Kalinin is abnormally expressed in epithelial basement membranes of Herlitz's junctional epidermolysis bullosa patients

Leading edge: emerging drug, cell, and gene therapies for junctional epidermolysis bullosa

INTRODUCTION

Junctional epidermolysis bullosa (JEB) is a rare inherited genetic disorder with limited treatments beyond palliative care. A major hallmark of JEB is skin blistering caused by functional loss or complete absence of major structural proteins of the skin. Impaired wound healing in patients with JEB gives rise to chronic cutaneous ulcers that require daily care. Wound care and infection control are the current standard of care for this patient population.

AREAS COVERED

This review covers research and clinical implementation of emerging drug, cell, and gene therapies for JEB. Current clinical trials use topical drug delivery to manipulate the inflammation and re-epithelialization phases of wound healing or promote premature stop codon readthrough to accelerate chronic wound closure. Allogeneic cell therapies for JEB have been largely unsuccessful, with autologous skin grafting emerging as a reliable method of resolving the cutaneous manifestations of JEB. Genetic correction and transplant of autologous keratinocytes have demonstrated persistent amelioration of chronic wounds in a subset of patients.

EXPERT OPINION

Emerging therapies address the cutaneous symptoms of JEB but are unable to attend to systemic manifestations of the disease. Investigations into the molecular mechanism(s) underpinning the failure of systemic allogeneic cell therapies are necessary to expand the range of effective JEB therapies.

Gene Therapy for Epidermolysis Bullosa

Epidermolysis bullosa is a family of diseases characterized by blistering and fragility of the skin in response to mechanical trauma. Advances in our understanding of epidermolysis bullosa pathophysiology have provided the necessary foundation for the first clinical trials of gene therapy for junctional and dystrophic epidermolysis bullosa. These therapies show that gene therapy is both safe and effective, with the potential to correct the molecular and clinical phenotype of patients with epidermolysis bullosa. Improvements in gene delivery and in preventing immune reactions will be among the challenges that lie ahead during further therapeutic development.

Upregulated LAMB3 increases proliferation and metastasis in thyroid cancer

Background

Thyroid cancer is the most commonly reported endocrine malignancy, and its increased incidence has been the highest in all human tumors in recent decades. To investigate the mechanism of papillary thyroid cancer (PTC) occurrence and progression, we performed RNA sequencing and found an upregulated gene, LAMB3. However, the biological function of LAMB3 is still not clear.

Materials and methods

We analyzed LAMB3 expression using The Cancer Genome Atlas (TCGA) database and hypothesized LAMB3 to be a gene associated with PTC. To test this hypothesis, we collected 89 pairs of thyroid nodules and adjacent normal thyroid tissues (56 pairs of PTCs, 33 pairs of benign thyroid nodules). Afterward, we performed real-time quantitative polymerase chain reaction (RT-qPCR) to investigate LAMB3 expression in thyroid nodule patients, and then analyzed clinicopathologic features. We performed proliferation, colony formation, migration, and invasion assays to determine the function of LAMB3 in PTC.

Results

We demonstrated that LAMB3 plays oncogenic roles in PTC. The relative expression of LAMB3 is significantly upregulated in PTC compared with matched thyroid normal tissues in validated cohort and TCGA cohort (P<0.001). We also checked area under the curve (AUC of receiver operator characteristic [ROC]) of 97.3% for validated cohort and 90.1% for TCGA cohort to differentiate PTC tumors from normal tissues. In clinicopathologic feature analysis, we found that upregulated LAMB3 is closely related to lymph node metastasis (P=0.018). Furthermore, knockdown of LAMB3 inhibited the proliferation, colony formation, migration, and invasive capacity of PTC.

Conclusion

This study indicated that LAMB3 is a gene associated with PTC.

Strategies for Optimizing the Soft Tissue Seal around Osseointegrated Implants

Percutaneous and permucosal devices such as catheters, infusion pumps, orthopedic, and dental implants are commonly used in medical treatments. However, these useful devices breach the soft tissue barrier that protects the body from the outer environment, and thus increase bacterial infections resulting in morbidity and mortality. Such associated infections can be prevented if these devices are effectively integrated with the surrounding soft tissue, and thus creating a strong seal from the surrounding environment. However, so far, there are no percutaneous/permucosal medical devices able to prevent infection by achieving strong integration at the soft tissue-device interface. This review gives an insight into the current status of research into soft tissue-implant interface and the challenges associated with these interfaces. Biological soft/hard tissue interfaces may provide insights toward engineering better soft tissue interfaces around percutaneous devices. In this review, focus is put on the history and current findings as well as recent progress of the strategies aiming to develop a strong soft tissue seal around osseointegrated implants, such as orthopedic and dental implants.

Gentamicin induces functional type VII collagen in recessive dystrophic epidermolysis bullosa patients

BACKGROUND

Recessive dystrophic epidermolysis bullosa (RDEB) is an incurable disease caused by mutations in the gene encoding type VII collagen, the major component of anchoring fibrils (AF). We previously demonstrated that gentamicin produced functional type VII collagen in RDEB cells harboring nonsense mutations. Herein, we determined whether topical or intradermal gentamicin administration induces type VII collagen and AFs in RDEB patients.

METHODS

A double-blind, placebo-controlled pilot trial assessed safety and efficacy of topical and intradermal gentamicin in 5 RDEB patients with nonsense mutations. The topical arm tested 0.1% gentamicin ointment or placebo application 3 times daily at 2 open erosion sites for 2 weeks. The intradermal arm tested daily intradermal injection of gentamicin solution (8 mg) or placebo into 2 intact skin sites for 2 days in 4 of 5 patients. Primary outcomes were induction of type VII collagen and AFs at the test sites and safety assessment. A secondary outcome assessed wound closure of topically treated erosions.

RESULTS

Both topical and intradermal gentamicin administration induced type VII collagen and AFs at the dermal-epidermal junction of treatment sites. Newly created type VII collagen varied from 20% to 165% of that expressed in normal human skin and persisted for 3 months. Topical gentamicin corrected dermal-epidermal separation, improved wound closure, and reduced blister formation. There were no untoward side effects from gentamicin treatments. Type VII collagen induction did not generate anti-type VII collagen autoantibodies in patients' blood or skin.

CONCLUSION

Topical and intradermal gentamicin suppresses nonsense mutations and induces type VII collagen and AFs in RDEB patients. Gentamicin therapy may provide a readily available treatment for RDEB patients with nonsense mutations.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02698735.

FUNDING

Epidermolysis Bullosa Research Partnership, Epidermolysis Bullosa Medical Research Foundation, NIH, and VA Merit Award.

