LAMC2 Research Articles

IGF-1 increases laminin, cyclin D1, and P21Cip1 expression in glomerular mesangial cells: An investigation of the intracellular signaling pathway and cell-cycle progression

Insulin-like growth factor (IGF)-1 is accumulated in the diabetic kidney and is considered to be involved in the development of glomerular sclerosis. Here, we investigate IGF-1 regulation of laminin, an extracellular matrix (ECM) component, and cyclin D1 and p21Cip1, cell-cycle progression factor, expressions in glomerular mesangial cells. We show that IGF-1 increases the level of laminin gamma1 and beta1 subunits approximately 1.5- and 2.5-fold, respectively, in a time-dependent manner. IGF-1 also stimulates protein kinase Akt/PKB phosphorylation at Thr 308, which correlates with its activity, up to 24 h. The Akt activation is coupled with Ser 9 phosphorylation of its downstream target, glycogen synthase kinase-3beta (GSK-3beta), which inhibits its kinase activity. Laminin beta1 is reduced significantly (P < 0.03) by inhibitors of Akt and p38MAPK whereas laminin gamma1 is not affected. Surprisingly, IGF-1 activates the expression of both cyclin D1 and cell-cycle arrest factor, p21Cip1 parallely. Pharmacological inhibition of calcineurin by cyclosporin A blocks IGF-1-induced cyclin D1 and p21Cip1expression significantly (P < 0.05). IGF-1 enhances cellular metabolic activity and viability of rat mesangial cells; however, they are arrested at the G1 phase of cell cycle as revealed by the FACS analysis. These results indicate that IGF-1 mediates mesangial cell-cycle progression, hypertrophy, and ECM protein synthesis. The Akt/GSK-3beta, p38MAPK, and calcineurin pathways may play an important role in IGF-1 signaling, cell-cycle regulation, and matrix gene expression in mesangial cells leading to the development of diabetic glomerulopathy.

血中ラミニンγ２鎖濃度測定による頭頸部癌診断に関する検討

Laminin gamma2 chain (LN gamma2), expressed in human cancer cells and correlated with cancer malignancy, is cleaved by proteases and secreted into circulation. We measured the blood concentration of LN gamma2 in patients with head and neck cancer by an immuno-fluorescence assay using monoclonal antibodies against human LN gamma2. The normal blood concen- showed normal LN gamma2 concentration less than 50 ng/ml and 20 (33%) increased concentration exceeding 50 ng/ml. The relative ratio of the number of patients who showed increased LN gamma2 concentration correlated with the clinical stages of cancer. The blood concentration of LN gamma2 in 24 who initially showed normal concentrations did not change after radical treatments. Five who initially showed increased LN gamma2 concentration showed decreased concentration of less than 50 ng/ml after radical treatment. Four showed increased LN gamma2 concentration after treatment, and presented residual cancer, which killed them. Three of the 4 patients showed marked increase in LN gamma2 concentration exceeding 100 ng/ml and developed multiple distant metastases to the lung, liver, bone, and skin. The blood concentration of LN gamma2 in patients with head and neck cancer may thus indicate the amount of highly malignant cancer cells expressing LN gamma2. The blood concentration of LN gamma2 could therefore serve as a new tumor marker that might indicate the malignancy of and efficacy of treatments for head and neck cancer.

The clinicopathologic significance of laminin-5 gamma2 chain expression in cervical squamous carcinoma and adenocarcinoma

Carcinoma of the uterine cervix is one of the most prevalent malignancies among women in developing countries and the third most common type worldwide. Squamous cell carcinoma predominates in the cervix uteri, while adenocarcinoma and adenosquamous carcinomas represent about 10-15% of all cervical cancers. Many studies have confirmed that the human papillomavirus (HPV) is the most important etiologic factor in the development of cervical cancer. The aim of our study was to investigate the expression of the laminin-5 gamma2 chain in primary malignancies of the cervix uteri and to focus on the clinicopathologic significance of the expression of the laminin-5 gamma2 chain in cervical squamous carcinoma and adenocarcinoma with respect to age and survival of the patients. The study consisted of a total of 89 cases of invasive cervical cancer (54 squamous carcinomas and 35 adenocarcinomas). The laminin-5 gamma2 chain was found in 80% of all the squamous carcinoma and in 66% of cervical adenocarcinoma. There was no correlation of the high expression of laminin-5 with survival. The univariate analysis in squamous cell carcinoma showed that factors such as the stage of the disease and positive lymph nodes had an impact on the survival of the patients, whereas in the multivariate analysis, only age at diagnosis was an independent prognostic factor. However, in cases with cervical adenocarcinoma, only the stage of the disease was an independent prognostic factor. There was no difference between HPV-positive and HPV-negative tumors concerning the high expression of laminin-5 gamma2 chain. Our results indicate that the majority of the primary cervical tumors, especially squamous cell carcinoma, showed expression of laminin-5 gamma2 chain immunoreactivity. Independent prognostic values for the survival of the patients were age and stage of the disease.

