Myelin/oligodendrocyte glycoprotein is a member of a subset of the immunoglobulin superfamily encoded within the major histocompatibility complex

Myelin/oligodendrocyte glycoprotein (MOG) is found on the surface of myelinating oligodendrocytes and external lamellae of myelin sheaths in the central nervous system, and it is a target antigen in experimental autoimmune encephalomyelitis and multiple sclerosis. We have isolated bovine, mouse, and rat MOG cDNA clones and shown that the developmental pattern of MOG expression in the rat central nervous system coincides with the late stages of myelination. The amino-terminal, extracellular domain of MOG has characteristics of an immunoglobulin variable domain and is 46% and 41% identical with the amino terminus of bovine butyrophilin (expressed in the lactating mammary gland) and B-G antigens of the chicken major histocompatibility complex (MHC), respectively; these proteins thus form a subset of the immunoglobulin superfamily. The homology between MOG and B-G extends beyond their structure and genetic mapping to their ability to induce strong antibody responses and has implications for the role of MOG in pathological, autoimmune conditions. We colocalized the MOG and BT genes to the human MHC on chromosome 6p21.3-p22. The mouse MOG gene was mapped to the homologous band C of chromosome 17, within the M region of the mouse MHC.

Demonstration of a specific localization of carbonic anhydrase C in the glial cells of rat CNS by an immunohistochemical method

The localization of carbonic anhydrase C isoenzyme in the central nervous system (CNS) of the rat has been investigated using the indirect immunoperoxidase technique, at both optic and electron microscopic levels. Evidence is presented for a specific localization of the enzyme in the cytoplasm of the oligodendrocytes and astrocytes. Myelinated fibers show a weak staining. The positive reaction is restricted to the cytoplasmic areas of the myelin sheath and does not appear in the compact myelin. Neuronal cell bodies do not stain at all. A strong positive reaction to the antiserum was also observed in the choroid plexus.

Postnatal development of rat cerebellum: massive and transient accumulation of concanavalin A binding glycoproteins in parallel fiber axolemma

Modifications of protein-bound sugars during postnatal development of rat cerebellum were studied. Glycoprotein-bound mannose accumulates, in the particulate fractions, at an earlier age than the bulk of glycoprotein sugar. This corresponds to a transient and massive accumulation of glycoproteins which bind to Concanavalin A (Con A). These glycoproteins were localized by using fluorescent Con A and the horseradish peroxidase-Con A method. Cerebellar white matter and the molecular layer bind massive amounts of Con A. The binding in the molecular layer is transient. It follows the same time course as the Con A-binding glycoproteins of particulate fractions, and it is largely confined to the axolemma of parallel fibers. Only growing or newly formed parallel fibers bind Con A. The disappearance of the binding is simultaneous with the maturation of parallel fibers and their synapse formation. These phenomena can be related to fiber growth and maturation and, also, to synapse formation. The possibility of a specific role of Con A-binding glycoproteins is discussed.

Arrest of proteolipid transport through the Golgi apparatus in Jimpy brain

Immunocytochemical investigations were performed on Jimpy and control mouse brains using three specific anti-myelin proteolipids antisera: immunoaffinity purified multivalent anti-(PLP + DM-20) proteolipid antibodies, anti-C-terminal hexapeptide 271-276 and anti-tridecapeptide 117-129 antisera. The results show that oligodendrocytes and myelin sheaths in normal mouse brain are labelled to the same extent by the three specific antisera; in contrast, in Jimpy brain these cellular structures are only stained by the multivalent antibodies and the site-specific, anti-tridecapeptide antiserum. The absence of labelling with C-terminal hexapeptide antiserum in mutant brain is interpreted as the result of either a large deletion or a point mutation producing a frameshift in the C-terminal part of the sequences of the proteolipids PLP and DM-20. Furthermore, we show that this mutation prevents the normal transport of proteolipid molecules through the Golgi apparatus. The existence of a minor, extra-Golgi apparatus metabolic route for proteolipids to myelin structures is also discussed.

