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K Tryggvason

Publications and source records attributed to K Tryggvason.

At least 73 records · Page 4Linked to original sources
PubMed1999

Roles of a macrophage receptor with collagenous structure (MARCO) in host defense and heterogeneity of splenic marginal zone macrophages.

Class A type I and type II macrophage scavenger receptors (MSR-A) and a macrophage receptor with collagenous structure (MARCO) are trimeric membrane glycoproteins mediating the uptake of chemically modified low density lipoproteins. MSR-A is expressed constitutively in several tissue macrophages and in liver sinusoidal endothelial cells, whereas MARCO is expressed constitutively in splenic marginal zone macrophages and in macrophages and endothelial cells in the lymphatic medullary sinuses of lymph nodes. The administration of LPS, zymosan, BCG, or L. monocytogenes to mice resulted in marked and transient MARCO expression and in the upregulation of MSR-A expression in the liver and spleen. In osteopetrotic (op) mutant mice defective in the production on M-CSF, ER-TR9-positive marginal zone macrophages and MOMA-1-positive marginal metallophilic macrophages were absent, whereas MARCO-expressing marginal zone macrophages were present, indicating the heterogeneity of marginal zone macrophages. Intravenous administration of BCG resulted in marked accumulation of BCG bacilli in the both marginal zone macrophages and marginal metallophilic macrophages in littermate control mice. In contrast, BCG bacilli were incorporated almost exclusively by MARCO-expressing marginal zone macrophages in op/op mice. These results indicate that MARCO is not only expressed constitutively in specific macrophage subpopulations but is also induced by various bacterial antigens and plays a role in host defense against bacteria.

Animals↗
PubMed1999

Discovery of the congenital nephrotic syndrome gene discloses the structure of the mysterious molecular sieve of the kidney.

The molecular nature of the glomerular slit diaphragm, the site of renal ultrafiltration, has until recently remained a mystery. However, the identification of the gene affected in congenital nephrotic syndrome has revealed the presence of a novel protein, possibly specific for the slit diaphragm. This protein, which has been termed nephrin, is a transmembrane protein that probably forms the main building block of an isoporous zipper-like slit diaphragm filter structure. Defects in nephrin lead to abnormal or absent slit diaphragm leading to massive proteinuria and renal failure. The discovery of nephrin sheds new light on the glomerular filtration barrier, provides new insight into the pathomechanisms of proteinuria, and even opens up possibilities for the development of novel therapies for this common and severe kidney complication.

Animals↗
PubMed1998

Three-dimensional structure of human tissue inhibitor of metalloproteinases-2 at 2.1 A resolution.

The three-dimensional structure of human tissue inhibitor of metalloproteinases-2 (TIMP-2) was determined by X-ray crystallography to 2.1 A resolution. The structure of the inhibitor consists of two domains. The N-terminal domain (residues 1-110) is folded into a beta-barrel, similar to the oligonucleotide/oligosaccharide binding fold otherwise found in certain DNA-binding proteins. The C-terminal domain (residues 111-194) contains a parallel stranded beta-hairpin plus a beta-loop-beta motif. Comparison of the structure of uncomplexed human TIMP-2 with that of bovine TIMP-2 bound to the catalytic domain of human MMP-14 suggests an internal rotation between the two domains of approximately 13 degrees upon binding to the protease. Furthermore, local conformational differences in the two structures that might be induced by formation of the protease-inhibitor complex have been found. The most prominent of these involves residues 27-40 of the A-B beta-hairpin loop. Structure-based alignment of amino acid sequences of representatives of the TIMP family maps the sequence differences mainly to loop regions, and some of these differences are proposed to be responsible for the particular properties of the various TIMP species.

Amino Acid Sequence↗
PubMed1998

Structure of the human macrophage MARCO receptor and characterization of its bacteria-binding region.

