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Julia Reichelt - One of the best experts on this subject based on the ideXlab platform.
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Arginine‐ but not alanine‐rich carboxy‐termini trigger nuclear translocation of mutant Keratin 10 in ichthyosis with confetti
Journal of cellular and molecular medicine, 2019Co-Authors: Patricia Renz, E. Imahorn, I. Spoerri, M. Aushev, Oliver P. March, Hedwig Wariwoda, Sarah Von Arb, Andreas Volz, Peter Itin, Julia ReicheltAbstract:Ichthyosis with confetti (IWC) is a genodermatosis associated with dominant-negative variants in Keratin 10 (KRT10) or Keratin 1 (KRT1). These frameshift variants result in extended aberrant proteins, localized to the nucleus rather than the cytoplasm. This mislocalization is thought to occur as a result of the altered carboxy (C)-terminus, from poly-glycine to either a poly-arginine or -alanine tail. Previous studies on the type of C-terminus and subcellular localization of the respective mutant protein are divergent. In order to fully elucidate the pathomechanism of IWC, a greater understanding is critical. This study aimed to establish the consequences for localization and intermediate filament formation of altered Keratin 10 (K10) C-termini. To achieve this, plasmids expressing distinct KRT10 variants were generated. Sequences encoded all possible reading frames of the K10 C-terminus as well as a nonsense variant. A Keratinocyte line was transfected with these plasmids. Additionally, gene editing was utilized to introduce frameshift variants in exon 6 and exon 7 at the endogenous KRT10 locus. Cellular localization of aberrant K10 was observed via immunofluorescence using various antibodies. In each setting, immunofluorescence analysis demonstrated aberrant nuclear localization of K10 featuring an arginine-rich C-terminus. However, this was not observed with K10 featuring an alanine-rich C-terminus. Instead, the protein displayed cytoplasmic localization, consistent with wild-type and truncated forms of K10. This study demonstrates that, of the various 3' frameshift variants of KRT10, exclusively arginine-rich C-termini lead to nuclear localization of K10.
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Loss of Keratin 10 is accompanied by increased sebocyte proliferation and differentiation.
European journal of cell biology, 2004Co-Authors: Julia Reichelt, Bernadette Breiden, Konrad Sandhoff, Thomas M. MaginAbstract:Summary Here, we present strong evidence that the targeted deletion of Keratin 10 (K10) alters sebocyte differentiation in mice, mediated by an increased proliferation and differentiation of cells located in the periphery of the glands. This was not accompanied by the induction of the proliferation-associated Keratins K6, K16 and K17. Sebaceous gland cells of K10−/− mice showed an accelerated turnover and secreted more sebum including wax esters, triglycerides, and cholesterol esters. The levels of the major epidermal lipids ceramides and cholesterol were also increased, whereas glycosylceramides and sphingomyelin were decreased which was not based on altered sphingolipid biosynthesis. The amount of Cer(OS), covalently bound to the cornified envelope, remained unchanged, as well as the amount of loricrin and involucrin. In agreement with the unaltered expression of β-catenin and its targets cyclin D1 and c-Myc, we conclude that the altered composition of the suprabasal intermediate filament cytoskeleton in K10−/− mice increased the differentiation of epidermal stem cells towards the sebocyte lineage.
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Loss of Keratin 10 Leads to Mitogen-activated Protein Kinase (MAPK) Activation, Increased Keratinocyte Turnover, and Decreased Tumor Formation in Mice
The Journal of investigative dermatology, 2004Co-Authors: Julia Reichelt, Gerhard Fürstenberger, Thomas M. MaginAbstract:Keratin 10 (K10) is the major protein in the upper epidermis where it maintains Keratinocyte integrity. Others have reported that K10 may act as a tumor suppressor upon ectopic expression in mice. Although K10 −/− mice show significant epidermal hyperproliferation, accompanied by an activation of the mitogen-activated protein kinase (MAPK) pathway, they formed no spontaneous tumors. Here, we report that K10 −/− mice treated with 7,12-dimethylbenz[ a ]anthracene (DMBA)/12- O -tetradecanoylphorbol-13-acetate (TPA) developed far less papillomas than wild-type mice. BrdU(5-bromo-2′-deoxyuridine)-labeling revealed a strongly accelerated Keratinocyte turnover in K10 −/− epidermis suggesting an increased elimination of initiated Keratinocytes at early stages of developing tumors. This is further supported by the absence of label-retaining cells 18 d after the pulse whereas in wild-type mice label-retaining cells were still present. The concomitant increase in K6, K16, and K17 in K10 null epidermis and the increased motility of Keratinocytes is in agreement with the pliability versus resilience hypothesis, stating that K10 and K1 render cells more stable and static. The K10 −/− knockout represent the first mouse model showing that loss of a Keratin, a cytoskeletal protein, reduces tumor formation. This is probably caused by an accelerated turnover of Keratinocytes, possibly mediated by activation of MAPK pathways.