Comparative localization of Wolfgram W1 and myelin basic proteins in the rat brain during ontogenesis

Antisera raised in rabbits against myelin basic proteins (MBP) and Wolfgram W1 protein isolated from rat myelin were used to study the maturation of oligodendrocytes in the developing rat nervous system. Both proteins were localized immunohistochemically at the light and electron microscopical levels in rat brain from the time of their first appearance to the adult stage. Oligodendrocytes were first detected by their positive staining with W1 antiserum two days after birth and at 1-3 days later with MBP antiserum. At 8-10 days, the number of oligodendrocytes labelled with both sera increases and the myelinated fibre pathways were clearly visible. Labelling with W1 antiserum was observed in oligodendrocytes at all stages from 2 days after birth to adulthood and in myelin fibers when they were present. In contrast, staining of oligodendroglial cells with MBP declined during the period of rapid myelination (20-25 days after birth) and finally disappeared, whereas myelin staining was still apparent. The electron microscopical study revealed that the synthesis of Wolfgram proteins occurred mostly at the peripheral cytoplasmic ribosomes of the cells, from where they were probably transported to processes engaged in myelination. The electron micrographs also showed that the sites of MBP synthesis seemed to be more uniformly distributed over the entire cytoplasm.

Structure and cellular distribution of mouse brain testican. Association with the postsynaptic area of hippocampus pyramidal cells

The complete deduced primary structure of mouse brain testican has been established from cDNA cloning. The cDNA encodes a polypeptide of 442 amino acids belonging to the proteoglycan family. The mouse brain testican core protein is 95% identical to its human testicular counterpart. In situ hybridization investigations revealed that mouse testican mRNA is mainly present in a subpopulation of pyramidal neurons localized in the CA3 area of the hippocampus. An immunocytochemical approach, with antibodies directed against an overexpressed chimeric antigen, produced in bacterial systems, showed that testican is associated with the postsynaptic region of these pyramidal neurons. Testican includes several putative functional domains related to extracellular or pericellular proteins associated with binding and/or regulatory functions. On the basis of its structural organization and its occurrence in postsynaptic areas, this proteoglycan might contribute to various neuronal mechanisms in the central nervous system.

Contributions of local and regional anthropogenic sources of metals in PM2.5 at an urban site in northern France

PM_2.5 have been related to various adverse health effects, mainly due to their ability to penetrate deeply and to convey harmful chemical components, such as metals inside the body. In this work, PM_2.5 were sampled at Saint-Omer, a medium-sized city located in northern France, in March-April 2011 and analyzed for their total carbon, water-soluble ions, major and trace elements. More specifically, the origin of 15 selected elements was examined using different tools including enrichment factors, conditional bivariate probability function (CBPF) representations, diagnostic ratios and receptor modelling. The results indicated that PM_2.5 metal composition is affected by both emissions of a local glassmaking factory and an integrated steelworks located at a distance of 35 km from the sampling site. For the first time, diagnostic ratios were proposed for the glassmaking activity. Therefore, metals in PM_2.5 could be attributed to the following anthropogenic sources: (i) local glassmaking industry for Sn, As, Cu and Cr, (ii) distant integrated steelworks for Ag, Fe, Cd, Mn, Rb and Pb, (iii) heavy fuel oil combustion for Ni, V and Co and (iv) non-exhaust traffic for Zn, Pb, Mn, Sb, and Cu. The impact of such sources on metal concentrations in PM_2.5 was assessed using a constrained receptor model. Despite their low participation to PM_2.5 concentration (2.7%), the latter sources were found as the main contributors (80%) to the overall concentration levels of the 15 selected elements in PM_2.5.

Strength, diversity and plasticity of postmating reproductive barriers between two hybridizing oak species (Quercus robur L. and Quercus petraea (Matt) Liebl.)

