RESUMEN
The distribution and clinical appearance of the telangiectasia in the CREST syndrome (calcinosis, Raynaud's phenomenon, oesophageal involvement, sclerodactyly, telangiectasia) and hereditary haemorrhagic telangiectasia (HHT) are very similar. Several previously reported cases of the CREST syndrome simulating HHT illustrate this diagnostic quandary. We report a patient who met the diagnostic criteria for both the CREST syndrome and HHT, and discuss the distinguishing features of the two diseases, including the distinctive histopathological findings of telangiectasia in HHT.
Asunto(s)
Síndrome CREST/diagnóstico , Telangiectasia Hemorrágica Hereditaria/diagnóstico , Síndrome CREST/patología , Diagnóstico Diferencial , Femenino , Humanos , Persona de Mediana Edad , Telangiectasia Hemorrágica Hereditaria/patologíaRESUMEN
PURPOSE: Meesmann corneal dystrophy is an autosomal dominant disorder characterized by fragility of the anterior corneal epithelium. We have previously demonstrated that this disease can be caused by mutations in the genes encoding keratins K3 or K12, the major intermediate filament proteins expressed in corneal epithelial cells. Here, we have carried out mutation analysis in a United States kindred presenting with typical features of Meesmann corneal dystrophy. METHODS: Exons 1 and 6 of the K12 gene (KRT12) were polymerase chain reaction amplified from the proband's and control DNA and subjected to direct automated sequencing. RESULTS: A heterozygous missense mutation 1300A-->G was detected in exon 6 of KRT12, predicting amino acid substitution 1426V in the helix termination motif of the K12 polypeptide. The mutation was confirmed in the proband and excluded from 50 normal individuals by restriction enzyme analysis of polymerase chain reaction products. CONCLUSION: We report a novel mutation in a critical molecular overlap region of K12 in a United States family with Meesmann corneal dystrophy. The results confirm that mutations in the corneal keratins (K3 or K12) can underlie Meesmann corneal dystrophy.
Asunto(s)
Distrofias Hereditarias de la Córnea/genética , Queratinas/genética , Mutación Missense , Mutación Puntual , Regiones Terminadoras Genéticas , Adulto , Distrofias Hereditarias de la Córnea/patología , Análisis Mutacional de ADN , Cartilla de ADN/química , Familia , Humanos , Masculino , Reacción en Cadena de la Polimerasa , Análisis de Secuencia de ADN , Estados UnidosRESUMEN
Hypotrichosis of Marie Unna (MU) is an autosomal dominant hair-loss disorder with onset in childhood. A genomewide search for the gene was performed in a large Dutch family using 400 fluorescent microsatellite markers. Linkage was detected with marker D8S258, and analysis of this family and a further British kindred with additional markers in the region gave a combined maximum two-point LOD score of 13.42, with D8S560. Informative recombinants placed the MU gene in a 2.4-cM interval between markers D8S258 and D8S298. Recently, recessive mutations in the hr gene were reported in families with congenital atrichia, and this gene was previously mapped close to the MU interval. By radiation-hybrid mapping, we placed the hr gene close to D8S298 but were unable to exclude it from the MU interval. This, with the existence of the semidominant murine hr allele, prompted us to perform mutation analysis for this gene. Full-length sequencing of hr cDNA obtained from an affected individual showed no mutations. Similarly, screening of all exons of the hr gene amplified from the genomic DNA of an affected individual revealed no mutations. Analysis of expressed sequences and positional cloning of the MU locus is underway.
Asunto(s)
Cromosomas Humanos Par 8/genética , Análisis Mutacional de ADN , Hipotricosis/genética , Repeticiones de Microsatélite , Mapeo Físico de Cromosoma , Proteínas/genética , Factores de Transcripción , Alopecia/genética , Inglaterra , Salud de la Familia , Femenino , Genes Dominantes , Genotipo , Haplotipos , Humanos , Células Híbridas , Escala de Lod , Masculino , Mutación/genética , Países Bajos , LinajeRESUMEN
Epidermolytic palmoplantar keratoderma (EPPK, MIM #144200) is an autosomal dominant disorder in which hyperkeratosis confined to the palms and soles is characterized histologically by cytolysis of suprabasal keratinocytes. Mutations in the keratin 9 gene (KRT9), a type 1 keratin expressed exclusively in the suprabasal keratinocytes of palmoplantar epidermis, have previously been demonstrated in this disorder. Here, we have studied four Northern Irish kindreds presenting with EPPK. By direct sequencing of polymerase chain reaction products, heterozygous missense mutations in exon 1 of KRT9 were detected in all the families. These included a novel mutation M156T; as well as M156V in two kindreds; and R162Q in the remaining family. All mutations were confirmed by reverse strand sequencing and restriction enzyme analysis. The point prevalence of EPPK in Northern Ireland was found to be 4.4 per 100,000. To date, all reported EPPK mutations occur in the helix initiation motif at the start of the central coiled-coil rod domain of K9.
