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T Gedde-Dahl

Publications and source records attributed to T Gedde-Dahl.

At least 37 records · Page 2Linked to original sources
PubMed1996

Genetic analysis of a severe case of Dowling-Meara epidermolysis bullosa simplex.

The epidermis serves an important protective function, which it manifests by producing an extensive cytoskeletal architecture, the unique feature of which are keratin filaments. Through studies that began with epidermolysis bullosa simplex (EBS) and now extend to a group of autosomal dominant human blistering skin disorders it was discovered that defects in the keratin genes lead to cell fragility and degeneration upon mechanical trauma. In most cases of EBS, point mutations occur in the keratin 5 (K5) and K14 genes expressed in the basal layer of the epidermis. The precise location of the mutation and the degree to which it causes perturbations in filament assembly correlate with disease severity. In the present study, we examine a case of EBS, which clinically lies at the severe end of the spectrum of Dowling-Meara EBS and which shows keratin filament clumping in suprabasal as well as basal cells. We show that one of the two K14 alleles has a single point substitution, giving rise to a Y129D mutation. This mutation resides 4 residues internal to the R125C/H hotspot known to account for the majority of Dowling-Meara cases. We provide functional and structural evidence to suggest why the Y129D mutation may be capable of creating such a severe form of EBS.

Adult↗
PubMed1996

Genetics of the Berardinelli-Seip syndrome (congenital generalized lipodystrophy) in Norway: epidemiology and gene mapping. Berardinelli-Seip Study Group.

Five of the six families with the Berardinelli-Seip syndrome in Norway cluster in six adjacent rural municipalities of south-western Norway. The six patients from this area were born between 1951 and 1973, none between 1974 and 1995. The absence of new cases may be explained by a decrease in the intraregion marriage rate and inbreeding. Genealogical investigations show that the mutation must have occurred at least 400 years ago. The sixth family was clinically different and geographically sporadic from a Finnish-descent rural East Norwegian population. A genetic linkage study of all six families revealed fresh crossovers versus the disease allele in nine DNA marker systems and the absence of recombination in three (maximum lod score + 1.3). None of the last showed allelic association. These families are included in an international effort to map the CLBS locus. The patients have been included in the homozygosity testing of totally 28 patients in an international collaborative study. The three patients, assumed identical in descent from both parents, were jointly homozygous in none of the 250 dinucleotide markers tested. A heterochromatic 9qh + segregated from one parent in two families.

Alleles↗
PubMed1996

On the genetics of hypodontia and microdontia: synergism or allelism of major genes in a family with six affected members.

Familial severe hypodontia of the permanent dentition is a rare condition. The genetics of this entity remains unclear and several modes of inheritance have been suggested. We report here an increase in the number of congenitally missing teeth after the mating of affected subjects from two unrelated Norwegian families. This condition may be the result of allelic mutations at a single gene locus. Alternatively, incompletely penetrant non-allelic genes may show a synergistic effect as expected for a multifactorial trait with interacting gene products. This and similar kindreds may allow identification of genes involved in growth and differentiation of dental tissues by linkage and haplotype association analysis. Brittle nails, delayed growth of the hair, and delayed teething in the probands support the grouping of these conditions among the ectodermal dysplasias.

Abnormalities, Multiple↗
PubMed1995

Immunohistochemical and mutation analyses demonstrate that procollagen VII is processed to collagen VII through removal of the NC-2 domain.

