Basement Membrane Zone Components Research Articles

Type XVII collagen: Relevance of distinct epitopes, complement-independent effects, and association with neurological disorders in pemphigoid disorders.

Pemphigoid diseases (PD) are autoimmune skin blistering diseases characterized by autoantibodies directed against proteins of the cutaneous basement membrane zone (BMZ). One of the major antigens is type XVII collagen (BP180), a transmembrane glycoprotein, which is targeted in four PDs: bullous pemphigoid, mucous membrane pemphigoid, linear IgA dermatosis, and pemphigoid gestationis. To date, different epitopes on BP180 have been described to be recognized by PD disease patients’ autoantibodies. Different BP180 epitopes were associated with distinct clinical phenotypes while the underlying mechanisms are not yet fully understood. So far, the main effects of anti-BP180 reactivity are mediated by Fcγ-receptors on immune cells. More precisely, the autoantibody–antigen interaction leads to activation of complement at the BMZ and infiltration of immune cells into the upper dermis and, by the release of specific enzymes and reactive oxygen species, to the degradation of BP180 and other BMZ components, finally manifesting as blisters and erosions. On the other hand, inflammatory responses independent of Fcγ-receptors have also been reported, including the release of proinflammatory cytokines and internalization and depletion of BP180. Autoantibodies against BP180 can also be found in patients with neurological diseases. The assumption that the clinical expression of PD depends on epitope specificity in addition to target antigens, autoantibody isotypes, and antibody glycosylation is supported by the observation that epitopes of PD patients differ from those of PD patients. The aim of the present review is to describe the fine specificities of anti-BP180 autoantibodies in different PDs and highlight the associated clinical differences. Furthermore, the direct effects after binding of the autoantibodies to their target are summarized.

Nutritional impairment of neonates with epidermolysis bullosa: a retrospective study.

Epidermolysis bullosa (EB) is a highly invalidating genodermatosis characterized by skin and mucosa fragility and blister-formation caused by mutations of genes encoding components of the cutaneous basement membrane zone. Nutritional impairment is one of the main complications of all forms of EB, having a huge impact on growth, pubertal development, wound healing, resistance to infections and quality of life. In our study we have retrospectively evaluated 17 children with EB to define whether nutritional impairment in those patients is already present in the neonatal period. As secondary outcomes we considered nutritional status differences among EB subtypes and relative percentages of underweight infants at birth, first and third month. Moreover, information concerning feeding modality, possible complications were also collected, as well as cutaneous or systemic infections and duration of hospital stay. Our study demonstrated that nutritional impairment of neonates with EB has an early onset since as at first month 35% of patients were below 5th centile for weight-for-age, and 94% were below the 50th percentile. Moreover, the number of infants at one month of life <5th centile for weight-for-age was significantly higher compared to birth. The nutritional status is also heavily related to the occurrence of complications, in particular infections; therefore, the prevention of these complications must play a central role in the treatment of these infants, also to avoid any nutritional impairment. Nutritional status of neonates with EB seems to be compromised already during the first month of life and it is heavily related to the occurrence of infections; therefore, the prevention of these complications must play a central role in the treatment of these infants, also to avoid any nutritional impairment.

Characterizing the proteome of bullous pemphigoid blister fluid utilizing tandem mass tag labeling coupled with LC-MS/MS.

Bullous pemphigoid is an autoimmune blistering disease caused by autoantibodies against components of the cutaneous basement membrane zone. Autoantibodies lead to complement-dependent and -independent inflammation and blistering. Blister fluid is a valuable biologic resource, as it provides insight into both systemic and local microenvironment responses. Here, we utilized liquid chromatography with tandem mass spectrometry to characterize the bullous pemphigoid blister fluid proteome. We then depleted exosomes to better understand the exosomal versus non-exosomal proteome. We identified 339 proteins in the blister fluid of bullous pemphigoid patients. Gene ontology demonstrated enrichment of several key biologic processes including innate immune response, neutrophil degranulation, platelet degranulation, and complement activation. Exosome depletion resulted in a significant decrease in normalized reporter intensities of 192 proteins, consistent with our observation of a large number of exosomal proteins found in the blister fluid. We then compared the bullous pemphigoid blister fluid proteome to prior proteomic datasets in suction blister fluid, snake bites, and thermal burns, identifying 76 proteins unique to bullous pemphigoid. These include major basic protein, eosinophil peroxidase, galectin-10, and the immunoglobulin epsilon heavy constant region, consistent with tissue eosinophilia. We lastly validated several previously reported blister fluid exosomal components. Blister fluid in bullous pemphigoid contains a mixture of numerous biologic processes. While many of these processes are shared with blistering from alternative causes, we have identified several notable features unique to bullous pemphigoid.

