Molecular complexity of the cutaneous basement membrane zone

Basement Membranes, Brittlestar Tendons, and Their Mechanical Adaptability

Basement membranes (BMs) are thin layers of extracellular matrix that separate epithelia, endothelia, muscle cells, and nerve cells from adjacent interstitial connective tissue. BMs are ubiquitous in almost all multicellular animals, and their composition is highly conserved across the Metazoa. There is increasing interest in the mechanical functioning of BMs, including the involvement of altered BM stiffness in development and pathology, particularly cancer metastasis, which can be facilitated by BM destabilization. Such BM weakening has been assumed to occur primarily through enzymatic degradation by matrix metalloproteinases. However, emerging evidence indicates that non-enzymatic mechanisms may also contribute. In brittlestars (Echinodermata, Ophiuroidea), the tendons linking the musculature to the endoskeleton consist of extensions of muscle cell BMs. During the process of brittlestar autotomy, in which arms are detached for the purpose of self-defense, muscles break away from the endoskeleton as a consequence of the rapid destabilization and rupture of their BM-derived tendons. This contribution provides a broad overview of current knowledge of the structural organization and biomechanics of non-echinoderm BMs, compares this with the equivalent information on brittlestar tendons, and discusses the possible relationship between the weakening phenomena exhibited by BMs and brittlestar tendons, and the potential translational value of the latter as a model system of BM destabilization.

High Strength and High Toughness Electrospun Multifibrillar Yarns with Highly Aligned Hierarchy Intended as Anisotropic Extracellular Matrix

Electrospun nanofibers can be effectively used as a surrogate for extracellular matrices (ECMs). However, in the context of cellular mechanobiology, their mechanical performances can be enhanced by using nanofibrous materials with a high level of structural organization. Herein, this work develops multifibrillar yarns with superior mechanical performance based on biocompatible polyacrylonitrile (PAN) as surrogate ECM. Nearly perfect aligned nanofibers along with the axis of the multifibrillar yarn are prepared. These highly aligned yarns exhibit high strength, high toughness, good stress relaxation behavior, and are robust enough for technical or medical applications. Further, this work analyzes the influence of the highly aligned-hierarchical topological structure of the material on cell proliferation and cell orientation using cells derived from epithelial and connective tissues. Compared to nonoriented electrospun multifibrillar yarns and flat films, the well-ordered topology in the electrospun PAN multifibrillar yarns triggers an improved proliferation of fibroblasts and epithelial cells. Fibroblasts acquire an elongated morphology analogous to their behavior in the natural ECM. Hence, this heterogeneous multifibrillar material can be used to restore or reproduce the ECM for tissue engineering applications, notably in the skeletal muscle and tendon.

Molecular Crosstalk between the Hepatitis C Virus and the Extracellular Matrix in Liver Fibrogenesis and Early Carcinogenesis

Simple Summary

In the era of direct-acting antivirals against the hepatitis C virus (HCV), curing chronic hepatitis C has become a reality. However, while replicating chronically, HCV creates a peculiar state of inflammation and oxidative stress in the infected liver, which fuels DNA damage at the onset of HCV-induced hepatocellular carcinoma (HCC). This cancer, the second leading cause of death by cancer, remains of bad prognosis when diagnosed. This review aims to decipher how HCV durably alters elements of the extracellular matrix that compose the liver microenvironment, directly through its viral proteins or indirectly through the induction of cytokine secretion, thereby leading to liver fibrosis, cirrhosis, and, ultimately, HCC.

Abstract

Chronic infection by the hepatitis C virus (HCV) is a major cause of liver diseases, predisposing to fibrosis and hepatocellular carcinoma. Liver fibrosis is characterized by an overly abundant accumulation of components of the hepatic extracellular matrix, such as collagen and elastin, with consequences on the properties of this microenvironment and cancer initiation and growth. This review will provide an update on mechanistic concepts of HCV-related liver fibrosis/cirrhosis and early stages of carcinogenesis, with a dissection of the molecular details of the crosstalk during disease progression between hepatocytes, the extracellular matrix, and hepatic stellate cells.

Localization of Integrin Beta-4 Subunit at Soft Tissue-Titanium or Zirconia Interface

Currently, along with titanium (Ti), zirconia is widely used as an abutment material for dental implants because it makes it possible to avoid gingival discoloration; however, the epithelial sealing capability of zirconia remains unknown. The purpose of the present study is to elucidate the localization of integrin β4 subunit (Inβ4), one of the main proteins in the attachment structure between gingival junctional epithelial (JE) cells and substrata. Maxillary first molars were extracted from rats, and implants were placed with Ti or zirconia transgingival parts; then, the localization of Inβ4 was observed. Morphological and functional changes in rat oral epithelial cells (OECs) cultured on a culture dish (Dish) and Ti and zirconia plates were also evaluated with Inβ4 immunofluorescence histochemistry and Western blotting. After four weeks of implant placement, the morphology of the peri-implant epithelium (PIE) and the localization of Inβ4 around the Ti and zirconia transgingival parts were similar. However, both exhibited markedly shorter Inβ4-positive bands in the PIE than in the JE around natural teeth. Decreased expression levels of Inβ4 were observed in OECs cultured on Ti and zirconia plates compared with those cultured on Dish. In conclusion, although inferior to natural teeth, zirconia implants are thought to have epithelial sealing properties comparable to those of titanium.

Autoantibodies to BPAG1e Trigger Experimental Bullous Pemphigoid in Mice

Bullous pemphigoid (BP) is an autoimmune blistering disease that targets the hemidesmosomal proteins BP180 and BP230/BPAG1e. Whereas the role of anti-BP180 antibodies has been extensively characterized, the pathogenicity of anti-BPAG1e antibodies remains unclear. The purpose of this study is to elucidate the role of antibodies to BPAG1e in the experimental bullous pemphigoid models. We generated Bpag1 conditional knockout mice, where the knockout of Bpag1 is restricted to keratin 5-expressing epithelial cells. Bpag1 conditional knockout mice were immunized with the C-terminal portion of BPAG1e, and the splenocytes were injected into Rag2^-/- mice intravenously. The recipient mice presented with erosion on the feet and tails. Microscopic examination showed subepidermal blisters and a linear deposition of IgG at the dermal-epidermal junction. To assess the potential role of trauma on BP development, we inflicted surface wounds on the dorsum of the Rag2^-/- recipient mice after adoptive transfer. The wounded Rag2^-/- mice had increased morbidity and severity of BP-like symptoms. Moreover, the depletion of B cells from splenocytes abolished a subepidermal blistering phenotype in vivo. These findings demonstrate that antibodies to BPAG1e might play a pathogenic role in causing subepidermal blistering, and external factors, including trauma, might be a trigger for BP development.