Collagen VII is the major structural constituent of anchoring fibrils in the skin. It is synthesized as a procollagen that is larger than the collagen deposited in the tissue. In this study, we investigated the conversion of procollagen VII to collagen VII in human skin and in cutaneous cells in vitro and identified the propeptide using domain-specific antibodies. For this purpose, two bacterial fusion proteins containing unique sequences of the carboxy-terminal globular NC-2 domain of procollagen VII were prepared, and polyclonal antibodies raised against them. Immunoblotting showed that the anti-NC2 antibodies reacted with procollagen VII isolated from cultured keratinocytes, but not with collagen VII extracted from the skin. Immunohistochemical experiments with the NC-2 antibodies revealed a strong reaction in cultured keratinocytes, but the basement membrane zone of normal skin remained negative. The staining could not be rendered positive by chemical or enzymatic unmasking of potential hidden epitopes in the skin, indicating that most of the NC-2 domain is absent from normal skin. In contrast, a positive staining with NC-2 antibodies was observed in the skin of a patient with NC-2 antibodies was observed in the skin of a patient with dystrophic epidermolysis bullosa, who carried a 14-bp deletion at one of the intro-exon junctions of the collagen VII gene. This aberration led to an in-frame skipping of exon 115 from the mRNA and eliminated 29 amino acids from the NC-2 domain which include the putative cleavage site for the physiological processing enzyme, procollagen C-proteinase. The results indicate that in normal human skin, the removal of the NC-2 domain from procollagen VII precedes its deposition at the dermal-epidermal junction. Furthermore, they suggest that an aberration in the procollagen VII cleavage interferes with the normal fibrillogenesis of the anchoring fibrils.

Amino Acid Sequence↗
PubMed1995

Genes and languages in Europe: an analysis of mitochondrial lineages.

When mitochondrial DNA sequence variation is analyzed from a sample of 637 individuals in 14 European populations, most populations show little differentiation with respect to each other. However, the Saami distinguish themselves by a comparatively large amount of sequence difference when compared with the other populations, by a different distribution of sequence diversity within the population, and by the occurrence of particular sequence motifs. Thus, the Saami seem to have a long history distinct from other European populations. Linguistic affiliations are not reflected in the patterns of relationships of mitochondrial lineages in European populations, whereas prior studies of nuclear gene frequencies have shown a correlation between genetic and linguistic evolution. It is argued that this apparent contradiction is attributable to the fact that genetic lineages and gene frequencies reflect different time perspectives on population history, the latter being more in concordance with linguistic evolution.

Base Sequence↗
PubMed1994

A K-ras 13Gly-->Asp mutation is recognized by HLA-DQ7 restricted T cells in a patient with colorectal cancer. Modifying effect of DQ7 on established cancers harbouring this mutation?

We have characterized and described in detail 2 CD4+ T-lymphocyte clones (TLC) from a colonic cancer patient. These TLC specifically recognize a K-ras-derived peptide carrying the 13Asp mutation commonly found in adenocarcinomas of the colon. The TLC were independently derived, as they carried 2 different T-cell receptors. The TLC recognized partly overlapping epitopes within the 13Asp peptide, presented by HLA-DQ7 molecules, suggesting that this molecule might confer some protective immunity against the mutation. On the basis of analysis of 251 colonic carcinomas, the presence of HLA-DQ7 did not seem to protect against the establishment of carcinomas carrying the 13Asp mutation, since the frequency of the DQ7 haplotype was not decreased among patients having this mutation. A modifying effect of DQ7 on the development of carcinomas with a 13Asp mutation was, however, observed, resulting in fewer tumours reaching advanced Dukes stages when DQ7 was present.

Amino Acid Sequence↗
PubMed1994

p21-ras-peptide-specific T-cell responses in a patient with colorectal cancer. CD4+ and CD8+ T cells recognize a peptide corresponding to a common mutation (13Gly-->Asp).