The anatomical distribution of genetic associations

Deeper understanding of the anatomical intermediaries for disease and other complex genetic traits is essential to understanding mechanisms and developing new interventions. Existing ontology tools provide functional, curated annotations for many genes and can be used to develop mechanistic hypotheses; yet information about the spatial expression of genes may be equally useful in interpreting results and forming novel hypotheses for a trait. Therefore, we developed an approach for statistically testing the relationship between gene expression across the body and sets of candidate genes from across the genome. We validated this tool and tested its utility on three applications. First, we show that the expression of genes in associated loci from GWA studies implicates specific tissues for 57 out of 98 traits. Second, we tested the ability of the tool to identify novel relationships between gene expression and phenotypes. Specifically, we experimentally confirmed an underappreciated prediction highlighted by our tool: that white blood cell count--a quantitative trait of the immune system--is genetically modulated by genes expressed in the skin. Finally, using gene lists derived from exome sequencing data, we show that human genes under selective constraint are disproportionately expressed in nervous system tissues.

The genetics of human skin disease

The skin is composed of a variety of cell types expressing specific molecules and possessing different properties that facilitate the complex interactions and intercellular communication essential for maintaining the structural integrity of the skin. Importantly, a single mutation in one of these molecules can disrupt the entire organization and function of these essential networks, leading to cell separation, blistering, and other striking phenotypes observed in inherited skin diseases. Over the past several decades, the genetic basis of many monogenic skin diseases has been elucidated using classical genetic techniques. Importantly, the findings from these studies has shed light onto the many classes of molecules and essential genetic as well as molecular interactions that lend the skin its rigid, yet flexible properties. With the advent of the human genome project, next-generation sequencing techniques, as well as several other recently developed methods, tremendous progress has been made in dissecting the genetic architecture of complex, non-Mendelian skin diseases.

Diagnosing epidermolysis bullosa type and subtype in infancy using immunofluorescence microscopy: the Stanford experience

The natural history of inherited epidermolysis bullosa (EB) varies significantly across subtypes. When confronted with an infant suspected to have EB, rapidly determining the type and subtype is critical in counselling families accurately about the infant's diagnosis and prognosis. Although transmission electron microscopy (TEM) has been considered the criterion standard for EB diagnosis, immunofluorescence microscopy (IFM) using monoclonal antibodies (mAbs) to EB-specific basement membrane zone proteins has several advantages, but few studies have evaluated the diagnostic utility of IFM. We sought to evaluate the clinical utility of IFM using an expanded panel of EB-specific mAbs. This was a retrospective review of pathology reports from infants younger < 1 year old with suspected EB primarily analyzed with IFM by the Stanford Dermatopathology service. Seventy-seven cases were identified for analysis, of which 20 were suboptimal for IFM analysis. Fifty-five cases were diagnosed with EB and classified as follows: EB simplex (n = 5), junctional EB (n = 31), dystrophic EB (n = 19). TEM was available in 36 of 55 cases (65%). IFM with an expanded panel of EB-specific mAbs should be considered the first-line diagnostic test to evaluate infants with clinically suspected EB.

Keratinocyte-targeted expression of human laminin γ2 rescues skin blistering and early lethality of laminin γ2 deficient mice

Laminin-332 is a heterotrimeric basement membrane component comprised of the α3, ß3, and γ2 laminin chains. Laminin-332 modulates epithelial cell processes, such as adhesion, migration, and differentiation and is prominent in many embryonic and adult tissues. In skin, laminin-332 is secreted by keratinocytes and is a key component of hemidesmosomes connecting the keratinocytes to the underlying dermis. In mice, lack of expression of any of the three Laminin-332 chains result in impaired anchorage and detachment of the epidermis, similar to that seen in human junctional epidermolysis bullosa, and death occurs within a few days after birth. To bypass the early lethality of laminin-332 deficiency caused by the knockout of the mouse laminin γ2 chain, we expressed a dox-controllable human laminin γ2 transgene under a keratinocyte-specific promoter on the laminin γ2 (Lamc2) knockout background. These mice appear similar to their wild-type littermates, do not develop skin blisters, are fertile, and survive >1.5 years. Immunofluorescence analyses of the skin showed that human laminin γ2 colocalized with mouse laminin α3 and ß3 in the basement membrane zone underlying the epidermis. Furthermore, the presence of “humanized” laminin-332 in the epidermal basement membrane zone rescued the alterations in the deposition of hemidesmosomal components, such as plectin, collagen type XVII/BP180, and integrin α6 and ß4 chains, seen in conventional Lamc2 knockout mice, leading to restored formation of hemidesmosomes. These mice will be a valuable tool for studies of organs deficient in laminin-332 and the role of laminin-332 in skin, including wound healing.

Molecular organization of the basement membrane zone

The dermal-epidermal basement membrane is a complex assembly of proteins that provide adhesion and regulate many important processes such as development, wound healing, and cancer progression. This contribution focuses on the structure and function of individual components of the basement membrane, how they assemble together, and how they participate in human tissues and diseases, with an emphasis on skin involvement. Understanding the composition and structure of the basement membrane provides insight into the pathophysiology of inherited blistering disorders, such as epidermolysis bullosa, and acquired bullous diseases, such as the pemphigoid group of autoimmune diseases and epidermolysis bullosa acquisita.

Oral manifestations in the epidermolysis bullosa spectrum

The craniofacial and oral manifestations of the different epidermolysis bullosa (EB) types vary markedly in character and severity depending largely on the EB type. The tissues affected and the phenotypes displayed are closely related to the specific abnormal or absent proteins resulting from the causative genetic mutations for these disorders. In this article, the major oral manifestations are reviewed for different EB subtypes and are related to the causative genetic mutations and gene expression.

Role of dermal-epidermal basement membrane zone in skin, cancer, and developmental disorders

The dermal-epidermal basement membrane zone is an important epithelial and stromal interface, consisting of an intricately organized collection of intracellular, transmembrane, and extracellular matrix proteins. The basement membrane zone has several main functions including acting as a permeability barrier, forming an adhesive interface between epithelial cells and the underlying matrix, and controlling cellular organization and differentiation. This article identifies key molecular players of the dermal-epidermal membrane zone, and highlights recent research studies that have identified structural and functional roles of these components in the context of various blistering, neoplastic, and developmental syndromes.

Defining the role of laminin-332 in carcinoma

The deadly feature of cancer, metastasis, requires invasion of cells through basement membranes (BM), which normally act as barriers between tissue compartments. In the case of many epithelially-derived cancers (carcinomas), laminin-332 (Ln-332) is a key component of the BM barrier. This review provides a historical examination of Ln-332 from its discovery through identification of its functions in BM and possible role in carcinomas. Current understanding points to distinct roles for the three Ln-332 subunits (alpha3, beta3, gamma2) in cell adhesion, extracellular matrix stability, and cell signaling processes in cancer. Given the large number of studies linking Ln-332 gamma2 subunit with cancer prognosis, particular attention is given to the crucial role of this subunit in cancer invasion and to the unanswered questions in this area.

