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K Tryggvason

Publications and source records attributed to K Tryggvason.

At least 109 records · Page 6Linked to original sources
PubMed1995

Cloning of a novel bacteria-binding receptor structurally related to scavenger receptors and expressed in a subset of macrophages.

A novel murine plasma membrane protein has been identified in subpopulations of macrophages. It has an intracellular N-terminal domain, a transmembrane domain, and an extracellular region with a short spacer, an 89 Gly-Xaa-Yaa repeat-containing collagenous domain, and a C-terminal cysteine-rich domain. In situ hybridization and immunohistochemical staining have localized the protein to a subset of macrophages in the marginal zone of the spleen and the medullary cord of lymph nodes. No expression was observed in macrophages of liver or lung. Transfected COS cells synthesized a native trimeric plasma membrane protein that bound labeled bacteria and acetylated LDL, but not yeast or Ficoll. The results suggest that the novel protein is a macrophage-specific membrane receptor with a role in host defense, as it shows postnatal expression in macrophages, which are considered responsible for the binding of bacterial antigens and phagocytosis.

Amino Acid Sequence↗
PubMed1995

92-kDa type IV collagenase and TIMP-3, but not 72-kDa type IV collagenase or TIMP-1 or TIMP-2, are highly expressed during mouse embryo implantation.

Expression of 72 kDa and 92 kDa type IV collagenases and the metalloproteinase inhibitors TIMPs 1, 2, and 3 was studied by in situ hybridization in implanting mouse embryos of days 5.5 to 7.5. The 92 kDa type IV collagenase was strongly expressed in invading trophoblasts, signals above background not being observed in the embryonic proper or placental tissue. In contrast, signals above background were not seen for the 72 kDa enzyme in any cells of the implantation region, including trophoblasts and stromal cells of the decidual tissue. Only cells in the mucosal stroma outside the decidual region displayed some expression. TIMP-3 was intensily expressed in maternal cells in the area surrounding the invading embryonic tissue. No expression was observed for TIMP-1 or TIMP-2 in the embryo proper, trophoblasts, or the area of the uterine decidual reaction. Weak signals appeared for TIMP-1 only in the circular layer of myometrial smooth muscle and in some uterine stroma cells distant from the site of embryo implantation. The results suggest a central role for 92 kDa type IV collagenase and TIMP-3 in the extracellular proteolysis associated with implantation of the early embryo.

Animals↗
PubMed1995

Detection of 12 novel mutations in the collagenous domain of the COL4A5 gene in Alport syndrome patients.

A population of 35 Alport syndrome patients, defined by strict diagnostic criteria, was screened for mutations in 23 exons of the COL4A5 gene by SSCP analysis. Mobility shifts were observed in 12 out of 35 patients and were shown to represent genuine mutations. 9 of these were glycine substitutions in the collagenous domain (in exons 20, 25, 26, 29, 31, and 41), 2 were small deletions resulting in frameshifts (in exons 21 and 31), and one was a splice site mutation (in exon 12).

Base Sequence↗
PubMed1995

The human laminin beta 2 chain (S-laminin): structure, expression in fetal tissues and chromosomal assignment of the LAMB2 gene.

The sequence of the human laminin beta 2 chain (previously s-laminin) was derived from cloned cDNAs. The complete translation product has 1798 amino acid residues, including a 32-residue signal peptide. The human chain lacks the tripeptide sequence LRE in domain I which is present in the rat polypeptide chain and has been shown to promote motor neuronal cell adhesion. The human gene (LAMB2) was localized to chromosome 3p21 using somatic cell hybrids and fluorescent in situ hybridization analysis. Northern and in situ hybridization analyses from numerous fetal tissues revealed that the beta 2 chain is generally widely expressed. beta 2, but not beta 1, was shown by in situ hybridization to be expressed in fetal brain and renal glomeruli. In fetal skin, beta 2 was expressed both in epidermal and dermal cells, while beta 1 was expressed only in the dermis. Expression of beta 2 in fetal liver was seen in hepatocytes, while no signals were observed for beta 1. In lung, both beta 1 and beta 2 were expressed in alveoli and bronchial smooth muscle cells, whereas only the beta 2 chain was expressed in bronchial epithelial cells. In striated muscle, however, the beta 1 chain, but not beta 2, was expressed. These results indicate different biological roles for the laminin beta 1 and beta 2 chains.

