palmoplantar epidermis, have been reported to cause EPPK. To date, all KRT9 defects reported in EPPK have been missense mutations in exon 1, which encodes the start of the alpha-helical rod domain. However, based on studies of other keratin disorders, it was postulated that mutations at the other end of the rod domain might also produce the EPPK phenotype. Here, we report the first mutation in the 2B domain of KRT9, 1362ins3, leading to an insertion of histidine in the helix termination motif of the K9 polypeptide. Insertional mutations have not been previously described in keratins. The phenotype of this case is similar to EPPK caused by 1A domain mutations, demonstrating that mutations in either of the helix boundary motif sequences of K9 are detrimental to keratin function and keratinocyte structure.     

A novel mutation of keratin 9 gene (R162P) in a Japanese family with epidermolytic palmoplantar keratoderma

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant inherited skin disorder characterized by hyperkeratosis of the skin over the palms and soles. Mutations in keratin 9 gene (KRT9) have been demonstrated in EPPK. In this study, we screened a Japanese family with EPPK for KRT9 mutation by polymerase chain reaction amplification of genomic sequences, followed by heteroduplex analysis and direct nucleotide sequencing. The mutation consisted of a G-to-C transversion at codon 162 in exon 1, which was located in the hot spot of the mutations that have been reported previously (R162Q and R162W). However, the amino acid substitution was proline for arginine (R162P) in the 1A rod domain, the highly conserved helix initiation motif of keratin 9. Our result illustrates the repertoire of KRT9 mutation underlying the occurrence of EPPK in a Japanese family and is an important contribution to the investigation of the genotype/phenotype correlation.     

Mutations in the keratin 9 gene in Pakistani families with epidermolytic palmoplantar keratoderma

Background. Keratins are heteropolymeric proteins that form the intermediate filament cytoskeleton in epithelial cells. The common basic structure of all keratins is organized in a central α‐helical rod domain flanked by nonhelical, variable head and tail regions. Most mutations in keratins are found in the central α‐helical rod domain. Keratin 9 (K9) is expressed only in the suprabasal layers of palmoplantar epidermis. Mutations in the keratin 9 gene (KRT9) have been shown to cause epidermolytic palmoplantar keratoderma (EPPK; OMIM 144200), an autosomal dominant genodermatosis characterized clinically by diffuse hyperkeratosis limited to the palms and soles, and histologically by epidermolysis in suprabasal layers of the epidermis. Aim. To elucidate the genetic basis of EPPK in five Pakistani families. Methods. Using microsatellite markers localized to the areas around the type I keratin gene cluster on chromosome 17q21, genotyping of these families was performed, followed by sequencing of the KRT9 gene. Results. The analysis resulted in the identification of two novel (p.M157K and p.Y454H) and two recurrent (p.M157T and p.R163Q) mutations in the KRT9 of all five families. All mutations occurred within the highly conserved helix initiation or termination motif of K9. Conclusions. The affected members of all five families possess mutations in the KRT9 gene that severely affect heterodimer formation with the type II keratin partner. The results of our study further underscore the crucial role of K9 protein in the palmoplantar epidermis.     

一个表皮松解性掌跖角化病家系的KRT1基因突变分析

目的 探讨一个中国汉族人表皮松解性掌跖角化病(EPPK)家系的角蛋白基因KRT1、KRT9、KRT10突变情况.方法 收集1个EPPK家系的临床资料,提取外周血DNA,通过PCR扩增角蛋白KRT1、KRT9、KRT10基因编码区的全部外显子及其侧翼序列并测序,以表型正常家系成员及50例健康人为正常对照.结果 发现家系内6例患者均存在KRT1基因错义突变c.1436T>C,导致第479位的异亮氨酸被苏氨酸取代(I479T),在家系中6例正常人及50例对照者未发现上述突变.结论 错义突变KRTI的c.1436T>C可能为导致该家系临床表型的主要原因.本例为国内首次发现的KRT1突变引起的EPPK家系.