Laminin-332 is a substrate for hepsin, a protease associated with prostate cancer progression

Hepsin, a cell surface protease, is widely reported to be overexpressed in more than 90% of human prostate tumors. Hepsin expression correlates with tumor progression, making it a significant marker and target for prostate cancer. Recently, it was reported that in a prostate cancer mouse model, hepsin up-regulation in tumor tissue promotes progression and metastasis. The underlying mechanisms, however, remain largely uncharacterized. Hepsin transgenic mice displayed reduced laminin-332 (Ln-332) expression in prostate tumors. This is an intriguing cue, since proteolytic processing of extracellular matrix macromolecules, such as Ln-332, is believed to be involved in cancer progression, and Ln-332 expression is lost during human prostate cancer progression. In this study, we provide the first direct evidence that hepsin cleaves Ln-332. Cleavage is specific, since it is both inhibited in a dose-dependent manner by a hepsin inhibitor (Kunitz domain-1) and does not occur when catalytically inactive hepsin is used. By Western blotting and mass spectrometry, we determined that hepsin cleaves the beta3 chain of Ln-332. N-terminal sequencing identified the cleavage site at beta3 Arg(245), in a sequence context (SQLR(245) LQGSCFC) conserved among species and in remarkable agreement with reported consensus target sequences for hepsin activity. In vitro cell migration assays showed that hepsin-cleaved Ln-332 enhanced motility of DU145 prostate cancer cells, which was inhibited by Kunitz domain-1. Further, hepsin-overexpressing LNCaP prostate cancer cells also exhibited increased migration on Ln-332. Direct cleavage of Ln-332 may be one mechanism by which hepsin promotes prostate tumor progression and metastasis, possibly by up-regulating prostate cancer cell motility.

The autoantigen in anti-p200 pemphigoid is synthesized by keratinocytes and fibroblasts and is distinct from nidogen-2

Anti-p200 pemphigoid is a subepidermal immunobullous disorder associated with tissue-bound and circulating autoantibodies reactive with a 200 kDa protein on the dermal side of salt-split-skin. The autoantigen, named p200, is a non-collagenous glycoprotein located at the lamina lucida-lamina densa border of the epidermal basement membrane. However, its identity and cellular origin remain elusive. Here, we used biochemical and genetic approaches to characterize the autoantibody reactivity in three new patients with anti-p200 pemphigoid. We show that the target antigen p200 is synthesized by both keratinocytes and fibroblasts, is disulfide-bonded, and participates in calcium-dependent molecular interactions. Lack of collagen XVII (BP 180), collagen VII, or laminin 332 (laminin 5) from the dermal-epidermal junction does not destabilize p200. Colocalization within the basement membrane zone and an identical molecular weight suggested nidogen-2 as candidate autoantigen in anti-p200 pemphigoid, but biochemical analysis demonstrated that p200 is distinct from nidogen-2. In conclusion, the results define further the biochemical characteristics of p200 and demonstrate its in vitro-synthesis by keratinocytes and fibroblasts, thus providing a basis for identification and further characterization of this autoantigen.

Tumour microenvironment: laminin 332 in squamous-cell carcinoma

Basement membranes can be a barrier to tumour growth, but basement membrane molecules, including laminins, are also important autocrine factors produced by cancers to promote tumorigenesis. Many studies have shown the importance of laminin 332 (previously known as laminin 5) in this process, especially in squamous cell carcinoma. Through interactions with several cell-surface receptors (including alpha6beta4 and alpha3beta1 integrins, epidermal growth factor receptor and syndecan 1) and other basement membrane components (including type VII collagen), laminin 332 drives tumorigenesis through phosphatidylinositol-3 kinase (PI3K) and RAC1 activation, promoting tumour invasion and cell survival. The extracellular interactions of laminin 332 appear amenable to antibody-mediated therapies.

Mesenchymal cells contribute to the synthesis and deposition of the laminin-5 gamma2 chain in the invasive front of oral squamous cell carcinoma

Tumour progression in oral squamous cell carcinoma (OSCC) is associated with a reorganisation of extracellular matrix. Laminin-5 (Ln-5) plays an important role for tumour migration and shows an increased expression in areas of direct tumour/stroma interactions. We have previously shown stromal spot like Ln-5/gamma2 chain deposits distant from the basement membrane region. In this study we have analysed which cell type is responsible for Ln-5/gamma2 chain synthesis in situ. Furthermore, we studied its spatial relation to TGF-beta1 as well as the Ln-5 modulating enzymes matrix metalloproteinase (MMP) 2, membrane type-1 (MT1-) MMP and bone morphogenetic protein (BMP-) 1 by different techniques including triple immunofluorescence labelling and in situ hybridisation in OSCC. We found that the stromal spot-like Ln-5 deposits occurred in the invasive front in the vicinity of mesenchymal cells and vessel structures. In particular, not only carcinoma cells but also mesenchymal cells were shown to express the Ln-5/gamma2 chain mRNA. Moreover, stromal Ln-5 deposits showed a spatial association with TGF-beta1 as well as with MT1-MMP and BMP-1. Based on these findings we suggest that mesenchymal cells contribute to the promotion of tumour cell migration as well as vessel formation in OSCC by providing and organising promigratory Ln-5 fragments.

A quantitative co-localization analysis of large unspliced tenascin-C(L) and laminin-5/gamma2-chain in basement membranes of oral squamous cell carcinoma by confocal laser scanning microscopy

BACKGROUND

A structural interaction of the oncofetal large tenascin-C splice variants (Tn-C(L)) and the gamma2-chain of laminin-5 (Ln-5/gamma2) was recently demonstrated in oral squamous cell carcinoma (OSCC). In situ different patterns of co-localization and co-deposition of both proteins could be detected. Especially the co-localization in re-established basement membrane (BM) structures seemed to be biologically meaningful within the process of tumour progression.

METHODS

The amount of Tn-C(L) incorporated in reorganized OSCC BM structures at the tumour margins was investigated by a laser scanning microscopy-based quantitative co-localization analysis.

RESULTS

In the BM of normal oral mucosa no Tn-C(L) could be detected. In dysplastic and neoplastic oral mucosa a distinct co-localization of Tn-C(L) and Ln-5/gamma2 in the BM region could be observed. The extent of Tn-C(L) arrangement into reorganized BM structures correlated with malignancy grade.

CONCLUSIONS

The results suggest at first, a modulation of carcinomatous BM structures by the inclusion of oncofetal matrix proteins during tumour progression and secondly, the BM incorporation of the adhesion-modulating molecule Tn-C(L) as a pre-invasive structural phenomenon in OSCC.

Complex formation of the laminin-5 γ2 chain and large unspliced tenascin-C in oral squamous cell carcinoma in vitro and in situ: implications for sequential modulation of extracellular matrix in the invasive tumor front

Invasion and metastasis in oral squamous cell carcinoma (OSCC) are associated with changes in the extracellular matrix (ECM). We have previously shown an extracellular co-deposition of laminin-5 (Ln-5) and large unspliced tenascin-C (Tn-C(L)) in OSCC. Using a co-culture model of hTERT-BJ1 fibroblasts and the OSCC cell line PE/CA-PJ15, we demonstrate in the present study that Ln-5 and Tn-C(L) are not only co-deposited, but also form a physical complex which can be recovered by co-immunoprecipitation. In agreement with these results, examination of OSCC tissue specimens of different malignancy grade by means of confocal laser scanning microscopy revealed different patterns of Ln-5 and Tn-C(L) co-localization implicating complex formation also in vivo. A ribbon like co-localization was detected in subepithelial basement membranes around well differentiated OSCC parts and tumor clusters. Furthermore, a fibrillar Ln-5 gamma2 chain/Tn-C(L) co-localization occurred in the carcinoma stroma beneath tumor clusters. Additionally, at the site of ruptured basement membranes there were dot or strand like co-deposits of both molecules, but co-localizations were only rarely detectable. These different patterns may reflect a sequential modulation and reorganization of the ECM in the tumor/stroma interface as it occurs in different stages of OSCC invasion.