Asunto(s)
Epidermólisis Ampollosa/epidemiología , Epidermólisis Ampollosa/genética , Queratinas/genética , Queratodermia Palmoplantar/epidemiología , Queratodermia Palmoplantar/genética , Epidermólisis Ampollosa/diagnóstico , Humanos , Queratodermia Palmoplantar/diagnóstico , Mutación Missense , Irlanda del Norte/epidemiologíaRESUMEN
We and others have previously shown that ichthyosis bullosa of Siemens, an autosomal dominant disorder characterized by epidermal thickening and blistering, is caused by mutations in the late-differentiation keratin K2e. Here, we have determined the genomic organization and complete sequence of the KRT2E gene, which consists of nine exons, spanning 7634 bp of DNA. The gene was mapped by high-resolution radiation-hybrid mapping to the interval between microsatellite markers D12S368 and CHLC.GATA11B02.1112. Several intragenic polymorphisms were detected, including an 18 bp duplication in exon 1, corresponding to the V1 domain of the K2e polypeptide. Genomic polymerase chain reaction conditions were optimized for all exons, and two novel mutations, N192Y in the 1A domain and E482K in the 2B domain of K2e, were found in ichthyosis bullosa of Siemens families. Mutations were excluded from 50 normal unrelated individuals by restriction analysis. These results emphasize that mutations in K2e underlie ichthyosis bullosa of Siemens and provide a comprehensive mutation detection strategy for ongoing studies of keratinizing disorders.
Asunto(s)
Queratinas/genética , Mapeo Cromosómico , Exones , Humanos , Células Híbridas/metabolismo , Ictiosis/genética , Intrones , Queratina-2 , Queratinas/química , Mutación , Linaje , Polimorfismo Genético , Estructura Terciaria de Proteína , Análisis de Secuencia de ADN , Reino UnidoRESUMEN
Pachyonychia congenita type 2 (PC-2; Jackson-Lawler syndrome) is an autosomal dominant disorder characterized by hypertrophic nail dystrophy, mild focal keratoderma, multiple pilosebaceous cysts and other features of ectodermal dysplasia. Keratin 17 (K17) is a differentiation-specific keratin expressed in the nail bed, hair follicle, sebaceous gland and other epidermal appendages. Previously, we have demonstrated that PC-2 is caused by mutations in K17 and that similar mutations in this gene can present as steatocystoma multiplex with little or no nail dystrophy. Here, we describe three unrelated kindreds carrying K17 mutations. Two of these families have identical missense mutations (R94C) in the 1A domain of K17. However, while affected members of one kindred have the classical features of PC-2, affected persons in the other family have the steatocystoma multiplex phenotype. In a third family with PC-2, mutation N92S was detected, bringing the total number of distinct mutations reported in K17 thus far to 11. These results demonstrate that K17 mutations commonly underlie both PC-2 and steatocystoma multiplex and that the alternate phenotypes which arise from these genetic lesions in K17 are independent of the specific mutation involved.
Asunto(s)
Quistes/genética , Queratinas/genética , Mutación , Enfermedades de la Piel/genética , Adolescente , Adulto , Análisis Mutacional de ADN , Femenino , Humanos , Mutación Missense , Enfermedades de la Uña/genética , Linaje , Fenotipo , Reacción en Cadena de la PolimerasaRESUMEN
Type I and type II keratins form the heteropolymeric intermediate filament cytoskeleton, which is the main stress-bearing structure within epithelial cells. Pachyonychia congenita (PC) is a group of autosomal dominant disorders whose most prominent phenotype is hypertrophic nail dystrophy accompanied by other features of ectodermal dysplasia. It has been shown previously that mutations in either K16 or K6a, which form a keratin expression pair, produce the PC-1 variant (MIM 184510). Mutations in K17 alone, an unpaired accessory keratin, result in the PC-2 phenotype (MIM 184500). Here, we describe a family with PC-2 in which the K17 locus on 17q was excluded and linkage to the type II keratin locus on 12q was obtained (Z max 3.31 at straight theta = 0). Mutation analysis of candidate keratins revealed the first reported missense mutation in K6b, implying that this keratin is the previously unknown expression partner of K17, analogous to the K6a/K16 pair. Co-expression of these genes was confirmed by in situ hybridization and immunohistochemical staining. These results reveal the hitherto unknown role of the K6b isoform in epithelial biology, as well as genetic heterogeneity in PC-2.
Asunto(s)
Queratinas/genética , Mutación Missense/genética , Enfermedades de la Uña/genética , Enfermedades de la Piel/genética , Femenino , Expresión Génica , Ligamiento Genético , Genotipo , Humanos , Queratinas/biosíntesis , Masculino , Enfermedades de la Uña/patología , Linaje , Fenotipo , Enfermedades de la Piel/patologíaRESUMEN
Glucocorticoids exert their action on gene expression through activation of cytoplasmic glucocorticoid receptors (GRs) that bind to glucocorticoid response elements (GREs). The consensus GRE consists of two half sites (underlined), AGAACANNNTGTTCT. We have recently cloned the entire human elastin gene. Nucleotide sequencing of the promoter region disclosed the presence of three putative GREs with the downstream half-site sequence TGTTCC that has homology with the consensus GRE, although the upstream half site showed no homology. To examine the functionality of these putative GREs in binding to the GRs, we performed gel mobility shift and supershift assays with synthetic oligomers containing the putative GREs and a recombinant GR protein, expressed in a baculovirus system. All three GREs identified in the elastin promoter bound the receptor. A chimeric oligonucleotide containing the upstream consensus GRE half site and the downstream elastin promoter GRE half site was capable of binding the receptor, and this binding could be competed with the elastin promoter GRE. Nonconservative substitution of single nucleotides (positions 1-6) in the elastin GRE indicated that mutations in the positions 1-3 and 6 had relatively little effect, but substitutions in positions 4 and 5 rendered the oligomer less effective in competing for the binding. These observations suggest that the downstream half site of GREs in the human elastin promoter is sufficient for receptor binding and certain nucleotides are critical for the efficient binding. The results also imply that the three GREs within the human elastin promoter are active and mediate the glucocorticoid-induced up-regulation of human elastin promoter activity.