Abstract：

Objective To analyze the mutations in keratin 1 (KRT1), KRT9 and KRT10 genes in a Chinese family with epidermolytic palmoplantar keratoderma (EPPK). Methods Clinical data were collected from a family with EPPK. Genomic DNA was extracted from the peripheral blood of 12 family members, including 6 patients and 6 unaffected members, as well as from 50 unrelated normal human controls. PCR was performed to amplify all the exons and flanking sequences of KRT1, KRT9 and KRT10 genes followed by DNA sequencing.Results A missense mutation C.1436T > C was found in the highly conserved helix termination motif of KRT1 gene of all the patients, resulting in a substitution of isoleucine by threonine at position 479 of the KRT1 protein. No mutation was found in the unaffected members or unrelated controls. Conclusions The missense mutation C.1436T > C in K.RT1 gene is likely to be the main cause of the phenotype of EPPK in this family.This is the first report of a pedigree with KRT1 gene mutation-induced EPPK in China.     

A novel mutation of keratin 9 in a large Chinese family with epidermolytic palmoplantar keratoderma

BACKGROUND: Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant inherited skin disorder characterized by diffuse yellow thickening of the skin of the palms and soles, sharply bordered with erythematous margins. Histologically and ultrastructurally, EPPK presents cytolysis of keratinocytes and abnormal aggregation of tonofilaments in the suprabasal layers of the epidermis. To date, 15 different mutations of the keratin 9 gene (KRT9) have been demonstrated to cause most cases of EPPK. OBJECTIVES: To identify the KRT9 mutation in a large Chinese family with EPPK. METHODS: Denaturing high-performance liquid chromatography (DHPLC), DNA sequencing and allele-specific polymerase chain reaction (AS-PCR) were used to screen exon 1 of the KRT9 gene for sequence variations. RESULTS: The DHPLC elution profiles of the DNA fragments amplified from the affected samples differed from those obtained from unaffected individuals, indicating that a sequence variation existed within the analysed fragment of KRT9. DNA sequencing revealed a novel insertion-deletion mutation in the exon 1 of KRT9, 497delAinsGGCT, resulting in the change of tyrosine(166) to tryptophan and leucine (Y166delinsWL). AS-PCR confirmed the mutation was not a common polymorphism. CONCLUSIONS: The results suggest the molecular basis of EPPK in this Chinese family and provide further evidence that mutations in the helix initiation motif of keratin 9 underlie Chinese EPPK.     

A novel keratin 9 gene mutation (Asn160His) in a Taiwanese family with epidermolytic palmoplantar keratoderma

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant inherited disorder of keratinization. Recent molecular studies have shown that EPPK is caused by mutations in keratin 9 gene (KRT9). We report a Taiwanese family with EPPK with a novel mutation with an A-->C transition at the first nucleotide of codon 160 in KRT9. The mutation is predicted to result in an asparagine to histidine substitution (N160H) at the beginning of the alpha-helical 1A domain of keratin 9. Mutations in this region could disrupt keratin filament assembly, leading to degeneration or cytolysis of keratinocytes. Our mutation analysis confirms that codon 160 in KRT9 is one of the mutation hot spots in EPPK.     

A novel mutation within the 2B rod domain of keratin 9 in a Chinese pedigree with epidermolytic palmoplantar keratoderma combined with knuckle pads and camptodactyly

Knuckle pads and camptodactyly are overlapping symptoms associated with many genetic and environmental factors. To the best of our knowledge, all reported cases of epidermolytic palmoplantar keratoderma (EPPK) with knuckle pads have been without accompanying camptodactyly. We here report a novel KRT9 mutation-EPPK family with combined knuckle pads and camptodactyly. All the EPPK-affected individuals in this southern Chinese pedigree suffered severe diffuse palmar and plantar hyperkeratosis including hyperhidrosis and cuticle splitting: 3 females presented EPPK only, 8 adult males had notably severe knuckle pads and camptodactyly as well as EPPK, and one 6-year-old boy manifested EPPK with knuckle pads. Haplotype analysis excluded the known candidate loci for camptodactyly and/or knuckle pad-like phenotypes on chromosomes 13q12, 3q11.2-q13.12, 1q24-q25, 4p16.3 and 16q11.1-q22, while only the markers D17S1787 and D17S579 flanking KRT9 showed co-segregation with EPPK. Then a novel c.T1373C (p.L458P) mutation within the sixth exon of KRT9 was validated, and this mutation presented a more severe pathogenicity than the previously reported p.L458F. We speculated that KRT9 plays a complicated role in the genesis of EPPK with knuckle pads and camptodactyly, which needs to be further investigated.