Very little is known about the nature and strength of reproductive isolation (RI) in Quercus species, despite extensive research on the estimation and evolutionary significance of hybridization rates. We characterized postmating pre- and postzygotic RI between two hybridizing oak species, Quercus robur and Quercus petraea, using a large set of controlled crosses between different genotypes. Various traits potentially associated with reproductive barriers were quantified at several life history stages, from pollen-pistil interactions to seed set and progeny fitness-related traits. Results indicate strong intrinsic postmating prezygotic barriers, with significant barriers also at the postzygotic level, but relatively weaker extrinsic barriers on early hybrid fitness measures assessed in controlled conditions. Using general linear modelling of common garden data with clonal replicates, we showed that most traits exhibited important genotypic differences, as well as different levels of sensitivity to micro-environmental heterogeneity. These new findings suggest a large potential genetic diversity and plasticity of reproductive barriers and are confronted with hybridization evidence in these oak species.

Immunocytochemical demonstration of the transport of myelin proteolipids through the Golgi apparatus

Purified antibodies directed against myelin proteolipids were isolated by affinity chromatography of whole serum obtained from rabbits inoculated with myelin. These antibodies were specific for light, medium and dark oligodendrocytes. Astrocytes, neurons and their processes were not reactive. Immunocytochemical investigations showed that the membranes of the Golgi complex are highly labeled by these antibodies. Diffuse cytoplasmic labeling was only observed on the light and medium oligodendrocytes and was absent from the dark types. Vesicles possessing a punctate staining were detected in the vicinity of the Golgi complex and the oligodendroglial membrane. A discontinuous labeling of the plasmalemma appears to be characteristic of the actively myelinating light and medium oligodendrocytes. In compact myelin sheaths positive immunostaining was only detected at the dense line. The immunocytochemical localization of the myelin proteolipids in the oligodendrocytes is in accordance with previously published biochemical data.

Effects of some amino acids (GABA, glycine, taurine) and of their antagonists (picrotoxin, strychnine) on spatial and temporal features of frog retinal ganglion cell responses

When intravitreally injected in the frog, GABA reduced the receptive field area of transient retinal ganglion cells, and it decreased the response duration and the number of spikes both at ON and at OFF. Conversely, its antagonist picrotoxin provoked an increase in the duration of both ON and OFF discharges as well as a marked increase in the number of spikes. Furthermore, picrotoxin provoked a marked increase in the size of the receptive field of both sustained and ON-OFF cells by abolishing the inhibition exerted by the surround upon the centre of the field. Glycine and taurine did not affect the size of the receptive field of these ganglion cells. They had no effect on the responses of sustained ganglion cells, while they totally suppressed OFF discharges of transient ganglion cells, without modifying their ON discharges. Conversely, their antagonist strychnine totally suppressed the ON dishcarges while the OFF discharges were still recorded, though with a reduced number of spikes and an increased latency, An histoautoradiographic study, carried out in parallel, showed that GABA is taken up by both horizontal cells and amacrine cells, while glycine and taurine are taken up by the amacrine cells only.

Immunohistochemical studies of the localization of neurons containing the enzyme that synthesizes dopamine, GABA, or gamma-hydroxybutyrate in the rat substantia nigra and striatum

