Ingrid Hausser

Loss of Corneodesmosin Leads to Severe Skin Barrier Defect, Pruritus, and Atopy: Unraveling the Peeling Skin Disease

Generalized peeling skin disease is an autosomal-recessive ichthyosiform erythroderma characterized by lifelong patchy peeling of the skin. After genome-wide linkage analysis, we have identified a homozygous nonsense mutation in CDSN in a large consanguineous family with generalized peeling skin, pruritus, and food allergies, which leads to a complete loss of corneodesmosin. In contrast to hypotrichosis simplex, which can be associated with specific dominant CDSN mutations, peeling skin disease is characterized by a complete loss of CDSN expression. The skin phenotype is consistent with a recent murine Cdsn knockout model. Using three-dimensional human skin models, we demonstrate that lack of corneodesmosin causes an epidermal barrier defect supposed to account for the predisposition to atopic diseases, and we confirm the role of corneodesmosin as a decisive epidermal adhesion molecule. Therefore, peeling skin disease will represent a new model disorder for atopic diseases, similarly to Netherton syndrome and ichthyosis vulgaris in the recent past.

Lack of plakoglobin leads to lethal congenital epidermolysis bullosa: a novel clinico-genetic entity

Epidermal integrity is essential for skin functions. It is maintained by adhesive structures between keratinocytes, mainly the desmosomes and adherens junctions, which provide resistance against mechanical stress and regulate the formation of the skin barrier. As a constituent of both types of intercellular junctions, plakoglobin has multiple interaction partners and mutations in its gene [junction plakoglobin (JUP)] have been associated with mild cutaneous disease, palmoplantar keratoderma and arrhythmogenic heart disease. Here we report a novel lethal phenotype caused by a homozygous nonsense JUP mutation, c.1615C>T, p.Q539X, which is very different from any human or murine JUP phenotype described so far. The patient suffered from severe congenital skin fragility with generalized epidermolysis and massive transcutaneous fluid loss, but apparently no cardiac dysfunction. In contrast to previously reported JUP mutations where truncated proteins were still present, in this case there was complete loss of plakoglobin in the patients skin, as demonstrated by immunofluorescence and immunoblot analysis. As a consequence, only very few abnormal desmosomes were formed and no adhesion structures between keratinocytes were recognizable. The expression and distribution of desmosomal components was severely affected, suggesting an essential role for plakoglobin in desmosomal assembly. Adherens junction proteins were localized to keratinocyte plasma membrane, but did not provide proper cell-cell adhesion. This lethal congenital epidermolysis bullosa highlights the fundamental role of plakoglobin in epidermal cohesion.

Ichthyosis prematurity syndrome: Clinical evaluation of 17 families with a rare disorder of lipid metabolism

BACKGROUNDnIchthyosis prematurity syndrome (IPS) is classified as a syndromic congenital ichthyosis based on the presence of skin changes at birth, ultrastructural abnormalities in the epidermis, and extracutaneous manifestations. Recently, mutations in the fatty acid transporter protein 4 gene have been identified in patients with IPS.nnnOBJECTIVEnWe sought to perform a detailed clinical evaluation of patients with IPS identified in Norway.nnnMETHODSnClinical examination and follow-up of all patients (n = 23) and light and electron microscopic examination of skin biopsy specimens were performed.nnnRESULTSnIPS was characterized prenatally by ultrasound findings of polyhydramnios, separation of membranes, echogenic amniotic fluid, and clear chorionic fluid. All patients were born prematurely with sometimes life-threatening neonatal asphyxia; this was likely caused by aspiration of corneocyte-containing amniotic fluid as postmortem examination of lung tissue in two patients revealed keratin debris filling the bronchial tree and alveoli. The skin appeared erythrodermic, swollen, and covered by a greasy, thick vernix caseosa-like scale at birth, and evolved rapidly to a mild chronic ichthyosis. Many patients subsequently had chronic, severe pruritus. Histopathologic and ultrastructural examination of skin biopsy specimens showed hyperkeratosis, acanthosis, dermal inflammation, and characteristic aggregates of curved lamellar structures in the upper epidermis. Peripheral blood eosinophilia was invariably present and most patients had increased serum immunoglobulin E levels. Over 70% of the patients had a history of respiratory allergy and/or food allergy.nnnLIMITATIONSnThe study included only 23 patients because of the rarity of the disease.nnnCONCLUSIONnIPS is characterized by defined genetic mutations, typical ultrastructural skin abnormalities, and distinct prenatal and postnatal clinical features.