A collagen Vα1-derived fragment inhibits FGF-2 induced-angiogenesis by modulating endothelial cells plasticity through its heparin-binding site

Type V collagen (ColV) is a component of the endothelial basement membrane zone. During angiogenesis, extracellular matrix remodelling results in the release of active protein fragments that display pro- or anti-angiogenic properties. The latter often exert their activity through their heparin-binding site. We previously characterized a ColVα1-derived fragment called HEPV that contains a high affinity-binding site for heparin and heparan sulphate chains. Here we show that HEPV binds to FGF2 through its heparin-binding site. Using in vitro and in vivo angiogenesis assays, we show that HEPV but not the HEPV mutant at the heparin-binding site, inhibits FGF2-dependant angiogenesis. On the opposite, HEPV does not bind to VEGFA and has no effect on VEGFA-mediated angiogenesis. In 3D collagen gels, the addition of HEPV abrogates endothelial cell invasion and sprouting induced by FGF2. Interestingly, in vivo experiments reveal that HEPV anti-angiogenic activity is associated with the appearance of endothelial to mesenchymal transition (EndMT) markers. Together, these findings indicate that the ColVα1-derived fragment HEPV functions as an anti-angiogenic factor that represses FGF2-mediated angiogenesis through the regulation of endothelial cell plasticity. Previous observations showing that ColV overexpression negatively regulates pathological angiogenesis were left unexplained. Our data provide insights into the possible molecular mechanisms.

Epidermolysis Bullosa-Associated Squamous Cell Carcinoma: From Pathogenesis to Therapeutic Perspectives.

Epidermolysis bullosa (EB) is a heterogeneous group of inherited skin disorders determined by mutations in genes encoding for structural components of the cutaneous basement membrane zone. Disease hallmarks are skin fragility and unremitting blistering. The most disabling EB (sub)types show defective wound healing, fibrosis and inflammation at lesional skin. These features expose patients to serious disease complications, including the development of cutaneous squamous cell carcinomas (SCCs). Almost all subjects affected with the severe recessive dystrophic EB (RDEB) subtype suffer from early and extremely aggressive SCCs (RDEB-SCC), which represent the first cause of death in these patients. The genetic determinants of RDEB-SCC do not exhaustively explain its unique behavior as compared to low-risk, ultraviolet-induced SCCs in the general population. On the other hand, a growing body of evidence points to the key role of tumor microenvironment in initiation, progression and spreading of RDEB-SCC, as well as of other, less-investigated, EB-related SCCs (EB-SCCs). Here, we discuss the recent advances in understanding the complex series of molecular events (i.e., fibrotic, inflammatory, and immune processes) contributing to SCC development in EB patients, cross-compare tumor features in the different EB subtypes and report the most promising therapeutic approaches to counteract or delay EB-SCCs.

Electron Microscopic and Immunohistochemical Findings of the Epidermal Basement Membrane in Two Families with Nail-patella Syndrome.

Nail-patella syndrome is an autosomal dominant disorder characterized by nail dysplasia and skeletal anomaly. Some patients have been shown to have ultrastructural abnormalities of the glomerular basement membrane that result in nephrosis. However, little has been reported on the epidermal basement membrane in this condition. This paper reports 2 families with nail-patella syndrome. Direct sequencing analysis of LMX1B revealed that family 1 and family 2 were heterozygous for the mutations c.140-1G>C and c.326+1G>C, respectively. To evaluate the epidermal basement membrane zone, ultrastructural and immunohistochemical analyses were performed using skin specimens obtained from the dorsal thumb. Electron microscopy showed intact hemidesmosomes, lamina lucida, lamina densa, and anchoring fibrils. Immunofluorescence studies with antibodies against components of the epidermal basement membrane zone revealed a normal expression pattern among the components, including type IV collagen. These data suggest that nail dysplasia in patients with nail-patella syndrome is not caused by structural abnormalities of the epidermal basement membrane.

