Activity-dependent remodeling of chondroitin sulfate proteoglycans extracellular matrix in the hypothalamo-neurohypophysial system

The hypothalamo-neurohypophysial system (HNS) consisting of arginine vasopressin (AVP) and oxytocin (OXT) magnocellular neurons shows the structural plasticity including the rearrangement of synapses, dendrites, and neurovascular contacts during chronic physiological stimulation. In this study, we examined the remodeling of chondroitin sulfate proteoglycans (CSPGs), main extracellular matrix (ECM), in the HNS after salt loading known as a chronic stimulation to cause the structural plasticity. In the supraoptic nucleus (SON), confocal microscopic observation revealed that the immunoreactivity of 6B4 proteoglycans (PG) was observed mainly at AVP-positive magnocellular neurons but that of neurocan was seen chiefly at OXT-positive magnocellular neurons. The immunoreactivity of phosphacan and aggrecan was seen at both AVP- and OXT-positive magnocellular neurons. Electron microscopic observation further showed that the immunoreactivity of phosphacan and neurocan was observed at astrocytic processes to surround somata, dendrites, and terminals, but not synaptic junctions. In the neurohypophysis (NH), the immunoreactivity of phosphacan, 6B4 PGs, and neurocan was observed at AVP-positive magnocellular terminals, but the reactivity of Wisteria floribunda agglutinin lectin was seen at OXT-positive ones. The immunoreactivity of versican was found at microvessel and that of aggrecan was not detected in the NH. Quantitative morphometrical analysis showed that the chronic physiological stimulation by 7-day salt loading decreased the level of 6B4 PGs in the SON and the level of phosphacan, 6B4 PGs, and neurocan in the NH. These results suggest that the extracellular microenvironment of CSPGs is different between AVP and OXT magnocellular neurons and activity-dependent remodeling of CSPGs could be involved in the structural plasticity of the HNS.

Neuronal expression of the chondroitin sulfate proteoglycans receptor-type protein-tyrosine phosphatase beta and phosphacan

Receptor-type protein-tyrosine phosphatase beta (RPTPbeta) and its spliced variant phosphacan are major components of chondroitin sulfate proteoglycans in the CNS. In this study, expression and localization of RPTPbeta and phosphacan were examined in developing neurons by immunological analyses using 6B4, 3F8, and anti-PTP antibodies and reverse transcription-polymerase chain reaction (RT-PCR). Light microscopic immunohistochemistry showed that 6B4 RPTPbeta/phosphacan immunoreactivity was observed around neurons in the cortical plate. Further ultrastructural observation showed that 6B4 RPTPbeta/phosphacan immunoreactivity was observed mainly at the membrane of migrating neurons and radial glia. Immunocytochemical analysis revealed that RPTPbeta immunoreactivity was observed in cultured cerebral, hippocampal, and cerebellar neurons in addition to type-1 and type-2 astrocytes. Western analysis further demonstrated that the shorter receptor form of RPTPbeta (sRPTPbeta) was detected from cell lysate of cortical and hippocampal neurons using 6B4 and anti-PTP antibodies, while sRPTPbeta of cerebellar neurons and type-1 astrocytes was recognized only by anti-PTP antibody. Phosphacan was detected from neuronal culture supernatants of cortical, hippocampal, and cerebellar neurons, but not from type-1 astrocytes using 6B4 and 3F8 antibodies. RT-PCR analysis demonstrated the prominent expression of sRPTPbeta and phosphacan mRNAs in cortical neurons, and that of sRPTPbeta mRNA in type-1 astrocytes. During culture development of cortical neurons, the immunoreactivity of 6B4 sRPTPbeta was observed entirely on the neuronal surface including somata, dendrites, axons, and growth cones at earlier stages of cortical neuronal culture such as stages 2 and 3, while, after longer culture, 6B4 sRPTPbeta immunoreactivity in stages 4 and 5 neurons was detected at dendrites and somata and disappeared from axons, and was not observed over axonal terminals and postsynaptic spines. These results demonstrate that neurons are able to express sRPTPbeta on their cellular surface and to secrete phosphacan, and neuronal expression of sRPTPbeta may modulate neuronal differentiation including neuritogenesis and synaptogenesis.

Construction of perineuronal net-like structure by cortical neurons in culture

Perineuronal nets consisting of chondroitin sulfate proteoglycans and hyaluronic acid are associated with distinct neuronal populations in mammalian brain. Whether neurons or glia cells produce these surface-associated chondroitin sulfate proteoglycan perineuronal nets has remained in question. In the present study, we observed perineuronal net-like structure by rat cortical neurons in dissociated culture using Wisteria floribunda aggulutinin, hyaluronic acid binding protein, and the antibodies recognizing chondroitin sulfate proteoglycans. The double labeling experiments showed that perineuronal net-like structure labeled with Wisteria floribunda aggulutinin was observed often at parvalbumin-positive neurons in dissociated cortical culture without glia. Perineuronal net-like structure was not seen at the early stage of culture, but they became visible concomitantly with neuronal maturation after longer culture. High magnification observation further demonstrated that Wisteria floribunda aggulutinin labeling on cortical neurons was seen as numerous puncta along surface of somata and proximal dendrites, but not axons and synapses. Perineuronal net-like structure on cultured neurons was also visualized using chondroitin sulfate proteoglycan-specific antibodies and hyaluronic acid binding protein. Double labeling study demonstrated that perineuronal net-like structure in cultured cortical neurons was composed of chondroitin sulfate proteoglycans such as neurocan and phosphacan. The hyaluronidase treatment of live neurons abolished cellular labeling of hyaluronic acid binding protein and concomitantly diminished that of Wisteria floribunda aggulutinin. These results indicate that cultured cortical neurons are able to construct perineuronal net-like structure without glial cells.

Transient expression of juvenile-type neurocan by reactive astrocytes in adult rat brains injured by kainate-induced seizures as well as surgical incision

Neurocan is one of the major chondroitin sulfate proteoglycans expressed in nervous tissues. The expression of neurocan is developmentally regulated, and full-length neurocan is detected in juvenile brains but not in adult brains. In the present study, we demonstrated by western blot analysis that full-length neurocan transiently appeared in adult rat hippocampus when it was lesioned by kainate-induced seizures. Immunohistochemical studies showed that neurocan was detected mainly around the CA1 region although the seizure resulted in neuronal cell degeneration in both the CA1 and CA3 regions of the hippocampus. Double-labeling for neurocan mRNA and glial fibrillary acidic protein demonstrated that many reactive astrocytes expressed neurocan mRNA. The re-expression of full-length neurocan was also observed in the surgically injured adult rat brain. In contrast, the expression of other nervous tissue chondroitin sulfate proteoglycans, such as phosphacan and neuroglycan C, was not intensified but rather was either reduced in the kainate-lesioned hippocampus or in the surgically injured cerebral cortex. These observations indicate that induction of neurocan expression by reactive astrocytes is a common phenomenon in the repair process of adult brain injury, and therefore, it can be postulated that juvenile-type neurocan plays some roles in brain repair.

Upregulated expression of N-syndecan, a transmembrane heparan sulfate proteoglycan, in differentiated neural stem cells

Adult rat hippocampus-derived neural stem cells are incorporated into neural tissues, and differentiate to neuronal and glial cells. However, the cell surface protein molecules are, to date, undefined. RT-PCR, immunoblotting and immunocytochemistry showed the increased expression of N-syndecan, a transmembrane heparan sulfate proteoglycan, in the neural stem cells after the differentiation induced by retinoic acid. Our data indicate that N-syndecan may be involved in the differentiation of neural stem cells.