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Hyperproliferation, induction of c-Myc and 14-3-3σ, but no cell fragility in Keratin-10-null mice
Journal of Cell Science, 2002Co-Authors: Julia Reichelt, Thomas M. MaginAbstract:In the past, Keratins have been established as structural proteins. Indeed, mutations in Keratin 10 (K10) and other epidermal Keratins lead to severe skin fragility syndromes. Here, we present adult K10-/- mice, which reveal a novel connection between the regulation of cell proliferation and K10. Unlike most Keratin mutant mice, the epidermis of adult K10-/- mice showed no cytolysis but displayed hyperproliferation of basal Keratinocytes and an increased cell size. BrdU labelling revealed a shortened transition time for Keratinocytes migrating outwards and DAPI staining of epidermal sheets uncovered an impaired organization of epidermal proliferation units. These remarkable changes were accompanied by the induction of c-Myc, cyclin D1, 14-3-3σ and of wound healing Keratins K6 and K16. The phosphorylation of Rb remained unaltered. In line with the downregulation of K10 in squamous cell carcinomas and its absence in proliferating cells in vivo, our data suggest that the tissue-restricted expression of some members of the Keratin gene family not only serves structural functions. Our results imply that the altered composition of the suprabasal cytoskeleton is able to alter the proliferation state of basal cells through the induction of c-Myc. A previous model based on transfection of K10 in immortalized human Keratinocytes suggested a direct involvement of K10 in cell cycle control. While those experiments were performed in human cultured Keratinocytes, our data establish, that in vivo, K10 acts by an indirect control mechanism in trans.
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Hyperproliferation, induction of c-Myc and 14-3-3sigma, but no cell fragility in Keratin-10-null mice.
Journal of cell science, 2002Co-Authors: Julia Reichelt, Thomas M. MaginAbstract:In the past, Keratins have been established as structural proteins. Indeed, mutations in Keratin 10 (K10) and other epidermal Keratins lead to severe skin fragility syndromes. Here, we present adult K10-/- mice, which reveal a novel connection between the regulation of cell proliferation and K10. Unlike most Keratin mutant mice, the epidermis of adult K10-/- mice showed no cytolysis but displayed hyperproliferation of basal Keratinocytes and an increased cell size. BrdU labelling revealed a shortened transition time for Keratinocytes migrating outwards and DAPI staining of epidermal sheets uncovered an impaired organization of epidermal proliferation units. These remarkable changes were accompanied by the induction of c-Myc, cyclin D1, 14-3-3sigma and of wound healing Keratins K6 and K16. The phosphorylation of Rb remained unaltered. In line with the downregulation of K10 in squamous cell carcinomas and its absence in proliferating cells in vivo, our data suggest that the tissue-restricted expression of some members of the Keratin gene family not only serves structural functions. Our results imply that the altered composition of the suprabasal cytoskeleton is able to alter the proliferation state of basal cells through the induction of c-Myc. A previous model based on transfection of K10 in immortalized human Keratinocytes suggested a direct involvement of K10 in cell cycle control. While those experiments were performed in human cultured Keratinocytes, our data establish, that in vivo, K10 acts by an indirect control mechanism in trans.
P.c.m. Van De Kerkhof - One of the best experts on this subject based on the ideXlab platform.
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The effect of the combination of calcipotriol and betamethasone dipropionate versus both monotherapies on epidermal proliferation, Keratinization and T-cell subsets in chronic plaque psoriasis.