gamma-Hydroxybutyrate (GHB) is an endogenous metabolite of gamma-aminobutyric acid (GABA), which is synthesized in the neuronal compartment of the central nervous system. This substance possesses several properties that support its role as a neurotransmitter/neuromodulator in brain. In particular, it is synthesized by a specific pathway that transforms GABA into succinic semialdehyde via GABA-T activity; then succinic semialdehyde is converted into GHB by a specific succinic semialdehyde reductase (SSR). The last enzyme is considered as a marker for neurons that synthesize GHB. This compound binds in brain to receptors whose distribution, ontogenesis, kinetics, and pharmacology are specific. Endogenous GHB, but also GHB exogenously administered to rats, participate in the regulation of dopaminergic activity of the nigrostriatal pathway. To investigate the distribution of GHB neurons in this pathway and the anatomic relationships between dopaminergic and GHB neurons, immunocytochemical identification of dopamine, GABA, and GHB neurons was carried out in the substantia nigra and striatum of the rat. The following markers for these neurons were used: anti-tyrosine hydroxylase (TH) antibodies for dopamine neurons, anti-glutamate decarboxylase (GAD) antibodies for GABA neurons, and anti-succinic semialdehyde reductase (SSR) antibodies for GHB neurons. GABA neurons were studied because GAD and SSR co-exist frequently in the same neuron, and GABA alone also exerts its own regulatory effects on dopaminergic neurons. This study reveals the co-existence of GAD/SSR and GAD/SSR/TH in numerous neurons of the substantia nigra. However, some neurons appear to be only GAD or SSR positive. In the striatum, TH-positive terminals surround many GHB neurons. GAD innervation is abundant in close contact with unlabeled neurons in the caudate-putamen, whereas distinct SSR-positive punctuates are also present. The existence of SSR-reactive synapses and neurons was confirmed in the striatum at the electron microscopic level. On the basis of these results, a clear anatomo-functional relationship between GHB and dopamine networks cannot be defined; however, we propose the modulation by GHB of striatal intrinsic neurons that could then interfere with the presynaptic control of dopaminergic activity.

Ultrastructural localization study of two Wolfgram proteins in rat brain tissue

The ultrastructural immunohistochemical localization of Wolfgram proteins W1 and W2 is described in young rat brain tissue. The labelling by the antiserum to W1 is restricted to oligodendroglial cells and myelin sheaths. The plasma membrane of the cells as well as the polysomes are positively stained whereas the mitochondria and the nuclei are always free of labelling. Glial cell processes with definite organelles, which are involved in the myelination of neighbouring axons, are also positive to the antiserum. In the myelin sheaths, the positive staining occurs predominantly at the dense period line of the innermost and outermost lamellae. The present results add further evidence for a specific local synthesis of these Wolfgram proteins in oligodendroglial cells during myelination.

Proteolipid DM-20 predominates over PLP in peripheral nervous system

The major central nervous system (CNS) myelin proteolipid (PLP) is also expressed in the peripheral nervous system (PNS). This paper gives evidence that DM-20, an isoform of PLP, also occurs in rat sciatic nerves, where, in contrast to what is seen in CNS myelin, it predominates over PLP. This conclusion was reached on the basis of results obtained by immunoblot analysis of a crude proteolipid extract from adult peripheral nerve with two site-specific anti-proteolipid (PLP and DM-20) antibodies. This finding was further corroborated by characterization of the products obtained by Polymerase Chain Reaction (PCR) amplification of cDNAs synthesized from total RNA of 14-day-old sciatic nerves. The significance of the occurrence of these proteolipids in PNS remains obscure.

A specific immunological probe for the major myelin proteolipid. Confirmation of a deletion in DM-20

Major myelin proteolipid (MMPL, also called PLP) and DM-20 are the two major intrinsic membrane proteins of CNS myelin. A specific immunological probe was obtained for MMPL by raising antibodies against the synthetic tridecapeptide 117-129 of MMPL. Antibodies against this peptide reacted with the MMPL but did not cross react with DM-20, while both proteolipids had been shown previously to be recognized by antibodies directed against the C-terminal hexapeptide of MMPL. This is in accordance with previous findings showing that DM-20 differs only from MMPL by a deletion of residues 100-140 (+/- few units). Furthermore, this site-specific immunological probe also recognizes MMPL in its native form in oligodendrocytes in primary glial cell cultures.

Functional interaction between matrix metalloproteinase-3 and semaphorin-3C during cortical axonal growth and guidance

In the developing cortex, axons and dendrites extend progressively in response to environmental cues attracting or repelling growing processes. Recent evidence suggests the existence of a functional link between guidance molecules and metalloproteinases. Here, we analyzed the putative functional interaction of matrix metalloproteinases (MMPs) with guidance cues of the semaphorin family during growth and guidance of cortical axons. Our results demonstrate that the expression pattern and the proteolytic activity of MMP-3 are consistent with a role of this particular MMP during cortical axon outgrowth. We found that MMP-3 is required for an optimal axon extension and is involved in the Sema3C-dependent chemoattraction of cortical axons by modulating both the growth capacity and the orientation of growth. Interestingly, the inhibitory Sema3A decreased both the expression and activity of MMP-3. Taken together, our results reveal a molecular interaction between MMPs and semaphorins providing new insight into the molecular mechanism allowing axonal growth cone to respond to environmental guidance cues in the context of cortical development.