Developmentally regulated expression of brain-specific chondroitin sulfate proteoglycans, neurocan and phosphacan, in the postnatal rat hippocampus

Developmental changes in the distribution of brain-specific chondroitin sulfate proteoglycans, neurocan and phosphacan/RPTPzeta/beta, in the hippocampus of the Sprague-Dawley rat were examined using monoclonal antibodies 1G2 and 6B4. The 1G2 immunoreactivity was predominant in the neonatal hippocampus while the 6B4 immunoreactivity was predominant in the mature hippocampus. Moderate 1G2 immunoreactivity was detected in the dentate gyrus and subiculum immediately after birth. Immunoreactivity reached a peak on postnatal days 7-10 (P7-P10) when intense 1G2 labeling was present throughout the neuropil layers of the hippocampus except the mossy fiber tract. 6B4 immunoreactivity was limited in the stratum lacunosum moleculare of CA1 in the neonatal hippocampus. It gradually increased by P21 when diffuse 6B4 immunoreactivity was detected in the stratum oriens and radiatum of Ammon's horn, and in the hilus and inner one-third molecular layer of the dentate gyrus, while 1G2 immunoreactivity decreased after P21. In the adult hippocampus, moderate 6B4 immunoreactivity was present in the stratum oriens and radiatum of Ammon's horn, and in the hilus and inner one-third molecular layer of the dentate gyrus, but not in the mossy fiber tract. In addition, strong 6B4 labeling appeared around a subset of neurons after P21. The results suggest that neurocan may have a role in the development of neuronal organization, while phosphacan/RPTPzeta/beta may contribute to the maintenance and plasticity of synaptic structure and function. Furthermore, the absence of 1G2 and 6B4 immunoreactivities in the stratum lucidum suggests that neurocan and phosphacan/RPTPzeta/beta may function as a barrier for the extension of mossy fibers and provide an environment permissive for fasciculation of the mossy fibers.

Inhibitory effects of neurocan and phosphacan on neurite outgrowth from retinal ganglion cells in culture

PURPOSE

Neurocan and phosphacan are nervous tissue-specific chondroitin sulfate proteoglycans (CSPGs) that are highly expressed in postnatal rat retina. To elucidate potential roles of neurocan and phosphacan on neurite outgrowth from retinal ganglion cells (RGCs), in vitro experiments were conducted with purified RGCs.

METHODS

Neurocan and phosphacan were purified from postnatal rat brain by DEAE-column chromatography and subsequent gel chromatography. RGCs were obtained from postnatal rat retinas by a two-step immunopanning procedure using an anti-Thy 1,1 antibody and an anti-macrophage antibody. Neurite outgrowth from RGCs was examined on poly-L-lysine (PLL)-conditioned plates, and PLL-conditioned plates treated with neurocan or phosphacan.

RESULTS

Compared with PLL-conditioned plates, neurocan and phosphacan inhibited neurite outgrowth from RGCs at 48 and 72 hours after seeding. When chondroitin sulfate side chains linked to the core proteins were digested by chondroitinase ABC, the inhibitory effect remained, indicating that the core proteins are related to the effect. Furthermore, the digestion of chondroitin sulfate side chains linked to phosphacan core protein significantly promoted the inhibitory effect of phosphacan on neurite outgrowth from RGCs.

CONCLUSIONS

Neurocan and phosphacan, which are highly expressed in postnatal rat retina, inhibit neurite outgrowth from postnatal rat RGCs, indicating that these proteoglycans may be inhibitory factors against neurite outgrowth from RGCs during retinal development.

Expression of brain specific chondroitin sulfate proteoglycans, neurocan and phosphacan, in the developing and adult hippocampus of Ihara's epileptic rats

Ihara's epileptic rats (IER) is an animal model of temporal lobe epilepsy with mycrodysgenesis, that exhibit abnormal migration of hippocampal neurons and recurrent spontaneous seizures. As an attempt to elucidate the roles of extracellular matrix molecules in the epileptogenecity and mossy fiber sprouting, immunohistochemical localization of brain specific chondroitin sulfate proteoglycans (CSPGs), neurocan and phosphacan, was examined in the hippocampus of postnatal IER and Sprague-Dawley (SD) rats using monoclonal antibodies 1G2 against neurocan and 6B4 against phosphacan. There was no difference in the expression of these two CSPGs between IER and SD rats in the 1st postnatal week. However, the expression of neurocan was poor in the hippocampus of IER in the 2nd and 3rd weeks whereas intense labeling of neurocan was present throughout the hippocampus of SD rats. Labeling of neurocan was almost absent in the hippocampus, while phosphacan was diffusely expressed in the stratum oriens and radiatum of Ammon's horn, and in the hilus and inner one-third molecular layer of the dentate gyrus at the 2nd month after birth. There was no difference in the expression of neurocan and phosphacan between IER and SD rats at the 2nd month after birth. By contrast, phosphacan was reduced in the inner molecular layer of the dentate gyrus in 8-month-old IER, while neurocan was reexpressed in the outer molecular layer and hilus in 3- and 8-month-old IER. It was suggested that the insufficient expression of neurocan may affect the development of neuronal organization in the hippocampus, and that the remodeling of extracellular matrix in the dentate gyrus may contribute to the mossy fiber sprouting into the inner molecular layer.

Regulation of neuregulin expression in the injured rat brain and cultured astrocytes

In this report, we investigated whether reactive astrocytes produce neuregulins (glial growth factor 2/heregulin/acetylcholine receptor-inducing activity or neu differentiation factor) and its putative receptors, ErbB2 and ErbB3 tyrosine kinases, in the injured CNS in vivo. Significant immunoreactivities with anti-neuregulin, anti-ErbB2, and anti-ErbB3 antibodies were detected on astrocytes at the injured site 4 d after injury to the adult rat cerebral cortex. To elucidate the mechanisms for the upregulation of neuregulin expression in astrocytes, primary cultured astrocytes were treated with certain reagents, including forskolin, that are known to elevate the intracellular level of cAMP and induce marked morphological changes in astrocytes. Western blot analysis showed that the expression of a 52 kDa membrane-spanning form of a neuregulin protein was enhanced in cultured astrocytes after administration of forskolin. The upregulation of glial fibrillary acidic protein was also observed in astrocytes treated with forskolin. In contrast, inactivation of protein kinase C because of chronic treatment with phorbol ester 12-O-tetradecanoyl phorbol 13-acetate downregulated the expression of the 52 kDa isoform, although other splice variants with apparent molecular sizes of 65 and 60 kDa were upregulated. These results suggest that the enhancement of neuregulin expression at injured sites is induced, at least in part, by elevation in intracellular cAMP levels and/or a protein kinase C signaling pathway. The neuregulin expressed on reactive astrocytes may stimulate their proliferation and support the survival of neurons surrounding cortical brain wounds in vivo.

Neuroglycan C, a neural tissue-specific transmembrane chondroitin sulfate proteoglycan, in retinal neural network formation

PURPOSE

Neuroglycan C (NGC) is a transmembrane chondroitin sulfate proteoglycan present exclusively in central nervous system tissues. In the current study the expression pattern and characterization of NGC during the development of the retina were investigated.

METHODS

Expressional changes of NGC mRNAs during rat retinal development were examined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). The localization and characterization of NGC core proteins were investigated by immunoblot analysis and immunohistochemistry using an anti-NGC antibody.

