PubMed Health⌕ Search

Biomedical subjects

M Schachner

Publications and source records attributed to M Schachner.

At least 19 recordsLinked to original sources
PubMed1992

Mouse P0 gene disruption leads to hypomyelination, abnormal expression of recognition molecules, and degeneration of myelin and axons.

We have used homologous recombination in embryonic stem cells to generate mice carrying a mutation in the gene encoding P0, an immunoglobulin-related recognition molecule and the major protein of peripheral nervous system myelin. These mice are deficient in normal motor coordination and exhibit tremors and occasional convulsions. Axons in their peripheral nerves are severely hypomyelinated and a subset of myelin-like figures and axons degenerate. The mutation leads to an abnormal regulation of some, but not all, molecules involved in myelination. These results demonstrate that P0 is essential for the normal spiraling, compaction, and maintenance of the peripheral myelin sheath and the continued integrity of associated axons. They further suggest that this protein conveys a signal that regulates Schwann cell gene expression.

Animals↗
PubMed1992

The adhesion molecule on glia (AMOG/beta 2) and alpha 1 subunits assemble to functional sodium pumps in Xenopus oocytes.

The adhesion molecule on glia, AMOG, an integral cell surface glycoprotein highly expressed by cerebellar astrocytes and involved in neuron to astrocyte adhesion and granule neuron migration (Antonicek, H., Persohn, E., and Schachner, M. (1987) J. Cell Biol. 104, 1587-1595) has been identified as a beta 2 subunit isoform of the mouse sodium pump (Gloor, S., Antonicek, H., Sweadner, K.J., Pagliusi, S., Frank, R., Moos, M., and Schachner, M. (1990) J. Cell Biol. 110, 165-174). Here we demonstrate that AMOG/beta 2 expressed by cRNA injection in Xenopus oocytes is capable of combining with endogenous Xenopus alpha 1 subunits or coexpressed Torpedo alpha 1 subunits to yield a functional alpha 1/AMOG sodium pump isozyme. Determinations of the number of ouabain binding sites and ouabain-sensitive 86Rb+ uptake suggest that the alpha 1/AMOG isozyme has slightly lower maximum transport rate and apparent affinity for external K+ than the alpha 1/beta 1 isozyme. Immunoprecipitation of alpha 1/AMOG complexes from digitonin extracts of [35S]methionine-labeled oocytes with a monoclonal anti-AMOG antibody provides direct evidence for a stable association between AMOG and the alpha 1 subunits of Xenopus and Torpedo.

Adenosine Triphosphatases↗
PubMed1992

Enhanced expression of the developmentally regulated extracellular matrix molecule tenascin following adult brain injury.

Tenascin is an extracellular matrix molecule synthesized and released by young astrocytes during embryonic and early postnatal development of the nervous system, and it is concentrated in boundaries around emerging functional neuronal units. In the adult nervous system, tenascin can be detected only in very low levels. Distinct spatial and temporal distributions of tenascin during developmental events suggest a role in the guidance and/or segregation of neurons and their processes within incipient functional patterns. We show here, using in situ hybridization and immunocytochemistry, that stab wounds of the adult mouse cerebellar and cerebral cortices result in an enhanced expression of tenascin in a discrete region around the lesion site that is associated with a subset of glial fibrillary acidic protein-positive astrocytes. Tenascin up-regulation in the lesioned adult brain may be directly involved in failed regeneration or indirectly involved through its interactions with other glycoconjugates that either inhibit or facilitate neurite growth.

Age Factors↗
PubMed1992

Differential expression of transforming growth factor-beta 1, -beta 2, and -beta 3 by glioblastoma cells, astrocytes, and microglia.

The type beta transforming growth factors (TGF) are potent regulators of the growth and functions of lymphocytes and macrophages. Recently the human glioblastoma cell line 308 was shown to produce TGF-beta 2. The relevance of this finding was evaluated further by comparing human glioblastoma cells with their nontransformed animal counterpart, astrocytes, with regard to the production of the three TGF-beta isoforms observed so far in mammals. In this report astrocytes are demonstrated to secrete also TGF-beta 2 and to express TGF-beta 1, -beta 2, and -beta 3 mRNA in vitro. In contrast, cultured murine brain macrophages release TGF-beta 1 and are positive for TGF-beta 1 mRNA only. Glia cell-derived TGF-beta 1 and -beta 2 are detected in latent form whereas both latent and active TGF-beta are identified in the supernatant of three human glioblastoma cell lines tested. These cell lines, however, show heterogeneity in regard to the isoform of TGF-beta expressed but share with astrocytes the inability to release TGF-beta 3. Provided production and activation of latent TGF-beta occur in vivo, astrocytes and microglia may then be expected to exert regulatory influences on immune mediated diseases of the central nervous system.