High Expression of Collagen XVII Compensates for its Depletion Induced by Pemphigoid IgG in the Oral Mucosa

The basement membrane zone consists of multiple components, including collagen XVII (COL17), which is the target of bullous pemphigoid. To our knowledge, no research has addressed the differences in basement membrane zone components between the skin and oral mucosa; therefore, we investigated the basement membrane zone proteins, with a focus on COL17. The mRNA and protein expression levels of COL17 were significantly higher in oral keratinocytes than in skin keratinocytes. Hemidesmosomal COL17 expression was markedly higher in oral keratinocytes than in skin keratinocytes, and its level was associated with adhesion strength. Oral keratinocytes adhered to the extracellular matrix more tightly than did skin keratinocytes invitro. Based on these results, we attempt to explain the clinical diversity of bullous pemphigoid. COL17 depletion was more prominent in skin keratinocytes than in oral keratinocytes after treatment with COL17-NC16A mAbs, which have invivo pathogenicity. COL17 C-terminus mAbs, which are not pathogenic, facilitated COL17 depletion in combination treatment with COL17-NC16A mAbs in both types of keratinocytes. In summary, the greater amount of COL17 in oral keratinocytes than in skin keratinocytes is associated with the higher strength of oral keratinocyte hemidesmosomal adhesion at the basement membrane zone. Our results may explain why bullous pemphigoid blistering tends to be more prevalent in the skin than in the oral mucosa.

Case of epidermolysis bullosa acquisita with concomitant anti‐laminin‐332 antibodies

Subepidermal autoimmune blistering disease including bullous pemphigoid, pemphigoid gestationis, mucous membrane pemphigoid, anti-laminin-γ1 pemphigoid, linear immunoglobulin A bullous disease and epidermolysis bullosa acquisita (EBA), are all characterized by direct immunofluorescence microscopy or immunoglobulin deposition on the basement membrane zone. Among them, EBA is a rare acquired subepidermal autoimmune blistering disease of the skin and mucous membranes reactive with type VII collagen, a major component of the epidermal basement membrane zone. Anti-laminin-332-type mucous membrane pemphigoid has pathogenic autoantibodies against laminin-332, which is a basement membrane heterotrimeric protein composed of α3, β3 and γ2 laminin chains. We describe a 73-year-old Japanese man presenting with multiple, annular, tense blisters on the lower legs and oral lesions. Despite the severe clinical manifestations, the disease was successfully controlled by combination therapy of oral prednisolone and mizoribine. This case was confirmed to have autoantibodies to both type VII collagen and laminin-332 α3 chain by indirect immunofluorescence of 1 mol NaCl-split normal human skin, various immunoblot analyses and enzyme-linked immunosorbent assays. This case was a rare case of EBA with concomitant anti-laminin-332 antibodies.

Genital lichen planus: update on diagnosis and treatment.

Lichen planus (LP) is an inflammatory autoimmune disease that affects both glabrous and mucosal skin. Although pathophysiology has not yet been fully defined, LP is a T-cell mediated disorder that demonstrates an increased Th1 cytokine expression as well as T-cell reactivity against basement membrane zone components. In males, genital LP often takes its more classic form as pink, shiny, flat-topped papules on the glans and coronal sulcus. In women, erosive disease is most common and often leads to significant scarring and sexual dysfunction. Therapeutic management is challenging, and control rather than cure is the goal. Topical corticosteroids remain first-line therapy, but some women will require systemic immunosuppressants to achieve remission. Surgery is less common for women with significant scarring who wish to resume sexual activity. Further research is needed on pathogenesis, and randomized controlled trials are necessary to better define best treatments for this chronic disease.