Experimental dermatology, 2004Co-Authors: W.h.p.m. Vissers, P.e.j. Van Erp, M.j. Berends, L. Muys, E.m.g.j. De Jong, P.c.m. Van De KerkhofAbstract:Several reports have indicated that the combination of calcipotriol ointment and potent or ultrapotent corticosteroids are more effective and better tolerated, as compared to the monotherapies. The aim of the present study was to find out the effect of combination of calcipotriol ointment once daily and betamethasone dipropionate ointment once daily vs. the effect of twice-daily applications of each of the two treatments as monotherapy during a four-week treatment period. Seven patients with chronic plaque psoriasis were included for treatment with the three treatment schedules. Biopsies were taken before treatment and after four weeks of treatment, and markers for epidermal proliferation (Ki-67) and epidermal differentiation (Keratin-10) were studied using a quantitative image analysis, and T-cell subsets in epidermis and dermis (CD4, CD8, CD25, CD45RO, CD45RA, CD94, CD161, and CD2) were studied using immunohistochemical scoring. The most impressive clinical result was reached with the combination. Calcipotriol proved to have a major effect on the proliferation marker Ki-67 and differentiation marker Keratin-10, whereas the effect on T-cell subsets was more selective with major reductions of CD45RO(+) and CD8(+) T cells. In contrast, the effect of betamethasone dipropionate on the epidermis was restricted to a normalization of differentiation with a highly significant increase of Keratin-10 positive epidermal surface without a significant effect on Ki-67 positive nuclei, and the effect on T-cell subsets was restricted to a reduction of natural killer T-cell receptors designated by CD94 and CD161 in the epidermis. The combination of the two treatments did not affect the proliferation marker Ki-67 and Keratinization marker Keratin-10, beyond the effect of calcipotriol monotherapy. However, the combination had a profound effect on, virtually, all T-cell subsets, beyond the effect of the monotherapies. It is concluded that the action spectra of calcipotriol and betamethasone on the psoriatic plaque are different and that the combination has effects on T-cell subsets, beyond the addition of the effects of monotherapies.
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Immunohistochemical differentiation between inflammatory linear verrucous epidermal nevus (ILVEN) and psoriasis
European journal of dermatology : EJD, 2004Co-Authors: W.h.p.m. Vissers, P.e.j. Van Erp, L. Muys, E.m.g.j. De Jong, P.c.m. Van De KerkhofAbstract:Inflammatory linear verrucous epidermal nevus (ILVEN) is a rare skin disorder with a clinical and histological resemblance to psoriasis. In the past clinical and histological criteria have been defined. However, there remains a discussion as to whether ILVEN is a disease entity distinct from linear psoriasis. Our objective was to compare by quantitative immunohistochemistry the subsets of T-lymphocytes and markers for epidermal growth and Keratinisation in biopsies taken from skin lesions of 4 patients with psoriasis and 3 patients with ILVEN: 1. patients with psoriasis (case 1-4) 2. patient with ILVEN cum psoriasis (case 5) 3. patients with ILVEN sine psoriasis (case 6 and 7). Our aim was to delineate ILVEN from psoriasis. Four patients with active psoriasis and three patients with signs and symptoms of ILVEN are described in this case report. Two patients of the ILVEN group had only linear verrucous lesions (ILVEN sine psoriasis), and one patient had linear lesions combined with widespread psoriasis outside the linear verrucous lesion (ILVEN cum psoriasis). The following markers were investigated in skin biopsies taken from the aforementioned patients by quantitative immunohistochemistry: CD2, CD4, CD8, CD25, CD161, CD94, CD45RO, CD45RA, HLA-DR, Keratin-10, Ki-67. In patients with ILVEN (cum and sine psoriasis) the number of Ki-67 positive nuclei, tended to be lower, the number of Keratin-10 positive cells and HLA-DR expression higher as compared to psoriasis. In ILVEN sine psoriasis all T-cell subsets and cells expressing NK receptors were reduced as compared to psoriasis, except for CD45RA+ cells, whereas in the patient with ILVEN cum psoriasis the number of these T cell subsets had an intermediary position. In particular the density of CD8+, CD45RO+ and CD2+, CD94 and CD161 showed a marked difference between ILVEN sine psoriasis and psoriasis. In addition to the increased Keratin 10 expression in ILVEN sine psoriasis, T cells relevant in the pathogenesis of psoriasis are markedly reduced in ILVEN sine psoriasis as compared to psoriasis. T-cell subsets in ILVEN cum psoriasis had an intermediary position.