RESULTS

Immunohistochemical analysis revealed that NGC was highly expressed in the nerve fiber layer (NFL) and inner plexiform layer (IPL) in rat postnatal developing retina. At embryonal stages, NGC immunoreactivities were faint. In contrast, at postnatal developmental stages (approximately postnatal day [P]7), intense immunoreactivity was observed in the NFL and IPL, where active dendrite branching was observed, and conventional synapses began to be formed. As retinal layer differentiation proceeded (from P14 to P42), immunoreactivities in the inner retinal layers gradually became fainter. Immunoblot and semiquantitative RT-PCR analyses showed that the peak level of NGC expression occurred on approximately P7 and P14. Glycosylation of the NGC core protein changed as the retinal layers matured. In immunoelectron microscopic analysis, NGC immunoreactivity was located on the axonal membranes of neuronal cells in the postnatal retina, whereas immunoreactivity was reduced on membranes at the adult stage. In retinal ganglion cells in vitro, NGC was highly localized in their spiny budding neurites.

CONCLUSIONS

The results show spatiotemporal expression patterns of NGC, and suggest that it plays a role in the formation of neural networks in retinal development.

Involvement of gangliosides in glycosylphosphatidylinositol-anchored neuronal cell adhesion molecule TAG-1 signaling in lipid rafts

The association of ganglioside GD3 with TAG-1, a glycosylphosphatidylinositol-anchored neuronal cell adhesion molecule, was examined by coimmunoprecipitation experiments. Previously, we have shown that the anti-ganglioside GD3 antibody (R24) immunoprecipitated the Src family kinase Lyn from the rat cerebellum, and R24 treatment of primary cerebellar cultures induced Lyn activation and rapid tyrosine phosphorylation of an 80-kDa protein (p80). We now report that R24 coimmunoprecipitates a 135-kDa protein (p135) from primary cerebellar cultures. Treatment with phosphatidylinositol-specific phospholipase C revealed that p135 was glycosylphosphatidylinositol-anchored to the membrane. It was identified as TAG-1 by sequential immunoprecipitation with an anti-TAG-1 antibody. Antibody-mediated cross-linking of TAG-1 induced Lyn activation and rapid tyrosine phosphorylation of p80. Selective inhibitor for Src family kinases reduced the tyrosine phosphorylation of p80. Sucrose density gradient analysis revealed that the TAG-1 and tyrosine-phosphorylated p80 in cerebellar cultures were present in the lipid raft fraction. These data show that TAG-1 transduces signals via Lyn to p80 in the lipid rafts of the cerebellum. Furthermore, degradation of cell-surface glycosphingolipids by endoglycoceramidase induced an alteration of TAG-1 distribution on an OptiPrep gradient and reduced the TAG-1-mediated Lyn activation and tyrosine phosphorylation of p80. These observations suggest that glycosphingolipids are involved in TAG-1-mediated signaling in lipid rafts.

Comparative mapping of seven genes in mouse, rat and Chinese hamster chromosomes by fluorescence in situ hybridization

By fluorescence in situ hybridization (FISH) using mouse probes, we assigned homologues for cathepsin E (Ctse), protocadherin 10 (Pcdh10, alias OL-protocadherin, Ol-pc), protocadherin 13 (Pcdh13, alias protocadherin 2c, Pcdh2c), neuroglycan C (Cspg5) and myosin X (Myo10) genes to rat chromosomes (RNO) 13q13, 2q24-->q25, 18p12-->p11, 8q32.1 and 2q22.1-->q22.3, respectively. Similarly, homologues for mouse Ctse, Pcdh13, Cspg5 and Myo10 genes and homologues for rat Smad2 (Madh2) and Smad4 (Madh4) genes were assigned to Chinese hamster chromosomes (CGR) 5q28, 2q17, 4q26, 2p29-->p27, 2q112-->q113 and 2q112-->q113, respectively. The chromosome assignments of homologues of Ctse and Cspg5 reinforced well-known homologous relationships among mouse chromosome (MMU) 1, RNO 13 and CGR 5q, and among MMU 9, RNO 8 and CGR 4q, respectively. The chromosome locations of homologues for Madh2, Madh4 and Pcdh13 genes suggested that inversion events were involved in chromosomal rearrangements in the differentiation of MMU 18 and RNO 18, whereas most of MMU 18 is conserved as a continuous segment in CGR 2q. Furthermore, the mapping result of Myo10 and homologues suggested an orthologous segment of MMU 15, RNO 2 and CGR 2.

Upregulated expression of neurocan, a nervous tissue specific proteoglycan, in transient retinal ischemia

PURPOSE

Neurocan, a nervous tissue-specific chondroitin sulfate proteoglycan synthesized primarily by neurons, is expressed abundantly in developing rat retina, whereas it is rarely expressed in adult rat retinas. This study investigated the reexpression of neurocan in a pathologic condition of adult rat retina.

METHODS

Transient retinal ischemia was produced by occlusion of the retinal artery for 60 minutes. After transient retinal ischemia, neurocan expression was investigated by reverse transcription-initiated polymerase chain reaction (RT-PCR), immunohistochemistry, and immunoblot analysis.

RESULTS

Semiquantitative analysis using RT-PCR revealed that mRNA expression for neurocan increased at 24 hours after reperfusion. Furthermore, on immunoblot analysis using an anti-neurocan antibody, MAb 1G2, the intensity of the 220-kDa band as well as the 150-kDa band increased markedly at 24 and 72 hours after reperfusion. The 220-kDa band was predominant at 24 hours after reperfusion, whereas the intensity of the 150-kDa band became almost the same as that of the 220-kDa band at 72 hours after reperfusion. Immunohistochemical analysis revealed that upregulated neurocan immunoreactivity was associated with glial Müller cells.

CONCLUSIONS

Thus, upregulated expression of neurocan in transient retinal ischemia was demonstrated. Furthermore, the immunohistochemical analysis revealed that the upregulated expression of neurocan is derived from Müller cells, although it has been thought that neurocan is synthesized by neurons so far. The neurocan expression by Müller cells suggests that this proteoglycan plays a role in the damage and repair processes in diseased retina.

Effects of lipid-derivatized glycosaminoglycans (GAGs), a novel probe for functional analyses of GAGs, on cell-to-substratum adhesion and neurite elongation in primary cultures of fetal rat hippocampal neurons

The effects of glycosaminoglycans (GAG) on cell-to-substratum adhesion and neurite elongation were examined in primary cultures of fetal rat hippocampal neurons using tissue culture dishes coated with GAGs coupled to dipalmitoylphosphatidylethanolamine (PE), a novel probe for biological functions of GAGs. Both chondroitin sulfate conjugate to PE (CS-PE) and hyaluronic acid conjugate to PE (HA-PE) promoted neurite elongation from neurons in a dose-dependent manner when immobilized onto polylysine-coated dishes at various concentrations up to 1.0 microg/ml. The coating of CS-PE or HA-PE at a concentration higher than 1.0 microg/ml resulted in failure of neurite extension and adhesion of neurons to the substrata. In contrast, heparin conjugate to PE (HP-PE) did not exert any effects on neurite elongation or on cell attachment at these concentrations. These findings suggest that GAGs serve as a modulator for neurite elongation during neuronal network formation in the developing central nervous system.

Spatiotemporal expression patterns of 6B4 proteoglycan/phosphacan in the developing rat retina

PURPOSE

To investigate expression of 6B4 proteoglycan/phosphacan, the major constituent of chondroitin sulfate proteoglycan and a possible modulator of neural network formation in the developing central nervous system, in developing rat retina.

METHODS

Changes in expression and localization of 6B4 proteoglycan in developing rat retina were investigated by reverse transcription-initiated polymerase chain reaction (RT-PCR), immunohistochemistry, and immunoblot analysis.