A systematic review with pooled analysis of clinical presentation and immunodiagnostic testing in mucous membrane pemphigoid: association of anti-laminin-332 IgG with oropharyngeal involvement and the usefulness of ELISA.

Mucous membrane pemphigoid (MMP) is characterized by subepithelial blistering due to IgG autoantibodies targeting various components of the dermal-epidermal basement membrane zone. Immunodiagnostics play an important role in making a precise diagnosis. Measures of test sensitivity and specificity, however, typically come from studies in diseases such as bullous pemphigoid, where the exact antigenic site may not be the same. Additionally, the association of clinical phenotype and autoantibody profiles has been an area of debate. We evaluated the sensitivity and specificity of ELISA in MMP for the known target antigens BP180 and laminin-332, as well as characterized the frequency of IgG antibodies against each laminin-332 subdomain. Lastly, we analysed whether IgG auto-antibody profiles were associated with clinical phenotype. We performed a systematic review of Medline/PubMed to compile MMP patient demographics, clinical manifestations and immunodiagnostic results. ELISA sensitivities and specificities for autoantigens were calculated in patients with positive immunoblot or immunoprecipitationstudies. IgG reactivity for each laminin-332 subunit was recorded. Associations between positive immunological tests and clinical presentation were evaluated using chi-squared test tests or Fisher's exact test when appropriate. For patients with a positive immunoblot or immunoprecipitation to NC16a, ELISA using both the NC16a and C-terminal portion of BP180 demonstrated a sensitivity and specificity of 73% and 93%. However, for individuals with IgG against the C-terminal domain of BP180, the sensitivity and specificity was 43% and 56%, respectively. LN-332 ELISA demonstrated 75% sensitivity, but only for patients with IgG reactivity against the α3 subunit. In patients with laminin-332 MMP, 86.4% demonstrated IgG against the α3 subunit. IgG autoantibodies against laminin-332 are significantly associated with pharyngo-laryngeal (P < 0.0001) and oro-pharyngo-laryngeal (P = 0.006) involvement. Immunodiagnostics play a major role in diagnosing MMP, though limited sensitivity may necessitate several forms of testing for confirmation.

Distribution of basement membrane zone components in bullous lesions of subepidermal blistering diseases

Distribution of basement membrane zone components in bullous lesions of subepidermal blistering diseases

Differences in basement membrane zone components of normal conjunctiva, conjunctiva in glaucoma and normal skin

To describe the distribution of basement membrane zone (BMZ) components in normal conjunctiva, conjunctiva of patients with glaucoma and normal skin. Thirty-five normal conjunctival biopsies and 16 conjunctival biopsies of patients with glaucoma under topical anti-glaucomatous therapy were examined by immunohistochemistry. Antibodies were directed against laminin α chains, laminin subchains α1, α2, α3, β1, β3, γ1, γ2, γ3, kalinin, β4-integrin, and collagens IV and VII. Results were compared to the antigen distribution at the BMZ in normal skin. The BMZ of skin stained positive for all antibodies tested. In contrast to skin, the BMZ of normal conjunctiva was negative for laminin subunits α2, β1, β3, γ2 and γ3 in most or all specimens. Positive findings at the conjunctival BMZ of patients with glaucoma were comparable to normal conjunctiva for laminin α, α1, β3, γ1, γ3, laminin 5, β4-integrin, collagen IV and collagen VII. However, staining of the BMZ with antibodies to laminin β1 (p=0.002) and γ2 (p=0.017) was seen in a significantly higher rate in glaucoma compared to controls. Characteristic differences exist in the antigenicity of the BMZ in normal skin, normal conjunctiva and conjunctiva from patients with glaucoma, especially for laminin subchains. These differences may explain the variable ocular involvement in diseases of the BMZ. Moreover, they may explain the susceptibility of patients with glaucoma to develop mucous membrane pemphigoid-like disease. Alterations in conjunctival BMZ in glaucoma may be induced by long-term topical anti-glaucoma medications including various preservation agents.

