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Behaviour of a sperm surface transmembrane glycoprotein basigin during epididymal maturation and its role in fertilization in mice.

Basigin (bsg) is a transmembrane glycoprotein belonging to an immunoglobulin superfamily and is localized on the surface of the sperm tail. The behaviour of bsg during epididymal maturation and its role in fertilization were examined using an anti-bsg antibody. Spermatozoa from caput, corpus and cauda epididymides were immunostained by indirect immunofluorescence (IIF). Immunostaining revealed that bsg is localized on the principal piece of caput spermatozoa and the molecule was found on the middle piece during transit in the corpus and cauda epididymides. Concomitantly, the molecular mass of bsg was reduced from 37 kDa (testis) to 26 kDa (cauda epididymidis). IVF experiments were designed to assess the effect of anti-bsg antibody on the fertilization events. Anti-bsg antibody significantly inhibited primary binding to the cumulus-invested oocytes with intact zonae pellucidae in a dose-dependent manner. Consequently, the fertilization rate of cumulus-invested oocytes with intact zonae pellucidae was also inhibited. The bsg molecule was also detected on the head of live capacitated spermatozoa by IIF under IVF conditions. These findings indicate that testicular bsg is a glycosylated protein that undergoes molecular processing and deglycosylation during its transit in the epididymis. The bsg molecule that was detected on the sperm head after capacitation may facilitate the primary binding or might be involved in distinct events required for primary binding of spermatozoa to the zona pellucida during capacitation and sperm-cumulus interaction.

Animals↗

Retinal dysfunction in basigin deficiency.

PURPOSE: To examine the retina of basigin (Bsg) knockout mice by electrophysiological and histologic methods and thereby to determine the possible function of Bsg in phototransduction and retinal development. METHODS: Scotopic and photopic electroretinograms (ERGs) were recorded from 11 wild-type, 12 heterozygous, and 8 homozygous Bsg gene knockout mice of different ages. The retinas were also examined by histologic and immunolabeling methods. RESULTS: Bsg knockout mice of 5 to 41 weeks of age showed a decrease in the amplitude of all components of both the photopic and scotopic ERGs. In contrast, the fundus and the fluorescein fundus angiography and morphology of the retina at the light microscopic level appeared to be normal until 8 weeks of age in Bsg knockout mice. Thereafter, the length of outer segment and outer nuclear layers decreased with increasing age. Immunohistochemical analysis localized Bsg protein in a variety of cells in the retina, especially in the pigment epithelium, the upper outer plexiform layer and the inner segments of photoreceptor cells. CONCLUSIONS: The results demonstrated that both rod and cone function were severely affected from an early age by the targeted disruption of the Bsg gene. In spite of abnormal ERGs, the photoreceptor cells maintained normal morphology up to 8 weeks. Thereafter, the photoreceptor cells degenerated gradually and were almost ablated by 41 weeks.

Animals↗

Human leukocyte activation antigen M6, a member of the Ig superfamily, is the species homologue of rat OX-47, mouse basigin, and chicken HT7 molecule.

Peripheral granulocytes from rheumatoid arthritis and reactive arthritis patients were recently found to express higher levels of a newly defined Ag, termed M6, in comparison to granulocytes from healthy subjects. We present here the molecular characterization of M6 Ag and show that it is a novel human leukocyte activation-associated cell surface glycoprotein. Peripheral lymphocytes do not significantly express M6 Ag, however, it appears upon 3-day PHA-activated T blasts. On monocytes, which constitutively express M6 Ag, it is down-regulated on day 1 but re-induced on day 3 of granulocyte-macrophage CSF stimulation. SDS-PAGE analysis of M6 immunoprecipitates shows a single band of 54 kDa under nonreducing conditions that shifts to 65 kDa under reducing conditions. Endoglycosidase F treatment of M6 immunoprecipitate reveals that 50% of the M6 molecule is composed of N-linked carbohydrates. By modifying the COS cell cloning strategy, we have isolated cDNA clones encoding M6 Ag. M6 cDNA hybridizes with a single mRNA transcript of approximately 1.7 kb in Northern blotting. Comparison analysis of the M6 sequence indicates that M6 Ag is a member of the Ig superfamily and the species homologue of rat OX-47 Ag, mouse basigin (gp42), and chicken HT7 molecule. The highly conserved remarkable transmembrane domain suggests that the M6 Ag may be a component of a multichain complex in the plasma membrane.