Peptides derived from mutated ras are immunogenic in mice and humans, and represent a group of specific tumor antigens that are potential targets for immunotherapy. T-cell responses against mutant p21 ras can be initiated in vitro by repeated stimulation of peripheral-blood mononuclear cells with mutant ras-derived peptides. Patients with tumors commonly harbouring ras mutations may therefore show evidence of in vivo reactivity against such mutations. Peripheral-blood mononuclear cells from 10 patients with colorectal adenocarcinoma were screened for reactivity against synthetic ras-derived peptides corresponding to the most commonly found mutations in this type of cancer. In one patient, T-cell reactivity against the 1-25,13Gly-->Asp peptide was detected. From this patient, both CD4+ and CD8+ T-cell clones specific for the 1-25,13Gly-->Asp mutation could be raised. We were not, however, able to detect the corresponding mutation in the cancer. The 13Gly-->Asp mutation in the ras oncogene is frequent and constitutes 9 to 27% of all K ras mutations found in biopsies from patients with colorectal carcinomas. Our study demonstrates a mutant ras-specific T-cell response of both the CD4+ and the CD8+ phenotype in a cancer patient. We speculate that in this patient a specific T-cell response resulted in eradication of tumor cells harboring the 13Gly-->Asp mutation.

Adenocarcinoma↗
PubMed1994

T cell epitopes encompassing the mutational hot spot position 61 of p21 ras. Promiscuity in ras peptide binding to HLA.

Activated ras carry a point mutation either in codon 12, 13 or 61 which is tumor specific. Peptides derived from this oncoprotein are therefore potential tumor antigens. Essential for the feasibility of using ras-derived peptides in therapy of cancer is whether p21 ras-derived peptides can be processed, bind to human histocompatibility leukocyte antigen (HLA) and be recognized by T cells. Here we report the fine specificity and HLA restriction of several T lymphocyte clones (TLC) specific for a peptide which is derived from the second mutational hot spot in ras encoding residue 61. These TLC were generated from memory T cells present in the blood of a cancer patient and recognized a ras-derived peptide carrying Leu instead of Gln at residue 61. By sequencing of the T cell receptor (TcR) genes three sets of "sister" TLC carrying highly different TcR were identified. Two of the TLC recognized a peptide carrying the 61 Leu mutation presented by HLA-DQ8 and one recognized the same peptide presented by HLA-DQ4. By using truncated peptides derived from residues 51 to 69 of p21 ras, partially overlapping minimal epitopes could be defined. All three TLC recognized the corresponding recombinant mutant p21 ras oncoprotein carrying Leu at residue 61 presented by autologous B-lymphoblastoid cell lines (B-LCL). This demonstrates that naturally derived ras peptides from this region of p21 ras encompass the three epitopes recognized by the TLC. These results indicate that immunogenic ras-derived peptides may be used in immunotherapy of cancer where transforming ras oncoproteins are involved.

Amino Acid Sequence↗
PubMed1994

Heterogeneity of T cells specific for a particular peptide/HLA-DQ complex.

Whether T cells specific for a particular peptide/HLA-DQ complex are restricted with respect to TCR usage has not been fully established. TCR usage of T cells specific for a peptide presented by a given HLA-DQ molecule has not been studied before. We therefore sequenced the TCR genes of five different TCCs derived from the same donor, which were specific for a p21 ras-derived synthetic peptide presented by the HLA-DQ(alpha 1*0102,beta*0602) (DQ6) molecule. We found that these T cells which recognized the same peptide/HLA-DQ complex used highly diverse TCRs. However, dose-response experiments using various truncations of the p21 ras-derived peptide revealed that the peptide fine specificities of the five TCCs were not completely identical. This may explain the heterogeneity in TCR usage.

Amino Acid Sequence↗
PubMed1994

Junctional epidermolysis bullosa inversa (locus EBR2A) assigned to 1q31 by linkage and association to LAMC1.

Junctional epidermolysis bullosa inversa is an autosomal recessive blistering skin disease with an ultrastructural hemidesmosome defect similar to that of the Herlitz disease, yet with a non-lethal and different course of the disease. Its delineation is based on five geographically associated Norwegian families where all parents are likely to carry a mutant EBR2A allele identical in descent. Three informative families show a lod score of +1.65 at zero recombination to a trinucleotide repeat marker in intron 20 of the laminin gamma 1 (LAMC1, previously LAMB2) locus on 1q31. The four patients of these families are all homozygous for the 146 bp LAMC1 allele present only on 5% of random Norwegian chromosomes. The daughter of a deceased patient in a fourth family carries the same 146 bp allele. This extreme association confirms that the disease locus, EBR2A, is at or closely linked to LAMC1. Localized and generalized Mitis types as well as the majority of tested families with the Herlitz type of junctional epidermolysis bullosa appeared not to be similarly linked or associated to LAMC1. The MspI and AluI RFLPs of LAMC1 showed absolute allelic association. Each of the two RFLP haplotypes showed association to either 'long' or 'short' intron 20 STR alleles.