The primary structure of human macrophage receptor with collagenous structure (MARCO) was determined from cDNA clones and shown to be highly similar to that of mouse (Elomaa, O., Kangas, M., Sahlberg, C. , Tuukkanen, J., Sormunen, R., Liakka, A., Thesleff, I., Kraal, G., and Tryggvason, K. (1995) Cell 80, 603-609). Features such as potential carbohydrate attachment sites in the extracellular spacer domain III and the interruption of Gly-Xaa-Yaa repeats in the collagenous domain IV were conserved between the two species. However, the human MARCO polypeptide chain lacked the intracellular cysteine present in mouse, as well as two extracellular cysteines that form interchain disulfide bonds in the murine protein. In situ hybridization showed MARCO to be strongly expressed in macrophages of several tissues of human individuals with sepsis. No expression was observed in other cell types. The bacteria-binding region of MARCO was determined in binding studies with full-length and truncated variants of MARCO, and localized to a region proximal to the cysteine-rich part of the COOH-terminal domain V. The intrachain disulfide bond pattern of domain V was established showing that these bonds are between cysteine pairs C1-C5, C2-C6, and C3-C4.

Amino Acid Sequence↗
PubMed1998

Structure of the human amyloid-precursor-like protein gene APLP1 at 19q13.1.

Amyloid-precursor-like protein 1 (APLP1) is a membrane-associated glycoprotein, whose gene is homologous to the APP gene, which has been shown to be involved in the pathogenesis of Alzheimer's disease. APLP1 is predominantly expressed in brain, particularly in the cerebral cortex postsynaptic density. The genomic organization of mouse APLP1 has been determined, and the human gene has been mapped to chromosomal region 19q13.1. In the present study, the entire sequence of human APLP1 has been determined from a cosmid clone, and the genomic structure has been determined. The gene is 11.8 kb long and contains 17 exons. We have previously mapped the gene for congenital nephrotic syndrome (CNF) to the APLP1 region, to the vicinity of marker D19S610 located between markers D19S191 and DS19608. APLP1 is the only known gene in the vicinity of the marker D19S610. Because of its location and the proposed interference of amyloid with basement membrane assembly, APLP1 has been considered a candidate gene for CNF. All exon regions of the gene were amplified by the polymerase chain reaction and sequenced from DNA of CNF patients. No differences were observed between CNF patients and controls, suggesting that mutations in APLP1 are not involved in the etiology of CNF.

Adult↗
PubMed1998

Positionally cloned gene for a novel glomerular protein--nephrin--is mutated in congenital nephrotic syndrome.

Congenital nephrotic syndrome of the Finnish type (NPHS1) is an autosomal-recessive disorder, characterized by massive proteinuria in utero and nephrosis at birth. In this study, the 150 kb critical region of NPHS1 was sequenced, revealing the presence of at least 11 genes, the structures of 5 of which were determined. Four different mutations segregating with the disease were found in one of the genes in NPHS1 patients. The NPHS1 gene product, termed nephrin, is a 1241-residue putative transmembrane protein of the immunoglobulin family of cell adhesion molecules, which by Northern and in situ hybridization was shown to be specifically expressed in renal glomeruli. The results demonstrate a crucial role for this protein in the development or function of the kidney filtration barrier.

Amino Acid Sequence↗
PubMed1998

PCR based mutation screening of the laminin alpha2 chain gene (LAMA2): application to prenatal diagnosis and search for founder effects in congenital muscular dystrophy.

Classical congenital muscular dystrophy with merosin deficiency is caused by mutations in the laminin alpha2 chain gene (LAMA2). Extended sequencing of the introns flanking the 64 LAMA2 exons was carried out and, based on these sequences, oligonucleotide primers were designed to amplify the coding region of each exon separately. By PCR-SSCP analysis, we identified eight new mutations in nine families originating from various countries. All induced a premature truncation of the protein, either in the short arm or in the globular C-terminal domain. A 2 bp deletion in exon 13, 2098delAG, was found in three French non-consanguineous families and a nonsense mutation of exon 20, Cys967stop, in two other non-consanguineous families originating from Italy. Determination of rare intragenic polymorphisms permitted us to show evidence of founder effects for these two mutations suggesting a remote degree of consanguinity between the families. Other, more frequent polymorphisms, G to A 1905 (exon 12), A to G 2848 (exon 19), A to G 5551 (exon 37), and G to A 6286 (exon 42), were used as intragenic markers for prenatal diagnosis. This study provides valuable methods for determining the molecular defects in LAMA2 causing merosin deficient congenital muscular dystrophy.