Low-level laser therapy for oral mucous membrane pemphigoid

Mucous membrane pemphigoid (MMP) describes a group of chronic, inflammatory, sub epithelial blistering diseases that manifest a heterogeneous pattern of oral, ocular, skin, genital, nasopharyngeal, oesophageal, and laryngeal lesions. MMP is histologically characterizedby lineardepositionof IgG, IgA,or C3 along the epithelial basement membrane zone (BMZ). Autoantibodies against various epithelial BMZ components probablyplaya role in thepathogenesisof thisgroupofdiseases [1, 2].MMPdoesnothaveapredictablenatural history. In some patients, the disease is localized and has a slowly progressive course without complications; in others, it is devastating, with severe morbidity. There have been no large-scale, wellcontrolled studies regarding therapy for MMP and most of the therapeutic experience is from studies on cutaneous bullous pemphigoid [3].The choice of agents for its treatment ismainly based upon the sites of involvement, clinical severity, and disease progression [3].Usually, limited oral lesions are treated with topical immunosuppressive drugs. Low-level laser therapy (LLLT) is a novel approach increasingly used in medicine, which has potential biostimulating effects when applied to oral tissues thus improving wound healing [4, 5]. The basic principle of LLLT is based upon the biostimulation or the biomodulation effect: irradiation at a specific wavelength is able to alter cellular behavior. Laser biostimulationcanobtaindifferent intracellular biological reactions to stimulate regenerative abilities, without undesired adverse effects, reducing also the pharmacological support [6–8]. To date, two MMP cases have been described in literature to have been successfully treated with LLLT but in addiction with systemic [9] and topical [10] immunosuppressive therapy. We have reviewed our experience of treating three patients with MMP using only LLLT.

Hair Loss in Autoimmune Cutaneous Bullous Disorders

The expression of the basement membrane zone (BMZ) components in the anagen hair follicles of the human scalp is similar to that of interfollicular epidermis. Expression of the BMZ components varies according to the different follicular portions. Blistering of the scalp, involving lamina lucida and below, usually leads to scarring alopecia secondary to the inflammatory process in the interfollicular epidermis and in the upper portion of the hair follicle. This article discusses the presence of alopecia in the most common acquired forms of bullous disorders.

Spatial and temporal control of laminin-511 and -332 expressions during catagen

We recently reported that the basement membrane (BM) zone components laminin-511 and -332 precisely regulate hair growth spatially and temporally during the anagen stage of the hair cycle. In this study, we examined the localization and roles of laminin-511 and -332 during catagen in mice. Using tissue from C57BL/6 hair depilation model mice, we performed immunohistochemistry, in situ hybridization, western blotting, and quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) studies. Although the distribution of laminin-332 around the BM of lower hair follicles changed during catagen, its total expression was stable throughout catagen stages at both the mRNA and protein levels. In sharp contrast, in situ hybridization, western blotting, and QRT-PCR studies of laminin alpha 5 showed that laminin-511 expression was gradually downregulated. Moreover, while the injection of recombinant laminin-332 at anagen stage VI did not affect catagen progression, injection of a laminin-511-rich A549 cell conditioned media protein extract at anagen stage VI delayed progression of catagen. These results indicated that downregulation of laminin-511 is important for hair regression.

T cells reactive with the NC16A domain of BP180 are present in vulval lichen sclerosus and lichen planus

Lichen sclerosus (LS) is a chronic inflammatory skin condition. The recent demonstration of circulating autoantibodies to extracellular matrix protein 1 and to basement membrane zone (BMZ) components, chiefly BP180, suggests that autoimmunity to these components might contribute to pathogenesis. However, there is no binding of autoantibodies in vivo and as LS is characterized by a lymphocytic infiltrate, it seems likely that LS is mediated, in part, by antigen-specific lymphocytes. Similar mechanisms may apply to vulval lichen planus (LP), an interface dermatitis, with clinical and immunological overlap with LS. This study aims to test the hypothesis that T cells reactive with the NC16A domain of BP180 are present in the peripheral blood of patients with vulval LS and LP. Isolated peripheral blood mononuclear cells from 14 patients with vulval LS, 5 with vulval LP and 4 healthy controls were grown in vitro. We examined for immunogenicity of overlapping peptides spanning the NC16A domain of BP180 using interferon-gamma enzyme-linked immunospot assay (ELIspot) on the cultured T-cell lines. BMZ antibodies were assayed, HLA type determined and clinical parameters noted. Significant interferon-gamma production was observed in response to the NC16A peptides in 6 of the 14 vulval LS and 2 of the 5 LP patients, but not in the control subjects. There was an associated autoantibody response to BP180 in 3 LS and 1 LP patient with T-cell responses. These data suggest that in some vulval LS and LP patients, NC16A domain-specific T cells circulate at sufficiently high frequency to be detectable in vitro and show rapid effector function. There was no association with HLA type or clinical parameters. We have demonstrated that in > 40% of our vulval LS and LP patients, the NC16A domain of BP180 is a target for circulating T cells, and in vulval LS and LP there are associated autoantibodies to BP180.