Animals↗
PubMed1992

Afferent-boundary interactions in the developing neostriatal mosaic.

The caudate-putamen (neostriatum) of the mammalian basal ganglia is composed of two neurochemically distinct compartments termed patch (island, striosome) and matrix that overall contribute to a mosaic organization. In the present study, the distribution of the developmentally regulated extracellular matrix molecule tenascin, as well as several other neural cell adhesion molecules, was examined in the neostriatal mosaic of the early postnatal mouse and compared with tyrosine hydroxylase distribution following partial destruction of the dopaminergic nigrostriatal projection. During normal neostriatal development, tenascin is most dense within the matrix compartment and highly concentrated in boundaries around patches. This pattern is apparent on embryonic day 18, and for the most part disappears by postnatal day 12. Tenascin immunoreactivity is altered in the neostriatum following lesions of the nigrostriatal pathway in the first postnatal week revealed by an overall reduced expression of this molecule and a marked reduction in tenascin staining of boundaries at the interface of tyrosine hydroxylase-rich patch and tyrosine hydroxylase-poor matrix compartments. When compared to tyrosine hydroxylase immunoreactivity, other cell adhesion molecules tested failed to show altered intensities and patterns of immunoreactivity within the neostriatum after similar lesions. Reduced levels of tenascin in the lesioned neostriatum, in register with altered levels of tyrosine hydroxylase immunostaining of dopaminergic inputs, suggests that axons may affect the expression of particular recognition molecules in their target structures. The fact that boundaries are malleable can be related to afferent-induced plastic events in the differentiation of cellular elements in the developing nigrostriatal system.

Animals↗
PubMed1992

Expression and function of the neural cell adhesion molecule L1 in mouse leukocytes.

The neural cell adhesion molecule L1 is a cell surface glycoprotein of the immunoglobulin superfamily which mediates adhesion between neural cells. The possibility that similar cell-cell recognition mechanisms may be shared by the nervous and immune systems prompted us to study the expression and function of L1 in cells of the hematopoietic system. Immunofluorescence analysis using monoclonal L1 antibody revealed that the molecule is expressed in the bone marrow, spleen, and thymus of the mouse. This observation was confirmed by amplifying cDNA derived from these organs by the polymerase chain reaction with L1-specific oligonucleotide primers. Two-color fluorescence analysis indicated that bone marrow lymphoid and granulocyte precursor cells express low and high levels of L1, respectively. In the thymus L1 is primarily expressed by mature cells that have a strong expression of CD3 and in the spleen both B cells and T cells express L1. The possible function of L1 in lymphoid cells was studied using subcloned ESb-MP lymphoma cells having high or low densities of L1 on the cell surface as well as activated splenic B lymphoblasts. Parental and subcloned ESb-MP cells that strongly expressed L1 could form homotypic aggregates in the presence of low Ca2+ levels, whereas subcloned ESb-MP cells with a weak expression of L1 did not aggregate, suggesting that L1 mediates the Ca(2+)-independent aggregation of the parental ESb-MP cells. Furthermore, the aggregation of activated B lymphoblasts under physiological concentrations of Ca2+ and Mg2+ was inhibited by 30% in the presence of Fab fragments of polyclonal L1 antibodies, implying that L1 also mediates adhesion among normal lymphoid cells. A possible role of L1 on lymphocytes in stimulating the innervation of lymphoid organs is discussed.

Animals↗
PubMed1992

Analysis of promoter activity and 5' genomic structure of the neural cell adhesion molecule L1.

To gain insight into the molecular mechanisms underlying the regulation of expression of the neural cell adhesion molecule L1 and into the exon-intron structure of the L1 gene, a genomic clone from the mouse was characterized. The clone was identified by screening an EMBL3 library with an L1-specific cDNA probe and comprises approximately 15 kb, in which the first 2,206 nucleotides of the coding region are included. Of the 5 of 6 immunoglobulin (Ig)-like domains sequenced, all are encoded by 2 exons, with the first exon being smaller than the second. The exon encoding the signal peptide is separated from a mini-exon containing 15 bp by a large intron, approximately 2.6 kb in length, whereas the other introns are smaller, with the coding information for the Ig-like domains 3-5 clustered in a 1,643-bp-long fragment with introns only 110-217 bp in length. The 5' upstream region of the clone comprises 5 kb, with the first 112 bp lying upstream to the coding sequence and containing a start site for transcription. No consensus sequence for a TATA box was found. Consensus DNA sequences for the binding of the gene products of Hox 1.3, engrailed and bicoid, are localized upstream to the transcription start site. A 1,262-bp fragment containing part of the first exon showed promoter activity in neuroblastoma cells, but hardly in L cells and not in CHO cells, indicating that this fragment is sufficient for neural cell directed promoter activity.