Long-Term Faithful Recapitulation of Transglutaminase 1–Deficient Lamellar Ichthyosis in a Skin-Humanized Mouse Model, and Insights from Proteomic Studies

Abbreviations: nCE, cornified envelope; DEJ, dermoepidermal junction; KPRP, keratinocyte proline-rich protein; LI, lamellar ichthyosis; NMF, natural moisturizing factor; TEWL, transepidermal water loss; TG1, transglutaminase 1

Molecular Consequences of the SERPINH1/HSP47 Mutation in the Dachshund Natural Model of Osteogenesis Imperfecta

Background: The collagen chaperone HSP47 is implicated in recessive osteogenesis imperfecta (OI). Results: In OI dachshunds, an HSP47(L326P) mutation affects the post-translational modification, secretion, and cross-linking of collagen type I. Conclusion: Impaired chaperone function, ER stress, and aberrant bone collagen cross-linking are implicated in the disease mechanism. Significance: Our findings are relevant for the diagnosis and pathological understanding of OI caused by an HSP47 defect. Osteogenesis imperfecta (OI) is a heritable connective tissue disease characterized by bone fragility and increased risk of fractures. Up to now, mutations in at least 18 genes have been associated with dominant and recessive forms of OI that affect the production or post-translational processing of procollagen or alter bone homeostasis. Among those, SERPINH1 encoding heat shock protein 47 (HSP47), a chaperone exclusive for collagen folding in the ER, was identified to cause a severe form of OI in dachshunds (L326P) as well as in humans (one single case with a L78P mutation). To elucidate the disease mechanism underlying OI in the dog model, we applied a range of biochemical assays to mutant and control skin fibroblasts as well as on bone samples. These experiments revealed that type I collagen synthesized by mutant cells had decreased electrophoretic mobility. Procollagen was retained intracellularly with concomitant dilation of ER cisternae and activation of the ER stress response markers GRP78 and phospho-eIF2α, thus suggesting a defect in procollagen processing. In line with the migration shift detected on SDS-PAGE of cell culture collagen, extracts of bone collagen from the OI dog showed a similar mobility shift, and on tandem mass spectrometry, the chains were post-translationally overmodified. The bone collagen had a higher content of pyridinoline than control dog bone. We conclude that the SERPINH1 mutation in this naturally occurring model of OI impairs how HSP47 acts as a chaperone in the ER. This results in abnormal post-translational modification and cross-linking of the bone collagen.

Molecular Consequences of Defective SERPINH1/HSP47 in the Dachshund Natural Model of Osteogenesis Imperfecta

Background: The collagen chaperone HSP47 is implicated in recessive osteogenesis imperfecta (OI). Results: In OI dachshunds, an HSP47(L326P) mutation affects the post-translational modification, secretion, and cross-linking of collagen type I. Conclusion: Impaired chaperone function, ER stress, and aberrant bone collagen cross-linking are implicated in the disease mechanism. Significance: Our findings are relevant for the diagnosis and pathological understanding of OI caused by an HSP47 defect. Osteogenesis imperfecta (OI) is a heritable connective tissue disease characterized by bone fragility and increased risk of fractures. Up to now, mutations in at least 18 genes have been associated with dominant and recessive forms of OI that affect the production or post-translational processing of procollagen or alter bone homeostasis. Among those, SERPINH1 encoding heat shock protein 47 (HSP47), a chaperone exclusive for collagen folding in the ER, was identified to cause a severe form of OI in dachshunds (L326P) as well as in humans (one single case with a L78P mutation). To elucidate the disease mechanism underlying OI in the dog model, we applied a range of biochemical assays to mutant and control skin fibroblasts as well as on bone samples. These experiments revealed that type I collagen synthesized by mutant cells had decreased electrophoretic mobility. Procollagen was retained intracellularly with concomitant dilation of ER cisternae and activation of the ER stress response markers GRP78 and phospho-eIF2α, thus suggesting a defect in procollagen processing. In line with the migration shift detected on SDS-PAGE of cell culture collagen, extracts of bone collagen from the OI dog showed a similar mobility shift, and on tandem mass spectrometry, the chains were post-translationally overmodified. The bone collagen had a higher content of pyridinoline than control dog bone. We conclude that the SERPINH1 mutation in this naturally occurring model of OI impairs how HSP47 acts as a chaperone in the ER. This results in abnormal post-translational modification and cross-linking of the bone collagen.