Proteolytic Processing of the Laminin α3 G Domain Mediates Assembly of Hemidesmosomes but Has No Role on Keratinocyte Migration

Laminin-5 (Lm5), the major adhesion ligand of basal epithelial cells, undergoes complex extracellular proteolytic processing that influences cell adhesion and migration. In tumor cell lines, the proteolytic truncation of the C-terminal G domain of the Lm alpha3 chain induces assembly of hemidesmosomes and downregulates cell migration. To define the biological functions of the alpha3 G domain processing in physiological conditions, we have expressed a series of mutant alpha3 complementary DNA in human primary alpha3-null keratinocytes immortalized by human papillomavirus E6E7 (HKalpha3 cells). Using monolayer and organotypic cell cultures we show that: (1) the hinge region between subdomains G3 and G4 carries the proteolytic cleavage sites; (2) nucleation of the hemidesmosomal proteins is independent of the proteolytic maturation of the alpha3 G domain, whereas formation of mature hemidesmosomes relies on proteolytic cleavage of alpha3; and (3) the proteolytic processing plays no role in cell migration, which suggests that nucleation of hemidesmosomal structures in culture does not reflect the migratory potential of the epithelial cells. Our results also demonstrate that HKalpha3 cells are a unique model system, which will be useful to dissect the functions and molecular interactions of Lm5.

Laminin‐5γ2 chain expression in cervical intraepithelial neoplasia and invasive cervical carcinoma

To analyze the expression of laminin-5 gamma 2 chain, a protein which plays a major role in keratinocyte migration, in cervical intraepithelial neoplasia (CIN), and invasive cervical carcinoma associated with high-risk oncogenic human papillomaviruses (HR-HPVs). The expression of laminin-5 gamma 2 chain protein has been analyzed by immunohistochemistry in 17 cases of low-grade squamous intraepithelial lesions (LSIL-CIN1), 35 high-grade squamous intraepithelial lesions (HSIL-CIN2/3), 18 microinvasive or invasive carcinomas, and three metastatic lymph nodes. All these lesions have been proved to contain HR-HPVs and were also positive for p16 protein which classically is overexpressed at all stages of cervical neoplasia and dysplasia linked with HR-HPVs. 20 cases of normal cervix served as controls. The expression of laminin-5 gamma 2 chain protein was observed in 100% of invasive or microinvasive carcinoma and in their related lymph node metastasis with an immunoreactivity located preferentially at the invasive front of the lesions. All the HSILs (100%) associated with invasive carcinoma were also positive. In contrast, in HSILs without associated invasive component, the expression of the protein has been found in only 34% of cases. In positive HSILs, laminin-5 gamma 2 protein was expressed in basal layers. In LSILs and normal epithelium, no expression of the protein was noted. We conclude the following: (i) the expression of laminin-5 gamma 2 is a late event in cervical carcinogenesis increasing with the grade of dysplastic lesions; (ii) laminin-5 gamma 2 expression facilitates the identification of invasive and microinvasive lesions which could be difficult to diagnose on the basis of routine stains; (iii) laminin-5 gamma 2 expression in HSILs could potentially identify those lesions with a more increased risk of tumor progression.