Animals↗
PubMed1992

L2/HNK-1 carbohydrate and protein-protein interactions mediate the homophilic binding of the neural adhesion molecule P0.

The neural adhesion molecule P0, the most abundant glycoprotein in peripheral myelin of mammals, is a member of the immunoglobulin superfamily and expresses the L2/HNK-1 and L3 oligosaccharides at a single N-glycosylation site. It acts in both homophilic and heterophilic binding mechanisms. To investigate the molecular requirements for homophilic interaction, we have used P0 from human sciatic nerve and the extracellular domain of P0 expressed in bacteria to determine binding of P0 to P0 in solid phase and bead aggregation assays. The binding of P0 to P0 could be partially inhibited in both assays by antibodies to the L2/HNK-1 epitope and by the L2/HNK-1 carbohydrate, but not by L3 antibodies or other carbohydrates. Inhibition of binding was also seen with polyclonal antibodies reacting with the protein backbone of P0. These observations indicate that both carbohydrate and protein structures are involved in the binding of P0 to P0 and that P0 acts as a presenter of and a receptor for a functionally important carbohydrate.

Animals↗
PubMed1992

Monoclonal M6 antibody interferes with neurite extension of cultured neurons.

Monoclonal M6 antibody binds to the surface of murine central nervous system neurons as well as to apical surfaces of epithelial cells in the choroid plexus and proximal tubules of the kidney. M6 antigen is expressed in the central nervous system as early as embryonic day 10, most strongly in the marginal zone of the neural tube, and remains detectable in adulthood. IgG or Fab fragments of M6 antibody interfere with the extension of neurites by cultured cerebellar neurons. Effects of the antibody on neurite extension are readily detectable after 24 h. No reduction of cell viability is detected during the first 3 days of antibody treatment. Cultures maintained in the presence of antibody for longer than 5 days exhibit reduced viability of neurons. This reduction in long-term viability in the presence of M6 antibody is largely avoided when 25 mM KCl is included in the culture medium. The antibody-mediated perturbation of neurite outgrowth is not blocked by the presence of elevated KCl. The unusually short and flattened appearance of neurites in these cultures suggests that the M6 antibody selectively affects neurite extension. Time-lapse cinematography of anti-M6-treated neurons reveals no apparent effect on movement of lamellipodia and filopodia of growth cones. Only the overall extension of the neurite appears to be inhibited. M6 antigen is a 35 kD glycoprotein that can be isolated from a deoxycholate- (DOC) solubilized membrane fraction from adult mouse brain.

Animals↗
PubMed1992

Use of large-scale hydrazinolysis in the preparation of N-linked oligosaccharide libraries: application to brain tissue.

In this report, we describe the preparation of a library of N-linked glycans from whole murine brain obtained by the large-scale hydrazinolysis of an acetone powder of the tissue followed by chromatographic procedures. 84% of the characterized oligosaccharides were found to be anionic, the remainder neutral. The anionic species were successively neutralized by neuraminidase (29%), aq. hydrofluoric acid (30%), and methanolysis (26%), indicating that approximately equal portions were sensitive to desialylation, dephosphorylation and desulfation, respectively. The presence of the sulfated fraction was confirmed by direct 35SO4 metabolic labelling. A residual partially characterized fraction was found to be anionic through possession of carboxylic acid groups, unrelated to sialic acid. The purified oligosaccharides, in the absence of their original protein conjugates, were shown to retain those immunological characteristics essential for recognition by a specific monoclonal antibody, LS (412), that is known to recognize a carbohydrate epitope present on a number of neural adhesion molecules and functional in neural cell adhesion. These properties confirm the viability of scaling up the size of the hydrazinolysis procedure and adapting it to whole tissue for the production of glycan libraries and for the probing of structures of interest.

Animals↗
PubMed1992

The differentiation of glial cell progenitor populations following transplantation into non-repairing central nervous system glial lesions in adult animals.