Isolation and immunohistochemical localization of a lectin-like molecule from the rat cerebellum

A lectin with a mannose specificity was isolated from the cerebellum of young rats. The method of purification was based on the observation that during homogenization of the tissue, the lectin binds to a class of mannose-rich glycoproteins highly insoluble in Triton X-100. Sequential extractions in saline buffer devoid of, then containing, 0.5% Triton X-100 allowed the elimination of a great part of other proteins. Using the same buffer containing 0.5 M mannose, a specific class of protein can be solubilized. This fraction was enriched by affinity adsorption on insolubilized mannose-rich glycoproteins followed by specific detachment with mannose. One of the protein subunits, of molecular weight (MW) 130,000, was isolated by preparative gel electrophoresis. Upon re-electrophoresis, this compound gives two bands of MW 65,000 and 130,000, which appear to be a monomer and a dimer of a molecule called R1. Antibodies were raised against R1 which react with the monomer and the dimer and not against other proteins of the rat cerebellum. The immunohistochemical localization of this lectin was performed in cerebella of 20-day-old rats. The antigen is concentrated in endothelial cells and in large and intermediate size neurons (Purkinje, Golgi, basket and deep nuclei neurons). Granule cell bodies are lightly stained and no label at all was found in glial cells. At the level of electron microscopy, the antigen was found to be very concentrated in multivesicular bodies and lysosomes of large neurons, on parts of the endoplasmic reticulum, on some mitochondrial outer membranes and on the plasma membrane of the dendrites. The possible role of this lectin in cerebella of young rats is discussed in relation to its interaction with a specific class of mannose-rich glycoproteins.

UDPgalactose:ceramide galactosyltransferase of rat brain: a new method of purification and production of specific antibodies

A new method for purification of UDPgalactose:ceramide galactosyltransferase (EC 2.4.1.45) is described. The principal steps involved solvent extraction at -70 degrees C, Triton X-100 extraction, and DEAE-Sephadex and Blue Sepharose chromatography. The active configuration of the enzyme was stabilized by phospholipids and a rapid loss of enzymatic activity was observed after removal of these lipids. The inactive enzyme could be fully reactivated in the presence of brain phospholipids dispersed in a Triton X-100-containing buffer. The purified enzyme preparation showed two major components by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate with apparent molecular weights of 50-70,000. The 53,000-dalton protein was isolated by preparative gel electrophoresis in the presence of sodium dodecyl sulfate and used to produce antibodies against UDPgalactose:ceramide galactosyltransferase.

PM2.5 source apportionment in a French urban coastal site under steelworks emission influences using constrained non-negative matrix factorization receptor model

The constrained weighted-non-negative matrix factorization (CW-NMF) hybrid receptor model was applied to study the influence of steelmaking activities on PM2.5 (particulate matter with equivalent aerodynamic diameter less than 2.5 μm) composition in Dunkerque, Northern France. Semi-diurnal PM2.5 samples were collected using a high volume sampler in winter 2010 and spring 2011 and were analyzed for trace metals, water-soluble ions, and total carbon using inductively coupled plasma--atomic emission spectrometry (ICP-AES), ICP--mass spectrometry (ICP-MS), ionic chromatography and micro elemental carbon analyzer. The elemental composition shows that NO3(-), SO4(2-), NH4(+) and total carbon are the main PM2.5 constituents. Trace metals data were interpreted using concentration roses and both influences of integrated steelworks and electric steel plant were evidenced. The distinction between the two sources is made possible by the use Zn/Fe and Zn/Mn diagnostic ratios. Moreover Rb/Cr, Pb/Cr and Cu/Cd combination ratio are proposed to distinguish the ISW-sintering stack from the ISW-fugitive emissions. The a priori knowledge on the influencing source was introduced in the CW-NMF to guide the calculation. Eleven source profiles with various contributions were identified: 8 are characteristics of coastal urban background site profiles and 3 are related to the steelmaking activities. Between them, secondary nitrates, secondary sulfates and combustion profiles give the highest contributions and account for 93% of the PM2.5 concentration. The steelwork facilities contribute in about 2% of the total PM2.5 concentration and appear to be the main source of Cr, Cu, Fe, Mn, Zn.