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Changes in Keratin 6 and Keratin 10 (co-)expression in lesional and symptomless skin of spreading psoriasis.
Dermatology (Basel Switzerland), 2000Co-Authors: J.m. Mommers, M.m. Van Rossum, P.e.j. Van Erp, P.c.m. Van De KerkhofAbstract:Background: Keratin 6 (K6) and Keratin 10 (K10) are markers for epidermal hyperproliferation and differentiation, respectively, and are both expressed in the suprabasal layers of th
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Flow-cytometric characterization of normal versus psoriatic epidermis using improved cell separation methodology.
Experimental dermatology, 2000Co-Authors: B.a.m.p.a. Seegers, P.e.j. Van Erp, G. J. De Jongh, C.a.e.m. Van Hooijdonk, C.p. Glade, P.c.m. Van De KerkhofAbstract:: Recently a new approach for epidermal cell characterization was developed: three-parameter flow cytrometrical analysis of pure and complete epidermal cell suspensions prepared from punch biopsies followed by dermoepidermal separation by thermolysin. The aim of the present communication is the comparison between psoriatic lesional skin and normal skin using this new approach with respect to the percentage of suprabasal Keratinocytes (Keratin 10+ cells), mesenchymal cells, including the infiltrate cells (vimentin+ cells) and the percentage of basal cells in SG2 M phase, in order to validate this methodology in studies on psoriatic skin. Punch biopsies were taken from 7 healthy volunteers and in 7 psoriatic patients 4 biopsies were taken in each of them from comparable lesions. The present study reconfirmed that the percentage of basal Keratinocytes in psoriasis was increased and the percentage of Keratin 10+ cells was substantially decreased as compared to normal skin. The new methodology revealed data with a narrow range. In psoriatic lesional skin the intra individual variation was less compared to the inter individual variation.
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CD 2394, a novel synthetic retinoid, initiates an embryonic type of differentiation in hyperproliferative skin.
Acta dermato-venereologica, 2000Co-Authors: M.m. Van Rossum, J.m. Mommers, P.e.j. Van Erp, E. Leyninger, A. Clucas, P.c.m. Van De KerkhofAbstract:In human skin, there are 2 types of epidermal differentiation: normal differentiation, characterized by Keratin 10 expression, and alternative differentiation. Alternative differentiation may be regeneration-associated differentiation (Keratin 6 and 16) or re-induction of embryonic differentiation (expression of Keratin 13, 15 and 19). The purpose of this study was to investigate the effect of the novel synthetic retinoid CD 2394 on hyperproliferative human skin, with respect to embryonic differentiation in particular. The effects of CD 2394 were compared with untreated and vehicle-treated skin 48 h after tape-stripping. In a multiparameter flow cytometric assay, parameters of proliferation, normal differentiation, embryonic differentiation and inflammation were assessed. With respect to proliferation, treatment with CD 2394 resulted in a decreased number of cells in the G 2 M-phase. Normal differentiation was decreased in CD 2394 treated skin. Furthermore, most of the CD 2394 treated samples showed expression of Keratin 13, which was not seen in the otherwise treated skin. A correlation between Keratin 10 and Keratin 13 expression could not be demonstrated. This study showed that CD 2394 is capable of inducing an embryonic pathway of differentiation, which is distinct from normal differentiation or regeneration-associated differentiation.
Keith A Choate - One of the best experts on this subject based on the ideXlab platform.
