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.     

Keratin-9 gene mutation in epidermolytic palmoplantar keratoderma combined with knuckle pads in a large Chinese family

Epidermolytic plamoplantar keratoderma (EPPK) is an autosomal dominant inherited disease. It caused by mutations in the highly conserved coil 1A domain of the keratin 9 gene, KRT9 . We studied a four-generation family with EPPK combined with knuckle pads from Jiangsu province, China. In this study, a heterozygous nucleotide T→C transition at position 500 in exon 1 of KRT9 was detected, which resulted in a leucine to serine (L167S) change. We describe this mutation in a Chinese pedigree with EPPK with knuckle pads for the first time, demonstrating the prevalence of this mutation in diverse population.     

表皮松解性掌跖角化病一家系KRT9基因突变检测

目的：检测一表皮松解性掌跖角化病(epidermolytic palmoplantar keratoderma,EPPK)家系中患者及其家族成员的KRT9基因突变。方法：收集该EPPK家系先证者及其家族成员临床资料,提取他们及100例无亲缘关系的健康对照外周血DNA,PCR扩增KRT9基因编码区的全部外显子及其侧翼序列,对产物直接测序,同时进行突变点的功能预测。结果：该家系所有患者的KRT9基因1号外显子第482位碱基均发生错义突变c.482A>G(p.Asn161Ser)。家系中未患病者及100名正常对照中均未发现此突变。SIFT和Polyphen-2软件预测c.482A>G(p.Asn161Ser)突变为有害变异位点。结论：KRT9基因的突变c.482A>G(p.Asn161Ser)可能是导致该家系发生表皮松解性掌跖角化病的原因。     

表皮松解性掌跖角皮症一家系KRT9基因新突变

目的:检测表皮松解性掌跖角皮症一家系患者角蛋白9(KRT9)基因突变。方法:收集家系成员的临床资料和血样,提取家系中4例患者和3名正常人及50名与本家系无关的正常对照外周血DNA,采用PCR技术扩增KRT9基因所有编码区并进行测序,分别检测家系中的突变情况。结果:该家系中所有患者均存在KRT9基因错义突变(c.484TC),导致第162位密码子由TCT(丝氨酸)转变为CCT(脯氨酸)(p.S162P),家系中3名正常个体和50名健康对照均未发现上述突变。结论:KRT9基因c.484TC错义突变是导致该家系发生表皮松解性掌跖角皮症的遗传基础。     

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.     

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 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.     

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 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.     

Epidermolysis Bullosa Simplex with mottled pigmentation: mutation analysis in the first reported Hispanic pedigree with the largest single generation of affected individuals to date

Epidermolysis bullosa simplex with mottled pigmentation (EBS-MP), characterized by trauma-induced blisters, distinct pigmentary changes of the trunk and extremities, and acral hyperkeratotic papules, is almost exclusively caused by a common KRT5 missense mutation affecting the V1 region of keratin 5. We studied the first Hispanic family, the largest single generation of affected family members in which 5 out of 10 siblings inherited EBS-MP from their affected father, as well a second large pedigree, the first reported of Finnish ancestry. In both families, the heterozygous transition mutation 74C-->T of the keratin 5 gene, which results in amino acid substitution P25L, completely co-segregated with the EBS-MP phenotype.     

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.     

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.     

Identification of the keratin 9 (KRT9) N161S mutation in a Chinese kindred with epidermolytic palmoplantar keratoderma

We present a family from Northeast China affected by epidermolytic palmoplantar keratoderma (EPPK) in which we confirmed the presence of the N161S mutation as the result of a 548A>G transition in exon1 of the keratin 9 gene. Genomic DNA from peripheral blood of all available members in this family was used for amplification of exon 1 of KRT9 by polymerase chain reaction. The mutation was detected by direct sequence analysis and identified by restriction endonuclease DdeI digestion. The finding of the same mutation in all available patients, together with the previous reports of the disease, strongly suggested that position 161 of the KRT9 gene also represents a mutation "hotspot" for EPPK. Our result is an important contribution to the investigation of the genotype/phenotype correlation and affords molecular genetic knowledge for future clinical diagnosis and gene therapy of 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.     