Alleles↗
PubMed1994

Heterogeneity of severe dystrophic epidermolysis bullosa: overexpression of collagen VII by cutaneous cells from a patient with mutilating disease.

Severe mutilating recessive dystrophic epidermolysis bullosa presents with extensive blistering, scarring, and pseudosyndactylies. The skin of most affected individuals lacks normal anchoring fibrils and contains no, or drastically reduced amounts of, collagen VII, the major fibril component. Here we present evidence for molecular heterogeneity of the mutations underlying this phenotype. A patient with severe mutilating disease, but with apparently normal anchoring fibrils and abundant collagen VII, was defined. Indirect immunofluorescence examination of the patient's skin exhibited a strong staining for collagen VII at the dermo-epidermal junction and at the roof of a natural blister, and immunoblotting of skin extracts revealed collagen VII of normal size. The patient's keratinocytes expressed two- to threefold increased amounts of collagen VII at the mRNA and protein level compared to controls. Synthesis of matrix metalloproteases by the patient's keratinocytes was comparable to normal cells, indicating that the overexpression of collagen VII did not affect the synthesis of these enzymes. We hypothesize that in this patient a mutation affecting interactions of the anchoring fibrils with other components of the basement membrane zone underlies the disease.

Adult↗
PubMed1994

Binding of ras oncogene peptides to purified HLA-DQ(alpha 1*0102,beta 1*0602) and -DR(alpha,beta 1*0101) molecules.

Mutated oncogene peptides may be presented to T cells by HLA molecules. To be able to design the optimal peptides for stimulation of T cells in individuals with different HLA molecules, it is important to analyse the binding characteristics of oncogene peptides to HLA. HLA-DQ6 (DQ(alpha 1*0102,beta 1*0602)) and HLA-DR1 (DR(alpha,beta 1*0101)) molecules were purified from lysates of homozygous EBV-transformed cell lines. Purified HLA molecules were then tested for their ability to bind synthetic peptides in gel filtration assays. A p21 ras oncogene peptide (previously found to stimulate DQ6-restricted T-cell clones) and an influenza matrix peptide were labelled with 125I and served as indicator peptides for binding to DQ6 and DR1 respectively. Binding of homologous truncated and mutated p21 ras peptides and unrelated peptides was then evaluated by their capacity to inhibit binding of the indicator peptides. p21 ras-derived peptides were found to bind to both DQ6 and DR1 molecules indicating the existence of a promiscuous binding motif in these peptides. The binding affinities seemed to vary between the different peptides, but the amino acid substitutions resulting from natural mutations were not critical for binding. Notably, the results obtained for DQ6 in the biochemical peptide binding assay correlated well with results obtained in a functional assay using T-cell clones as probes.

Amino Acid Sequence↗
PubMed1994

Keratinocytes from junctional epidermolysis bullosa do adhere and migrate on the basement membrane protein nicein through alpha 3 beta 1 integrin.