Amino Acid Sequence↗

Inactivation of the Basigin gene impairs normal retinal development and maturation.

5A11/Basigin is an immunoglobulin-like glycoprotein expressed on the surface of Müller cells, the apical and basal surfaces of the retinal pigmented epithelium, and photoreceptor cell bodies and their inner segments. Disruption of the 5A11/Basigin gene in the mouse results in photoreceptor degeneration and a corresponding decrease in electroretinogram amplitudes in mature mice. The purpose of this study was to examine the electrophysiology of the 5A11/Basigin null mouse retina at earlier ages than previously examined. Although the architecture of the 5A11/Basigin null mouse retina appears normal, the ERG amplitudes are severely depressed at eye opening, indicating failure in retinal maturation.

Animals↗

Inhibition of basigin expression in glioblastoma cell line via antisense RNA reduces tumor cell invasion and angiogenesis.

Basigin/CD147, also named extracelluar matrix metalloproteinase inducer (EMMPRIN), has been implicated in playing very important roles in several aspects of tumor progression. In this study, we examined the inhibitory effects of antisense RNA of CD147 on invasion and angiogenesis of human glioblastoma U251 cells in vitro. The U251 cell line was transfected by a plasmid containing antisense CD147 cDNA. Gelatin zymography was used to determine the effect on reducing secretions of MMP-2 and MMP-9 of the transfected cells. Boyden chamber was employed to test the invasion of U251 cells in vitro. We found that downregulation of CD147 resulted in reducing secretions of MMP-2, MMP-9, and VEGF. Moreover, the invasion of stable antisense transfectants was inhibited. Wound-induced migration assay also showed decreased migration in stable antisense transfectants compare to parental- and empty vector-transfected cells. Taken together, these results provide evidence that invasion of human glioblastoma cells can be inhibited by antisense RNA of CD147. Basigin/CD147 may be used as a potential target of drugs for anti-invasion and metastasis of human glioblastoma cells.

Basigin↗

Abnormalities of sensory and memory functions in mice lacking Bsg gene.

Basigin is a highly glycosylated transmembrane protein belonging to the immunoglobulin superfamily. We used mutant mice lacking the basigin gene (Bsg) to investigate its involvement in learning and memory. Mutations were generated by the gene targeting method. Various kinds of learning and memory tasks were performed in mutant, hetero and wild type mice. The mutant mice showed worse performance than the wild and hetero mice in the Y-maze task, which assesses short-term memory, and in the water finding task, which examines latent learning, without any motor dysfunction. Moreover, the mutant mice showed less acclimation in the habituation task compared with the wild-type mice. The mutant mice were also more sensitive to electric foot-shock. These findings are consistent with the expression profile of basigin in the central nervous system. Thus, basigin may play an important role in learning and memory as well as in the sensory functions.

Animals↗

Embigin/basigin subgroup of the immunoglobulin superfamily: different modes of expression during mouse embryogenesis and correlated expression with carbohydrate antigenic markers.