Amino Acid Sequence↗
PubMed1995

A nonsense mutation in the COL4A5 collagen gene in a family with X-linked juvenile Alport syndrome.

The X-linked form of Alport syndrome is associated with mutations in the COL4A5 gene encoding the alpha 5-chain of type IV collagen. By using PCR-amplification and direct sequencing we identified a novel mutation involving a deletion of the last two bases in the codon GGA for Glycine-1479 in exon 47 of the COL4A5 gene in a patient with a juvenile form of X-linked Alport syndrome with deafness. This two base deletion caused a shift in the reading frame and introduced a premature stop codon which resulted in an alpha 5(IV)-chain shortened by 202 residues and lacking almost the entire NC1 domain. The mutation was found to co-segregate with the disease in the family. The information of the sequence variation in this family was used to perform carrier detection and prenatal diagnosis by allele-specific oligonucleotide hybridization analysis and direct sequencing of PCR amplified exon 47. Prenatal diagnosis on chorionic villi tissue, obtained from one of the female carriers in the family, revealed a male fetus hemizygous for the mutated allele. A subsequent prenatal test in her next pregnancy revealed a normal male fetus. Prenatal diagnosis of Alport syndrome has not previously been reported.

Adult↗
PubMed1995

Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy.

Congenital muscular dystrophies (CMDs), are heterogeneous autosomal recessive disorders. Their severe manifestations consist of early hypotonia and weakness, markedly delayed motor milestones and contractures, often associated with joint deformities. Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue. Diagnosis is based on clinical features and on morphological changes. In several CMD cases, we have demonstrated an absence of one of the components of the extracellular matrix around muscle fibres, the merosin M chain, now referred to as the alpha 2 chain of laminin-2 (ref.3). We localized this CMD locus to chromosome 6q2 by homozygosity mapping and linkage analysis. The laminin alpha 2 chain gene (LAMA2) maps to the same region on chromosome 6q22-23 (ref. 5). We therefore investigated LAMA2 for the presence of disease-causing mutations in laminin alpha 2 chain-deficient CMD families and now report splice site and nonsense mutations in two families leading presumably to a truncated laminin alpha 2 protein.

Adult↗
PubMed1995

Identification of a homozygous exon-skipping mutation in the LAMC2 gene in a patient with Herlitz's junctional epidermolysis bullosa.

We describe a family with the Herlitz type of junctional epidermolysis bullosa, in which the disease is associated with a homozygous splice-site mutation in the gamma 2-chain gene (LAMC2) of laminin-5. The mutation consists of a G-to-T substitution resulting in the out-of-frame skipping of exon 7, a frame shift, and premature stop codon accompanied by a severe reduction in the level of mRNA from the mutant allele. The distribution of the wild-type and mutated gamma 2-chain alleles in family members implicates the mutation in the pathology and confirms the haplotypes of the healthy carriers previously determined by genetic linkage analysis. Our results confirm that the lethal Herlitz junctional epidermolysis bullosa phenotype is caused by mutations resulting in an altered synthesis of laminin-5.

Base Sequence↗
PubMed1995

Fine mapping and haplotype analysis of the locus for congenital nephrotic syndrome on chromosome 19q13.1.