Expression of Laminin γ2 Proteolytic Fragments in Murine Skin Following Exposure to Sulfur Mustard

Laminin-332 is a basement membrane protein composed of three genetically distinct polypeptide chains that actively promote both skin epidermal cell adhesion and migration. Proteolytic fragments of the laminin γ2 chain stimulate migration and scattering of keratinocytes and cancer cells. Sulfur mustard (SM) is a bifunctional alkylating agent that induces separation of basal keratinocytes from the dermal-epidermal junction and invokes a strong inflammatory response leading to delayed wound repair. In the present studies, the role of laminin γ2 in SM-induced skin injury and wound repair was investigated using the mouse ear vesicant model. We found that laminin γ2 chain mRNA was preferentially upregulated in mouse ear skin exposed to SM. In situ hybridization confirmed overexpression of laminin γ2 transcript. Western blot analysis showed increased protein expression of the full-length proform of laminin γ2 and smaller processed fragments of laminin γ2 in skin exposed to SM. Dual immunofluorescence labeling indicated that laminin γ2 fragments are prevalent in suprabasal keratinocytes behind the leading edge in areas of hyperplasia in injured skin. In addition, co-expression of laminin γ2 and the senescent marker, p16^-INK4a was found to overlap with the hyperplastic migratory epithelial sheet. This observation is similar to hypermotile keratinocytes reported in invasive carcinoma cells. Overall, our studies indicate that laminin γ2 is preferentially expressed in skin post SM exposure and that protein expression appears to become progressively more fragmented. The laminin γ2 fragments may play a role in regulating SM-induced skin wound repair. Anat Rec, 2020. © 2020 American Association for Anatomy.

Identification of novel enriched recurrent chimeric COL7A1-UCN2 in human laryngeal cancer samples using deep sequencing

BACKGROUND

As hybrid RNAs, transcription-induced chimeras (TICs) may have tumor-promoting properties, and some specific chimeras have become important diagnostic markers and therapeutic targets for cancer.

METHODS

We examined 23 paired laryngeal cancer (LC) tissues and adjacent normal mucous membrane tissue samples (ANMMTs). Three of these pairs were used for comparative transcriptomic analysis using high-throughput sequencing. Furthermore, we used real-time polymerase chain reaction (RT-PCR) for further validation in 20 samples. The Kaplan-Meier method and Cox regression model were used for the survival analysis.

RESULTS

We identified 87 tumor-related TICs and found that COL7A1-UCN2 had the highest frequency in LC tissues (13/23; 56.5%), whereas none of the ANMMTs were positive (0/23; p < 0.0001). COL7A1-UCN2, generated via alternative splicing in LC tissue cancer cells, had disrupted coding regions, but it down-regulated the mRNA expression of COL7A1 and UCN2. Both COL7A1 and UCN2 were down-expressed in LC tissues as compared to their paired ANMMTs. The COL7A1:β-actin ratio in COL7A1-UCN2-positive LC samples was significantly lower than that in COL7A1-UCN2-negative samples (p = 0.019). Likewise, the UCN2:β-actin ratio was also decreased (p = 0.21). Furthermore, COL7A1-UCN2 positivity was significantly associated with the overall survival of LC patients (p = 0.032; HR, 13.2 [95%CI, 1.2-149.5]).

CONCLUSION

LC cells were enriched in the recurrent chimera COL7A1-UCN2, which potentially affected cancer stem cell transition, promoted epithelial-mesenchymal transition in LC, and resulted in poorer prognoses.

Revertant mosaicism in genodermatoses

Inherited monogenic skin disorders include blistering disorders, inflammatory disorders, and disorders of differentiation or development. In most cases, the skin is broadly involved throughout the affected individual's lifetime, but rarely, appearance of normal skin clones has been described. In these cases of revertant mosaicism, cells undergo spontaneous correction to ameliorate the effects of genetic mutation. While targeted reversion of genetic mutation would have tremendous therapeutic value, the mechanisms of reversion in the skin are poorly understood. In this review, we provide an overview of genodermatoses that demonstrate widespread reversion and their corrective mechanisms, as well as the current research aimed to understand this "natural gene therapy".

Efficient in vivo gene editing using ribonucleoproteins in skin stem cells of recessive dystrophic epidermolysis bullosa mouse model

The prokaryotic CRISPR/Cas9 system has recently emerged as a powerful tool for genome editing in mammalian cells with the potential to bring curative therapies to patients with genetic diseases. However, efficient in vivo delivery of this genome editing machinery and indeed the very feasibility of using these techniques in vivo remain challenging for most tissue types. Here, we show that nonreplicable Cas9/sgRNA ribonucleoproteins can be used to correct genetic defects in skin stem cells of postnatal recessive dystrophic epidermolysis bullosa (RDEB) mice. We developed a method to locally deliver Cas9/sgRNA ribonucleoproteins into the skin of postnatal mice. This method results in rapid gene editing in epidermal stem cells. Using this method, we show that Cas9/sgRNA ribonucleoproteins efficiently excise exon80, which covers the point mutation in our RDEB mouse model, and thus restores the correct localization of the collagen VII protein in vivo. The skin blistering phenotype is also significantly ameliorated after treatment. This study provides an in vivo gene correction strategy using ribonucleoproteins as curative treatment for genetic diseases in skin and potentially in other somatic tissues.

Gene therapy for skin diseases

The skin possesses qualities that make it desirable for gene therapy, and studies have focused on gene therapy for multiple cutaneous diseases. Gene therapy uses a vector to introduce genetic material into cells to alter gene expression, negating a pathological process. This can be accomplished with a variety of viral vectors or nonviral administrations. Although results are promising, there are several potential pitfalls that must be addressed to improve the safety profile to make gene therapy widely available clinically.

Dermal templates and the wound-healing paradigm: the promise of tissue regeneration

Dermal regeneration templates arguably represent the first and most clinically successful 'tissue engineering' solution designed for organ reconstruction. Wound healing in the skin normally occurs on a continuum. At one extreme of the continuum lies the promise of tissue regeneration and the complete restoration of normal structure and function. Unfortunately, in the adult, all too often, wound healing occurs at the other extreme of the continuum and the dermis is reconstituted as scar tissue. Dermal regeneration templates are designed to manage the wound-healing process and tip the scales toward regeneration. This review discusses the architecture and molecular composition of the skin and the events that mediate wound healing and scar formation. The development, evolution and commercialization of dermal templates are examined and the clinical and business considerations that drive the product-development cycle are discussed. In the near term, dermal templates cannot be expected to dramatically change in overall composition. Product development will be dominated by continued refinements of existing templates and the field of use will continue to expand as manufacturers seek to increase revenue and capture market share. Continued exploration of novel processing strategies, such as electrospinning, that can be used to fabricate nanoscale biomaterials, may provide a gateway to the next generation of dermal templates.