The alpha-3 polypeptide chain of laminin 5: insight into wound healing responses from the study of genodermatoses

Laminin 5 (kalinin/epiligrin/nicein) is an essential structural component of the dermal-epidermal junction, composed of three polypeptide subunits: laminin alpha3, beta3 and gamma2. Studies of the inherited skin fragility disorder junctional epidermolysis bullosa (JEB) have suggested that the major role of this heterotrimeric protein is to act as an adhesive ligand essential for binding the epidermis to the underlying dermis and thus maintaining the integrity of the skin. Protein interaction studies have shown that the C terminus of the alpha3 subunit binds to a range of integrin complexes depending on the motility status of keratinocytes. This allows laminin 5 to interact with either hemidesmosomes or the actin cytoskeleton. Recently we have reported that the absence of the N-terminal region of laminin alpha3a in laryngo-onchyo-cutaneous syndrome causes excessive granulation tissue production at wound sites. As granulation tissue production is also a problem in JEB, this implicates laminin 5 in control of this wound healing response.

Laminin-5 offsets the efficacy of gefitinib ('Iressa') in hepatocellular carcinoma cells

Prognosis and survival of patients with hepatocellular carcinoma (HCC) is still very poor, and no therapies are currently available to inhibit tumour growth and metastases. Recently, we reported that the expression of an extracellular matrix component (ECM), namely Laminin-5 (Ln-5), is directly related to poor prognosis in HCC patients. The aim of our study is to investigate the preclinical effect of gefitinib in an in vitro HCC model. We found that the IC(50) of gefitinib in HCC cells ranged from 0.7 to 10.0 muM, whereas Ln-5 inhibited the activity of gefitinib in a dose-dependent manner. Complete inhibition of phosphorylated (p)-EGFR (epidermal growth factor receptor) was obtained within 6 h exposure to gefitinib and complete restoration of the receptor status was obtained after 24 h. A downstream effect yields a decrease in p-Akt and p-Erk 1/2. The addition of exogenous Ln-5 has no effect on p-EGFR, whereas it restores p-Erk 1/2 and p-Akt. Consistently, Ln-5 induces recovery of HCC cells from Gefitinib-induced apoptosis. In conclusion, gefitinib inhibits HCC cell growth and we report for the first time that Ln-5, but not other ECM molecules, reduces the ability of gefitinib to inhibit cell growth via Akt. As patients with HCC have different Ln-5 expression levels, these results may help to better understand which patients might benefit from gefitinib treatment.

Epidermolysis bullosa: new and emerging trends

Epidermolysis bullosa is a family of inherited blistering skin disorders characterized by blister formation in response to mechanical trauma. Major types of epidermolysis bullosa include epidermolysis bullosa simplex, hemidesmosomal epidermolysis bullosa, junctional epidermolysis bullosa, and dystrophic epidermolysis bullosa. Current treatment for epidermolysis bullosa consists of supportive care for skin and other organ systems and entails a combination of wound management, infection support for chronic wounds, surgical management as needed, nutritional support, and preventative screening for squamous cell carcinoma in recessive dystrophic epidermolysis bullosa. The regimen must be tailored specifically to the severity and extent of skin and systemic involvement in each case. Recent studies have identified specific protein and genetic abnormalities for most epidermolysis bullosa subtypes. These new advancements in the understanding of molecular pathophysiology have provided much of the basis for current efforts to develop effective gene and protein therapy for epidermolysis bullosa.

Thermo-responsive culture dishes allow the intact harvest of multilayered keratinocyte sheets without dispase by reducing temperature

To develop new technology for harvesting transplantable cultured epithelium without dispase treatment, human keratinocytes were plated on culture dishes grafted with a thermo-responsive polymer, poly(N-isopropylacrylamide). The grafted dish surfaces are slightly hydrophobic above 32 degrees C, but reversibly change to hydrophilic below this temperature. According to the method of Rheinwald and Green, keratinocytes proliferated and made a multilayer on the grafted surfaces at 37 degrees C, as on the nongrafted culture dishes. The multilayered keratinocyte sheets were detached from the grafted surfaces only by reducing temperature to 20 degrees C without need for dispase. No cell remnants were observed on the dishes. Such cell sheet detachment was not observed on nongrafted dishes. Immunoblotting of harvested keratinocyte sheets revealed that dispase treatment disrupted E-cadherin and laminin 5, while these molecules remained intact in the keratinocyte sheets harvested by only reducing temperature from the grafted dishes. Transmission electron microscopy revealed that desmosomes were destroyed in dispase treatment but retained in low-temperature treatment. Use of thermo-responsive dishes was examined as a new tool for tissue engineering to achieve the preparation of artificial epithelium for cell transplantation as well as for the investigation of intact multilayered keratinocyte sheets.

Human hepatocellular carcinoma (HCC) cells require both alpha3beta1 integrin and matrix metalloproteinases activity for migration and invasion

Hepatocellular carcinoma (HCC) is the most frequent malignant tumor of the liver; prognosis depends on the tendency to metastasize. Cancer cell invasion is regulated by proteolytic remodeling of extracellular matrix components and by integrin expression. We have shown that matrix metalloproteinase-2 (MMP-2) and membrane-type-1 matrix metalloproteinase (MT1-MMP) cleave Laminin-5 (Ln-5), stimulating cell migration. Here we report that all HCC cells express MT1-MMP, migrate on Ln-1 and Collagen IV, whereas only HCC cells that express alpha3beta1 integrin secrete detectable levels of gelatinases, migrate on Ln-5, and invade through a reconstituted basement membrane (BM). Migration on Ln-5 is blocked by BB-94, an MMP inhibitor, and by MIG1, a monoclonal antibody that hinders migration on MMP-2-cleaved Ln-5. Invasion through a reconstituted BM is also inhibited by BB-94. HCC alpha3beta1-negative cells migrate on Ln-1 and Collagen IV, but not on Ln-5, and do not invade through a reconstituted BM, although they express MT1-MMP. Anti-alpha3beta1 blocking antibodies inhibit gelatinase activation, cell motility, and cell invasion through MATRIGEL: In vivo, alpha3beta1 integrin and Ln-5 are expressed in HCC tissue but not in normal liver. In conclusion, our data suggest that both alpha3beta1 integrin and gelatinase activity are required for HCC migration and invasion.