Embigin and basigin are highly glycosylated transmembrane glycoproteins with two immunoglobulin domains and form a subgroup in the immunoglobulin superfamily. Previous studies have demonstrated the functional significance of these molecules. In the present study, in situ hybridization analysis of their expression was performed during mouse embryogenesis. Embigin was strongly expressed in the endoderm during early postimplantation embryogenesis, and in the somite stage in the gut and visceral endoderm. Embryonic ectoderm and its derivative tissues weakly to moderately expressed this molecule. From day 10 to 15 of gestation, no embigin signal was detected. Basigin was more broadly expressed. During the organogenesis period, basigin was expressed in various epithelial tissues, brain ventricles, the spinal cord and dorsal root ganglion. The modes of expression of these two proteins throughout the egg cylinder stage correlated with the expression of the carbohydrate markers that they carry; embigin with Dolichos biflorus agglutinin binding sites and basigin with LeX antigen and more closely with fucosyltransferase IV, which forms the antigenic epitope. These findings imply that proteins with specific carbohydrate epitopes play roles in early postimpantation embryogenesis.

Animals↗

Integrin-dependent apposition of Drosophila extraembryonic membranes promotes morphogenesis and prevents anoikis.

BACKGROUND: Two extraembryonic tissues form early in Drosophila development. One, the amnioserosa, has been implicated in the morphogenetic processes of germ band retraction and dorsal closure. The developmental role of the other, the yolk sac, is obscure. RESULTS: By using live-imaging techniques, we report intimate interactions between the amnioserosa and the yolk sac during germ band retraction and dorsal closure. These tissue interactions fail in a subset of myospheroid (mys: betaPS integrin) mutant embryos, leading to failure of germ band retraction and dorsal closure. The Drosophila homolog of mammalian basigin (EMMPRIN, CD147)-an integrin-associated transmembrane glycoprotein-is highly enriched in the extraembryonic tissues. Strong dominant genetic interactions between basigin and mys mutations cause severe defects in dorsal closure, consistent with basigin functioning together with betaPS integrin in extraembryonic membrane apposition. During normal development, JNK signaling is upregulated in the amnioserosa, as midgut closure disrupts contact with the yolk sac. Subsequently, the amnioserosal epithelium degenerates in a process that is independent of the reaper, hid, and grim cell death genes. In mys mutants that fail to establish contact between the extraembryonic membranes, the amnioserosa undergoes premature disintegration and death. CONCLUSIONS: Intimate apposition of the amnioserosa and yolk sac prevents anoikis of the amnioserosa. Survival of the amnioserosa is essential for germ band retraction and dorsal closure. We hypothesize that during normal development, loss of integrin-dependent contact between the extraembryonic tissues results in JNK-dependent amnioserosal disintegration and death, thus representing an example of developmentally programmed anoikis.

Amino Acid Sequence↗

Genetic expression of monocarboxylate transporters during human and murine oocyte maturation and early embryonic development.

During the early preimplantationes of human embryos, pyruvate and lactate, but not glucose, are the preferred energy substrates. Transport of these monocarboxylates is mediated, in mammalian cells, by a family of transporters, designated as monocarboxylate transporters (MCTs). Human and mouse genetic expression of MCT members 1, 2, 3, 4 and basigin, a chaperone protein of MCT1 and MCT4, was qualitatively analysed using the reverse transcription nested polymerase chain reaction (RT-nested PCR) in immature oocytes (germinal vesicle stage; GV), in non-fertilised metaphase II (MII) oocytes and in embryos from 2-cell stage to blastocysts. Transcripts encoding for MCT1 and MCT2 were present, under a polyadenylated form, in the majority of the human and mouse oocytes and early embryos. MCT3 transcripts were not detected in either human or mouse. MCT4 mRNA was not detected in human oocytes and embryos, but was present in mouse oocytes and embryos. This fact could imply differences in lactate transport and regulation of intracellular pH between human and murine early embryos. Basigin transcripts were present in mouse and human MII oocytes and preimplantation embryos, but were not detected at GV stage. However, using 3' end-specific primers in the RT reaction instead of Oligo(dT)12-18 primers, transcripts encoding for this protein were then detected at GV stage in both species. This result suggests that a regulated polyadenylation process occurs during oocyte maturation for these transcripts. Thus, basigin mRNA can be considered as a marker of oocyte cytoplasmic maturation in human and mouse species.