Transforming growth factor-β1 regulation of laminin γ1 and fibronectin expression and survival of mouse mesangial cells

The transforming growth factor-beta (TGF-beta) 1 is a mediator of extracellular matrix (ECM) gene expression in mesangial cells and the development of diabetic glomerulopathy. Here, we investigate the effects of TGF-beta1 on laminin gamma1 and fibronectin polypeptide expression and cell survival in mouse mesangial cells (MES-13). TGF-beta1 (10 ng/ml) stimulates laminin-gamma1 and fibronectin expression approximately two-fold in a time-dependent manner (0-48 h). TGF-beta1 treatment also retards laminin-gamma1 mobility on SDS-gels, and tunicamycin, an inhibitor of the N-linked glycosylation, blocks the mobility shift. TGF-beta1 increases the binding of laminin gamma1 to WGA-agarose and the binding is abolished by tunicamycin suggesting that laminin gamma1 is modified by N-linked glycosylation. TGF-beta1 also elevates fibronectin glycosylation but its mobility is not altered. The degradation of laminin gamma1 and fibronectin proteins is reduced by their glycosylation. In addition, TGF-beta1 enhances mesangial cell viability and metabolic activities initially (0-24 h); however, eventually leads to cell death (24-48 h). TGF-beta1 elevates pro-apoptotic caspase-3 activity and decrease cell cycle progression factor cyclin D1 expression, which parallels cell death. These results indicate that TGF-beta1 plays an important role in ECM expression, protein glycosylation and demise of mesangial cells in the diabetic glomerular mesangium.

Diffuse expression of laminin γ2 chain in disseminating and infiltrating cancer cells indicates a highly malignant state in advanced tongue cancer

The expression of laminin (LN)gamma2 chain in the primary lesions of 20 patients with advanced tongue cancer was analyzed. Positive expressions of LNgamma2 were noted in all of the primary tissue specimens, however, the expression patterns clearly differed according to the mode of growth and invasion of cancer cells. In tumor nests where cancer cells preserved cell-cell adhesiveness and showed polar differentiation, LNgamma2 was expressed only in the peripheral cells of the tumor nests; peripheral expression. On the other hands when cancer cells diminished their cell-cell adhesiveness and strongly infiltrated through stroma, almost all of the cancer cells diffusely expressed LNgamma2; diffuse expression. The peripheral expression of LNgamma2 were noted in 13 patients and the diffuse expressions were noted in 7 patients. The rates of positive cervical metastases according to the expression type were 7/13 for the peripheral expression and 7/7 for the diffuse expression (p = 0.02). The diseases specific 3-year survival rates for the patients with the peripheral expression and the diffuse expression were 68% and 14%, respectively (p = 0.02). The diffuse expression of LNgamma2 in the disseminating and infiltrating cancer cells might indicate a highly malignant state in advanced tongue cancer. Therefore, a more intensive treatment modality would be necessary for the patients with advanced tongue cancer showing the diffuse LNgamma2 expression.

The expression pattern of laminin isoforms in Hirschsprung disease reveals a distal peripheral nerve differentiation

Hirschsprung disease (HD), a developmental disorder, is associated with failure of enteric ganglia formation. Signaling molecules, including secreted basement membrane molecules, derived from the mesenchyme of the gut wall play an important role in the colonization and/or differentiation of the enteric nervous system. The current study aims to define the possible alterations of laminins involved in the pathogenesis of HD. Expression of the various laminin alpha, beta, and gamma chains, was assessed in the aganglionic, transitional, and ganglionic bowel segments of patients with HD or with other motor disorders. Cytoskeletal, neuronal, and glial markers were also included in this study. The major finding highlighted by the present work concerns the clear identification and location of myenteric aganglionic plexuses in HD with some of the laminin antibodies, which reveal a peripheral nerve type of differentiation. Furthermore, we could show an increase of laminin alpha5 chain immunostaining in the dilated muscle of the ganglionic bowel upstream the distal aganglionic region in a subgroup of patients with HD, as well as a relocalization of laminin alpha2 chain in the subepithelial basement membrane. Overall, these basement membrane molecules could provide useful markers for diagnosis of aganglionosis or hypoganglionosis.

Laminin α1 Chain Corrects Male Infertility Caused by Absence of Laminin α2 Chain

Laminins are important for basement membrane structure and function. The laminin alpha2 chain is a major component of muscle basement membranes, and mutations in the laminin alpha2 gene lead to congenital muscular dystrophy in humans and mice. Although the laminin alpha2 chain is prominently expressed in testicular basement membranes, its role in testis has remained unclear. Here, we show that laminin alpha1, alpha2, beta1, beta2, gamma 1, and gamma 3 chains are the major laminin chains in basement membranes of seminiferous tubules. In laminin alpha2 chain-deficient dy(3 K)/dy(3 ASK) mice, lack of laminin alpha2 chain led to concurrent reduction of laminin gamma 3 chain and abnormal testicular basement membranes. Seminiferous tubules of laminin alpha2 chain-deficient dy(3 K)/dy(3 K) mice displayed a defect in the timing of lumen formation, resulting in production of fewer spermatides. We also demonstrate that overexpression of laminin alpha1 chain in testis of dy(3 K)/dy(3 K) mice compensated for laminin alpha2 chain deficiency and significantly reversed the appearance of the histopathological features. We thus provide genetic data that laminin alpha chains are essential for normal testicular function in vivo.