Laminins and human disease

The laminin protein family has diverse tissue expression patterns and is involved in the pathology of a number of organs, including skin, muscle, and nerve. In the skin, laminins 5 and 6 contribute to dermal-epidermal cohesion, and mutations in the constituent chains result in the blistering phenotype observed in patients with junctional epidermolysis bullosa (JEB). Allelic heterogeneity is observed in patients with JEB: mutations that results in premature stop codons produce a more severe phenotype than do missense mutations. Gene therapy approaches are currently being studied in the treatment of this disease. A blistering phenotype is also observed in patients with acquired cicatricial pemphigoid (CP). Autoantibodies targeted against laminins 5 and 6 destabilize epithelial adhesion and are pathogenic. In muscle cells, laminin alpha 2 is a component of the bridge that links the actin cytoskeleton to the extracellular matrix. In patients with laminin alpha 2 mutations, the bridge is disrupted and mature muscle cells apoptose. Congenital muscular dystrophy (CMD) results. The role of laminin in diseases of the nervous system is less well defined, but the extracellular protein has been shown to serve an important role in peripheral nerve regeneration. The adhesive molecule influences neurite outgrowth, neural differentiation, and synapse formation. The broad spatial distribution of laminin gene products suggests that laminin may be involved in a number of diseases for which pathogenic mechanisms are still being unraveled.

Update on inherited bullous dermatoses

Bullous diseases are becoming increasingly better understood owing to the active research which has taken place in this field over the past decade. Advances in understanding of bullous disease pathophysiology is translating into clinical applications for diagnosis and therapy that will greatly enhance the quality of care bullous disease patients may receive now and in the future. This review focuses on the progress which has been achieved in inherited bullous dermatoses.

Pretreatment of human keratinocyte sheets with laminin 5 improves their grafting efficiency

Laminin 5 is essential in epithelial attachment to stromal tissues, suggesting that it might improve keratinocyte attachment in a variety of clinical situations. In this study, we examined the effect of exogenous laminin 5 upon the efficiency of transplantation of keratinocyte sheets in animal models. Keratinocyte sheets were prepared according to the method of Rheinwald & Green (1975). Purified laminin 5 was added to the sheets of group 1 (1.0 microg per cm2), Dulbecco's modified Eagle's medium alone was added to group 2. The sheets were grafted to the panniculus carnosus of nude mice (BALB/C nu/nu) (n = 12) and nude rats (Fisher 344) (n = 15). The take rate was assessed by measurement of the area of surviving epithelium at 7 d postgrafting. Laminin 5 bound the keratinocyte sheets of group 1. At 7 d postgrafting, the area of epithelialization of group 1 was significantly larger than that of group 2. Immunohistochemistry staining showed that collagen IV, laminin 5, and collagen VII stained more strongly at the dermal-epidermal junction in group 1 than in group 2. Integrin chains alpha6 and beta4 were similar in both groups. Electron microscopy at day 3 after grafting, showed the lamina densa of group 1 to be more continuous than in group 2. Pretreatment of cultured human keratinocyte sheets with laminin 5 improved the extent of epithelial coverage and increased the rate of neobasement membrane formation. The results suggest that laminin 5 promotes epithelial attachment by increasing the rate of basement membrane assembly.

Expression of matrix metalloprotease-2-cleaved laminin-5 in breast remodeling stimulated by sex steroids

The extracellular matrix plays an important role in breast remodeling. We have shown that matrix metalloprotease-2 (MMP2) cleaves laminin-5 (Ln-5), a basement membrane component, generating a fragment called gamma2x. Human breast epithelial cells, while constitutively immobile on intact Ln-5, acquire a motile phenotype on MMP2-cleaved Ln-5. We hypothesize that this mechanism may underlie cell mobilization across the basement membrane during branching morphogenesis in breast development regulated by sex steroids. We report that the expression of MMP2 and cleavage of Ln-5 correlate well with tissue remodeling and epithelial rearrangement of the breast both in vivo and in vitro. Thus, the Ln-5 gamma2x fragment was detected by immunoblotting in sexually mature, pregnant, and postweaning, but not in prepubertal or lactating mammary glands. Furthermore, cleaved Ln-5, as well as MMP2, became detectable in remodeling glands from sexually immature rats treated with sex steroids. In rat mammary gland explants, epithelial reorganization and luminal cell morphological changes were induced by the addition of exogenous MMP2, in parallel to the appearance of cleaved Ln-5. Similar effects were observed in epithelial monolayers plated on human Ln-5 and exposed to MMP2. These results suggest that cleavage of Ln-5 by MMP2 might be regulated by sex steroids and that it may contribute to breast remodeling under physiological and possibly pathological conditions.

LAD-1 is absent in a subset of junctional epidermolysis bullosa patients

The anchoring filament protein LAD-1 has been recently identified as the target of autoantibodies in the acquired blistering disorder linear IgA bullous dermatosis. Because this protein appears to be involved in the process of dermal-epidermal cohesion, this study sought to determine the involvement of LAD-1 in the pathology of junctional epidermolysis bullosa (JEB). To this end, 44 patients with a variety of subtypes of JEB were analyzed by indirect immunofluorescence microscopy with antibodies to LAD-1, BP180, and laminin-5. We found that only patients with generalized atrophic benign epidermolysis bullosa (GABEB) contained LAD-1 defects. Of the 16 GABEB patients studied, 13 showed absent or greatly reduced expression of LAD-1 (including 2 patients with a peculiar interrupted staining pattern) and 3 patients showed defects of laminin-5 expression with normal LAD-1 expression. Patients who showed LAD-1 defects also showed abnormal expression of BP180. Keratinocytes were cultured from the skin of two GABEB patients and analyzed by indirect immunofluorescent microscopy. One culture demonstrated defects of BP180 and LAD-1 expression (which was also verified by radioimmunoprecipitation assay), and one culture showed decreased laminin-5 expression but normal BP180 and LAD-1 expression. Thus, these studies demonstrate that: (i) LAD-1 and BP180 are normally expressed in all subtypes of JEB except GABEB, (ii) the majority of GABEB patients show absent or near absent expression of both LAD-1 and BP180 but normal expression of laminin-5, and (iii) a smaller subset of GABEB patients show normal LAD-1 and BP180 expression but express persistent but reduced levels of laminin-5.

Immunodissection of the connective tissue matrix in human skin

Much of what has been learned of the components and structure of human skin over the past few years has been accomplished with the aid of antibody technology. Antibodies are used in techniques such as affinity chromatography to isolate individual molecules and by immunofluorescence and immunoelectron microscopy to identify each of those molecules as components of specific macromolecular assemblies present within the dermis. This manuscript is meant not as a review of technique but instead as a summary of recent progress made in the understanding of dermal matrix architecture.