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mutations affecting Keratin 10 surface exposed residues highlight the structural basis of phenotypic variation in epidermolytic ichthyosis
Journal of Investigative Dermatology, 2015Co-Authors: Haris Mirza, Corey Saraceni, Richard Torbeck, Bruce Ragsdale, Brittany G Craiglow, Paul Rehder, Annamari Ranki, Anil Kumar, Jing Zhou, Keith A ChoateAbstract:Epidermolytic ichthyosis (EI) due to KRT10 mutations is a rare, typically autosomal dominant, disorder characterized by generalized erythema and cutaneous blistering at birth followed by hyperkeratosis and less frequent blistering later in life. We identified two KRT10 mutations p.Q434del and p.R441P in subjects presenting with a mild EI phenotype. Both occur within the mutational "hot spot" of the Keratin 10 (K10) 2B rod domain, adjacent to severe EI-associated mutations. p.Q434del and p.R441P formed collapsed K10 fibers rather than aggregates characteristic of severe EI KRT10 mutations such as p.R156C. Upon differentiation, Keratinocytes from p.Q434del showed significantly lower apoptosis (P-value<0.01) compared with p.R156C as assessed by the TUNEL assay. Conversely, the mitotic index of the p.Q434del epidermis was significantly higher compared with that of p.R156C (P-value<0.01) as estimated by the Ki67 assay. Structural basis of EI phenotype variation was investigated by homology-based modeling of wild-type and mutant K1-K10 dimers. Both mild EI mutations were found to affect the surface-exposed residues of the K10 alpha helix coiled-coil and caused localized disorganization of the K1-K10 heterodimer. In contrast, adjacent severe EI mutations disrupt key intermolecular dimer interactions. Our findings provide structural insights into phenotypic variation in EI due to KRT10 mutations.
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Mutations Affecting Keratin 10 Surface-Exposed Residues Highlight the Structural Basis of Phenotypic Variation in Epidermolytic Ichthyosis
Journal of Investigative Dermatology, 2015Co-Authors: Haris Mirza, Corey Saraceni, Richard Torbeck, Bruce Ragsdale, Brittany G Craiglow, Paul Rehder, Annamari Ranki, Anil Kumar, Jing Zhou, Keith A ChoateAbstract:Epidermolytic ichthyosis (EI) due to KRT10 mutations is a rare, typically autosomal dominant, disorder characterized by generalized erythema and cutaneous blistering at birth followed by hyperkeratosis and less frequent blistering later in life. We identified two KRT10 mutations p.Q434del and p.R441P in subjects presenting with a mild EI phenotype. Both occur within the mutational "hot spot" of the Keratin 10 (K10) 2B rod domain, adjacent to severe EI-associated mutations. p.Q434del and p.R441P formed collapsed K10 fibers rather than aggregates characteristic of severe EI KRT10 mutations such as p.R156C. Upon differentiation, Keratinocytes from p.Q434del showed significantly lower apoptosis ( P -value P -value KRT10 mutations.
Daniel Hohl - One of the best experts on this subject based on the ideXlab platform.
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Induction of p38, tumour necrosis factor-α and RANTES by mechanical stretching of Keratinocytes expressing mutant Keratin 10R156H.
British Journal of Dermatology, 2010Co-Authors: Magdalena Obarzanek-fojt, Stephan Ryser, Pierre Jean Wipff, B. Hinz, Bertrand Favre, Marcel Huber, Angus M. Moodycliffe, Daniel HohlAbstract:Epidermolytic hyperkeratosis (bullous congenital ichthyosiform erythroderma), characterized by ichthyotic, rippled hyperkeratosis, erythroderma and skin blistering, is a rare autosomal dominant disease caused by mutations in Keratin 1 or Keratin 10 (K10) genes. A severe phenotype is caused by a missense mutation in a highly conserved arginine residue at position 156 (R156) in K10.
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A human Keratin 10 knockout causes recessive epidermolytic hyperkeratosis
Human Molecular Genetics, 2006Co-Authors: Felix B. Müller, Marcel Huber, Daniel Hohl, Bernhard P. Korge, Tamar Kinaciyan, Ingrid Hausser, Christina Schaffrath, Thomas Krieg, Meral J. ArinAbstract:Epidermolytic hyperkeratosis (EHK) is a blistering skin disease inherited as an autosomal-dominant trait. The disease is caused by genetic defects of the epidermal Keratin K1 or K10, leading to an impaired tonofilament network of differentiating epidermal cells. Here, we describe for the first time a kindred with recessive inheritance of EHK. Sequence analysis revealed a homozygous nonsense mutation of the KRT10 gene in the affected family members, leading to a premature termination codon (p.Q434X), whereas the clinically unaffected consanguineous parents were both heterozygous carriers of the mutation. Semi-quantitative RT-PCR and western blot analysis demonstrated degradation of the KRT10 transcript, resulting in complete absence of Keratin K10 protein in the epidermis and cultured Keratinocytes of homozygous patients. This K10 null mutation leads to a severe phenotype, clinically resembling autosomal-dominant EHK, but differing in form and distribution of Keratin aggregates on ultrastructural analysis. Strong induction of the wound-healing Keratins K6, K16 and K17 was found in the suprabasal epidermis, which are not able to compensate for the lack of Keratin 10. We demonstrate that a recessive mutation in KRT10 leading to a complete human K10 knockout can cause EHK. Identification of the heterogeneity of this disorder has a major impact for the accurate genetic counseling of patients and their families and also has implications for gene-therapy approaches.