The corneal epithelial basement membrane: structure, function, and disease

The corneal epithelial basement membrane (BM) is positioned between basal epithelial cells and the stroma. This highly specialized extracellular matrix functions not only to anchor epithelial cells to the stroma and provide scaffolding during embryonic development but also during migration, differentiation, and maintenance of the differentiated epithelial phenotype. Basement membranes are composed of a diverse assemblage of extracellular molecules, some of which are likely specific to the tissue where they function; but in general they are composed of four primary components--collagens, laminins, heparan sulfate proteoglycans, and nidogens--in addition to other components such as thrombospondin-1, matrilin-2, and matrilin-4 and even fibronectin in some BM. Many studies have focused on characterizing BM due to their potential roles in normal tissue function and disease, and these structures have been well characterized in many tissues. Comparatively few studies, however, have focused on the function of the epithelial BM in corneal physiology. Since the normal corneal stroma is avascular and has relatively low keratocyte density, it is expected that the corneal BM would be different from the BM in other tissues. One function that appears critical in homeostasis and wound healing is the barrier function to penetration of cytokines from the epithelium to stroma (such as transforming growth factor β-1), and possibly from stroma to epithelium (such as keratinocyte growth factor). The corneal epithelial BM is also involved in many inherited and acquired corneal diseases. This review examines this structure in detail and discusses the importance of corneal epithelial BM in homeostasis, wound healing, and disease.

Hypodermal delivery of cosmetic actives for improved facial skin morphology and functionality

OBJECTIVE

Skin compartments traditionally targeted by cosmetic actives - epidermis and dermis - are anchored and nourished by the underlying hypodermis, which therefore should be a key target for skin-rejuvenating formulations. However, given the difficulty to reach even the superficial layers of the skin, and to its 'unglamorous' fatty composition, the regenerative potential of hypodermis remains largely untapped. Therefore, this study was to investigate the capacity of a cosmetic material to trigger a regenerative response in dermis and epidermis through a selective action on hypodermis. Furthermore, it aimed to establish the effect of such cosmetic material in transbuccal hypodermal delivery form, on the hypodermal precursor cells - the preadipocytes.

METHODS

A combination of grape seed extract and soy phospholipids was formulated and standardized for elastase activity and free radical inhibition. This formulation was then used to contact the hypodermal layer of human skin biopsies and - under a transbuccal delivery vehicle form - the 3T3-L1 preadipocytes, and its effects were quantified using PCR arrays and histochemistry.

RESULTS

Application of the standardized grape/soy material to the hypodermal layer of skin triggered modulation of gene expression in the upper layers of the skin and resulted in the clear morphological improvement at the dermal and epidermal levels. Furthermore, when this material was formulated in a mucoadhesive, intraoral film and applied on 3T3-L1 preadipocytes, the resulting modulation of gene expression in these cells was consistent with differentiation and detoxification effects.

CONCLUSIONS

These results suggest that transbuccal formulations of nutraceutical grade cosmetics have potential to induce signal transduction pathways in facial hypodermis, resulting in anti-aging effects throughout all skin compartments, including dermal and epidermal layers.

Effect of electrospun non-woven mats of dibutyryl chitin/poly(lactic acid) blends on wound healing in hairless mice

The aim of this study was to examine the proliferative ability of dibutyryl chitin (DBC) on scratch wounds in HaCaT keratinocytes and to evaluate the effect of nanoporous non-woven mat (DBCNFM) on skin wound healing in hairless mice using the advantages of DBCNFM, such as high porosity and high surface area to volume. The cell spreading activity of DBC was verified through a cell spreading assay in scratched human HaCaT keratinocytes. Scratch wound experiments showed that DBC notably accelerates the spreading rate of HaCaT keratinocytes in a dose dependent manner. The molecular aspects of the healing process were also investigated by hematoxylin & eosin staining of the healed skin, displaying the degrees of reepithelialization and immunostaining on extracellular matrix synthesis and remodeling of the skin. Topical application of DBCNFM significantly reduced skin wound rank scores and increased the skin remodeling of the wounded hairless mice in a dose dependent way. Furthermore, DBCNFM notably increased the expression of the type 1 collagen and filaggrin. These results demonstrate that DBC efficiently accelerates the proliferation of HaCaT keratinocytes and DBCNFM notably increases extracellular matrix synthesis on remodeling of the skin, and these materials are a good candidate for further evaluation as an effective wound healing agent.

Long-term type VII collagen restoration to human epidermolysis bullosa skin tissue

In spite of advances in the molecular diagnosis of recessive dystrophic epidermolysis bullosa (RDEB), an inherited blistering disease due to a deficiency of type VII collagen at the basement membrane zone (BMZ) of stratified epithelium, current therapy is limited to supportive palliation. Gene delivery has shown promise in short-term experiments; however, its long-term sustainability through multiple turnover cycles in human tissue has awaited confirmation. To characterize approaches for long-term genetic correction, retroviral vectors were constructed containing long terminal repeat-driven full-length and epitope-tagged COL7A1 cDNA and evaluated for durability of type VII collagen expression and function in RDEB skin tissue regenerated on immune-deficient mice. Type VII collagen expression was maintained for 1 year in vivo, or over 12 epidermal turnover cycles, with no abnormalities in skin morphology or self-renewal. Type VII collagen restoration led to correction of RDEB disease features, including reestablishment of anchoring fibrils at the BMZ. This approach confirms durably corrective and noninjurious gene delivery to long-lived epidermal progenitors and provides the foundation for a human clinical trial of ex vivo gene delivery in RDEB.

Autoimmune oral mucosal diseases: clinical, etiologic, diagnostic, and treatment considerations

This article discusses the classic autoimmune diseases: pemphigus vulgaris, mucosal pemphigoid, and oral lichen planus. These are generally considered of autoimmune origin or, at a minimum, immune system mediated. Cause, diagnosis, and treatment are discussed. As management of these diseases progresses, continued advances in molecular pathogenesis will allow insight into which strategies can be employed in interfering with the complex cascade of events leading to mucosal impairment and clinical morbidity.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

Collagens

The collagens represent a family of trimeric extracellular matrix molecules used by cells for structural integrity and other functions. The three alpha chains that form the triple helical part of the molecule are composed of repeating peptide triplets of glycine-X-Y. X and Y can be any amino acid but are often proline and hydroxyproline, respectively. Flanking the triple helical regions (i.e., Col domains) are non-glycine-X-Y regions, termed non-collagenous domains. These frequently contain recognizable peptide modules found in other matrix molecules. Proper tissue function depends on correctly assembled molecular aggregates being incorporated into the matrix. This review highlights some of the structural characteristics of collagen types I-XXVIII.