We have recently localized the gene for congenital nephrotic syndrome of the Finnish type (CNF) to chromosome 19q12-13.1. On the basis of observed recombination events, the gene was localized between markers D19S416/D19S425/D19S213/D19S208/D19S191 and D19S224. Here we have extended the mapping efforts, on the basis of a detailed physical map of the region. By means of three new polymorphic markers--D19S608, D19S609, and D19S610--developed in this study, the critical candidate region could be further restricted. Significant linkage disequilibrium was observed with markers D19S610, D19S608, D19S224, and D19S220, the strongest allelic association being 84% with marker D19S610 at 19q13.1. This suggests that the CNF gene locus lies in close proximity to marker D19S610. Combination of the informative markers revealed four main haplotype categories. Different geographic distribution was observed between these haplotype groups when they were placed on the map of finland according to the birthplaces of grandparents.

Base Sequence↗
PubMed1994

Complete primary structure of the human type IV collagen alpha 4(IV) chain. Comparison with structure and expression of the other alpha (IV) chains.

The entire sequence of the human alpha 4(IV) collagen chain was determined from cDNA clones and polymerase chain reaction-amplified DNAs. The complete translation product has 1,690 amino acid residues and the processed alpha 4(IV) chain proper 1,652 residues. There is a 38-residue putative signal peptide, a 1,421-residue collagenous domain starting with a 23-residue noncollagenous sequence, and a 231-residue NC1 domain. The Gly-Xaa-Yaa-repeat sequence of the collagenous domain is interrupted at 26 locations by noncollagenous sequences of 1-12 residues in length. The alpha 4(IV) chain contains 31 cysteine residues of which 18 are conserved in the other type IV collagen alpha chains. The calculated molecular weight of the mature alpha 4(IV) chain is 164,123. Analysis of the primary structure showed that the alpha 4(IV) chain belongs to the alpha 2-like type IV collagen chains together with alpha 2(IV) and alpha 6(IV). Northern analyses with RNA from several human fetal tissues revealed quite similar expression patterns for the alpha 4(IV) and alpha 3(IV) chains, but there were also distinct differences in some tissues. The expression patterns of alpha 5(IV) and alpha 6(IV) differed extensively between each other and they also differed from those of alpha 3(IV) and alpha 4(IV).

Amino Acid Sequence↗
PubMed1994

Complete primary structure of the human alpha 3(IV) collagen chain. Coexpression of the alpha 3(IV) and alpha 4(IV) collagen chains in human tissues.

We report the entire primary structure of the human alpha 3(IV) collagen chain determined from cDNA clones and polymerase chain reaction-amplified DNAs. The deduced amino acid sequence demonstrates that the complete translation product consists of 1670 amino acid residues and the mature alpha 3(IV) chain contains 1642 residues with a corresponding calculated molecular mass of 161,753. The full-length translated polypeptide has a signal peptide of 28 amino acids, a 1410-residue collagenous domain starting with a 14-residue noncollagenous sequence, and a 232-residue NC1 domain. There are 23 noncollagenous interruptions in the Gly-X-Y repeat sequence of the collagenous domain. The major transcription start site of the alpha 3(IV) chain gene was also determined from genomic DNA by primer extension and S1 nuclease protection assays. Northern analysis revealed coexpression of the alpha 3(IV) and alpha 4(IV) chains in tissues where expression was observed such as in kidney, muscle, and lung.

Amino Acid Sequence↗
PubMed1994

Modulation of M(r) 72,000 and M(r) 92,000 type-IV collagenase (gelatinase A and B) gene expression by interferons alpha and gamma in human melanoma.