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A novel substitution in Keratin 10 in epidermolytic hyperkeratosis.
Journal of Investigative Dermatology, 1999Co-Authors: Meral J. Arin, Marcel Huber, Daniel Hohl, Mary A. Longley, Joseph A. Rothnagel, Ingrun Anton-lamprecht, Gunter Kurze, Dennis R RoopAbstract:Epidermolytic hyperkeratosis is characterized by tonofilament clumping, cytolysis, and blister formation in suprabasal Keratinocytes. It has been shown that the tonofilament aggregates in these areas are composed of Keratin 1 (K1) and Keratin 10 (K10), and several K1 and K10 point mutations have been identified as the molecular basis of epidermolytic hyperkeratosis. In this report we identify a novel, single base pair substitution resulting in an amino acid exchange from tyrosine to serine at residue 14 within the conserved 1A region of K10 (Y14S). This A to C transversion in codon 160 was only present in the affected individual and was associated with a very severe disease phenotype. Our observations are in agreement with previous reports documenting that this tyrosine residue, located at the beginning of the rod domain of type I Keratins, is particularly sensitive to amino acid substitutions, and that alterations in this residue can have deleterious effects on filament assembly and stability.
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a novel dinucleotide mutation in Keratin 10 in the annular epidermolytic ichthyosis variant of bullous congenital ichthyosiform erythroderma
Journal of Investigative Dermatology, 1997Co-Authors: Marcel Huber, Daniel Hohl, Mary A. Longley, Joseph A. Rothnagel, Gwangyeol Joh, Heiko Traupe, Dieter Metze, Dorothee Nashan, Dennis R RoopAbstract:Annular epidermolytic ichthyosis has recently been delineated as a distinct clinical phenotype within the spectrum of epidermolytic Keratinization disorders. The pattern of inheritance of the disorder is consistent with an autosomal dominant mode of transmission. Here we report a second incidence of this disorder in a family with two affected generations. The proband suffered from bullous ichthyosis and had bouts of disease activity associated with the development of numerous annular and polycyclic erythematous, hyperkeratotlc plaques on the trunk and the proximal extremities. Histologic examination showed the typical pathology of epidermolytic hyperkeratosis, and ultrastructural analysis revealed abnormal Keratin filament networks and tonofilament clumping with a perinuclear distribution. Molecular analysis revealed a novel tandem CG to GA 2-bp mutation in the same allele of Keratin 10 in affected individuals, resulting in an arginine to glutamate substitution at residue 83 (R83E) of the 2B helical segment. We conclude that annular epidermolytic ichthyosis should be considered a variant of bullous congenital ichthyosiform erythroderma.
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abnormal Keratin 1 and 10 cytoskeleton in cultured Keratinocytes from epidermolytic hyperkeratosis caused by Keratin 10 mutations
Journal of Investigative Dermatology, 1994Co-Authors: Marcel Huber, Dennis R Roop, Joseph A. Rothnagel, Corinne Scaletta, Messod Benathan, Edgar Frenk, David A Greenhalgh, Daniel HohlAbstract:Epidermolytic hyperkeratosis is caused by mutations of the differentiation-specific Keratins K1 and R10. These mutations produce a weakened cytoskeleton that is prone to collapse resulting in cell fragility and lysis. In this study we have analyzed cultured Keratinocytes from EHK patients bearing 10R-to-H and 15L-to-S mutations within the 1A segment of the K10 rod domain. Keratinocytes were grown submerged in serum-free medium and induced to differentiate by growing to confluence and increasing the Ca++ concentration in the medium. Cultures were either harvested for mRNA sequence analysis or subjected to immunofluorescence microscopy. Differentiating Keratinocytes from these patients were found to express these K10 mutations in their mRNA. Moreover, these cells could be distinguished from normal kerati- nocytes by their aberrrant morphology. EHK Keratinocytes frequently exhibited a collapsed perinuclear network of K1/ K10 filaments and sometimes peripheral granules of K1 and K10 aggregates, reminiscent of the cells of the suprabasal layers in these patients. This report documents the expression of mutant Keratin 10 in cultured EHK Keratinocytes.