RESULTS

Semiquantitative RT-PCR revealed that mRNA expression of 6B4 proteoglycan in retinas peaked at postnatal day 14 (P14) and then decreased at P42. Immunohistochemical analyses using MAb 6B4, a monoclonal antibody against 6B4 proteoglycan, revealed faint immunoreactivity in the inner aspects of the retina at embryonal day 16 (E16). At birth, weak immunoreactivity was present in the nerve fiber layer (NFL) and inner plexiform layer (IPL). At P7 and P14, the NFL, IPL, and outer plexiform layer (OPL) stained intensely, but the ganglion cell layer (GCL) remained unstained. Between P21 and P42, immunoreactivity in the NFL and IPL weakened slightly. Immunoblot analyses showed a MAb 6B4 immunopositive band in the retinal soluble fraction treated with chondroitinase ABC. The amount of the immunopositive band increased rapidly as retinal development proceeded. Surprisingly, a significant amount of the immunopositive band was present in the retina even before digestion with chondroitinase ABC, indicating that at least part of 6B4 proteoglycan in rat retina exists in a non-proteoglycan form.

CONCLUSIONS

The existence of 6B4 proteoglycan/phosphacan was thus demonstrated in rat retina, although some biochemical parameters were different from those of the 6B4 proteoglycan seen in brain.

Neurocan is upregulated in injured brain and in cytokine-treated astrocytes

Injury to the CNS results in the formation of the glial scar, a primarily astrocytic structure that represents an obstacle to regrowing axons. Chondroitin sulfate proteoglycans (CSPG) are greatly upregulated in the glial scar, and a large body of evidence suggests that these molecules are inhibitory to axon regeneration. We show that the CSPG neurocan, which is expressed in the CNS, exerts a repulsive effect on growing cerebellar axons. Expression of neurocan was examined in the normal and damaged CNS. Frozen sections labeled with anti-neurocan monoclonal antibodies 7 d after a unilateral knife lesion to the cerebral cortex revealed an upregulation of neurocan around the lesion. Western blot analysis of extracts prepared from injured and uninjured tissue also revealed substantially more neurocan in the injured CNS. Western blot analysis revealed neurocan and the processed forms neurocan-C and neurocan-130 to be present in the conditioned medium of highly purified rat astrocytes. The amount detected was increased by transforming growth factor beta and to a greater extent by epidermal growth factor and was decreased by platelet-derived growth factor and, to a lesser extent, by interferon gamma. O-2A lineage cells were also capable of synthesizing and processing neurocan. Immunocytochemistry revealed neurocan to be deposited on the substrate around and under astrocytes but not on the cells. Astrocytes therefore lack the means to retain neurocan at the cell surface. These findings raise the possibility that neurocan interferes with axonal regeneration after CNS injury.

Molecular interactions of neural chondroitin sulfate proteoglycans in the brain development

Aggrecan family proteoglycans, phosphacan/RPTPzeta/beta, and neuroglycan C (NGC) are the major classes of chondroitin sulfate proteoglycan in the developing mammalian brain. A multidomain is a common structural feature of these proteoglycans which can interact with various molecules including growth factors, cell adhesion molecules, and extracellular matrix molecules. Individual proteoglycans are distributed in the developing brain in a distinct temporal and spatial pattern, suggesting that they are involved in distinct phases of the brain development through multiple molecular interactions. This review mainly summarizes recent studies on the involvement of these three classes of proteoglycan in cell-cell and cell-substratum interactions during the brain development. Their expressions and proposed functional roles in injured brains are also mentioned. In addition, this review briefly covers potential functions of other neural chondroitin sulfate proteoglycans such as decorin, testican, NG2 proteoglycan, and amyloid precursor protein (APP) in developing and injured brains.

Genomic organization and expression pattern of mouse neuroglycan C in the cerebellar development

Neuroglycan C (NGC) is a membrane-spanning chondroitin sulfate proteoglycan with an epidermal growth factor module that is expressed predominantly in the brain. Cloning studies with mouse NGC cDNA revealed the expression of three distinct isoforms (NGC-I, -II, and -III) in the brain and revealed that the major isoform showed 94. 3% homology with the rat counterpart. The NGC gene comprised six exons, was approximately 17 kilobases in size, and was assigned to mouse chromosome band 9F1 by fluorescence in situ hybridization. Western blot analysis demonstrated that, although NGC in the immature cerebellum existed in a proteoglycan form, most NGC in the mature cerebellum did not bear chondroitin sulfate chain(s), indicating that NGC is a typical part-time proteoglycan. Immunohistochemical studies showed that only the Purkinje cells were immunopositive in the cerebellum. In the immature Purkinje cells, NGC, probably the proteoglycan form, was immunolocalized to the soma and thick dendrites on which the climbing fibers formed synapses, not to the thin branches on which the parallel fibers formed synapses. This finding suggests the involvement of NGC in the differential adhesion and synaptogenesis of the climbing and parallel fibers with the Purkinje cell dendrites.

Identification of a nervous tissue-specific chondroitin sulfate proteoglycan, neurocan, in developing rat retina

PURPOSE

To identify the expression of neurocan, a nervous tissue-specific chondroitin sulfate proteoglycan, in retina and to elucidate its changes during development.

METHODS

Expressional changes of neurocan mRNAs in developing rat retinas were investigated by a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). The localization and characterization of neurocan core proteins were also investigated with the use of Western blot analysis and immunohistochemistry.

RESULTS

Gene expression of neurocan was identified in retinas by RT-PCR. Semiquantitative analysis using Southern blot analysis revealed that mRNA expression for neurocan increased at increasing postnatal stages and that it reached its peak around postnatal day 7 (P7). Immunohistochemical studies demonstrated that in differentiating rat retinal (neuroblast) cells weak neurocan immunoreactivities were observed throughout the retina on embryonal days 14 (E14) and E16. During the early postnatal period, the immunoreactivities became most conspicuous in the inner and outer plexiform layers on P7 through P14. In adult retinas, only faint immunostaining was detected. Immunoblot analysis showed two positive bands of 220- and 150-kDa core glycoproteins after treatment with chondroitinase ABC. Further immunoblot analysis revealed that the expression of these two immunolabeled variants was regulated differently during retinal development.

CONCLUSIONS

The temporal and spatial regulation of expression of neurocan and its proteolytic variant during retinal development suggest that it may play a role in differentiation and neural network formation.

[Ocular blood flow defect in gaze-evoked amaurosis]

PURPOSE

To investigate the mechanism of gaze-evoked amaurosis.

CASE

A patient with an optic nerve tumor presented gaze-evoked amaurosis. A large central scotoma and constricted visual field were detected after shifting the gaze laterally. However, the patient did not notice this change until his fellow eye was occluded. Computed tomography/magnetic resonance imaging (CT/MRI) demonstrated a tubularly enlarged optic nerve extending for 1 cm from the eye ball, and the condition was judged to be optic nerve sheath meningioma. He underwent fluorescein fundus angiography twice, once during straight gaze and again during lateral gaze.

RESULTS

Manifestly decreased blood flow in the central retinal artery and filling defect in the optic nerve head were seen during lateral gaze.

CONCLUSION

Forced lateral gaze may have increased the intra-optic nerve pressure at the optic nerve head and decreased the blood flow of the central retinal artery and peripapillary choroidal flow irrigating the optic nerve head.