Differential localization of laminin γ2 and integrin β4 in primary cultures of the rat gingival epithelium

The aim of this study was to investigate the differential immunolocalization of laminin gamma(2) and integrin beta(4) in primary cultures of the rat gingival epithelium. The gingival epithelium was obtained from Sprague-Dawley rats and was cultured in serum-free keratinocyte growth medium (DK-SFM). Western blotting analysis, immunofluorescence, confocal laser scanning microscopy (CLSM), and immuno-gold labeling for laminin gamma(2) and integrin beta(4) were employed. CLSM images for laminin and integrin were analyzed in horizontal (x-y axis) and in vertical (x-z axis) sections. Both laminin gamma(2) and integrin beta(4) were detected by Western blot analysis in the gingival epithelium. Immunolocalization of laminin gamma(2) was distinct in the cytoplasm to form one or two irregular rings in gingival epithelial cells. By contrast, integrin beta(4) was localized diffusely in the cytoplasm. F-actin (indicating actin filaments) was clearly discernible at the periphery of the cytoplasm to form a cellular fringe. In x-z axis images obtained by CLSM, laminin gamma(2) was recognized as large foci in the most inner portion just above the basal plasma membrane. Integrin beta(4) existed in the area where F-actin was labeled surrounding the membrane. Immuno-electron microscopy showed that 10nm colloidal gold particles indicating laminin gamma(2) were mainly localized at the extracellular portion and in the peripheral cytoplasm, whereas integrin beta(4) was distributed in the cytoplasm close to the basal plasma membrane but not in extracellular regions. In primary cultures of the rat gingival epithelium, both laminin gamma(2) and integrin beta(4) may be produced by the epithelium, and irregular rings of laminin gamma(2) are formed in areas where gingival cells adhere to the extracellular matrix.

Analysis of activated EGFR signalling pathways and their relation to laminin-5 γ2 chain expression in oral squamous cell carcinoma (OSCC)

Overexpression of epidermal growth factor receptor (EGFR) was shown for the majority of squamous cell carcinomas. The EGFR expression correlates to tumour size, stage and cytoplasmic accumulation of the laminin-5 gamma2 chain (Ln-5/gamma2), which is known as a marker of invading tumour cells. There is only limited knowledge if and how EGFR signalling pathways are important for invasion-associated processes and for the regulation of Ln-5/gamma2. Therefore the distribution of phosphorylated Erk1/2, p38 MAPK and Akt was immunohistochemically defined in oral squamous cell carcinoma (OSCC) of different histological grade and compared to histological criteria of invasion and cytoplasmic Ln-5/gamma2 deposition. With raising histological grade, there is a slight increase in nuclear pErk1/2-stained tumour cells (P=0.398) and a loss of nuclear (P=0.593) and increased cytoplasmic staining (P=0.144) of pAkt mainly in invading OSCC cells. Nuclear pp38 MAPK could only be sporadically detected in few cases. In case of pErk1/2 and pAkt, only a partial co-localisation could be revealed in cases with abundant kinases and Ln-5/gamma2. Among the investigated kinases, only pAkt shows a relation to histological grade and invasion in OSCC. pErk1/2, pp38 MAPK and pAkt do not represent a direct link between EGFR and Ln-5 synthesis. Therefore, enhanced Ln-5/gamma2 may be a secondary phenomenon of EGFR-induced tumour cell proliferation and dissemination.