Laminin-5 inhibits human keratinocyte migration

Laminin-5 (previously known as kalinin, epiligrin, and nicein) is an adhesive protein localized to the anchoring filaments within the lamina lucida space of the basement membrane zone lying between the epidermis and dermis of human skin. Anchoring filaments are structures within the lamina lucida and lie immediately beneath the hemidesmosomes of the overlying basal keratinocytes apposed to the basement membrane zone. Human keratinocytes synthesize and deposit laminin-5. Laminin-5 is present at the wound edge during reepithelialization. In this study, we demonstrate that laminin-5, a powerful matrix attachment factor for keratinocytes, inhibits human keratinocyte migration. We found that the inhibitory effect of laminin-5 on keratinocyte motility can be reversed by blocking the alpha3 integrin receptor. Laminin-5 inhibits keratinocyte motility driven by a collagen matrix in a concentration-dependent fashion. Using antisense oligonucleotides to the alpha3 chain of laminin-5 and an antibody that inhibits the cell binding function of secreted laminin-5, we demonstrated that the endogenous laminin-5 secreted by the keratinocyte also inhibits the keratinocyte's own migration on matrix. These findings explain the hypermotility that characterizes keratinocytes from patients who have forms of junctional epidermolysis bullosa associated with defects in one of the genes encoding for laminin-5 chains, resulting in low expression and/or functional inadequacy of laminin-5 in these patients. These studies also suggest that during reepithelialization of human skin wounds, the secreted laminin-5 stabilizes the migrating keratinocyte to establish the new basement membrane zone.

Laminin-6 and laminin-5 are recognized by autoantibodies in a subset of cicatricial pemphigoid

We characterized basement membrane zone (BMZ) autoantigens targeted by autoantibodies (AAb) from patients with cicatricial pemphigoid. Serum from a patient with severe oral cicatricial pemphigoid contained IgG anti-BMZ AAb. The AAb labeled a lower BMZ component on salt-split skin and localized to the lower lamina lucida/lamina densa by direct and indirect immunoelectron microscopy (IEM) but did not label blood vessels. The AAb did not react with EHS laminin-1 and type IV collagen, pepsinized human type IV collagen, recombinant entactin, or NC1 domain of type VII collagen by dot blotting and western blotting. We focused our studies on the laminin family, as laminin-5 was identified as an autoantigen in cicatricial pemphigoid. Culture-conditioned media from normal keratinocytes (containing laminin-6 and laminin-5) and JEB keratinocytes (containing laminin-6 but not laminin-5) were studied by western blotting. Under nonreducing conditions, the patient's AAb recognized a 600-kDa protein (laminin-6) intensely and a 400-kDa protein (laminin-5) weakly in normal keratinocyte medium even though abundant laminin-5 was present. InJEB keratinocyte medium, however, the 600-kDa protein (laminin-6) alone was recognized by the patient's AAb. The AAb also immunolabeled BMZ of JEB skin that lacked laminin-5. The AAb from this patient and two other patients with anti-laminin-5 cicatricial pemphigoid immunoprecipitated both laminin-6 and laminin-5. Taken together, the results of IEM, non-reducing western blotting, immunoprecipitation, and JEB skin BMZ immunolabeling indicate that laminin-6, as well as laminin-5, is identified by the AAb from a subset of cicatricial pemphigoid patients. We propose the name "anti-laminin cicatricial pemphigoid" for this subset.

The chemical composition of tooth enamel in recessive dystrophic epidermolysis bullosa: significance with respect to dental caries

Previous reports have linked the prevalence of tooth abnormalities with high caries experience in the different types of epidermolysis bullosa (EB). However, it is not known to what extent the apparent susceptibility to enamel caries is due to disease-related altered enamel chemistry in these cases. The aim of this study was to characterize the enamel of teeth from patients suffering from recessive epidermolysis bullosa dystrophica (rEBD) in terms of its mineral content, carbonate content, protein content, and amino acid composition. The results showed that dental enamel from these patients was essentially normal in terms of its chemistry. It is therefore concluded that the high caries experience in recessive dystrophic epidermolysis bullosa patients is probably related to other factors, such as compromised oral hygiene and prolonged oral clearance due to extensive oral soft tissue damage and a cariogenic diet.

Defective integrin alpha 6 beta 4 expression in the skin of patients with junctional epidermolysis bullosa and pyloric atresia

Junctional epidermolysis bullosa (JEB) is a heterogeneous group of rare inherited skin disorders in which defects in cell adhesion components cause incomplete formation of hemidesmosomes. We have immunohistochemically examined the skin from ten JEB patients (JEB gravis, n = 4; JEB mitis, n = 3; JEB plus pyloric atresia [JEB/PA], n = 3) using monoclonal antibodies specific for the integrin adhesion receptors alpha 3 beta 1 and alpha 6 beta 4, and for the alpha 3, beta 3, and gamma 2 subunits of the basement membrane ligand, laminin 5. Consistent with our previous reports, only the JEB gravis patients without associated pyloric atresia expressed reduced or absent epitopes for laminin-5 subunits in their epidermal basement membrane. In contrast, all three JEB/PA cases showed abnormalities in integrin alpha 6 beta 4, but not in laminin 5, expression in their basal epidermal cells. Integrin beta 4 subunit was undetectable in the biopsied epidermis of these JEB/PA individuals using five different monoclonal antibodies that recognize both intra- and extracellular epitopes. The absence of the beta 4 subunit in the epidermis of JEB/PA specimens was confirmed by Western blot analysis of tissue extracts. Epidermal expression of the integrin alpha 6 subunit was variable in the JEB/PA patients. Abnormal integrin alpha 6 beta 4 expression may define the subset of JEB cases with pyloric atresia. These results strongly implicate a functional role for alpha 6 beta 4 in the formation of complete hemidesmosomes and in stable adhesion of basal keratinocytes to the basement membrane in vivo.

Developmental expression of laminin-5 and HD1 in the intestine: epithelial to mesenchymal shift for the laminin gamma-2 chain subunit deposition

We report the expression pattern of hemidesmosome-associated proteins laminin-5, composed of alpha 3 beta 3 gamma 2 chains, and HD1 in the developing mouse and human intestine, an organ in which variations in structure and function parallel morphogenesis and differentiation. Immunocytochemistry analysis revealed the coexpression of laminin-5 and HD1 at the basal pole of differentiating epithelial cells. Distinct noticeable variations occurring in the location of laminin alpha 3 chain in development of mouse gut were stressed by the reverse transcriptase-polymerase chain reaction data. A peculiar finding was also the location of laminin gamma 2 chain in the intestinal muscle coat. The cellular origin of laminin gamma 2 chain was examined by immunocytochemistry on interspecies hybrid intestines with specific antibodies recognizing mouse antigens. Complementary and sequential production of laminin gamma 2 chain was observed, by epithelial cells as establishment of the basement membrane occurs and by mesenchymal cells in the more differentiated organ. These results support the concept of mesenchymal involvement in deposition of basement membrane molecules, a crucial process for intestinal differentiation. Taken together these data provide the first evidence for the coexpression of hemidesmosome-associated proteins in the gut, a non-stratified tissue.