表皮松解性掌跖角化病二家系基因突变检测

目的：检测表皮松解性掌跖角化病二家系患者致病基因。方法：收集二家系资料,提取二家系成员及100名（无亲缘关系）正常对照血样DNA,采取聚合酶链反应技术对KRT1、KRT9和KRT16基因进行扩增,并对其产物进行测序。结果：家系1先证者中检测到 KRT1基因突变c.598T>C（p.F200L）。家系2三例患者中检测到KRT9基因含杂合突变c.488G>A（p.R163Q）。而家系正常成员及家系外无亲缘关系的100名正常对照中均不存在以上突变。结论：本研究表皮松解性掌跖角化病二家系发病与KRT1、KRT9基因突变有关,且KRT1基因突变p.F200L为国内首次报道。     

Ⅱ型先天性厚甲症一家系KRT基因突变检测

目的:检测先天性厚甲症一家系中KRT6b和KRT17基因突变位点。方法:提取先证者、其父母(母亲为患者,父亲正常人)及100名正常对照者外周静脉血DNA,PCR技术扩增KRT6b和KRT17基因编码序列,Sanger测序法对PCR扩增产物进行测序。结果:先症者及其母亲在KRT17基因1号外显子上存在错义突变(c.275AG),KRT6b基因不存在任何突变。先证者父亲及100名正常对照者中未检测到任何突变。结论:此家系患者是由于KRT17基因突变(c.275AG,p.Asn92Ser)所致。     

Weber-Cockayne亚型单纯型大疱性表皮松解症一家系报告

目的:研究Weber-Cockayne亚型单纯型大疱性表皮松解症(EBS-WC)一家系的基因突变,并进行产前诊断。方法:应用PCR及DNA直接测序方法明确突变位点,针对所发现的突变以限制性内切酶片段长度多态性(RFLP)分析加以验证,在此基础上于妊娠24周时对从胎儿羊水所提取的DNA进行测序及酶切验证。结果:该家系患者存在角蛋白(keratin,KRT)5基因突变:第7外显子第1388位碱基由胸腺嘌呤突变为胞嘧啶,导致第463位氨基酸由亮氨酸变为脯氨酸(L463P)。50名健康对照者不存在此突变。羊水细胞DNA不存在此突变的胎儿,出生后未患大疱性表皮松解症。结论:KRT5第7外显子的突变是引起该家系临床症状的特异性突变。     

表皮松解性掌跖角化病研究进展

表皮松解性掌跖角化病是一种常染色体显性遗传性单基因病,以掌跖部对称性弥漫性角化过度为主要特征,其组织学特点为表皮松解性角化过度.目前已从分子水平上阐明表皮松解性掌跖角化病由角蛋白9及角蛋白1的基因突变引起.此外,环境及药物卡培他滨也可能为其致病因素.表皮松解性掌跖角化病主要以对症治疗为主,小干扰RNA的研究逐步成为热点,为表皮松解性掌跖角化病的基因治疗提供一定的理论基础.随着对此病分子基础的研究,产前诊断的技术正不断发展.     

Generic and personalized RNAi-based therapeutics for a dominant-negative epidermal fragility disorder

Epidermolytic palmoplantar keratoderma (EPPK) is one of >30 autosomal-dominant human keratinizing disorders that could benefit from RNA interference (RNAi)-based therapy. EPPK is caused by mutations in the keratin 9 (KRT9) gene, which is exclusively expressed in thick palm and sole skin where there is considerable keratin redundancy. This, along with the fact that EPPK is predominantly caused by a few hotspot mutations, makes it an ideal proof-of-principle model skin disease to develop gene-specific, as well as mutation-specific, short interfering RNA (siRNA) therapies. We have developed a broad preclinical RNAi-based therapeutic package for EPPK containing generic KRT9 siRNAs and allele-specific siRNAs for four prevalent mutations. Inhibitors were systematically identified in vitro using a luciferase reporter gene assay and validated using an innovative dual-Flag/Strep-TagII quantitative immunoblot assay. siKRT9-1 and siKRT9-3 were the most potent generic K9 inhibitors, eliciting >85% simultaneous knockdown of wild-type and mutant K9 protein synthesis at picomolar concentrations. The allele-specific inhibitors displayed similar potencies and, importantly, exhibited strong specificities for their target dominant-negative alleles with little or no effect on wild-type K9. The most promising allele-specific siRNA, siR163Q-13, was tested in a mouse model and was confirmed to preferentially inhibit mutant allele expression in vivo.