A novel classification of tumour budding in colorectal cancer based on the presence of cytoplasmic pseudo‐fragments around budding foci

Tumour budding is an adverse prognostic factor in colorectal cancer (CRC). We have investigated the significance of cytoplasmic fragments occurring in the immediate vicinity of tumour budding foci. Seventy-three CRCs with high-grade budding (> 10 budding foci in a x 20 objective field) were classified according to extent of budding (10-19 versus 20+ foci) and by the presence or absence of cytoplasmic fragments identified by immunostaining for cytokeratin. In serial sections, cytoplasmic fragments were shown to be dendritic cell processes in continuity with budding tumour cells and were renamed pseudo-fragments. Cytoplasmic pseudo-fragments, but not extent of budding, were associated with aberrant expression of beta-catenin (P = 0.045) and laminin-5 gamma2 (P < 0.0001), and with absent peritumoral lymphocytic infiltration (P = 0.0077). Cytoplasmic pseudo-fragments had a stronger association with infiltrating growth pattern (P = 0.0014) than extent of tumour budding (P = 0.014). There was no association between extent of budding and cytoplasmic pseudo-fragments (P = 0.12). Cytoplasmic pseudo-fragments may be a marker for an activated budding phenotype that is associated with cell motility and increased invasiveness in CRC and is independent of the extent of budding.

Basement membrane composition in the early mouse embryo day 7

Basement membranes (BM) are specialized structures of the extracellular matrix known to be involved in various early developmental processes. Despite numerous investigations on the localization of BM components, it remains unknown which molecules are expressed in early developmental stages and by which germ layers these proteins are produced. Therefore, we tested for all known laminin chains, nidogens, collagen type IV, and perlecan by means of light microscopic immunostaining and performed in situ reverse transcriptase-polymerase chain reaction to detect the mRNAs specific for laminin alpha1, laminin beta1, the alpha1 chain of collagen type IV, nidogen-2, and perlecan in the early mouse embryo, day 7, in vivo. Only the laminin chains alpha1, beta1, and gamma1 were detected immunohistochemically throughout the entire endodermal and ectodermal BM zones of the embryo proper. The mRNA of laminin alpha1, laminin beta1, collagen type IV, nidogen-2 and perlecan were expressed in the ectoderm-derived mesoderm, in the endoderm as well as in the ectoderm. In contrast, Reichert's membrane was positive for all laminin chains except for the alpha4, alpha5, beta3, and gamma3 chains. Moreover, maternal epithelial as well as mesenchymal cells expressed laminins, nidogen-1 and nidogen-2, collagen type IV, and perlecan. In conclusion, laminin-1 might be the only laminin isoform in the early mouse embryo that, together with the other main BM components, nidogens, collagen type IV, and perlecan, is synthesized by all three germ layers.

Comparative chromosomal studies of E. caballus (ECA) and E. przewalskii (EPR) in a female F1 hybrid

Previous research revealed that the karyotypes of Equus przewalskii (2n = 66) and Equus caballus (2n = 64) differ by one pair of metacentric chromosomes, present in ECA but not in EPR, and two pairs of acrocentric chromosomes found only in the EPR karyotype. The formation of a trivalent during meiosis in a male F1 hybrid and the homologies in G-banding patterns suggest that ECA 5 corresponds to two acrocentric EPR chromosomes resulting from a Robertsonian fusion or fission event. Chromosomal investigations of a female interspecies F1 hybrid including banded karyograms and fluorescence in situ hybridization (FISH) studies focusing on the p and q arm of ECA 5 were conducted. Q- and G-banding patterns of E. caballus, E. przewalskii and the hybrid revealed interspecies homology between all chromosome pairs except for ECA 5, EPR 23 and EPR 24, which were unique for that particular species. Furthermore, they indicated homology between ECA 5p and EPR 23 as well as between ECA 5q and EPR 24. FISH revealed hybridization of the BACs laminin beta 3 (LAM B3) and laminin gamma 2 (LAM C2) to ECA 5p and EPR 23. However, nuclear factor I (NFIA) and immunoglobulin lambda (IGL@), primarily assigned to ECA 5q, mapped to ECA 7 and EPR 6 respectively. Thus the karyotypes of E. caballus and E. przewalskii differ solely by one Robertsonian translocation (ECA 5 =EPR 23 + EPR 24).