The purpose of this study was to determine how interferons alpha and gamma influence the expression of M(r) 72,000 type-IV collagenase (gelatinase A) and M(r) 92,000 type-VI collagenase (gelatinase B) genes and whether there are differences in their gene expression. Special emphasis was focused on the treatment time. Total cellular RNA from A2058 human melanoma cells treated for various time periods with IFN-alpha or gamma was analyzed by Northern- and slot-blot hybridization. Both M(r) 72,000 and M(r) 92,000 type-IV collagenase mRNAs were detectable in A2058 cells and mRNA levels for both gelatinases were significantly up-regulated in the cells treated for a short time period with either IFN-alpha or gamma. In contrast, a long-term treatment (7 days) with these drugs markedly down-regulated the genes for both gelatinase A and B. Zymographic analysis showed that human melanoma primarily secretes the gelatinase-A activity, which showed changes similar to those seen in the corresponding mRNA after the treatments with interferons. The expression of gelatinase-B activity was, however, detectable only transiently during the stimulating phase with IFN-alpha. Western immunoblot analysis showed that alterations in the levels of immunoreactive protein of gelatinase A in the cells correlated with the mRNA levels after the treatments. These findings suggest that IFN-alpha and IFN-gamma are potent regulators of both M(r) 72,000 and M(r) 92,000 type-IV collagenase/gelatinase A and B genes in human melanoma showing biphasic and parallel effects on mRNA levels of both enzymes, depending on the treatment time, and that the M(r) 72,000 metalloproteinase/gelatinase A is the predominant basement-membrane-degrading type-IV collagenase in human melanoma.

Base Sequence↗
PubMed1994

Structure of the human type IV collagen COL4A5 gene.

The complete exon size and distribution pattern of the human alpha 5(IV) collagen gene COL4A5 has been determined. Seventeen genomic lambda phage clones, eight of which have been described previously (Zhou, J., Hostikka, S.L., Chow, L.T., and Tryggvason, K. (1991) Genomics 9, 1-9), spanning about 160 kilobases of DNA contained 140 kilobases of the gene itself. The clones covered the entire gene with the exception of exons 2 and 37 and their flanking regions so that the exact gene size could not be determined. The sequences of these two exons were, however, determined from polymerase chain reaction products. The COL4A5 gene has a structure highly homologous with that of COL4A1 which encodes the alpha 1(IV) chain. However, the COL4A5 gene contains 51 exons, or one less than COL4A1. The exon size pattern of the genes are similar, with 41 exons having identical sizes. All the exons were assigned to distinct EcoRI restriction fragments. The results may be useful for characterization of mutations in COL4A5 in patients with X chromosome-linked Alport syndrome.

Amino Acid Sequence↗
PubMed1994

Congenital nephrotic syndrome of the Finnish type is not associated with the Pax-2 gene despite the promising transgenic animal model.

Congenital nephrotic syndrome of the Finnish type (CNF) is an autosomal recessive disease with an incidence of 1 in 8000 in Finland. CNF is characterized by massive proteinuria and nephrotic syndrome at birth. In a recent report, deregulation of expression of the gene coding for the Pax-2 DNA-binding protein was shown to generate severe kidney abnormalities in transgenic mice resembling the clinical and pathological findings in congenital nephrotic syndrome, making it a candidate gene for CNF. However, in this study, we have unequivocally excluded the Pax-2 gene locus as a causative for congenital nephrotic syndrome of the Finnish type.

Animals↗
PubMed1994

Exclusion of eight genes as mutated loci in congenital nephrotic syndrome of the Finnish type.

The congenital nephrotic syndrome of the Finnish type (CNF) is an autosomal recessive disease characterized by massive proteinuria already at birth. The gene locus defective in CNF was searched for using polymorphic markers of candidate genes coding for components of the basement membrane (BM). The linkage analyses in 17 Finnish CNF families demonstrated exclusion of obligatory recombination events between the disease and eight genes coding for BM components. The genes coding for the alpha 1(IV), alpha 2(IV), alpha 3(IV) and alpha 4(IV) chain of type IV collagen, the B1e, B2e and B2t chains of laminin, as well as the BM heparan sulfate proteoglycan core protein were all excluded in this Finnish family material. Since the defect is not in any of the genes coding for major components of BM, the identification of the gene defect will most probably reveal a new gene important for the development and function of the glomerular basement membrane.

Cell Line↗