BACKGROUND: Junctional epidermolysis bullosa (JEB) encompasses several genodermatoses characterized by skin blistering, and possibly disturbed wound healing. Although the molecular defects underlying JEB are not known, we have demonstrated previously that nicein, an adhesive laminin-related basement membrane component, is immunologically altered in the very severe JEB of Herlitz type (H-JEB), and was expressed to a lesser extent in skin from patients with inversa JEB (I-JEB). In this study, we assessed adhesion and migration of H-JEB and I-JEB keratinocytes on exogenous nicein and laminin to get insights on the biologic function defective in JEB skin. EXPERIMENTAL DESIGN: Adhesion of cultured epidermal keratinocytes from H-JEB and I-JEB patients was assayed by quantitation of cell attachment 1 hour after seeding into microtiter wells coated with nicein or laminin. Cell migration and modulation by function-blocking antibodies to integrins was quantified by computer-assisted image analysis of the tracks left by the cells in a phagokinetic assay using gold particles coated with nicein or laminin. RESULTS: In spite of the fact that H-JEB keratinocytes do not produce normal immunoreactive nicein, they were able to adhere on exogenous nicein similarly to normal and I-JEB keratinocytes which produce nicein. Adhesion of both JEB and normal keratinocytes to laminin was weak compared with nicein. At low and high concentrations of nicein, a reduced migration response occurred with H-JEB keratinocytes whereas I-JEB cells behaved like their normal counterparts. Integrin alpha 3 beta 1 was dominantly involved in adhesion and migration of all these cells. Laminin did not support the migration of either JEB or normal keratinocytes. CONCLUSIONS: H-JEB and I-JEB keratinocytes which produce no or less nicein than normal keratinocytes are able to adhere and migrate on exogenous nicein. Integrin alpha 3 beta 1 which is specifically involved in migration and adhesion of keratinocytes on nicein does not appear altered in JEB. These data indicate that defective nicein rather than modifications of the nicein-recognizing receptor play a central role in the pathogenesis of H-JEB.

Adult↗
PubMed1994

Growth inhibition of a colonic adenocarcinoma cell line (HT29) by T cells specific for mutant p21 ras.

Mutations at codons 12, 13 or 61 of the ras proto-oncogenes are found in adenocarcinomas of the colon and rectum. Mutated ras encode tumor-specific proteins, and can elicit CD4+ HLA-class-II-restricted T cell responses both in mouse and man. The function of such T cells is, however, unclear. In a model system, we investigated whether HLA-class-II restricted CD4+ T cells, specific for a particular peptide derived from mutant p21 ras (Gln61-->Leu), might inhibit the growth of a colonic cancer cell line, when it was cultured in the presence of the corresponding peptide. We found in this case that the growth of the colonic adenocarcinoma cell line HT29, when also induced to express HLA class II molecules by interferon gamma treatment, was inhibited. The inhibition was peptide-specific and required the presence of HLA-DQ8 molecules on the target cell. However, HLA-DQ8-expressing HT29 cells functioned poorly as antigen-presenting cells and could only induce a weak proliferative T cell response in the presence of interleukin-2. The results suggest that colonic cancer cells expressing peptides derived from mutant p21 ras protein in a complex with HLA class II molecules may be a target for tumor-specific T cells. The results also indicate, however, that an initiation of the immune response will require "professional" antigen-presenting cells.

Adenocarcinoma↗
PubMed1993

T cell clones specific for p21 ras-derived peptides: characterization of their fine specificity and HLA restriction.

Peptides corresponding to the mutated regions of the oncoprotein p21 ras are immunogenic and capable of eliciting HLA class II-restricted T cell responses. Here we report studies on the fine specificity of four T lymphocyte clones (TLC) from a single donor, using various truncated peptides derived from the residues 6-19 of p21 ras and a panel of well-characterized HLA homozygous cells as antigen-presenting cells. Putative minimum peptides of nine or ten amino acids could be defined for each TLC. Two of the TLC recognized peptides presented by DR2, and the two others recognized peptides presented by DQ6. Some notable differences in the requirement for certain amino acids were seen between the DR- and DQ-restricted TLC. Thus, Ser at residue 17 was required for stimulation of the DQ6-but not the DR2-restricted TLC. Val at residue 8 was essential for stimulation of all TLC, whereas one of the DR2-restricted TLC also required Val at residue 7. Some peptides which were nonstimulatory were still capable of binding to DQ6 molecules in peptide competition experiments. The results may be of importance for potential immunotherapy of cancer where transforming ras oncoproteins are involved.

Amino Acid Sequence↗