Thomas M. Magin - One of the best experts on this subject based on the ideXlab platform.
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Loss of Keratin 10 is accompanied by increased sebocyte proliferation and differentiation.
European journal of cell biology, 2004Co-Authors: Julia Reichelt, Bernadette Breiden, Konrad Sandhoff, Thomas M. MaginAbstract:Summary Here, we present strong evidence that the targeted deletion of Keratin 10 (K10) alters sebocyte differentiation in mice, mediated by an increased proliferation and differentiation of cells located in the periphery of the glands. This was not accompanied by the induction of the proliferation-associated Keratins K6, K16 and K17. Sebaceous gland cells of K10−/− mice showed an accelerated turnover and secreted more sebum including wax esters, triglycerides, and cholesterol esters. The levels of the major epidermal lipids ceramides and cholesterol were also increased, whereas glycosylceramides and sphingomyelin were decreased which was not based on altered sphingolipid biosynthesis. The amount of Cer(OS), covalently bound to the cornified envelope, remained unchanged, as well as the amount of loricrin and involucrin. In agreement with the unaltered expression of β-catenin and its targets cyclin D1 and c-Myc, we conclude that the altered composition of the suprabasal intermediate filament cytoskeleton in K10−/− mice increased the differentiation of epidermal stem cells towards the sebocyte lineage.
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Loss of Keratin 10 Leads to Mitogen-activated Protein Kinase (MAPK) Activation, Increased Keratinocyte Turnover, and Decreased Tumor Formation in Mice
The Journal of investigative dermatology, 2004Co-Authors: Julia Reichelt, Gerhard Fürstenberger, Thomas M. MaginAbstract:Keratin 10 (K10) is the major protein in the upper epidermis where it maintains Keratinocyte integrity. Others have reported that K10 may act as a tumor suppressor upon ectopic expression in mice. Although K10 −/− mice show significant epidermal hyperproliferation, accompanied by an activation of the mitogen-activated protein kinase (MAPK) pathway, they formed no spontaneous tumors. Here, we report that K10 −/− mice treated with 7,12-dimethylbenz[ a ]anthracene (DMBA)/12- O -tetradecanoylphorbol-13-acetate (TPA) developed far less papillomas than wild-type mice. BrdU(5-bromo-2′-deoxyuridine)-labeling revealed a strongly accelerated Keratinocyte turnover in K10 −/− epidermis suggesting an increased elimination of initiated Keratinocytes at early stages of developing tumors. This is further supported by the absence of label-retaining cells 18 d after the pulse whereas in wild-type mice label-retaining cells were still present. The concomitant increase in K6, K16, and K17 in K10 null epidermis and the increased motility of Keratinocytes is in agreement with the pliability versus resilience hypothesis, stating that K10 and K1 render cells more stable and static. The K10 −/− knockout represent the first mouse model showing that loss of a Keratin, a cytoskeletal protein, reduces tumor formation. This is probably caused by an accelerated turnover of Keratinocytes, possibly mediated by activation of MAPK pathways.