The non-human primate as a model for studying COPD and asthma

This review evaluates the current status of information regarding the nonhuman primate as an experimental model for defining mechanisms of chronic airways disease in humans, using the concept of the epithelial-mesenchymal trophic unit (EMTU) as a basis for comparison with other laboratory species. All of the cellular and acellular compartments within the walls of tracheobronchial airways which interact as the EMTU are present throughout the airway tree in human and nonhuman primates. The epithelial compartment contains mucous goblet and basal cells in the surface epithelium and submucosal glands within the wall. The interstitial compartment of primates has a prominent subepithelial basement membrane zone (BMZ) with an attenuated fibroblast sheath and cartilage throughout the tree. In primates, there is an extensive transition zone between distal conducting airways and lung parenchyma composed of numerous generations of respiratory bronchioles. None of these features are characteristic of intrapulmonary airways in rodents, whose airways do share ciliated cells, smooth muscle cells, nerve networks, vasculature and inflammatory cell populations with primates. While the numbers of intrapulmonary airway branches are similar for most mammals, branching patterns, which dictate distribution of inhaled materials, are more uniform (dichotomous) in primates and less so (monopodial) in rodents. Development of tracheobronchial airways (both differentiation of the EMTU and overall growth) occurs over an extensive postnatal period (months to years) in primates and a comparably shorter time period (2-3 weeks) in rodents. As with allergic airways disease in humans, experimental exposure of nonhuman primates to a known human allergen, house dust mite, produces extensive remodeling of all compartments of the EMTU: mucous goblet cell hyperplasia, epithelial sloughing, basement membrane zone (BMZ) thickening and reorganization, altered attenuated fibroblast function, subepithelial fibrosis and smooth muscle thickening. Experimental allergic airways disease in nonhuman primates also shares other features with asthmatic humans: positive skin test to allergen; allergen-specific circulating IgE; airway hyper responsiveness to allergen, histamine and methacholine; increased eosinophils, IGE positive cells and mucins in airway exudate; and migratory leukocyte accumulations in the airway wall and lumen. Experimental exposure of nonhuman primates to reactive gases, such as ozone, produces the chronic respiratory bronchiolitis and other airway alterations associated with restricted airflow and chronic respiratory bronchiolitis characteristic of COPD in young smokers. We conclude that nonhuman primate models are appropriate for defining mechanisms as they relate to allergic airways disease and COPD in humans.

Zebrafish Hoxb1a regulates multiple downstream genes including prickle1b

Despite 30 years of Hox gene study, we have a remarkably limited knowledge of the downstream target genes that Hox transcription factors regulate to confer regional identity. Here, we have used a microarray approach to identify genes that function downstream of a single vertebrate Hox gene, zebrafish hoxb1a. This gene plays a critical and conserved role in vertebrate hindbrain development, conferring identity to hindbrain rhombomere (r) 4. For example, zebrafish Hoxb1a, similar to mouse Hoxb1, is required for the migration of r4-derived facial branchiomotor neurons into the posterior hindbrain. We have screened microarrays carrying more than 16,000 expressed sequence tags (ESTs) for genes that are differentially regulated in normal versus Hoxb1a-deficient r4 tissue. Using this approach, we have identified both positively and negatively regulated candidate Hoxb1a target genes. We have used in situ hybridization to validate twelve positively regulated Hoxb1a targets. These downstream targets are expressed in a variety of subdomains within r4, with one gene, a novel prickle homolog (pk1b), expressed specifically within the facial branchiomotor neurons. Using morpholino knock-down and cell transplantation, we demonstrate that the Hoxb1a target Prickle1b functions cell-autonomously to control facial neuron migration, a single aspect of r4 identity.

High-affinity binding of the NC1 domain of collagen VII to laminin 5 and collagen IV

Anchoring functions of collagen VII depend on its ability to form homotypic fibrils and to bind to other macromolecules to form heterotypic complexes. Biosensor-based binding assays were employed to analyze the kinetics of the NC1 domain-mediated binding of collagen VII to laminin 5, collagen IV, and collagen I. We showed that collagen VII interacts with laminin 5 and collagen IV with a Kd value of 10(-9) M. In contrast, the NC1-mediated binding to collagen I was weak with a Kd value of 10(-6) M. Binding assays also showed that the NC1 domain utilizes the same region to bind to both laminin 5 and collagen IV. We postulate that the ability of the NC1 domains to bind with high affinities to laminin 5 and collagen IV facilitates stabilization of the structure of the basement membrane itself and that the NC1-collagen I interaction may be less important for stabilization of the dermal-epidermal junction.

Plectin regulates the organization of glial fibrillary acidic protein in Alexander disease

Alexander disease (AxD) is a rare but fatal neurological disorder caused by mutations in the astrocyte-specific intermediate filament protein glial fibrillary acidic protein (GFAP). Histologically, AxD is characterized by cytoplasmic inclusion bodies called Rosenthal fibers (RFs), which contain GFAP, small heat shock proteins, and other undefined components. Here, we describe the expression of the cytoskeletal linker protein plectin in the AxD brain. RFs displayed positive immunostaining for plectin and GFAP, both of which were increased in the AxD brain. Co-localization, co-immunoprecipitation, and in vitro overlay analyses demonstrated direct interaction of plectin and GFAP. GFAP with the most common AxD mutation, R239C (RC GFAP), mainly formed abnormal aggregates in human primary astrocytes and murine plectin-deficient fibroblasts. Transient transfection of full-length plectin cDNA converted these aggregates to thin filaments, which exhibited diffuse cytoplasmic distribution. Compared to wild-type GFAP expression, RC GFAP expression lowered plectin levels in astrocytoma-derived stable transfectants and plectin-positive fibroblasts. A much higher proportion of total GFAP was found in the Triton X-insoluble fraction of plectin-deficient fibroblasts than in wild-type fibroblasts. Taken together, our results suggest that insufficient amounts of plectin, due to RC GFAP expression, promote GFAP aggregation and RF formation in AxD.

Number 1Epithelial biology

The oral mucous membrane has features similar to skin but also differs in several ways. This paper reviews the aspects of epithelial biology necessary for an understanding of the vesiculoerosive disorders.