Cloning and chromosomal mapping of the human gene of neuroglycan C (NGC), a neural transmembrane chondroitin sulfate proteoglycan with an EGF module

Neuroglycan C (NGC) is a 150 kDa transmembrane chondroitin sulfate proteoglycan with a 120 kDa core glycoprotein that was originally isolated from the developing rat brain. A rabbit antiserum, raised against a recombinant polypeptide representing a protein of the rat NGC core protein, recognized an NGC homolog in homogenates of brains of various vertebrates including humans. Because of the possible involvement of this proteoglycan in the etiology of a human neuronal disease, we cloned a complete coding sequence from a human brain cDNA library using a rat NGC cDNA as a probe. The predicted protein contains 539 amino acids and shows 86% homology with the rat counterpart. The domain structure characteristic of rat NGC was completely conserved in human NGC, which consisted of an N-terminal signal sequence, a chondroitin sulfate-attachment domain, an acidic amino acid cluster, an EGF-like domain, a transmembrane domain and a cytoplasmic tail. Northern blot analysis revealed that a single transcript of 2.4 kb was detectable in the brain, but not in other human tissues. By fluorescence in situ hybridization (FISH) analysis, the human NGC gene was assigned to the chromosomal 3p21.3 band, where the Sotos syndrome has been mapped. Involvement of the NGC gene in the etiology of the Sotos syndrome remains to be examined.

Two types of brain chondroitin sulfate proteoglycan: their distribution and possible functions in the rat embryo

The distribution of neurocan-like and 6B4 proteoglycan-like immunoreactivities in the rat embryo was investigated from gestational days 10.5-15.5 with monoclonal antibody 1G2 or 6B4 that immunoreacted with neurocan and 6B4 proteoglycan, respectively. In the brain region, the leptomeningeal layer in the myelencephalon, metencephalon, diencephalon or telencephalon was first stained with monoclonal antibody 1G2 at embryonic day 12.5. In the spinal cord, monoclonal antibody 1G2 stained the regions corresponding to the boundary caps (designated the boundary caps) after embryonic day 11.5 and the roof plate after embryonic day 12.5. The intensity of staining in the boundary caps reached a maximum at embryonic day 13.5, at around the time when the axons from the dorsal root ganglia reach this region. However, the points of contact of the axons with the boundary caps were hardly stained. By contrast, the roof plate was most strongly and widely stained at embryonic day 14.5, at around the time when the axons enter the spinal cord. Western blotting of preparations from the spinal cord that included the boundary caps revealed the presence of neurocan in this region. Thus, it is likely that neurocan serves as a barrier molecule to regulate the direction of axonal growth from the dorsal root ganglia. By contrast, in addition to staining of the future brain and spinal cord, monoclonal antibody 6B4 stained the trigeminal and sympathetic ganglia in the rat embryo on and after embryonic day 12.5, as well as the vestibular, facial and dorsal root ganglia after embryonic day 12.5. In studies in tissue culture, monoclonal antibody 6B4 prevented the inhibitory effects of 6B4 proteoglycan on the proliferation of PC12D cells. No immunostaining with monoclonal antibody 6B4 was observed in cells that had incorporated bromodeoxyuridine in vivo. Possible functions of 6B4 proteoglycan in the rat embryo are discussed.

Coordinate expression of L1 and 6B4 proteoglycan/phosphacan is correlated with the migration of mesencephalic dopaminergic neurons in mice

Mesencephalic dopaminergic (DA) neurons of mice are generated from embryonic day 10 to 12 (E10-12) in the ventricular zone of the mesencephalon. They first migrate toward the ventral mesencephalon, and then turn laterally, or tangentially, in the basal part of the mesencephalon. With immunohistochemical analysis of E10-E15 ICR mice, we found that cell adhesion molecule L1 was transiently expressed on the median part of tangential fibers coincident with the lateral migration of DA neurons from E11 to E13, when neurons move along the tangential fibers toward their final destinations: the reticular formation, the substantia nigra pars compact, and the ventral tegmental area. While L1 expression was not observed in DA neurons, they expressed a chondroitin sulfate proteoglycan, 6B4 proteoglycan/phosphacan, which has been shown to bind to L1/Ng-CAM in vitro. These results suggest that the heterophilic interaction between 6B4 proteoglycan on the neurons and L1 on the fibers is involved in the lateral migration of mesencephalic DA neurons in mice.

Occurrence of a N-terminal proteolytic fragment of neurocan, not a C-terminal half, in a perineuronal net in the adult rat cerebrum

Neurocan is a nervous tissue-unique chondroitin sulfate proteoglycan (CSPG) whose expression and proteolytic cleavage are developmentally regulated. In the adult rat brain, neurocan is completely cleaved into some proteoglycan fragments including the C-terminal half known as neurocan-C and a N-terminal fragment with a 130 kDa core glycoprotein (neurocan-130). We describe here the differential distribution of these two neurocan-derived CSPGs in the adult rat cerebrum and the occurrence of neurocan-130 as a new member of a perineuronal net-constituting molecule. At the light microscopic level, neurocan-130 exhibited pericellular localization around a subset of neurons in addition to diffuse distribution in the neuropil. In contrast, neurocan-C was distributed only diffusely in the neuropil. Double staining with anti-neurocan-130 and anti-synaptophysin antibodies suggested that neurocan-130 was localized in the vicinity of the synapses, but not at the synapses. Immunoelectron microscopy showed that neurocan-130 was mainly localized in the cytoplasm of glial cell processes, the so-called glial perineuronal net, encompassing the cell bodies of certain neurons. The presence of neurocan-130 in a limited number of glial cells may reflect some functional heterogeneity of the glia.

Immunohistochemical localization of neurocan in the lower auditory nuclei of the dog

Chondroitin sulfate proteoglycans are present at high levels in the lower auditory system of mammals. Axon terminals on the principal neurons in the superior olivary nuclei contain chondroitin 4- and 6-sulfate, while the broad extracellular matrix around axon terminals contains chondroitin sulfate D, a highly sulfated chondroitin sulfate rich in the disaccharide unit of GlcA(2S)beta1 --> 3GalNAc(6S), in the dog. In the present study, we investigated the immunohistochemical staining of neurocan, a brain-specific proteoglycan, in the lower auditory tract of the dog, including an analysis by immunoelectron microscopy. Immunolocalization of neurocan was conspicuous in the medial and lateral superior olivary nuclei and much less intense immunostaining was seen in the cochlear nucleus and posterior colliculus. No immunoreactivity were found in other nuclei. The immunostaining in the medial and lateral superior olivary nuclei was observed as perineuronal nets around large principal neurons at the light-microscopic level, while no immunostaining was observed in the upper segment of the medial superior olivary nucleus and the medial segment of the lateral superior olivary nucleus, in which medium-sized and small neurons were located. Immunoelectron microscopy revealed the reaction products of immunostaining on cell membranes of the perikarya of principal neurons and on cell membranes of presynaptic terminals which made axo-somatic synapses on the principal cells. No immunoreactivity was detected at synaptic junctions, in the extracellular matrix or within axon terminals. In the cochlear nucleus, immunoreactive perineuronal nets were found around a small number of neurons and immunoreactive nerve fibers were scattered in the anterior ventral cochlear nucleus. In the posterior colliculus, perineuronal nets, which were weakly immunostained, were sparsely distributed in the central nucleus. These results suggest that different locations of chondroitin sulfate proteoglycans, including neurocan, may be associated with focal sites composed of neuronal surface, terminal boutons and extracellular matrix in the lower auditory tract of the adult dog.