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Hyperproliferation, induction of c-Myc and 14-3-3σ, but no cell fragility in Keratin-10-null mice
Journal of Cell Science, 2002Co-Authors: Julia Reichelt, Thomas M. MaginAbstract:In the past, Keratins have been established as structural proteins. Indeed, mutations in Keratin 10 (K10) and other epidermal Keratins lead to severe skin fragility syndromes. Here, we present adult K10-/- mice, which reveal a novel connection between the regulation of cell proliferation and K10. Unlike most Keratin mutant mice, the epidermis of adult K10-/- mice showed no cytolysis but displayed hyperproliferation of basal Keratinocytes and an increased cell size. BrdU labelling revealed a shortened transition time for Keratinocytes migrating outwards and DAPI staining of epidermal sheets uncovered an impaired organization of epidermal proliferation units. These remarkable changes were accompanied by the induction of c-Myc, cyclin D1, 14-3-3σ and of wound healing Keratins K6 and K16. The phosphorylation of Rb remained unaltered. In line with the downregulation of K10 in squamous cell carcinomas and its absence in proliferating cells in vivo, our data suggest that the tissue-restricted expression of some members of the Keratin gene family not only serves structural functions. Our results imply that the altered composition of the suprabasal cytoskeleton is able to alter the proliferation state of basal cells through the induction of c-Myc. A previous model based on transfection of K10 in immortalized human Keratinocytes suggested a direct involvement of K10 in cell cycle control. While those experiments were performed in human cultured Keratinocytes, our data establish, that in vivo, K10 acts by an indirect control mechanism in trans.
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Hyperproliferation, induction of c-Myc and 14-3-3sigma, but no cell fragility in Keratin-10-null mice.
Journal of cell science, 2002Co-Authors: Julia Reichelt, Thomas M. MaginAbstract:In the past, Keratins have been established as structural proteins. Indeed, mutations in Keratin 10 (K10) and other epidermal Keratins lead to severe skin fragility syndromes. Here, we present adult K10-/- mice, which reveal a novel connection between the regulation of cell proliferation and K10. Unlike most Keratin mutant mice, the epidermis of adult K10-/- mice showed no cytolysis but displayed hyperproliferation of basal Keratinocytes and an increased cell size. BrdU labelling revealed a shortened transition time for Keratinocytes migrating outwards and DAPI staining of epidermal sheets uncovered an impaired organization of epidermal proliferation units. These remarkable changes were accompanied by the induction of c-Myc, cyclin D1, 14-3-3sigma and of wound healing Keratins K6 and K16. The phosphorylation of Rb remained unaltered. In line with the downregulation of K10 in squamous cell carcinomas and its absence in proliferating cells in vivo, our data suggest that the tissue-restricted expression of some members of the Keratin gene family not only serves structural functions. Our results imply that the altered composition of the suprabasal cytoskeleton is able to alter the proliferation state of basal cells through the induction of c-Myc. A previous model based on transfection of K10 in immortalized human Keratinocytes suggested a direct involvement of K10 in cell cycle control. While those experiments were performed in human cultured Keratinocytes, our data establish, that in vivo, K10 acts by an indirect control mechanism in trans.
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normal ultrastructure but altered stratum corneum lipid and protein composition in a mouse model for epidermolytic hyperkeratosis
Journal of Investigative Dermatology, 1999Co-Authors: Julia Reichelt, Thomas M. Magin, Thomas Doering, Esther Schnetz, Manige Fartasch, Konrad SandhoffAbstract:Recently, we established Keratin 10-deficient mice, serving as a model for the hyperkeratotic skin disorder epidermolytic hyperkeratosis. The considerable ichthyosis in these mice suggested alterations in terminal differentiation and in the formation of a functional epidermal barrier. Here, we report on the ultrastructural organization and composition of the stratum corneum lipids and on the expression of two major cornified envelope proteins. Electron microscopy of ruthenium tetroxide postfixed skin samples demonstrated a normal extrusion and morphology of lamellar bodies as well as the formation of bona fide lamellar layers in neonatal Keratin 10-deficient mice. When we studied the composition of the major stratum corneum lipids, however, we found significant changes. Most importantly, the analysis of ceramide subpopulations revealed that the total amount of ceramide 2 was elevated in Keratin 10-deficient mice, whereas ceramides 1, 3, 4, and 5 were decreased among total stratum corneum lipids. The amount of the ceramide precursors sphingomyelin and glucosylceramide was reduced in the stratum corneum without accompanying changes in the mRNA coding for acid sphingomyelinase. Notably, we found an increased mRNA and protein content for involucrin in neonatal Keratin 10-deficient mice, whereas the expression of loricrin was not changed. Our data demonstrate that, although the formation of lipid layers in the stratum corneum appeared to be normal, its lipid composition is significantly altered in Keratin 10-deficient mice.