Basement membrane changes in lichen planopilaris

Lichen planopilaris (LPP) is an inflammatory disease that affects the scalp and tends to produce cicatricial alopecia. The inflammatory process frequently results in the disruption of the basal cell of the external root sheath of the hair follicle. To investigate the alterations in the basement membrane zone (BMZ) in LPP by immunohistochemistry. Skin biopsies from six patients with LPP plus six normal controls were studied by immunohistochemistry with antibodies to the following BMZ components: cytokeratin 5, cytokeratin 14, BP230 (bullous pemphigoid), BP180, plectin, laminin 5, collagen IV and collagen VII. The localization and staining of the hemidesmosome, laminin and collagen components were strikingly different in the inflamed follicular epithelium when compared to the uninvolved follicles or interfollicular epithelium in active LPP lesions. The hemidesmosome-associated complexes were weakly expressed and discontinuous in involved hair follicles. The expression of laminin-5, type IV collagen and type VII collagen was disrupted and not linear along the BMZ with finger-like projections of the staining protruding into the dermis. The expression of the intermediate filaments was normal. These alterations in the BMZ in LPP may explain the abnormal healing at follicular level which leads to irreversible hair loss and scarring in this condition.

Corneal Limbal Microenvironment Can Induce Transdifferentiation of Hair Follicle Stem Cells into Corneal Epithelial-like Cells

The aim of this study was to investigate the transdifferentiation potential of murine vibrissa hair follicle (HF) stem cells into corneal epithelial-like cells through modulation by corneal- or limbus-specific microenvironmental factors. Adult epithelial stem cells were isolated from the HF bulge region by mechanical dissection or fluorescence-activated cell sorting using antibodies to α6 integrin, enriched by clonal expansion, and subcultivated on various extracellular matrices (type IV collagen, laminin-1, laminin-5, fibronectin) and in different conditioned media derived from central and peripheral corneal fibroblasts, limbal stromal fibroblasts, and 3T3 fibroblasts. Cellular phenotype and differentiation were evaluated by light and electron microscopy, real-time reverse transcription-polymerase chain reaction, immunocytochemistry, and Western blotting, using antibodies against putative stem cell markers (K15, α6 integrin) and differentiation markers characteristic for corneal epithelium (K12, Pax6) or epidermis (K10). Using laminin-5, a major component of the corneo-limbal basement membrane zone, and conditioned medium from limbal stromal fibroblasts, clonally enriched HF stem and progenitor cells adhered rapidly and formed regularly arranged stratified cell sheets. Conditioned medium derived from limbal fibroblasts markedly upregulated expression of cornea-specific K12 and Pax6 on the mRNA and protein level, whereas expression of the epidermal keratinocyte marker K10 was strongly downregulated. These findings suggest that adult HF epithelial stem cells are capable of differentiating into corneal epithelial-like cells in vitro when exposed to a limbus-specific microenvironment. Therefore, the HF may be an easily accessible alternative therapeutic source of autologous adult stem cells for replacement of the corneal epithelium and restoration of visual function in patients with ocular surface disorders.