Microarray assessment of fibronectin, collagen and integrin expression and the role of fibronectin-collagen coating in the growth of normal, SV40 T-antigen-immortalised and malignant human oral keratinocytes

Extracellular matrix proteins affect the growth and survival of epithelial tissues. Accordingly, surface coating with fibronectin and collagen is a common practice for promoting keratinocyte culture. In this study, the expression of fibronectin and collagen-related factors, including integrins, by normal (NOK), SV40 T-antigen-immortalised (SVpgC2a) and malignant (SqCC/Y1) human oral keratinocytes, under standardised, serum-free conditions, was investigated by using microarray analysis. Cell growth was also studied in the presence and absence of a matrix consisting of human fibronectin and bovine collagen type I (FN-COL). Fibronectin transcripts were abundant in all cells, whereas 16 of 29 collagen chains and 14 of 24 integrin subunits were variably detected. With regard to both the expression level and the number of transcripts, higher collagen and lower integrin expression was observed in SVpgC2a cells than in NOKs and SqCC/Y1 cells. The cell types differed with regard to colony-forming efficiency and the rate and kinetics of growth at high cell density. For all cell types, FN-COL coating consistently stimulated cell migration, without influencing growth in mass culture or clonal density. The results demonstrate the transcription of genes associated with the formation and function of fibronectin and collagen in oral epithelium, and variably altered expression patterns in transformed states, and show that keratinocyte lines can be successfully transferred without the stimulus from extracellular FN-COL.

Diffusible factors released by fibroblasts support epidermal morphogenesis and deposition of basement membrane components

Epithelial-mesenchymal interactions play an important role in controlling epidermal morphogenesis and homeostasis but little is known about the mechanisms of these interactions. To examine whether diffusible factors produced by fibroblasts and/or keratinocytes support epidermal morphogenesis and basement membrane formation, organotypic keratinocyte monocultures were established in media collected either from organotypic fibroblast or keratinocyte-monocultures or from keratinocyte-fibroblast cocultures, and the expression of keratin 10, 16, and 17 and basement membrane components (types IV and VII collagen, laminin 5, nidogen, BP 180, LAD-1) were examined. We found that diffusible factors released by keratinocytes were not sufficient to support the establishment of normalized epidermal phenotype and deposition of basement membrane components in contrast to fibroblast- or keratinocyte/fibroblast-derived factors. Keratinocytes appear to affect the spectrum of secreted soluble factors, as keratinocyte/fibroblast-derived factors were more effective to accomplish continuous linear deposition of laminin 5 and of nidogen. The finding that released amounts of keratinocyte growth factor and granulocyte macrophage colony stimulating factor were not sufficient to fully support epidermal morphogenesis and deposition of basement membrane components is suggestive for the involvement of other released diffusible factors. Generation of organotypic keratinocyte monocultures in the presence of fibroblast- or keratinocyte/fibroblast-derived soluble factors resulted in enhanced expression of keratins K16 and K17 and the absence of type IV collagen. This observation indicates that next to paracrine acting factors, epidermal homeostasis is controlled by mutual keratinocyte-fibroblast interaction.

Opposite Smad and chicken ovalbumin upstream promoter transcription factor inputs in the regulation of the collagen VII gene promoter by transforming growth factor-beta

A critical component of the epidermal basement membrane, collagen type VII, is produced by keratinocytes and fibroblasts, and its production is stimulated by the cytokine transforming growth factor-beta (TGF-beta). The gene, COL7A1, is activated by TGF-beta via Smad transcription factors in cooperation with AP1. Here we report a previously unsuspected level of complexity in this regulatory process. We provide evidence that TGF-beta may activate the COL7A1 promoter by two distinct inputs operating through a common region of the promoter. One input is provided by TGF-beta-induced Smad complexes via two Smad binding elements that function redundantly depending on the cell type. The second input is provided by relieving the COL7A1 promoter from chicken ovalbumin upstream promoter transcription factor (COUP-TF)-mediated transcriptional repression. We identified COUP-TFI and -TFII as factors that bind to the TGF-beta-responsive region of the COL7A1 promoter in an expression library screening. COUP-TFs bind to a site between the two Smad binding elements independently of Smad or AP1 and repress the basal and TGF-beta-stimulated activities of this promoter. We provide evidence that endogenous COUP-TF activity represses the COL7A1 promoter. Furthermore, we show that TGF-beta addition causes a rapid and profound down-regulation of COUP-TF expression in keratinocytes and fibroblasts. The results suggest that TGF-beta signaling may exert tight control over COL7A1 by offsetting the balance between opposing Smad and COUP-TFs.

Proteolytic processing of laminin-5 by MT1-MMP in tissues and its effects on epithelial cell morphology

The extracellular matrix macromolecule laminin-5 (Ln-5) is converted by matrix metalloproteinases (MMP) MT1-MMP and MMP-2 into a migration-promoting substrate in vitro. We now report that cleavage of Ln-5 by MT1-MMP occurs in vivo and affects epithelial tissue organization and probably Ln-5 turnover. In MT1-MMP knockout (KO) mice, the kidneys showed increased levels of total Ln-5 gamma2 subunit, but significantly reduced amounts of gamma2', an amino-terminal truncated proteolytic form of gamma2. The kidney tubular epithelia of KO animals were poorly differentiated, a phenotype reminiscent of human congenital mixed hypoplastic/dysplastic disorders. To establish a better link between Ln-5 proteolytic cleavage and epithelial morphology, MT1-MMP expression was reconstituted by transfection of MT1-MMP into a Ln-5 positive, MT1-MMP deficient epithelial cell line. MT1-MMP transfectants demonstrated increased levels of processed Ln-5 gamma2 chain and enhanced spreading on Ln-5, but not fibronectin. Recombinant MT1-MMP cleaved gamma2 constructs in vitro at a known in vivo gamma2 gamma2' processing site. These results strongly indicate that Ln-5 is a physiological substrate of MT1-MMP in vivo. Proteolytic processing of gamma2 subunit by MT1-MMP may influence Ln-5 turnover in epithelial basement membranes and affect epithelial morphogenesis.