Prognostic implication of laminin-5 gamma 2 chain expression in the invasive front of colorectal cancers, disclosed by area-specific four-point tissue microarrays

The laminin-5 gamma 2 chain (LN-5γ2) is known to be a marker of invasion in several cancer types. Our purpose was to examine the prognostic significance of LN-5γ2 expression in different areas of individual colorectal cancers (CRCs) by using tissue microarrays (TMAs), and to clarify the optimal areas for prognostic assessment. Using formalin-fixed paraffin-embedded tissue blocks of pT3 primary CRCs resected from 120 patients, we constructed TMA blocks of tissue core specimens taken from the submucosal invasive front, subserosal invasive front, central area, and rolled edge of each tumor. Using these four-point TMA sets, cytoplasmic LN-5γ2 expression was immunohistochemically surveyed, and the area-specific prognostic significance of LN-5γ2 expression was evaluated. The data revealed that 35, 30, 15 and 10% of the 120 CRCs showed high-grade LN-5γ2 expression in the submucosal invasive front, subserosal invasive front, central area and rolled edge, respectively. Disease-specific survival curves for the groups with high- and low-grade LN-5γ2 in the submucosal invasive front and subserosal invasive front were different significantly or of marginal difference (respective 5-year survival rates: 54 and 78% for submucosal invasive front (P=0.030) and 58 and 75% for subserosal invasive front (P=0.055)). Multivariate analysis revealed that the grades of LN-5γ2 expression in submucosal invasive front (hazard ratio=2.0, P=0.047) and subserosal invasive front (hazard ratio=2.9, P=0.0033) were independent prognostic factors. In contrast, the grades of LN-5γ2 expression in the central area and rolled edge did not have a significant impact on patient prognosis. Analysis using area-specific four-point TMAs clearly demonstrated that LN-5γ2 expression in the invasive front largely influences the degree of clinical aggressiveness of CRC and its tendency to metastasize.

Junctional epidermolysis bullosa in two domestic shorthair kittens

This article describes two cases of junctional epidermolysis bullosa in nonrelated kittens. Both cats exhibited pinnal erosions, oral ulcerations and severe onychomadesis. Histopathology, electron microscopy and/or indirect immunoperoxidase revealed subepidermal clefting, with the lamina densa remaining attached to the floor of the vesicles. Indirect immunofluorescence revealed reduced staining for laminin-5 gamma2 subunit in case 1 and beta3 subunit in case 2.

Entactin and laminin gamma1-chain gene expression in the early chick embryo

The expression patterns of entactin and laminin gamma1 chain genes were examined by in situ hybridization of their mRNAs in the early chick embryo from stage X (morula) to stage HH10-11 (10-somites). The entactin and laminin gamma1 transcripts were found in abundance in the embryo at stage X. Entactin polypeptides were detected in embryos at stage X by immunoprecipitation. The expression of the laminin transcripts was intense and of entactin milder in the epiblast and in the hypoblast of embryos at stage XIII (blastula). During gastrulation (stage HH3-4), the laminin gamma1 and entactin cRNAs gave strong signals in the cells ingressing through the primitive streak, in the migrating mesenchymal cells and the cells of the lower layer. At the neurula stage (stage HH5-6), punctate groups of cells expressed laminin gamma1 strongly in the neural ectoderm, while the signal of expression was milder and more uniform in chordamesoderm. The entactin cRNAs gave a strong punctate pattern of mRNA expression in the neural ectoderm, in mesoderm and in endoderm in embryos at the late gastrula stage (HH4), but mRNA expression was mild in the neural plate and in mesoderm and gave no signal in endoderm and lateral ectoderm in embryos at stage HH6 (neurula). At the 10-somite stage, the laminin gamma1 cRNAs gave strong signals in the neural tube and in neural crest cells migrating along the neural tube ventrally and low signals in ectoderm, intense signals in the myotome and milder signals in the dermatome and sclerotome of somites and intense signals in the mesonephric tubules. The punctate pattern of entactin expression was notable in cells at all stages studied. Ubiquitous expression of laminin gamma1 and entactin genes during the morula and blastula stages becomes restricted to specific cell populations as the first cell commitments start.

Complete paternal uniparental isodisomy of chromosome 1 resulting in Herlitz junctional epidermolysis bullosa

Herlitz junctional epidermolysis bullosa (JEB) is an autosomal recessive mechanobullous disorder that results from loss-of-function mutations in the genes encoding the basement membrane component, laminin 5. Typically, there are frameshift, splice site or nonsense mutations on both alleles of either the LAMA3, LAMB3 or LAMC2 genes, with affected individuals inheriting one mutated allele from each parent. In this report, we describe a patient with Herlitz JEB in whom DNA analysis revealed homozygosity for the recurrent nonsense mutation R635X in LAMB3, located on chromosome 1q32.2. However, screening of parental DNA showed that although the patient's father was a heterozygous carrier of this mutation, the mother's DNA showed only wild-type sequence. Subsequent genotype analysis using 13 microsatellite markers spanning chromosome 1 revealed that the affected child was homozygous for the entire series of markers tested and that all of the alleles originated from the father. These results indicate that the Herlitz JEB phenotype in this patient is due to complete paternal isodisomy of chromosome 1 and reduction to homozygosity of the mutant LAMB3 gene locus. This is the fourth case of uniparental disomy to be described in Herlitz JEB, but it represents the first example of complete paternal isodisomy for chromosome 1 with a pathogenic mutation in the LAMB3 gene. These findings have important implications for mutation screening in JEB and for genetic counselling.