Child↗
PubMed1998

High mutation detection rate in the COL4A5 collagen gene in suspected Alport syndrome using PCR and direct DNA sequencing.

Approximately 85% of patients with Alport syndrome (hereditary nephritis) have been estimated to have mutations in the X chromosomal COL4A5 collagen gene; the remaining cases are autosomal with mutations in the COL4A3 or COL4A4 genes located on chromosome 2. In the present work, the promoter sequence and previously unknown intron sequences flanking exons 2 and 37 of COL4A5 were determined. Furthermore, intron sequences flanking the other 49 exons were expanded from 35 to 190 to facilitate mutation analysis of the gene. Using this information, all 51 exons and the promoter region were PCR-amplified and sequenced from DNA of 50 randomly chosen patients with suspected Alport syndrome. Mutations were found in 41 patients, giving a mutation detection rate of 82%. Retrospective analysis of clinical data revealed that two of the cases might be autosomal. Although it could not be determined whether the remaining seven cases (14%) were autosomal or X chromosome-linked, it is likely that some of them were autosomal. It is concluded that PCR amplification and direct DNA sequencing of the promoter and exons is currently the best procedure to detect mutations in COL4A5 in Alport syndrome.

Amino Acid Substitution↗
PubMed1997

Primary structure, developmental expression, and immunolocalization of the murine laminin alpha4 chain.

The complete primary structure of the mouse laminin alpha4 chain was derived from cDNA clones. The translation product contains a 24-residue signal peptide preceding the mature alpha4 chain of 1,792 residues. Northern analysis on whole mouse embryos revealed that the expression was weak at day 7, but it later increased and peaked at day 15. In adult tissues the strongest expression was observed in lung and cardiac and skeletal muscles. Weak expression was also seen in other adult tissues such as brain, spleen, liver, kidney, and testis. By in situ hybridization of fetal and newborn tissues, expression of the laminin alpha4 chain was mainly localized to mesenchymal cells. Strong expression was seen in the villi and submucosa of the developing intestine, the mesenchymal stroma surrounding the branching lung epithelia, and the external root sheath of vibrissae follicles, as well as in cardiac and skeletal muscle fibers. In the developing kidney, intense but transient expression was associated with the differentiation of epithelial kidney tubules from the nephrogenic mesenchyme. Immunohistologic staining with affinity-purified IgG localized the laminin alpha4 chain primarily to lung septa, heart, and skeletal muscle, capillaries, and perineurium.

Amino Acid Sequence↗
PubMed1997

Evidence for the existence of multiple heparan sulfate proteoglycans in the human glomerular basement membrane and mesangial matrix.

Heparan sulfate proteoglycans (HSPGs) are essential components of the glomerular basement membrane (GBM) carrying a strong anionic charge. A well-characterized extracellular HSPG is perlecan, ubiquitously expressed in basement membranes. A cDNA construct encoding domains I and II of human perlecan was expressed as a fusion protein with glutathione S-transferase. This fusion protein was used to generate monoclonal antibody 95J10. We compared the staining pattern of 95J10 with that of M215, a previously prepared mAb that recognizes HSPG isolated from human GBM. In kidney cortex, the anti-perlecan mAb 95J10 showed a strong staining of the mesangium, Bowman's capsule, the tubular basement membrane, and stained the GBM only slightly. In contrast, M215 predominantly stained the GBM in a linear fashion. Immunoelectron microscopy supported these results, showing concentrations of perlecan in some regions of the GBM, whereas the unidentified M215 antigen was homogenously distributed throughout the GBM. In other human tissues, both antibodies also produced a different staining pattern. Furthermore, a polyclonal antiserum recognizing HSPG isolated from the GBM did not recognize perlecan from EHS tumors. These results provide evidence for the presence of another HSPG in the GBM that is immunologically distinct from perlecan. The absence of perlecan splice variants in the kidney suggests that this component is encoded by a different gene than perlecan. Given its marked expression in the GBM, this component could be a determining factor in the maintenance of selective glomerular permeability.