The non-repairing nature of the locally x-irradiated ethidium bromide (EB)-induced demyelinating white matter lesion has been further validated by showing that injections of two cultures which promote host remyelination of EB lesions in normal tissue do not do so in x-irradiated lesions. The behaviour of an oncogene-immortalized glial cell line and a growth-factor-expanded glial progenitor population have been examined following transplantation into the non-repairing EB lesion. Our studies indicate that the selected glial cell populations were each capable of establishing glial environments around demyelinated axons. Extensive oligodendrocyte remyelination with little astrocytic presence was observed in lesions transplanted with growth-factor-expanded optic nerve progenitors, while less extensive oligodendrocyte remyelination with the establishment of astrocyte-like cells was found in lesions transplanted with ts A58-SV40T immortalized glial cells. Prolonged expansion of both populations resulted in a loss of differentiation to normal glial phenotypes.

Animals↗
PubMed1992

Neural cell adhesion molecules modulate tyrosine phosphorylation of tubulin in nerve growth cone membranes.

Triggering neural cell adhesion molecules of the immunoglobulin superfamily with specific ligands or antibodies inhibited the phosphorylation of tryosyl residues in a subpopulation of alpha- and beta-tubulin associated with membranes from a subcellular fraction of nerve growth cones from fetal rat brain. Preincubation of these membranes with purified extracellular fragments of L1, N-CAM, or myelin-associated glycoprotein, or with antibodies directed against the extracellular domains of L1 or N-CAM, inhibited pp60c-src-dependent phosphorylation of tubulin in an endogenous membrane kinase reaction. Other proteins that affect neurite outgrowth (fibronectin, laminin, antibodies against N-cadherin) had no effect. The results suggest that cell adhesion molecules transduce cell surface events to intracellular signals by modulating the activity of protein tyrosine kinases or phosphatases in axonal membranes to influence cytoskeletal dynamics at the growth cone.

Animals↗
PubMed1992

Interactions of the neural cell adhesion molecule and the myelin-associated glycoprotein with collagen type I: involvement in fibrillogenesis.

To gain insights into the functional role of the molecular association between neural adhesion molecules and extracellular matrix constituents, soluble forms of the myelin-associated glycoprotein (MAG) and the neural cell adhesion molecule (N-CAM), representing most of the extracellular domains of the molecules, were investigated in their ability to modify fibrillogenesis of collagen type I. MAG and N-CAM retarded the rate of fibril formation, as measured by changes in turbidity, and increased the diameter of the fibrils formed, but did not change the banding pattern when compared to collagen type I in the absence of adhesion molecules. Scatchard plot analysis of the binding of MAG and N-CAM to the fibril-forming collagen types I, II, III, and V suggest one binding site for N-CAM and two binding sites for MAG. Binding of MAG, but not of N-CAM, to collagen type I was decreased during fibril formation, probably due to a reduced accessibility of one binding site for MAG during fibrillogenesis. These results indicate that the neural adhesion molecules can influence the configuration of extracellular matrix constituents, thus, implicating them in the modulation of cell-substrate interactions.

Animals↗
PubMed1992

Tenascin promotes cerebellar granule cell migration and neurite outgrowth by different domains in the fibronectin type III repeats.

The extracellular matrix molecule tenascin has been implicated in neuron-glia recognition in the developing central and peripheral nervous system and in regeneration. In this study, its role in Bergmann glial process-mediated neuronal migration was assayed in vitro using tissue explants of the early postnatal mouse cerebellar cortex. Of the five mAbs reacting with nonoverlapping epitopes on tenascin, mAbs J1/tn1, J1/tn4, and J1/tn5, but not mAbs J1/tn2 and J1/tn3 inhibited granule cell migration. Localization of the immunoreactive domains by EM of rotary shadowed tenascin molecules revealed that the mAbs J1/tn4 and J1/tn5, like the previously described J1/tn1 antibody, bound between the third and fifth fibronectin type III homologous repeats and mAb J1/tn3 bound between the third and fifth EGF-like repeats. mAb J1/tn2 had previously been found to react between fibronectin type III homologous repeats 10 and 11 of the mouse molecule (Lochter, A., L. Vaughan, A. Kaplony, A. Prochiantz, M. Schachner, and A. Faissner. 1991. J. Cell Biol. 113:1159-1171). When postnatal granule cell neurons were cultured on tenascin adsorbed to polyornithine, both the percentage of neurite-bearing cells and the length of outgrowing neurites were increased when compared to neurons growing on polyornithine alone. This neurite outgrowth promoting effect of tenascin was abolished only by mAb J1/tn2 or tenascin added to the culture medium in soluble form. The other antibodies did not modify the stimulatory or inhibitory effects of the molecule. These observations indicate that tenascin influences neurite outgrowth and migration of cerebellar granule cells by different domains in the fibronectin type III homologous repeats.