Molecular complexity of the cutaneous basement membrane zone. Revelations from the paradigms of epidermolysis bullosa

Spectacular success has recently been made towards elucidation of the molecular basis of various forms of epidermolysis bullosa (EB), a group of heritable blistering skin diseases. The information derived from these studies has already had a profound impact in terms of precise diagnosis and classification, early prenatal prediction of the phenotype and genetic counseling in families at risk for recurrence. This review highlights recent progress made in defining the molecular basis of junctional and dystrophic forms of EB and the genotype/phenotype relationships established from these studies. Extensive molecular studies, such as the ones captured in this review, form a foundation for the rational design of gene therapies to counteract these conditions in the future.

Mutational hotspots in the LAMB3 gene in the lethal (Herlitz) type of junctional epidermolysis bullosa

The Herlitz type of junctional epidermolysis bullosa (H-JEB) is a severe blistering disease affecting the skin and mucous membranes, and laminin 5 has been implicated as the candidate gene/protein system for most patients with H-JEB. In this study, we have examined a cohort of 14 families with H-JEB for mutations in the LAMB3 gene. Premature termination codon mutations were delineated in both alleles of each proband in all pedigrees. Interestingly, two recurrent mutations, R42X and R635X, were noted in over 50% of the mutant LAMB3 alleles. These nonsense mutations occurred at CpG dinucleotide sequences, suggesting hypermutability of 5-methylcytosine to thymine. Additional evidence suggested that R42X and R635X represent mutational hotspots. First, the inheritance of R635X in a homozygous individual on two different genetic backgrounds was demonstrated by haplotype analysis. Furthermore, in one family, R42X was shown to be inherited on the maternal allele which lacked this mutation, suggesting that it arose as a result of maternal germline mutation. Elucidation of these two hotspot mutations will facilitate screening of additional JEB patients for the underlying mutations.

Structural and compositional alteration of tooth enamel in hereditary epidermolysis bullosa

Epidermolysis bullosa (EB) is a group of conditions characterized by basement membrane and cellular defects that result in skin fragility and variable extra-cutaneous involvement. The teeth can be severely affected with marked enamel malformations. The purpose of this study was to characterize the structure and composition of teeth from individuals representing the major EB groups (EB simplex, dystrophic EB and junctional EB). Teeth were examined from 28 individuals with EB and 10 healthy people unaffected by EB. Teeth from individuals with junctional EB had marked enamel hypoplasia with varying abnormalities in the enamel structure. Minor structural defects of enamel, including areas of surface pitting, were seen in the other EB types. Although there was a slight reduction (approximately 10%) in the enamel mineral content in several dystrophic EB and junctional EB teeth, the mean mineral content was similar for all EB enamel types and normal enamel. This study shows that while individuals with junctional EB have marked alteration of the enamel structure, the composition may be normal to only mildly altered. Laminin-5, the molecular defect in junctional EB, is associated primarily with alteration in the amount and/or structure of enamel while the mineralization process appears relatively intact. The marked enamel hypoplasia in this EB type suggests that laminin-5 plays an important role in the secretory phase of enamel development.

Prenatal diagnosis of Herlitz junctional epidermolysis bullosa by amniocentesis

Herlitz junctional epidermolysis bullosa (HJEB) is a severe blistering disorder which usually results in death during infancy. We have previously shown that the anchoring filament protein laminin-5 (kalinin/nicein), which mediates keratinocyte attachment and dermal-epidermal cohesion, is abnormally expressed in individuals with HJEB. Laminin-5 was detected by Western blot analysis in amniotic fluid from 44 consecutive normal second-trimester control pregnancies, but was undetectable in second-trimester amniotic fluid from four pregnancies with fetuses affected by HJEB. In one case of severe non-Herlitz JEB, laminin-5 was detected in both amniotic fluid and skin. In human amniotic fluid, the laminin-5 a3 subunit was processed to a major 165 kD species and a minor 145 kD species and the beta 2 subunit was partially processed to 105 kD. Although laminin-5 was covalently associated with laminin-6 (K-laminin) in amniotic membrane, no covalent interaction was detected in amniotic fluid. Laminin-5 from amniotic fluid strongly supported keratinocyte attachment. These results suggest that Western blot analysis of second-trimester amniotic fluid is useful in determining the prenatal diagnosis of HJEB and that laminin-5 may serve a physiologically important function in amniotic fluid.

Studies of patients with anti-epiligrin cicatricial pemphigoid

We have recently identified patients with a form of cicatricial pemphigoid who have IgG anti-basement membrane autoantibodies directed against epiligrin, a laminin isoform closely related if not identical to laminin 5. These patients' autoantibodies bind the lower lamina lucida of human epidermal basement membrane and immunoprecipitate this laminin isoform from extracts and media of biosynthetically radiolabeled human keratinocytes. Immunoblot studies show that these patients' autoantibodies specifically bind the alpha subunit of this laminin (i.e., laminin subunit alpha 3). We have found no evidence of these autoantibodies in normal volunteers or patients with other bullous skin diseases (including those with other forms of CP). These studies have identified a group of patients with an acquired, autoimmune, subepidermal bullous disorder who have disease-specific autoantibodies directed against the alpha subunit of epiligrin/laminin 5. These findings correlate with prior reports showing that a monoclonal antibody directed against this laminin subunit induces detachment of keratinocytes from extracellular matrix in vitro as well as epidermis from human skin in situ. Together, these findings suggest that this laminin mediates attachment of basal keratinocytes to epidermal basement membrane and that autoantibodies directed against it may be pathogenic. Moreover, recent studies showing that subunits of this laminin isoform are mutated in some patients with Herlitz's junctional epidermolysis bullosa indicate that acquired or inherited abnormalities in this adhesion ligand are associated with skin diseases characterized by separation of epidermis from epidermal BM.

Diminished expression of the extracellular domain of bullous pemphigoid antigen 2 (BPAG2) in the epidermal basement membrane of patients with generalized atrophic benign epidermolysis bullosa

Generalized atrophic benign epidermolysis bullosa (GABEB) is a nonlethal form of junctional epidermolysis bullosa characterized by generalized skin and mucosal blisters that heal with atrophy; other features include alopecia, nail dystrophy, large melanocytic nevi, and autosomal recessive inheritance. The specific aim of this study was to identify an abnormality in epidermal basement membrane adhesion molecules in well characterized GABEB patients that would explain why these subjects' epidermis separates from their epidermal basement membrane. Cryostat sections of nonlesional skin from 8 GABEB patients in 5 different families as well as skin from normal volunteers (controls) were studied by indirect immunofluorescence microscopy using rabbit antiserum directed against a BPAG1 fusion protein or monoclonal antibodies directed against the extracellular domain of BPAG2 (HD18 and 233), epiligrin (P1E1), laminin 5 (GB3), types IV and VII collagen, or integrin subunits alpha 2, alpha 3, beta 1, alpha 6, or beta 4. In these studies, monoclonal antibodies HD18 and 233 showed no reactivity and diminished reactivity, respectively, to the epidermal BM of all GABEB patients. Interestingly, in one patient, the absent or diminished reactivities of monoclonal anti-BPAG2 antibodies were limited to well demarcated portions of an otherwise intact epidermal basement membrane. Moreover, BPAG1, epiligrin, laminin 5, types IV and VII collagen, and all integrin subunits under study were expressed in the same manner in both GABEB and normal human skin. These findings identify an abnormality in the extracellular domain of BPAG2 in the skin of GABEB patients. BPAG2 (type XVII collagen) is a transmembrane, hemidesmosome-associated molecule whose extracellular domain resides at the exact level where blisters develop in the skin of patients with GABEB.(ABSTRACT TRUNCATED AT 250 WORDS)