Animals↗
PubMed1997

Genetics of laminin alpha 2 chain (or merosin) deficient congenital muscular dystrophy: from identification of mutations to prenatal diagnosis.

Congenital muscular dystrophies (CMD) are a clinically and genetically heterogeneous group of muscle disorders, with autosomal recessive inheritance. Absence of the laminin alpha 2 chain in the skeletal muscle of patients with classical CMD has permitted the identification of a subgroup, referred to as 'merosin-deficient CMD or laminin alpha 2 chain deficient CMD'. We first identified a nonsense and a splice site mutation in laminin alpha 2 gene (LAMA2) (Glu1241 stop, 4573-2A-->T). We report here new mutations: nonsense mutations (Glu210stop, Trp2316stop) and 1- and 2-bp deletions (2418 delta C, 6968 delta TA), which result in truncation of the protein either in the short arm domains or in the C terminal globular domain and complete merosin deficiency. Another subgroup, referred to as 'partially-deficient in laminin alpha 2 chain' has been identified recently, and a LAMA2 missense mutation (Cys996Arg) has been shown to cause this partial deficiency. The laminin alpha 2 chain, together with the beta 1 or beta 2 and gamma 1 chains forms either laminin-2 (alpha 2-beta 1-gamma 1) or laminin-4 (alpha 2-beta 2-gamma 1). The LAMA2 mutations induce the formation of abnormal laminins which probably dramatically disturb the assembly and stability of the laminin network, one of the major components of the extracellular matrix in skeletal muscle. We report also the first prenatal diagnosis performed by direct mutation analysis.

Chromosome Mapping↗
PubMed1997

Improved prenatal diagnosis of the congenital nephrotic syndrome of the Finnish type based on DNA analysis.

Haplotype analysis and alpha-fetoprotein quantitation comprise a prenatal diagnosis of congenital nephrosis. Congenital nephrotic syndrome of the Finnish type (CNF) is an autosomal recessive disease characterized by massive proteinuria and nephrotic syndrome from birth. Prenatal diagnosis of CNF has previously been based on the quantitation of alpha-fetoprotein (AFP) in the amniotic fluid and maternal serum, but an increased AFP is not specific for the disease. We have recently localized the CNF gene to the chromosome 19q13.1 region and observed a strong linkage disequilibrium to the genetic markers D19S610, D19S608, D19S224 and D19S220 in this chromosomal area. Four main CNF-haplotypes have been observed in Finnish kindreds. In the present study, linkage and haplotype analyses have been applied to prenatal diagnosis of six families with a history of CNF. The results diminish the risk of false positive diagnosis and abortions of healthy fetuses in families at risk.

Amniotic Fluid↗
PubMed1997

Mild congenital muscular dystrophy in two patients with an internally deleted laminin alpha2-chain.

Congenital muscular dystrophy (CMD) is a group of clinically and genetically heterogeneous disorders inherited in an autosomal recessive mode. The alpha2-chain of laminin-2 (previously called merosin) has been shown by immunohistochemical and genetic analyses to be implicated in the pathogenesis of the 'classic' form of CMD. In the 'merosin-deficient' subgroup, which represents about half of the cases, more definite evidence of the involvement of the laminin alpha2-chain has recently been reported with the identification of mutations in the gene encoding the alpha2-chain of laminin 2 (LAMA2) in CMD patients. Here we report on two siblings from a consanguineous family expressing an internally deleted laminin alpha2-chain as a result of a splice site mutation in the LAMA2 gene which causes the splicing of exon 25. The predicted protein lacks 63 amino acids in domain IVa which forms a globular structure on the short arm of the alpha2-chain. Interestingly, these patients appear mildly affected compared to others who completely lack this protein. This situation presents a striking analogy with Becker muscular dystrophy, where in-frame deletions in the dystrophin gene result in the expression of a semi-functional protein and lead to a mild phenotype.