Congenital Ichthyosis in Severe Type II Gaucher Disease with a Homozygous Null Mutation

This paper describes a neonate with type II Gaucher disease. The phenotype was unusually severe with congenital ichthyosis, hepatosplenomegaly, muscular hypotonia, myoclonus and respiratory failure. Electron microscopy of the skin revealed lamellar body contents in the stratum corneum interstices, appearances considered to be typical of type II Gaucher disease. The baby died from respiratory failure 1 month postpartum having made no neurological progress. Molecular analysis identified a previously not reported homozygous null mutation, c.1505G→A of the β-glucocerebrosidase gene.

Mutations in SULT2B1 Cause Autosomal-Recessive Congenital Ichthyosis in Humans

Ichthyoses are a clinically and genetically heterogeneous group of genodermatoses associated with abnormal scaling of the skin over the whole body. Mutations in nine genes are known to cause non-syndromic forms of autosomal-recessive congenital ichthyosis (ARCI). However, not all genetic causes for ARCI have been discovered to date. Using whole-exome sequencing (WES) and multigene panel screening, we identified 6 ARCI-affected individuals from three unrelated families with mutations in Sulfotransferase family 2B memberxa01 (SULT2B1), showing their causative association with ARCI. Cytosolic sulfotransferases form a large family of enzymes that are involved in the synthesis and metabolism of several steroids in humans. We identified four distinct mutations including missense, nonsense, and splice site mutations. We demonstrated the loss of SULT2B1 expression at RNA and protein levels in keratinocytes from individuals with ARCI by functional analyses. Furthermore, we succeeded in reconstructing the morphologic skin alterations in a 3D organotypic tissue culture model with SULT2B1-deficient keratinocytes and fibroblasts. By thin layer chromatography (TLC) of extracts from these organotypic cultures, we could show the absence of cholesterol sulfate, the metabolite of SULT2B1, and an increased level of cholesterol, indicating a disturbed cholesterol metabolism of the skin upon loss-of-function mutation in SULT2B1. In conclusion, our study reveals an essential role for SULT2B1 in the proper development of healthy human skin. Mutation in SULT2B1 leads to an ARCI phenotype via increased proliferation of human keratinocytes, thickening of epithelial layers, and altered epidermal cholesterol metabolism.

Increased Prevalence of Filaggrin Deficiency in 51 Patients with Recessive X-Linked Ichthyosis Presenting for Dermatological Examination

Abstract X-linked ichthyosis (XLI) is a keratinization disorder caused by deficient activity of steroidsulfatase. In contrast, ichthyosis vulgaris is due to semidominant mutations of the filaggrin gene ( FLG ). In view of phenotypic variations of these ichthyoses we speculated that XLI may be influenced by additional FLG mutations in a significant number of patients. We characterized a group of 51 patients with XLI and systematically analyzed them for additional FLG mutations (R501X, 2282del4, R2447X, S3247X). The study was complemented by morphological analyses. Full FLG sequencing for rare mutations was performed in special cases. Interestingly, prevalence of FLG mutations was significantly increased compared to a population-based control cohort of 1,377 individuals (17.6% vs. 8.4%, p=0.038). Palmoplantar hyperlinearity was significantly associated with the FLG mutation status. Ichthyosis severity score seemed to be increased in XLI with FLG mutations, but the difference was not significant (p=0.124). To our surprise, percentages of atopic manifestations were highly prevalent in both subgroups, 40% and 33% in XLI without and with filaggrin deficiency, respectively. Of note, reduction of filaggrin staining or keratohyalin could not be explained by FLG mutations in all patients. However, we conclude that FLG mutations represent a significant genetic modifier of XLI. [196 words]

Early venous manifestation of Ehlers-Danlos syndrome Type IV through a novel mutation in COL3A1.

Ehlers-Danlos syndrome (EDS) leads to abnormalities in the synthesis of collagen and complications involving arterial vessels. We describe here a mutation in the intron 14 of the COL3A1 gene leading to EDS Type IV (EDS IV) associated with venous manifestations only. The patient, an 18-year-old male, suffered from truncal varicosity of the long saphenous vein on both sides. Conventional stripping surgery of the left saphenous vein revealed an extremely vulnerable ectatic superficial femoral vein. An inserted vein graft occluded, and venous thrombectomy was unsuccessful. A conservative anticoagulant and compression therapy finally succeeded. This is the first report describing EDS IV due to a mutation in intron 14 of the COL3A1 gene leading to venous manifestations without affecting arterial vessels at clinical presentation. Our findings imply that molecular genetic analysis should be considered in patients with unusual clinical presentation and that conservative therapy should be applied until a suspected clinical diagnosis has been secured.