Animals↗

Expression of emmprin (CD147), a cell surface inducer of matrix metalloproteinases, in normal human brain and gliomas.

EMMPRIN (extracellular matrix metalloproteinase inducer), also called CD147, basigin or M6 in the human, is a member of the immunoglobulin superfamily that is present on the surface of tumor cells and stimulates adjacent fibroblasts to produce matrix metalloproteinases (MMPs). In our study, we investigated expression of EMMPRIN in human normal brain and gliomas, since mouse basigin and chicken HT7, the species homologues of human EMMPRIN, are associated with neuronal interactions and normal blood-brain barrier function, respectively. EMMPRIN expression was detected in all samples of non-neoplastic brain and glioma tissues examined. However, expression levels of EMMPRIN mRNA and protein were significantly higher in gliomas than in non-neoplastic brain. Moreover, levels of mRNA expression and immunohistochemical staining correlated with tumor progression in gliomas: They were highest in the most malignant form of glioma, glioblastoma multiforme, followed by anaplastic astrocytoma and then low-grade astrocytoma. Also, immunolocalization revealed quite different distributions in non-neoplastic brain and glioma: EMMPRIN was demonstrated only in vascular endothelium in non-neoplastic regions of the brain, whereas it was present in tumor cells but not in proliferating blood vessels in malignant gliomas. These data indicate that an MMP inducer molecule EMMPRIN is differently expressed in human normal brain and gliomas and could be associated with astrocytoma progression. Possible mechanisms whereby glioma cell EMMPRIN could influence tumor progression will be discussed.

Antigens, CD↗

Genomic organization and promoter activity of embigin, a member of the immunoglobulin superfamily.

Embigin is a transmembrane glycoprotein belonging to the immunoglobulin superfamily, which is preferentially expressed in early stages of mouse embryogenesis and enhances integrin-mediated cell-substratum adhesion. The mouse embigin gene, which we cloned, spanned more than 50kb, in which nine exons were present. All exons contained protein-coding sequences. Each of the two immunoglobulin domains was encoded by two exons, and the C-proximal half of the second immunoglobulin domain and the transmembrane domain were in the same exon. These features are shared by the basigin gene; together with protein sequence homology, our results defined a family in the immunoglobulin superfamily, to which embigin and basigin both belong. The major transcriptional initiation site of embigin gene was 103 bases upstream from the translation initiation site, as determined by 5' rapid amplification of cDNA ends. A 3kb DNA fragment upstream from the transcriptional initiation site contained three Sp1 binding sites and had a promoter sequence capable of expressing the downstream gene not only in F9 embryonal carcinoma cells which express the gene, but also in L and G401 cells which do not, indicating the presence of a regulatory region outside the 3kb DNA region. Deletion analysis of the 3.5kb DNA fragment revealed that the region between -125 to +1, containing a single Sp1 binding site, is essential for transcription of the embigin gene.

Amino Acid Sequence↗

Protein-bound carbohydrates on cell-surface as targets of recognition: an odyssey in understanding them.

Multidisciplinary approaches by a number of investigators have established that cell-surface carbohydrates are integral components of recognition systems regulating survival, migration, adhesion, growth and differentiation of various cells. Our own experience and contributions to this exciting field are described. We discovered Endo D as the first endoglycosidase acting on glycoproteins, found complementary specificity of two endoglycosidases (Endo D and Endo H), and applied these enzymes for glycoprotein research. Endo-beta-galactosidase C, which hydrolyzes Galalpha1-3Galbeta1-4GlcNAc xenoantigenic determinant, was later found and molecularly cloned. We also found highly branched poly-N-acetyllactosamines in early embryonic cells, and demonstrated developmentally regulated carbohydrate changes during early mammalian development. The binding site for Dolichos biflorus agglutinin was introduced as a new differentiation marker. Basigin and embigin, two related members of the immunoglobulin superfamily, a sialomucin MGC-24 and other glycoproteins were discovered as carriers of developmentally regulated carbohydrate markers. We proposed enhancement of integrin action as a function of sugar chains with Lewis X epitope, and observed a relationship between the expression of carbohydrate markers and invasive properties of human carcinoma. Midkine, a heparin-binding growth factor, was discovered more recently and its interaction with heparin and oversulfated chondroitin sulfate was elucidated. N-Acetylglucosamine-6-sulfotransferase was cloned and used to reconstitute L-selectin ligands. Gene knockout was applied to reveal in vivo function of basigin, syndecan-4 and chondroitin 6-sulfate. Throughout my research on all these subjects, I have been fortunate in obtaining unexpected observations and enjoying fruitful collaborations.