Amino Acid Sequence↗
PubMed1997

Detection of novel LAMC2 mutations in Herlitz junctional epidermolysis Bullosa.

BACKGROUND: Laminin 5, an anchoring filament attachment protein within the lamina lucida of the basement membrane zone involved in the pathogenesis of junctional epidermolysis bullosa (JEB), consists of three polypeptide subunits, the alpha 3, beta 3, and gamma 2 chains which are encoded by the LAMA3, LAMB3, and LAMC2 genes, respectively. To facilitate identification of pathogenetic mutations in LAMC2, a strategy based on direct amplification of genomic DNA by PCR or mRNA by RT-PCR, followed by heteroduplex analysis of the PCR products, was developed. MATERIALS AND METHODS: Primer pairs for amplification of the complete cDNA as well as the 23 individual exons in the genomic DNA, which encode the entire gamma 2 chain of laminin 5, were established. The primers for amplification of exons from genomic DNA were positioned at least 24 bp away from the intron-exon borders in the flanking intronic sequences. For amplification of cDNA generated by RT-PCR, eight primer pairs covering overlapping segments of the entire coding sequence of LAMC2 mRNA were used. The amplified sequences were scanned for pathogenetic mutations and sequence variations in JEB patients and unrelated control individuals by heteroduplex analysis by means of conformation sensitive gel electrophoresis (CSGE). RESULTS: Utilizing the strategy developed in this study, we identified pathogenetic mutations in three patients with the Herlitz (lethal) variant of JEB, and eight intragenic normal polymorphisms, which are useful for linkage analysis, in the LAMC2 gene. CONCLUSIONS: The methodology described in this study is capable of detecting single-base substitutions or small insertions and deletions in the LAMC2 gene. Demonstration of mutations in this gene in JEB patients further emphasizes the role of laminin 5 in providing integrity to the cutaneous basement membrane zone.

Epidermolysis Bullosa, Junctional↗
PubMed1997

Altered distribution and synthesis of laminin-5 (kalinin) in oral lichen planus, epithelial dysplasias and squamous cell carcinomas.

Laminin-5 is a glycoprotein which mediates epithelial cell adhesion to the basement membrane. This study describes the distribution and synthesis of laminin-5 in oral lichen planus, epithelial dysplasias, squamous cell carcinomas and a lymph node metastasis using immunohistochemistry and in situ hybridization. In normal oral mucosa and lichen planus, immunoreaction to the laminin-5 was seen as a thin continuous, delicate line in the basement membrane region, although slight irregularities in the thickness and intensity of the immunoreaction could be detected in some cases with lichen planus. In epithelial dysplasias, the laminin-5 staining was discontinuous and more diffuse compared to lichen planus and normal mucosa. The immunoreaction was generally extracellular, although in some cases with lichen planus and epithelial dysplasia there were a few basal epithelial cells showing cytoplasmic staining. The invasive carcinomas and the lymph node metastasis showed a striking, intense cytoplasmic, staining of the carcinoma cells along the invasive border of the neoplastic islands and in individual infiltrating carcinoma cells. Using in situ hybridization, the laminin-5 gamma 2 chain mRNA expression could not be detected in normal oral mucosa whereas, in non-dysplastic lichen planus and, more strongly, in dysplasias, there was a clear increase in the expression of laminin-5 mRNA in the basal epithelial cells. The most intensive signal was detected in the invasive front of the oral squamous cell carcinomas and the lymph node metastasis. We conclude that, in oral squamous cell carcinoma, there is altered synthesis and secretion of laminin-5 mRNA and protein. It is also evident that in dysplastic lesions of oral epithelium the synthesis and distribution of laminin-5 is abnormal.

Carcinoma, Squamous Cell↗