Immunohistochemical localization of neurocan and L1 in the formation of thalamocortical pathway of developing rats

We used immunohistochemistry to examine possible molecular interactions between the subplate and growing thalamocortical axons in rat fetuses. In the cortical anlage of embryonic day 16 (E16), the subplate first appeared below the cortical plate. Among chondroitin sulfate proteoglycans, phosphacan was uniformly distributed throughout the cortical wall, whereas neurocan was localized only in the subplate at E16. Neural cell adhesion molecules, NCAM-H, TAG-1, and L1, were detected in the cortical anlage. Both cortical neurons and growing axons were diffusely immunopositive for NCAM-H, and TAG-1 immunoreactivity was found on immature neurons and cortical efferent axons but not on thalamocortical axons. L1 immunoreactivity was specifically localized on the growing thalamocortical axons. When the locations of neurocan and L1 were compared in the developing cortex, L1-bearing axons were found to extend to neurocan-immunopositive regions; neurocan immunoreactivity was intense in the subplate at E16, when small numbers of L1-immunoreactive thalamocortical axons began to invade the cortex. At E17, many L1-positive axons were observed in the subplate that expressed neurocan specifically. Double immunostaining showed that L1-positive axons and neurocan immunoreactivity overlapped in the subplate at E17. After E18, neurocan expression gradually extended to the lower part of the cortical plate; it extended to the entire cortex by E21, 1 day before birth. By E21, L1-bearing axons had invaded the lower part of the cortical plate. The present study demonstrated that the neurocan expression precedes growth of L1-bearing thalamocortical afferent fibers. Because neurocan can bind to L1 molecule in vitro, these results suggest that neurocan and L1 play some important roles in pathfinding of the thalamocortical afferent fibers during rat corticogenesis.

Identification of monoclonal antibody At5 as a new member of HNK-1 antibody family: the reactivity with myelin-associated glycoprotein and with two brain-specific proteoglycans, phosphacan and neurocan

Monoclonal antibody At5 was primarily developed against chordin, a notochord-specific antigen of Acipenseridae (sturgeon fishes). In higher vertebrates the antibody reacted mainly with neural tissue antigens. In this study we have shown that the specificity of monoclonal antibody At5 is similar to that of antibodies of HNK-1 family which react with two glycolipids and with several high molecular weight glycoconjugates of neural tissue. We have demonstrated by protein sequencing and immunoblotting that one of At5 target antigens of human brain is dMAG, a derivative of myelin-associated glycoprotein. In the preparations of At5 antigens proteoglycans phosphacan and neurocan were identified by immunoblotting with specific monoclonal antibodies 6B4 and 1G2, respectively. The distribution of At5 and 6B4 immunoreactivity was studied on sections of mixed oligoastrocytoma. Oligodendroglioma area of this tumor was intensely stained with both antibodies, whereas astrocytoma area did not exhibit any At5 or 6B4 immunoreactivity.

Restrictive strabismus after retrobulbar anesthesia

Two rare cases of strabismus resulting from contracture of the extraocular rectus muscles after retrobulbar anesthesia for cataract surgery are described. Clinical signs in both cases suggested that the development of the impaired function of the lateral and superior rectus muscles followed the same pattern: initial stimulation followed by paretic and restrictive stages. Abnormal enlargement of the muscles was identified by computed tomography (CT) and magnetic resonance imaging (MRI). The data indicate that the strabismus was the result of direct injection of anesthetics into the rectus muscle.

Influence on visual function by a stereoscopic TV programme with binocular liquid crystal shutter and Hi-Vision TV display

Influence on visual functions by field sequential stereoscopic Hi-Vision TV programme with liquid crystal shutter were investigated in 24 subjects. Ocular alignment, fusional amplitude, AC/A ratio, stereoacuity, accommodation and pupil size were measured before and after the visual load. Symptoms related to asthenopia were also examined. No significant difference were found, although two aged subjects showed large changes in a few of these functions. This type of 3-D display may not be hazardous to visual functions, although further study may be required for aged or visually handicapped people.

A membrane-bound heparan sulfate proteoglycan that is transiently expressed on growing axons in the rat brain

Monoclonal antibodies were raised to membrane-bound proteoglycans derived from rat brain and three monoclonal antibodies that recognized a 200-kDa heparan sulfate proteoglycan (designated H5-PG) with a core glycoprotein of 140 kDa were obtained. The expression of H5-PG was spatially and temporally regulated in the central nervous system. In the cerebellar cortex, H5-PG was associated mainly with the actively growing parallel fibers of granule cells. The expression was abruptly down-regulated in parallel with the formation of synapses on dendrites of Purkinje cells. In the cerebral cortex, the proteoglycan was widely distributed throughout the cortex. The temporal pattern of expression was similar to that in the cerebellar cortex; the peak level of expression was observed during the period from postnatal days 0 to 20 when neuritogenesis and synaptogenesis occur most extensively in the rat cerebral cortex. H5-PG in the central nervous system disappeared prior to adulthood except in the olfactory bulb. High-level expression was recognized on the olfactory nerves and glomeruli, where the renewal of both axons and synapses is occurring constantly. The data suggest that H5-PG is a glycoconjugate on axonal surface that is involved in axonal outgrowth and/or synaptogenesis.

Neuroglycan C, a novel membrane-spanning chondroitin sulfate proteoglycan that is restricted to the brain

Monoclonal antibodies were raised to membrane-bound proteoglycans derived from rat brain, and four monoclonal antibodies that recognized a 150-kDa chondroitin sulfate proteoglycan with a core glycoprotein of 120 kDa were obtained. Immunohistological study revealed that the proteoglycan was associated with developing neurons. We screened rat brain cDNA libraries using the four monoclonal antibodies and isolated overlapping cDNA clones that encoded the entire core protein of 514 amino acids plus a 30-residue signal peptide. The deduced amino acid sequence suggested an integral membrane protein divided into five structurally different domains: an N-terminal domain to which chondroitin sulfate chains might be attached, a basic amino acid cluster consisting of seven arginine and two lysine residues, a cysteine-containing domain, a membrane-spanning segment, and a C-terminal cytoplasmic domain of 95 amino acids. On Northern blots, the cDNA hybridized with a single mRNA of 3.1 kilobases that was detectable in brains of neonatal and adult rats but not in kidney, liver, lung, and muscle of either. The sequence of the proteoglycan did not exhibit significant homology to any other known protein, indicating that the proteoglycan, designated neuroglycan C, is a novel integral membrane proteoglycan.

Purification, characterization and developmental expression of a brain-specific chondroitin sulfate proteoglycan, 6B4 proteoglycan/phosphacan