Transcriptional Control of the Mouse Col7a1 Gene in Keratinocytes: Basal and Transforming Growth Factor-β Regulated Expression

Anchoring fibrils at the cutaneous basement membrane zone of the stratified squamous epithelia are essential to maintaining skin integrity, as absence of these structures leads to the chronic blistering disease, dystrophic epidermolysis bullosa. Type VII collagen, the major component of anchoring fibrils, is synthesized primarily by basal keratinocytes and to a lesser degree by dermal fibroblasts. To elucidate the transcriptional control elements of the type VII collagen gene (Col7a1), 3 kb of 5' flanking sequence of the mouse gene was cloned, sequenced, and fused to the chloramphenicol acetyltransferase reporter gene. Promoter deletion analyses revealed that 560 bp of Col7a1 5' flanking sequence was sufficient and necessary for basal level of transcription in cultured murine keratinocytes. Mutagenesis of DNA sequences with similarity to consensus binding sites for transcription factors, including Sp1/Sp3, AP2, AP1, and Smads, within the p-560Col7a1 promoter/chloramphenicol acetyltransferase construct, coupled with DNA binding assays, revealed the importance of these sites for basal Col7a1 expression. The effect of transforming growth factor beta, an activator of Col7a1 expression in keratinocytes and dermal fibroblasts, was examined using the same Col7a1 promoter/chloramphenicol acetyltransferase constructs. These analyses demonstrated that transforming growth factor beta1 stimulation of Col7a1 transcription is dependent on a putative interaction between Smads and AP1. Interestingly, the Smad-like binding site was essential for both basal and transforming growth factor beta1 stimulated Col7a1 transcription. Collectively, these findings attest to the complex regulation of Col7a1 transcription in epidermal keratinocytes.

PhiC31 integrase-mediated nonviral genetic correction of junctional epidermolysis bullosa

Patients afflicted with severe laminin 5-deficient junctional epidermolysis bullosa (JEB) often die in infancy with massive cutaneous blistering. Prior approaches to genetically correct this disorder have relied on stable integration of wild-type LAMB3 sequences, using retroviral vectors. To develop a nonviral approach to JEB gene therapy, we used the phiC31 integrase, which mediates unidirectional genomic integration of plasmids containing a specific attB site. An attB-containing laminin 5 beta3 expression plasmid was integrated into the genomes of primary keratinocytes from four unrelated, genetically characterized JEB patients. phiC31 integrase supported genomic integration into epidermal progenitor cells. Regeneration of human skin on immunedeficient mice, using these cells, produced human skin tissue with restored laminin 5 expression. Furthermore, corrected JEB tissue restored hemidesmosome formation and abolished histologic evidence of subepidermal blistering. These findings provide an approach to durable nonviral correction of JEB.

Pemphigus vulgaris: update on etiopathogenesis, oral manifestations, and management

Pemphigus is a group of potentially life-threatening diseases characterized by cutaneous and mucosal blistering. There is a fairly strong genetic background to pemphigus with linkage to HLA class II alleles. Certain ethnic groups, such as Ashkenazi Jews and those of Mediterranean origin, are especially liable to pemphigus. Pemphigus vulgaris (PV), the most common and important variant, is an autoimmune blistering disease characterized by circulating pathogenic IgG antibodies against desmoglein 3 (Dsg3), about half the patients also having Dsg1 autoantibodies. Oral lesions are initially vesiculobullous but readily rupture, new bullae developing as the older ones rupture and ulcerate. Biopsy of perilesional tissue, with histological and immunostaining examinations, is essential to the diagnosis. Serum autoantibodies to either Dsg1 or Dsg3 are best detected by both normal human skin and monkey esophagus or by enzyme-linked immunosorbent assay (ELISA). Before the introduction of corticosteroids, pemphigus vulgaris was typically fatal mainly from dehydration or secondary systemic infections. Current treatment is largely based on systemic immunosuppression using systemic corticosteroids, with azathioprine, dapsone, methotrexate, cyclophosphamide, and gold as adjuvants or alternatives, but mycophenolate mofetil and intravenous immunoglobulins also appear promising.

Genomic organization, amplification, fine mapping, and intragenic polymorphisms of the human hemidesmosomal tetraspanin CD151 gene

CD151 is a member of the tetraspanin family that is involved in cellular processes including cell adhesion. The protein is expressed in a variety of tissues including vascular endothelium and epidermis, and has been shown to be a component of hemidesmosomes. Mutations in genes encoding other hemidesmosomal proteins give rise to a range of human disorders, characterized by fragility of the skin and/or mucous membranes. It is, therefore, plausible that inherited or acquired mutations in the gene encoding CD151 may be fundamental to the integrity and maturation of basal cell keratinocytes. To aid mutation analysis, we have characterized the intron-exon organization of the CD151 gene which comprises 8 exons spanning approximately 4.3 kb, and have developed a comprehensive PCR-based mutation detection strategy. In addition, to aid linkage analysis of CD151 in genetic disease we have fine-mapped the gene by radiation-hybrid methodology to 11p15.5, and detected a number of intragenic polymorphisms.

Dilated cardiomyopathy in dystrophic epidermolysis bullosa

BACKGROUND

Dystrophic epidermolysis bullosa (DEB) is an uncommon genetic disorder of the skin and mucosae. In 1996, we reported the occurrence of lethal dilated cardiomyopathy (DCM) in two affected children.

METHODS

In the past seven years we have routinely screened patients with severe DEB who have been under the care of this hospital by yearly clinical review, echocardiography, and quantification of plasma selenium and carnitine concentrations, as deficiency of these micronutrients is known to be associated with the development of DCM.

RESULTS

Six of 61 children have developed DCM over the seven year period of this study, four of whom have not been previously reported, and three of whom have since died. We compared the concentrations of selenium and free and total carnitine in the children who developed DCM to concentrations in those with severe DEB who did not. The concentrations of free and total carnitine when first measured were significantly lower in the children with DCM, but the selenium concentrations were not.

CONCLUSIONS

We now believe that DCM is a not infrequent complication of severe recessive DEB, and may be related in part to carnitine concentrations, though the exact mechanism remains unclear. We therefore recommend that patients with this condition should undergo regular cardiac review including echocardiography.

A novel component of epidermal cell-matrix and cell-cell contacts: transmembrane protein type XIII collagen

Type XIII collagen is a short chain collagen which has recently been shown to be a transmembrane protein. The purpose of this study was to elucidate the presence and localization of type XIII collagen in normal human skin and cultured keratinocytes. Expression of type XIII collagen was demonstrated in normal human skin and epidermis at the RNA level using reverse transcription followed by polymerase chain reaction and at the protein level using western blotting and indirect immunofluorescence labeling. Immunolabeling of epidermis revealed type XIII collagen both in the cell-cell contact sites and in the dermal-epidermal junction. In cultured keratinocytes type XIII collagen epitopes were detected in focal contacts and in intercellular contacts. The results of this study show very little colocalization of type XIII collagen and desmosomal components at the light microscopic level. Thus, these results suggest that type XIII collagen is unlikely to be a component of desmosomes. Instead, the punctate labeling pattern of type XIII collagen at the cell-cell contact sites and high degree of colocalization with E-cadherin suggests that type XIII collagen is very likely to be closely associated with adherens type junctions, and may, in fact, be a component of these junctions.