Animals↗

Lewis X structure increases cell substratum adhesion in L cells.

cDNAs of alpha-1,3-fucosyltransferase as well as alpha-1,3/4-fucosyltransferase were placed under the control of a beta-actin promoter and cytomegalovirus enhancer and were introduced into L cells. The transfected cells expressing Le(x) antigen showed increased cell substratum adhesion as compared to the antigen-negative cells, when they were cultured for 2 to 4 h in Dulbecco-modified minimum essential medium containing 0.05% bovine serum albumin. The increased cell substratum adhesion was completely inhibited by cycloheximide and anti-integrin antiserum, and partly by an RGD peptide and EGTA. These findings indicate that Le(x) structure promotes cell adhesion to substratum-bound material secreted by cells, and that the increased adhesion is mediated by integrin. Western blotting experiments have revealed an 85 kDa protein and a 50-60 kDa protein as carriers of Le(x) antigen in transfected cells. The latter is likely to be basigin, which is a member of the immunoglobulin superfamily and is considered to be an integrin-associated protein. We hypothesize that fucosylation of basigin enhances integrin-mediated cell substratum adhesion.

Animals↗

Characterization of novel secreted and membrane proteins isolated by the signal sequence trap method.

We recently described a method, called the signal sequence trap (SST) method, to clone cDNAs of secreted proteins and/or type I transmembrane proteins containing N-terminal signal sequences by using an epitope-tagging expression plasmid vector. In this paper we describe the summary of a large-scale screening of approximately 5900 clones of an SST cDNA library constructed from mouse bone marrow stromal cell line ST-2 cells. Of 26 positive clones obtained and sequenced, 11 clones appeared to contain authentic signal sequences. Five of the clones corresponded to the 5' ends of the cDNA of known genes containing N-terminal signal sequences. The full-length cDNA clones of the 6 other unknown clones were isolated and sequenced. One clone, termed SDF3, encoded a mouse counterpart of human pigment epithelium-derived factor. Another clone, termed SDR1, had considerable homology with basigin, a member of the immunoglobulin superfamily. A third clone, termed SDF5, had partial homology with a Drosophila tissue polarity gene frizzled (fz) and its rat homologues, fz-1 and fz-2. The other three clones had no significant homology with sequences in the databases. These results indicate that the SST method is effective and useful for the isolation of secreted and membrane proteins without knowledge of their functions.

Amino Acid Sequence↗

Effects of flanking genes on the phenotypes of mice deficient in basigin/CD147.

The induction of null mutations by means of homologous recombination is a powerful technique for clarifying the biological activities of target genes. However, the problems of the genetic background and flanking genes should be borne in mind. Here we employed a breeding strategy to compare three lines of mice deficient in the basigin (Bsg)/CD147 gene. The first line was F2 from F1 hybrid offspring of the 129/SV chimera and C57BL/6J. The second one was from a C57BL/6J congenic line. Both lines showed high embryonic lethality, sterility, and blindness. The third one was 'reverse F2' from 'reverse F1' hybrid offspring of the C57BL/6J congenic line and 129/SV. Surprisingly, this line showed a normal birth rate, while sterility and blindness persisted. Our results clearly separate the effects of the induced null mutation from those of flanking genes and the genetic background, and provide a useful means of investigating the biological functions of Bsg.

Animals↗