Membrane-type Matrix Metalloproteinase-1 (MT1-MMP) Is a Processing Enzyme for Human Laminin γ2 Chain

Processing of the laminin-5 (Ln-5) gamma 2 chain by membrane-type-1 matrix metalloproteinases (MT1-MMP) promotes migration and invasion of epithelial and tumor cells. We previously demonstrated that MT1-MMP cleaves the rat gamma 2 chain at two sites, producing two major C-terminal fragments of 100 (gamma 2') and 80 (gamma 2 x) kDa and releasing a 30-kDa fragment containing epidermal growth factor (EGF)-like motifs (domain III (DIII) fragment). The DIII fragment bound the EGF receptor (EGF-R) and stimulated cell scattering and migration. However, it is not yet clear whether human Ln-5 is processed in a similar fashion to rat Ln-5 because one of the two MT1-MMP cleavage sites present in rat gamma 2 is not found in human gamma 2. To identify the exact cleavage site for MT1-MMP in human Ln-5, we purified both the whole molecule as well as a monomeric form of human gamma 2 that is frequently expressed by malignant tumor cells. Like rat Ln-5, both the monomer of gamma 2, as well as the gamma 2 derived from intact Ln-5, were cleaved by MT1-MMP in vitro, generating C-terminal gamma 2' (100 kDa) and gamma 2 x (85 kDa) fragments and releasing DIII fragments (25 and 27k Da). In addition to the conserved first cleavage site used to generate gamma 2', two adjacent cleavage sites (Gly(559)-Asp(560) and Gly(579)-Ser(580)) were found that could generate the gamma 2 x and DIII fragments. Two of the three EGF-like motifs present in the rat DIII fragment are present in the 27-kDa human fragment, and like the rat DIII, this fragment can promote breast carcinoma cell migration by engaging the EGF-R. These results suggest that MT1-MMP processing of Ln-5 in human tumors may stimulate the EGF-R, resulting in increased tumor cell scattering and migration that could possibly increase their metastatic potential.

Segment‐specific but pathologic laminin isoform profiles in human labial salivary glands of patients with Sjögren's syndrome

To assess the laminins in basement membrane of the labial salivary glands of patients with Sjogren's syndrome (SS) and healthy controls. Labeling of laminin alpha1-alpha5, beta1, beta2, gamma1, and gamma2 chains was performed using immunohistochemistry with chain-specific monoclonal antibodies and pattern recognition analysis of the labeled specimens. Laminin alpha1, alpha2, and alpha4 chains were detected exclusively in the acinar basement membranes, whereas laminin alpha3, alpha5, beta1, gamma1, and gamma2 chains were also detected in ductal basement membranes. Laminin beta2 chain was not found. In patients with SS, laminin alpha1 and alpha2 chains were weakly labeled, but laminin alpha4 labeling was also intense in areas not infiltrated by lymphocytes. Pattern recognition analysis suggested that laminin alpha1, alpha2, and alpha4 chains were associated with acinar cells, myoepithelial cells, and tissue damage/repair, respectively. All salivary gland basement membranes signal through laminin 5, laminin 6, and laminin 10 trimers, but acinar basement membranes also signal through laminin 1, laminin 2, and laminin 8 trimers. Laminin alpha1 chain/laminin 1 may play a central role in the maintenance of acinar cells in healthy glands. This possibility was supported by the finding of variable expression of laminin alpha1 chain/laminin 1 in acinar basement membrane and its weak expression in SS with acinar cell atrophy. The impairment of myoepithelial laminin alpha2 chain/laminin 2 in patients with SS indicates a double defect in the acinar compartment and pathologic extracellular matrix-to-cell signaling, which may contribute to structural deterioration and functional abnormality of the exocrine glands.