A large brain-specific chondroitin sulfate proteoglycan, identified with monoclonal antibody 6B4 (6B4 proteoglycan/phosphacan), was isolated from rat brain. Soluble proteoglycans in the phosphate-buffered saline extract from 20-day-old rat whole brain were fractionated by anion exchange chromatography and CsCl density gradient centrifugation. 6B4 proteoglycan was further purified by gel filtration and additional ion exchange chromatography. The molecular mass of 6B4 proteoglycan shifted from 800 to 300 x 10(3) mol. wt after chondroitinase ABC digestion. The core protein was substituted with chondroitin sulfate chains with an average molecular weight of 21,000, keratan sulfate and HNK-1 carbohydrates. Glycosidase digestion of 6B4 proteoglycan with O-glycanase, N-glycanase, endo-beta-galactosidase, or keratanase did not remove the HNK-1 epitopes. The expression of 6B4 proteoglycan was developmentally regulated in the rat cerebral cortex; appearing first at embryonic day 14, peaking at postnatal day 0, and persisting throughout adulthood at a lower level. Immunohistochemical analysis indicated that 6B4 proteoglycan was distributed along the radial glial fibers and on the migrating neurons in the embryonal rar cerebrum. The radial glial fibers were stained intensely all along their length, but the neurons in the cortical plate were not stained in contrast to the moderate staining of the migrating neurons in the intermediate zone and the subplate. From postnatal day 5 to postnatal day 20, 6B4 proteoglycan was present throughout the cortex. After postnatal day 30, staining of the neuropil was weakened, and the expression of 6B4 proteoglycan was restricted around subsets of neurons. The positive neurons were mostly non-pyramidal cells (> 95%) and were relatively concentrated in layers IV and VI of the primary somatosensory cortex. Immunohistochemical analysis of the dissociated cortical neurons indicated that 6B4 proteoglycan was distributed on the cell bodies and neurites. 6B4 proteoglycan strikingly promoted neurite extension of cortical neurons from embryonic day-16 rat embryos when coated on coverslips as a substrate. 6B4 proteoglycan is a brain-specific chondroitin sulfate proteoglycan which carries keratan sulfate and HNK-1 carbohydrates. The spatiotemporal expression profile and effects on the dissociated cerebral neurons suggest that 6B4 proteoglycan plays important roles in the migration and differentiation of neurons in the immature cortex, and also in the maintenance of subsets of neurons in the mature cortex.

Detection of Alzheimer's beta-amyloid precursor related proteins bearing chondroitin sulfate both in the juvenile rat brain and in the conditioned medium of primary cultured astrocytes

Alzheimer's beta-amyloid precursor related proteins bearing chondroitin sulfate chains were detected in the conditioned media of primary cultured astrocytes obtained from fetal rat brains by Western blotting using the monoclonal antibody 22C11 against Alzheimer's beta-amyloid precursor protein (APP), but not in the media of cortical neurons. The chondroitin sulfate proteoglycan form of APP was also detectable in a soluble proteoglycan fraction prepared from 10-day-old rat brains. However, the amount of proteoglycan form of APP in the brain was very small compared to non-proteoglycan forms at all the developmental stages from embryonic day 14 to 2 years. These observations suggest that astrocytes are one cellular source of the proteoglycan form of APP in the brain.

Distribution of a brain-specific proteoglycan, neurocan, and the corresponding mRNA during the formation of barrels in the rat somatosensory cortex

Neurocan is a developmentally regulated chondroitin sulphate proteoglycan in the rat brain. In the present study, spatiotemporal patterns of expression of neurocan and the corresponding mRNA were examined in the developing cortical barrel field of the rat brain by using a monoclonal antibody that was highly specific to neurocan and a riboprobe for a portion of the mRNA. Immunohistochemical analysis revealed that neurocan was distributed throughout the cerebral cortex during early postnatal development but was excluded from the centres of cortical barrels at the time of entry and arborization of thalamocortical axons. At this developmental stage, expression of neurocan mRNA was shown by in situ hybridization to be down-regulated in the barrel centres. When a row of whisker follicles was laser-cauterized on postnatal day 1, the pattern of expression of neurocan was disturbed in the row of barrels that corresponded to the lesioned whisker follicles in the contralateral somatosensory cortex. From these observations, it appears that neuronal stimuli through early thalamocortical fibres from the sensory periphery cause reduced expression of neurocan mRNA in neurocan-producing cells in the presumptive barrel centres. Our findings also suggest that the pattern of distribution of neurocan in early postnatal barrel fields may be due mainly to the down-regulation of expression of neurocan mRNA.

[Proteoglycans in the developing brain]

The occurrence of multiple proteoglycan species is a characteristic of the brain. To identify each proteoglycan molecule, we have raised several monoclonal antibodies against either the soluble or membrane-bound proteoglycan fraction from 10-day-old rat brains. The monoclonal antibody 1G2 recognized neurocan, a soluble chondroitin sulfate proteoglycan (CSPG) unique to the brain. Immunohistological and cell biological results suggested that neurocan regulates neurite outgrowth through specific binding to N-CAM and Ng-CAM at the surface of neurons. In addition, the expression of neurocan was dependent upon neuronal activity evoked by environmental stimuli at least in the developing barrel field. Another CSPG, 6B4-PG, was expressed specifically in the cerebellar mossy fiber system in the rat hindbrain, suggesting that it plays roles in the establishment of this particular neuronal circuit. A membrane-bound heparan sulfate proteoglycan with a 140 kDa core glycoprotein (tentatively designated growth-can) was shown immunohistologically to be transiently expressed in association with growing axons and at the sites of synapse formation. Thus, many neuronal proteoglycans may be involved in various phases of neuronal network formation in the brain. In the near future, progress both in molecular cloning of core proteins and in glycobiology of carbohydrates of proteoglycans will probably produce much experimental evidence to show that neural proteoglycans play pivotal roles during various stages of brain development.

Chondroitin sulphate proteoglycans in the rat brain: candidates for axon barriers of sensory neurons and the possible modification by laminin of their actions

The addition of chondroitin sulphate proteoglycans (CSPGs), purified from the rat brain, to the culture medium of PC12D cells inhibited their proliferation and neurite outgrowth. Therefore, we investigated the effects of several extracellular components on the inhibitory actions of CSPGs on PC12D cells, as well as their immunocytochemical distribution in the rat embryo to determine whether the findings in vitro could be reproduced in vivo. Coating of the substratum with polylysine was necessary for the appearance of the inhibitory effects of brain CSPGs on PC12D cells. The additional pretreatment of polylysine-coated dishes with laminin or fibronectin promoted the outgrowth of neurites from PC12D cells. Laminin and fibronectin, but not collagen (types I and IV) and CELL-TAK (cell adhesion molecules), prevented the inhibitory effects of brain CSPGs in a concentration-dependent manner. Doses producing 50% reduction by laminin (or fibronectin) of the CSPG effects were 1.5 (or 25) micrograms/ml for neurite outgrowth and 2.2 (or 28) micrograms/ml for proliferation. The ratio of dish-attached CSPGs to laminin necessary for 50% reduction was about approximately 50:1 (wt/wt). Laminin from any source had the same effect. Brain CSPGs also obviously impeded the growth of fibres from dorsal root ganglion explants and primary cultured dorsal root ganglion neurons. Neurocan (a major CSPG in the brain)-like immunoreactivity was detected in the boundary caps and roof plate in the rat embryo at 13.5 days of gestation, when DRG neurons were extending their axons to the neural tube. The distributions of laminin and tenascin appeared, respectively, to be slightly and considerably different from that of neurocan.(ABSTRACT TRUNCATED AT 250 WORDS)

[Incidence of acute idiopathic optic neuritis and its therapy in Japan. Optic Neuritis Treatment Trial Multicenter Cooperative Research Group (ONMRG)]

Data on the incidence of and treatment for acute idiopathic optic neuritis were obtained by questionnaire sent to departments of ophthalmology, university hospitals, and general hospitals throughout Japan. Inquiry was made as to the number of cases which developed idiopathic optic neuritis from April 1992 to March 1993 along with their clinical features. The response rate was 53.6%. There were a total of 550 cases, and the male to female ratio was 1:1.22. Patients 14 to 55 years old were 65.9%; bilateral involvement: 28.2%; recurrence: 18.6%; positive past history of the other eye; 7.5%. Assuming the answering rate to be 100% and two thirds of the patients to be included, annual incidence of this disease (the annual number of patients) was determined to be 1.62 for an adult population of 100,000 (1.03 cases/100,000 people). Tochigi, Tokyo, Kanagawa, Hyogo, Wakayama, Okayama, Yamaguchi, Tottori, Shimane, Ehime, and Fukuoka showed an annual incidence exceeding 2.0/100,000 adults. At more than 95% of all medical institutions questioned, patients with optic neuritis were usually treated with systemic corticosteroids. Oral corticosteroid therapy, which was shown in a recent study in USA to be contraindicated, was still being used at 15% of the institutions.