Treatment strategies in mucous membrane pemphigoid

Mucous membrane pemphigoid (MMP) is an autoimmune blistering disorder that is characterized by subepithelial bullae. Various basement membrane zone components have been identified as targets of autoantibodies in MMP. Considerable variability exists in the clinical presentation of MMP. Mucous membranes that may be involved include the oral cavity, conjunctiva, nasopharynx, larynx, esophagus, genitourinary tract, and anus. A multidisciplinary approach is essential in the management of MMP. Early recognition of this disorder and treatment may decrease disease-related complications. The choice of agents for treatment of MMP is based upon the sites of involvement, clinical severity, and disease progression. For more severe disease, or with rapid progression, systemic corticosteroids are the agents of choice for initial treatment, combined with steroid-sparing agents for long-term maintenance. Due to the rarity of this disease, large controlled studies comparing the efficacy of various agents are lacking.

Role of the Basement Membrane Zone in Skin Development

Patterning of the skin during development requires precise reciprocol signaling between adjacent cells. Over the past two decades, several key studies have demonstrated a critical role for basement membrane zone (BMZ) components during epithelial pattern formation. In contrast to a static cellular glue, these papers provide a firm foundation for the notion that the BMZ actively shapes local cellular responses and tissue morphology. A major component of the BMZ are the integrins, a family of cell-surface receptors that adhere cells to the BMZ and mediate mechanical and chemical signals from it. These signals regulate the activities of growth factor receptors and ion channels, and control remodeling of the intracellular actin cytoskeleton. An early indication of the importance of integrins was in the identification of integrin b4 in the development of junctional epidermolyisis bullosa (Vidal et al., 1995). This suggested that skin integrity critically relied on these adhesion molecules. Later studies demonstrated that the key developmental role that integrins play came from mouse knockout experiments such as those that specifically removed integrin b1 in the skin (Brakebusch et al., 2000). The abnormal BMZ and lack of hair follicle proliferation demonstrated the multiple roles integrin b1 plays during development. Additional studies with other individual integrins such as a6 and av have also reinforced the idea that integrins play an instructive role in tissue morphogenesis apart from adhesion, although the precise mechanism of action is still poorly understood. The trimeric laminin family of proteins that acts as integrin coreceptors also play key roles in adhering cells to the BMZ as well as facilitating integrin signaling. Early reports of the role of laminin 5 (laminin 332) in junctional epidermolysis bullosa suggested it worked in a manner similar to integrin b4 in skin integrity and played an important role in epithelial development (Aberdam et al., 1994). However, additional studies by other groups, including that of Miner and co-workers, suggested the existence of numerous laminin genes and laminin isoforms, and suggested that each may play a key role in the process. Subsequent functional studies have shown the diversity of functions for each of the isoforms during skin development, including laminin 10 (laminin 511) and laminin 1 (laminin 111), in hair follicle morphogenesis. In addition to integrins and laminins, other components of the BMZ aid in regulating organ development by acting as growth factor co-receptors. For example, long after the morphogen fibroblast growth factor was identified, the key role for BMZ components as a fibroblast growth factor coreceptor was identified (Rapraeger et al., 1991). In this landmark paper, heparin sulfate proteoglycan was shown to be an obligate molecule to allow fibroblast growth factor to bind and activate its cognate receptor. This suggested that the orientation of surface glycosaminoglycans could regulate the activity of a morphogen substance. Since this study, similar types of BMZ coreceptor activities have also been shown for other developmental morphogens that regulate muscle, hair and other appendage development, including Wnt and Sonic hedgehog (Shh) ligands. Apart from signaling, BMZ components appear to shape the distance and distribution of key morphogens during epithelial development. In one of several landmark papers, The et al., (1999) demonstrated that the product of the tout-velu gene in Drosophila controls the distance that hedgehog ligand can travel through cells of the tissue, but not the absolute activity of the ligand on its receptor. The tout-velu gene encodes a heparin sulfate polymerase whose function is to modify glycosaminoglycan moeties of heparin sulfate proteoglycans. Subsequent studies in flies and vertebrate cells have identified other genes that regulate the process of cell-surface glycosylation such as sister of tout-velu, brother of tout velu, dally and dally-like and implicate cellular glycosylation in morphogen movement across a cell. Moreover, the vertebrate homologs of these molecules were also shown to be encoded by the EXT family of tumor suppressor genes, implicating morphogen tissue distribution as a novel tumor mechanism.