Membrane topology of the myelin/oligodendrocyte glycoprotein

Myelin/oligodendrocyte glycoprotein (MOG), a specific component of the mammalian central nervous system, is located on the surface of the oligodendrocyte plasma membrane and the outermost lamellae of mature myelin; it is expressed during the latter steps of myelinogenesis. It has been shown that MOG may play a pathological role in autoimmune demyelinating diseases of the central nervous system, although its physiological function remains unknown. MOG is an integral membrane glycoprotein with an extracellular immunoglobulin-like domain and two hydrophobic segments which were predicted to be membrane-spanning on the basis of hydropathy analysis. As a first step in elucidation of MOG function, we have investigated its membrane topology, combining immunofluorescence studies on cultured oligodendrocytes and MOG-transfected Chinese hamster ovary cells with biochemical analyses, including in vitro translation, membrane insertion and protease-digestion assays. Our results indicate that the C-terminal tail of MOG is located into the cytoplasm, and that only the first hydrophobic region of MOG spans the membrane whereas the second hydrophobic region appears to be semi-embedded in the lipid bilayer, lying partially buried in the membrane with its N-terminal and C-terminal boundaries facing the cytoplasm.

Immunohistochemical localization of a lectin-like molecule, R1, during the postnatal development of the rat cerebellum

The immunohistochemical localization of an endogenous lectin R1 isolated from the rat cerebellum was studied during its postnatal development. The lectin is present in the cerebellum from birth to adulthood, essentially in lysosomes, multivesicular bodies, and parts of the endoplasmic reticulum, principally of large and intermediate size neurons. During the period of massive synaptogenesis in the molecular layer, there is a sprouting of R1 in some distal dendrites of Purkinje cells. The lectin appears to be particularly concentrated on their plasma membranes, in coated pits, in coated vesicles, multivesicular bodies and lysosomes. At the same period, in cerebella of rats treated with chloroquine (an inhibitor of lysosomal function), both the lectin and mannose-rich glycoproteins of newly formed parallel fibres (able to bind specifically this lectin) are found in the same non-functional lysosomes of Purkinje cells. It is thus suggested that both this lectin (with a high-affinity for the glycans of the mannose-rich glycoproteins of the membrane of the newly formed parallel fibres) and these glycoproteins could be the recognition molecules allowing a specific contact between parallel fibres and Purkinje cells at the period of synaptogenesis.

Differential MAP kinases activation during semaphorin3A-induced repulsion or apoptosis of neural progenitor cells

Semaphorins are multifunctional factors implicated in various developmental processes. Little is known about the intracellular pathways ensuring appropriate signal transduction that encode the diverse functions observed. In this study, we investigated whether mitogen-activated protein kinases (MAPK), which are key elements of signal transduction in eukaryotic cells, were activated during semaphorin 3A (Sema3A)-induced repulsion or apoptosis of neural progenitor cells. We found that selective recruitment of the ERK1/2 pathway occurred during Sema3A-induced neural progenitor cell repulsion, whereas p38 MAPK activation was necessary for induction of apoptosis. Moreover, we provide evidence for the involvement of vascular endothelial growth factor receptor 1 (VEGFR1) in the activation of ERK1/2. Additional experiments performed with native cerebellar progenitors confirmed such a selective recruitment of MAPK during Sema3A-dependent migration or apoptosis. Altogether, our results suggest a model to explain how a single factor can exert different functions for a given cell type by the selective recruitment of intracellular pathways.