The alpha3 laminin subunit, alpha6beta4 and alpha3beta1 integrin coordinately regulate wound healing in cultured epithelial cells and in the skin

Previously, we demonstrated that proteolytic processing within the globular domain of the alpha3 subunit of laminin-5 (LN5) converts LN5 from a cell motility-inducing factor to a protein complex that can trigger the formation of hemidesmosomes, certain cell-matrix attachment sites found in epithelial cells. We have prepared a monoclonal antibody (12C4) whose epitope is located toward the carboxy terminus of the globular domain of the alpha3 laminin subunit. This epitope is lost from the alpha3 subunit as a consequence of proteolytic processing. Antibody 12C4 stains throughout the matrix of cells that fail to process the alpha3 laminin subunit, but does not recognize the matrix of confluent cultures of MCF-10A cells, which efficiently process their alpha3 laminin chain. In subconfluent populations of MCF-10A cells, 12C4 only stains matrix deposited at the outer edges of cell colonies. In these cells, integrin alpha3beta1 occasionally colocalizes with the staining generated by the 12C4 antibody but alpha6beta4 integrin does not. In wounded MCF-10A cell cultures, the 12C4 antibody stains the extracellular matrix beneath those cells at the very edge of the cellular sheet that moves to cover the wound site. A similar phenomenon is observed in human skin wounds, since we also detect expression of the unprocessed alpha3 laminin subunit at the leading tip of the sheet of epidermal cells that epithelializes skin wounds in vivo. In addition, using alpha3 laminin subunit and integrin function-inhibiting antibodies, we provide evidence that LN5 and its two integrin receptors (alpha6beta4 and alpha3beta1) appear necessary for wound healing to occur in MCF-10A cell culture wounds. We propose a model for healing of wounded epithelial tissues based on these results.

Update on mucous membrane pemphigoid: a heterogeneous immune-mediated subepithelial blistering entity

Most oral involvement in the skin diseases (dermatoses) is related to mucous membrane pemphigoid or lichen planus. Mucous membrane pemphigoid was the subject of a European Symposium held in Turin, Italy, in June 1997. This review is based on that symposium. Mucous membrane pemphigoid is a subepithelial vesiculobullous disorder mainly of late middle age; it has a slight predilection for women. Whereas mucous membrane pemphigoid was formerly considered a single entity, it is now quite evident that a number of subepithelial vesiculobullous disorders may produce similar clinical pictures and also that a range of variants of mucous membrane pemphigoid exists, with antibodies directed against various hemidesmosomal components or components of the epithelial basement membrane. The term immune-mediated subepithelial blistering diseases has therefore been used. Diagnosis and management of immune-mediated subepithelial blistering diseases on clinical grounds alone are impossible; a full history, general and oral examinations, and biopsy with immunostaining are now invariably required, sometimes supplemented with other investigations. Most patients with mucous membrane pemphigoid affecting the mouth manifest desquamative gingivitis, a fairly common complaint typically seen in women who are middle-aged or older. Oral vesicles and erosions may also occur, and there can be a positive Nikolsky sign. Some patients have lesions of other stratified squamous epithelia, presenting as conjunctival, nasal, oesophageal, laryngeal, vulval, penile, or anal involvement. Apart from improving oral hygiene, immunomodulatory-in particular, immunosuppressive-therapy is typically required to control oral lesions in mucous membrane pemphigoid. No single treatment regimen reliably controls all these disorders.

180-kD bullous pemphigoid antigen/type XVII collagen: tissue-specific expression and molecular interactions with keratin 18

The 180-kD bullous pemphigoid antigen (BPAG2) is a hemidesmosomal transmembrane protein, also known as type XVII collagen. In this study, potential interactions of BPAG2 with other proteins expressed in epidermal keratinocytes were explored by yeast two-hybrid system using the amino-terminal intracellular domain of BPAG2 as a bait. Several independent interacting clones encoding keratin 18 (K18) were identified when the keratinocyte cDNA library, cloned into the yeast two-hybrid activation domain vector, was screened. The peptide sequence responsible for the interaction of BPAG2 was restricted to amino acids 15-25, and substitution of a valine residue in the middle of this sequence by a proline (V23P) by site-directed mutagenesis abolished the interaction. Further examination of the K18 sequences by restricted cDNA constructs in yeast two-hybrid system identified a carboxyl-terminal segment corresponding to helix 2B domain as critical for BPAG2 binding. The interaction of BPAG2/K18 was confirmed by an in vitro protein-protein interaction assay, which also confirmed that normal human keratinocytes express K18 in culture. The tissue specific expression of BPAG2 was first examined using a multi-tissue RNA blot. Human multiple tissue cDNA panels representing a variety of adult and fetal tissues as well as tumor cells were used as PCR-templates to study the expression patterns of both BPAG2 and K18. The results demonstrated significant level of expression of BPAG2, besides in epidermal keratinocytes, also in a variety of tissues with predominant epithelial component, such as mammary, salivary and thyroid glands, colon, prostate, testis, placenta, and adult and fetal thymus, as well as in colon, pancreatic and prostatic adenocarcinoma cell lines, and an ovarian carcinoma. As expected, K18 transcript is present in liver, pancreas, colon, placenta, and in fetal kidney. Collectively, the results suggest that BPAG2 has a relatively broad tissue distribution including specialized and simple epithelia, and that within the tissues such as colon and placenta, BPAG2 may have direct interactions with K18, a keratin characteristically expressed in a simple epithelia.

Hemidesmosomal molecular changes in dermatitis herpetiformis; decreased expression of BP230 and plectin/HD1 in uninvolved skin

Recent BP230-knockout experiments with subsequent blistering and recently identified plectin/HD1 mutations in epidermolysis bullosa simplex patients suggest that defective expression of BP230 and plectin/HD1 may predispose to blister formation in human skin. We have studied the expression of the epithelial adhesion complex as well as the basement membrane and anchoring fibril antigens in uninvolved dermatitis herpetiformis skin to find out if alterations can be detected in these structures predisposing to the blister formation typical of the disease. Ten uninvolved dermatitis herpetiformis skin specimens, which all showed clear granular deposits of IgA under the basement membrane in direct immunofluorescence and five normal skin specimens, were studied by indirect immunofluorescence technique. Six uninvolved dermatitis herpetiformis skin specimens showed distinctly decreased immunoreaction for BP230 and four uninvolved dermatitis herpetiformis skin specimens showed distinctly decreased immunoreaction for plectin/HD1. All five skin controls showed strong immunoreactions for BP230 and plectin/HD1. Other hemidesmosomal proteins including BP180 and integrin alpha6beta4, as well as basement membrane proteins laminin-5, laminin-1, nidogen and type IV collagen, and the anchoring fibril protein type VII collagen showed a normal strong expression. Our results suggest that alterations in BP230 and plectin/HD1 may contribute or predispose to blister formation in dermatitis herpetiformis skin.