Epiligrin is decreased in papulonodular basal cell carcinoma tumor nest basement membranes and the extracellular matrix of transformed human epithelial cells

Patients with anti-epiligrin cicatricial pemphigoid have anti-basement membrane autoantibodies that immunoprecipitate a set of disulfide-linked human keratinocyte polypeptides that co-migrate in sodium dodecyl sulfate polyacrylamide gel electrophoresis with the same complex identified by monoclonal anti-epiligrin (P1E1) and monoclonal anti-nicein/kalinin (GB3) antibodies. In an attempt to further compare the reactivity of patient autoantibodies, P1E1 and GB3, these reagents were tested against the tumor nest basement membranes of 7 papulonodular basal cell carcinomas. These studies found that all of these reagents showed markedly decreased or no reactivity against this substrate. Though their concordant lack of reactivity failed to distinguish these antibodies, these studies did identify a significant defect in papulonodular basal cell carcinoma tumor nest basement membranes. Similarly, integrin subunits alpha 6, beta 4, alpha 3, and alpha 2 as well as bullous pemphigoid antigens 1 and 2 (all potential receptors for the extracellular matrix ligands epiligrin and nicein/kalinin) were also reduced in these tumor nest basement membranes. These findings signify an extensive impairment in the lamina lucida of this neoplasm's basement membrane. Related comparative studies of normal human keratinocytes and transformed human epithelial cell lines (specifically, A-431 and HaCat cells) showed that epiligrin production is markedly decreased in the latter. Decreased expression of epiligrin and nicein/kalinin in papulonodular basal cell carcinoma tumor nest basement membranes in vivo and transformed epithelial cells in vitro indicate that this complex is a transformation-sensitive cell adhesion ligand.

Altered laminin 5 expression due to mutations in the gene encoding the beta 3 chain (LAMB3) in generalized atrophic benign epidermolysis bullosa

The anchoring filament component laminin 5 (kalinin/nicein) is a candidate protein for mutations in some hereditary blistering skin disorders. In this study, laminin 5 expression was assessed in a family with generalized atrophic benign epidermolysis bullosa, a non-lethal variant of the junctional form of epidermolysis bullosa. Immunofluorescence microscopy of the skin basement-membrane zone with a monoclonal antibody (GB3) revealed reduced anti-laminin 5 staining compared to normal controls. The labeling, when examined by immunoelectron microscopy, was present within the lower lamina lucida, immediately below the plane of blister formation. Numerous hemidesmosomes and well-formed anchoring filaments were seen on transmission electron microscopy. Polymerase chain reaction amplification of genomic DNA encoding the beta 3 subunit (LAMB3) of laminin 5, heteroduplex analysis of the polymerase chain reaction products, and nucleotide sequencing of the heteroduplexes revealed two putative mutations within the LAMB3 gene; these consisted of a premature termination codon in exon 3 and a missense mutation in exon 7. Exons 3 and 7 encode part of domain VI of the laminin 5 beta 3 chain short arm. This globular domain of the protein has been postulated to have an important function in the interaction of laminin 5 with other structural components of the basement membrane zone, such as laminin 6 (K-laminin). Thus the mutations delineated in this family may have a critical pathogenetic significance in reducing adhesion between the epidermis and the dermis.

Ultrastructural identification of basic abnormalities as clues to genetic disorders of the epidermis

The present article discusses specific, directly gene-dependent ultrastructural markers of dominantly inherited epidermal disorders that serve as clues to their underlying molecular genetic abnormalities. These are epidermolysis bullosa simplex Koebner and Weber-Cockayne with rupture or non-assembly of basal cell keratins and point mutations in keratins 5 and 14. Clumping of basal cell keratins is pathognomonic of EB Dowling-Meara and caused by mutations in hot spots of the rod domain of K5 and K 14. Clumps and aggregates of basal keratins occur side by side in the same cell and thus do not indicate specific different types of mutations. Similar clumping of suprabasal keratins in bullous CIE Brocq and in palmoplantar keratoderma Voerner have been assigned to identical types of mutations in the same critical position of the rod domain in K 1, K 10, and K 9, respectively. Highly unusual tubular keratins are pathognomonic of another dominant palmoplantar keratoderma type the genetic basis of which still awaits elucidation. Shell formation of (low molecular weight?) keratins in ichthyosis hystrix Curth-Macklin is not linked to the keratin gene clusters on chromosomes 12 and 17 and might be related to regulatory genes of keratin expression. Suprabasal shells in congenital reticular ichthyosiform erythroderma do not consist of keratins but resemble glycoprotein networks. Finally, the keratohyalin abnormality in ichthyosis vulgaris was the clue for the identification of a filaggrin deficiency, at the same time giving evidence to the heterogeneity of keratohyalin proteins.

Ultrastructural clues to genetic disorders of skin: the dermal-epidermal junction

The candidate gene approach in tracking the underlying cause of a number of genetic skin disorders has proved remarkably effective over the past few years. Electron microscopy has had a unique role in identifying morphologic abnormalities of various fibers, fibrils, and filaments, and helping to localize biochemical constituents to these structures. Nowhere is this approach more strongly demonstrated than in its application to different forms of epidermolysis bullosa, of which two major forms, junctional and dystrophic epidermolysis bullosa, are caused by mutations of genes encoding structural proteins in the dermal-epidermal junction.

Molecular basis of the dystrophic and junctional forms of epidermolysis bullosa: mutations in the type VII collagen and kalinin (laminin 5) genes

Epidermolysis bullosa (EB) is a group of heritable mechano-bullous skin diseases classified into three major categories, the simplex, junctional, and dystrophic forms, on the basis of the level of tissue separation within the dermal-epidermal basement membrane zone. Approaches of molecular biology have demonstrated that these three different forms of EB result from mutations in distinct genes: the simplex forms are due to mutations in the genes encoding keratins 5 and 14 expressed in basal keratinocytes; the junctional forms are associated with mutations in the kalinin/laminin 5 genes; and the dystrophic forms result from mutations in the type VII collagen gene (COL7A1). In this overview, we summarize our recent discoveries of pathogenic mutations in COL7A1, including premature termination codons that result in the severe, mutilating (Hallopeau-Siemens) type of recessive dystrophic EB and a glycine substitution in the collagenous region resulting in dominant dystrophic EB. Furthermore, we present evidence that implicates mutations in the kalinin/laminin 5 gamma 2 chain gene (LAMC2) in some forms of junctional EB. This information has provided the basis for DNA-based prenatal diagnosis during the first trimester of gestation, and sets the stage for the application of gene therapy to these devastating skin diseases in the future.