Animals↗
PubMed1992

Different extracellular domains of the neural cell adhesion molecule (N-CAM) are involved in different functions.

The neural cell adhesion molecule (N-CAM) engages in diverse functional roles in neural cell interactions. Its extracellular part consists of five Ig-like domains and two fibronectin type III homologous (type III) repeats. To investigate the functional properties of the different structural domains of the molecule in cell interactions and signal transduction to the cell interior, we have synthesized, in a bacterial expression system, the individual domains and tandem sets of individual domains as protein fragments. These protein fragments were tested for their capacity to influence adhesion and spreading of neuronal cell bodies, promote neurite outgrowth, and influence cellular migration patterns from cerebellar microexplants in vitro. Ig-like domains I and II and the combined type III repeats I-II were most efficient for adhesion of neuronal cell bodies, when coated as substrates. Neurite outgrowth was best on the substrate-coated combined type III repeats I-II, followed by the combined Ig-like domains I-V and Ig-like domain I. Spreading of neuronal cell bodies was best on substrate-coated combined type III repeats I-II, followed by Ig-like domain I and the combined Ig-like domains I-V. The cellular migration pattern from cerebellar microexplant cultures plated on a mixture of laminin and poly-L-lysine was modified by Ig-like domains I, III, and IV, while Ig-like domains II and V and the combined type III repeats I-II did not show significant modifications, when added as soluble fragments. Outgrowth of astrocytic processes from the explant core was influenced only by Ig-like domain I. Metabolism of inositol phosphates was strongly increased by Ig-like domain I and less by the Ig-like domains II, III, IV, and V, and not influenced by the combined type III repeats I-II. Intracellular concentrations of Ca2+ and pH values were increased only by the Ig-like domains I and II. Intracellular levels of cAMP and GMP were not influenced by any protein fragment. These experiments indicate that different domains of N-CAM subserve different functional roles in cell recognition and signal transduction, and are functionally competent without nervous system-derived carbohydrate structures.

Animals↗
PubMed1992

Nectadrin, the heat-stable antigen, is a cell adhesion molecule.

Nectadrin, the cell surface glycoprotein recognized by the novel mAb 79, was found to be immunologically identical to the heat-stable antigen (HSA). It is a glycoprotein with a polypeptide core of only 30 amino acids and a very high carbohydrate content (Wenger, R. H., M. Ayane, R. Bose, G. Köhler, and P. J. Nielsen. 1991. Eur. J. Immunol. 21:1039-1046). Immunocytological studies using cultured splenic B-lymphocytes, neuroblastoma cells, and cerebellar cells indicated that nectadrin is preferentially expressed at sites of cell-cell contact. Purified nectadrin and monoclonal nectadrin antibody 79, but not other monoclonal nectadrin antibodies, inhibited the aggregation of B-lymphocytes by 70%, suggesting that nectadrin may act as a cell adhesion molecule. Nectadrin was purified from a mouse lymphoma cell line in two forms of 40-60 and 23-30 kD. The lower molecular weight form appears to be generated from the higher molecular weight form by degradative removal of saccharide residues characteristic of complex type oligosaccharide side chains. Latex beads coated with purified nectadrin aggregated and the rate of their aggregation depended on the molecular form of nectadrin, with the larger form being more potent than the smaller one in mediating bead aggregation. Nectadrin thus appears to be a self-binding cell adhesion molecule of a structurally novel type in that its extensive glycan structures may be implicated in mediating cell adhesion.

Animals↗
PubMed1992

Application of testosterone accelerates oligodendrocyte maturation in brains of zebra finches.

The effects of exogenously applied hormones on glial cell maturation of telencephalic song motor centers, midbrain and cerebellar structures was studied in juvenile male zebra finches. Testosterone was administered and the development of oligodendrocytes was studied using immunochemistry and computer aided image analysis on silver impregnated brain sections. A testosterone induced acceleration of oligodendrocyte maturation could be detected in several brain areas by using the monoclonal antibody O 10 recognizing an oligodendrocyte-specific cell surface antigen and by the silver impregnation for myelin. The increase in myelin density was higher in the testosterone treated animals than in the control animals in the forebrain and in the cerebellum, whereas two regions in the midbrain showed no difference between treated and controls.

Aging↗