New insights into the immunoultrastructural organization of cutaneous basement membrane zone molecules

The epidermal basement membrane zone (BMZ) is composed of various molecules, each of which plays an important role in dermo-epidermal adhesion. Genetic abnormality of certain BMZ molecules leads to an inherited group of skin diseases collectively referred to as epidermolysis bullosa, whose hallmark is skin fragility of varying degrees. Furthermore, development of autoantibodies to certain BMZ molecules leads to the onset of a number of acquired autoimmune blistering diseases in which dermo epidermal separation occurs, including bullous pemphigoid and epidermolysis bullosa acquisita. The ultrastructural location of each BMZ molecule has been studied using a range of immunoelectron microscopy (immuno-EM) techniques. Recent technical advances in immuno-EM and in molecular engineering for production of epitope-specific antibodies have enabled a more correct and precise elucidation of the native ultrastructural molecular organization of the respective molecules and their relationship to each other. These recent studies have also revealed several misinterpretations in the previously established model of the immunoultrastructural organization of BMZ molecules. In response to these findings, this review focuses on three major BMZ-related molecules, type VII collagen, BPAG2 and laminin 5, for which recent immuno-EM studies have produced a revision in the accepted dogma on their ultrastructural distribution at the BMZ.

kakapo, a gene required for adhesion between and within cell layers in Drosophila, encodes a large cytoskeletal linker protein related to plectin and dystrophin

Mutations in kakapo were recovered in genetic screens designed to isolate genes required for integrin-mediated adhesion in Drosophila. We cloned the gene and found that it encodes a large protein (>5,000 amino acids) that is highly similar to plectin and BPAG1 over the first 1,000-amino acid region, and contains within this region an alpha-actinin type actin-binding domain. A central region containing dystrophin-like repeats is followed by a carboxy domain that is distinct from plectin and dystrophin, having neither the intermediate filament-binding domain of plectin nor the dystroglycan/syntrophin-binding domain of dystrophin. Instead, Kakapo has a carboxy terminus similar to the growth arrest-specific protein Gas2. Kakapo is strongly expressed late during embryogenesis at the most prominent site of position-specific integrin adhesion, the muscle attachment sites. It is concentrated at apical and basal surfaces of epidermal muscle attachment cells, at the termini of the prominent microtubule bundles, and is required in these cells for strong attachment to muscles. Kakapo is also expressed more widely at a lower level where it is essential for epidermal cell layer stability. These results suggest that the Kakapo protein forms essential links among integrins, actin, and microtubules.

The laminins: role in intestinal morphogenesis and differentiation

Dynamic and reciprocal heterotypic cell interactions are crucial for intestinal morphogenesis and differentiation. This paper emphasizes the role of basement membrane molecules and in particular of laminins as potent mediators in this intercellular cross talk. Changes in the expression or localization of laminin isoforms or of integrins during development and cell migration strengthen the concept that heterogeneity in cell-matrix interactions could mediate distinct cell responses. A combination of genetic or biochemical approaches associated with in vitro models allows us to study the potential role of each laminin isoform in basement membrane assembly, cell migration, or cell differentiation.

Characterization of a tight molecular complex between integrin alpha 6 beta 4 and laminin-5 extracellular matrix

In many adult epithelia, e.g., epidermis or intestine, adhesion of epithelial cells to basement membrane requires the integrin alpha6 beta4 and laminin-5 (Ln-5). In the absence of one or the other, extensive blistering and exfoliation occur. While alpha6 beta4 was reported to be a receptor for Ln-5, this interaction is poorly understood. We characterize complexes between alpha6 beta4 and Ln-5 in cell-free preparations of extracellular matrix (ECM) from the epithelial cell line, 804G. By microsequencing, Ln-5 and alpha6 beta4 were the major proteins in this ECM and were likely engaged in receptor/ligand complexes because, by immunofluorescence, alpha6 beta4 was colocalized with Ln-5 both in cell monolayers and in cell-free ECM preparations, but they disappeared after preincubation of the monolayers with alpha6 beta4 or Ln-5 function-blocking antibodies. The alpha6 beta4/Ln-5 complexes were resistant to dissociation by extreme pH, urea, chaotropes, eDTA, non-ionic detergents, and b-mercaptoethanol. They were only dissociated by strong anionic detergents, e.g., 1% SDS, suggesting receptor/ligand interactions based on high affinity or avidity. We propose that these alpha6 beta4/Ln-5 complexes may provide links between plasma membrane and basement membrane that resist mechanical stress and support epithelial integrity.

Junctional epidermolysis bullosa with pyloric atresia: A case with favourable outcome

BACKGROUND

Pyloric atresia is a rare but serious condition that can occur with junctional epidermolysis bullosa (PA-JEB). Early recognition is necessary for timely intervention, but prognosis can be serious and mortality is high.

OBJECTIVE

We describe the case of a patient with PA-JEB who not only survived past infancy, but showed improvement in cutaneous blistering as she grew older.

CONCLUSION

With early surgical intervention, some patients with PA-JEB can survive and look forward to a favourable prognosis, with improvement of cutaneous blistering by early childhood.

A recurrent glycine substitution mutation, G2043R, in the type VII collagen gene (COL7A1) in dominant dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is caused by mutations in the type VII collagen gene (COL7A1). Nearly all cases of dominant DEB are caused by glycine substitution mutations occurring within the triple helical region of type VII collagen, and most of the mutations are unique to individual families. In this study, we identified a patient of Hispanic-Mexican origin with a mild form of DEB, which resulted from a de novo dominant glycine substitution, G2043R, in exon 73 of COL7A1. We also investigated a Scottish family with a three-generation pedigree of dominant DEB, in whom the same glycine to arginine substitution mutation was demonstrated. This particular mutation has also been detected previously in three other families with dominant DEB: one Italian, one Hungarian and one Norwegian. Given the widespread geographical distribution of this mutation and the demonstration of its occurrence as a de novo event, G2043R therefore represents the first example of a mutational hotspot in dominant DEB. Interestingly, although both the Mexican and Scottish families we studied had some clinical features in keeping with the Pasini form of the disorder, there was considerable interfamilial variability as well as intrafamilial diversity in the affected individuals.