Immunological identification of two proteoglycan fragments derived from neurocan, a brain-specific chondroitin sulfate proteoglycan

Neurocan is a brain-unique chondroitin sulfate proteoglycan (CSPG) whose expression and proteolytic cleavage are developmentally regulated. One of the proteolytic products (C-terminal half) is known to be a CSPG with a 150 kDa core glycoprotein (CSPG-150). To identify the N-terminal half of neurocan, we raised an anti-neurocan polyclonal antibody (PAb 291) using a synthetic peptide whose amino acid sequence matched a part of the N-terminal half of neurocan. Western blots showed that PAb 291 recognized two CSPGs, one with a 220 kDa core glycoprotein (CSPG-220, namely neurocan) and one with a 130 kDa core glycoprotein (CSPG-130) isolated from young rat brains. CSPG-130 was co-purified along with CSPG-220 by PAb 291-immunoaffinity column chromatography. The amino acid sequence of the N-terminus of the immunopurified CSPG-130 was exactly the same as the N-terminal sequence of CSPG-220. These results suggest that not only the C-terminal half (CSPG-150) but also the N-terminal half (CSPG-130) of CSPG-220 exists in a CSPG form in rat brain. Using PAb 291 and monoclonal antibody 1G2 (MAb 1G2) which recognizes CSPG-150 in addition to CSPG-220, we found that the contents of CSPG-130 and CSPG-150 in the rat brain reached maximum levels around the time of birth. Both CSPG-130 and 150 were observed, while CSPG-220 was hardly detectable in extracts from the adult rat brain. Immunohistochemical investigation showed that the PAb 291 antigen had a similar distribution pattern to the MAb 1G2 antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain development and multiple molecular species of proteoglycan

The occurrence of multiple proteoglycan species is a characteristic of the brain. The structural features of individually characterized proteoglycans in the brain are first introduced in brief, then some examples are shown that suggest a relationship between multiple proteoglycans and the many distinct cell types and neural circuits in the brain. Typical experiments demonstrated the neuronal-activity-dependent expression of neural proteoglycans during the critical developmental period of some functional systems such as the visual and vibrissal barrel systems. In addition, the binding properties of neural proteoglycans to other cell surface molecules are discussed in conjunction with their involvement in cell-cell and cell-substratum interactions. This review also covers other potential functions of proteoglycans not only in the development and maintenance of the brain but also in the pathogenesis of Alzheimer's disease. Proteoglycans are really coming of age in neuroscience.

Developmentally regulated expression of a brain specific species of chondroitin sulfate proteoglycan, neurocan, identified with a monoclonal antibody IG2 in the rat cerebrum

The mammalian brain contains many species of proteoglycan. To identify each proteoglycan species, we have raised monoclonal antibodies against soluble chondroitin sulfate proteoglycans purified from 10-day-old rat brains. One monoclonal antibody, named monoclonal antibody 1G2, recognized two proteoglycan species with 220,000 and 150,000 mol. wt core glycoproteins (chondroitin sulfate proteoglycan-220 and chondroitin sulfate proteoglycan-150). Partial amino acid sequences of N-termini of their core proteins coincided with those of neurocan, a brain-unique chondroitin sulfate proteoglycan species, whose complete coding sequence was recently reported [Rauch et al. (1992) J. biol. Chem. 269, 19,536-19,547]. Western blots revealed that chondroitin sulfate proteoglycan-220 became detectable in the rat cerebrum on embryonic day 14, and that it disappeared from the brain around postnatal day 30. In contrast, a fairly large amount of chondroitin sulfate proteoglycan-150 remained in the mature brain. Immunohistochemical studies revealed that 1G2 antigen was first localized in the preplate zone, then both in the marginal zone and in the subplate of the rat cerebrum on embryonic day 16, prior to arrival of the first thalamic afferents at the cortex. On embryonic day 20, immunolabeling with monoclonal antibody 1G2 began to spread from the subplate into the developing cortical plate. On postnatal day 10, the neuropil of the cerebrum, except for the barrel field, was diffusely stained with the antibody, intensely in the hippocampus and superficial layers (I-III) of the cerebral cortex and weakly elsewhere. The barrel hollows were stained very weakly compared with the barrel walls at this stage. The immunoreactivity in the hippocampus and superficial cortical layers was weakened in the mature brain, so that no particular staining pattern, but weak and diffuse staining was observed in the adult rat cerebrum. The 1G2 antigen was immunohistochemically associated largely with glial fibrillary acidic protein-positive cells in primary cultures of the neonatal rat cerebrum. Both chondroitin sulfate proteoglycan-220 and chondroitin sulfate proteoglycan-150 were detected in the conditioned media not only of highly enriched cultures of fetal rat cortical neurons but also of pure cultures of mature astrocytes; more (12- to 20-fold) in the astrocyte conditioned media. Astrocytes, in addition to neurons, may be a cellular source of neurocan in brain at least under certain physiological conditions. The spaciotemporal expression pattern of 1G2 epitope-bearing proteoglycan, or neurocan, suggests that this proteoglycan species plays some roles at least in forming the elongation pathway for early cortical afferent fibers as well as the functional barrel structure in the somatosensory cortex.

Cell function during chondrogenesis and osteogenesis induced by bone morphogenetic protein enclosed in diffusion chamber. Biochemical studies on native products derived from outside differentiating cells

A diffusion chamber containing rabbit bone morphogenetic protein (BMP) was implanted in the abdominal muscle of a Sprague-Dawley rat. Outside of the chamber, cartilage differentiated one to two weeks after implantation, and bone replaced the cartilage three to four weeks after implantation. The interstitial fluid inside the chamber contained only biologic substances produced by cells proliferating and differentiating outside of the chamber. To investigate the cell function during chondrogenesis and osteogenesis, alkaline phosphatase activity and the amounts of S-100 alpha protein, S-100 beta protein, creatine kinase subunits M (CK-M), creatine kinase subunits B (CK-B), hyaluronic acid (HA), and chondroitin sulfate (CS) were measured in the supernatant of interstitial fluid inside the chamber. Alkaline phosphatase activity increased two to four weeks after implantation. The amount of S-100 beta protein acutely increased during the fourth week. The amount of CK-B also increased during the fourth week. The increased levels of HA and CS were also observed after two to four weeks. The examination of such native products may help not only to clarify the mechanisms of cartilage and bone development, but also to develop a sensitive bioassay for BMP.

Core proteins of soluble chondroitin sulfate proteoglycans purified from the rat brain block the cell cycle of PC12D cells

The effects of soluble chondroitin sulfate proteoglycans (CSPGs) purified from the rat brain on proliferation of and neurite outgrowth from PC12D cells (Katoh-Semba et al., J Neurosci Res 17:36, 1987) were investigated. When PC12D cells are cultured under standard conditions, they proliferate with a doubling time of about 2 days, irrespective of the presence or absence of NGF. However, the addition of a mixture of several types of purified soluble brain CSPG (50 nmol uronic acid/ml) to the culture medium prevented the increase in the number of PC12D cells as well as the nerve growth factor (NGF)-induced neurite extension. The dose for 50% inhibition (ID50) was 1.6 nmol/ml for cell proliferation and 2.7 nmol/ml for neurite elongation. The increase in cell number seemed to stop around 6 h after exposure to culture medium supplemented with brain-derived CSPGs, and even substratum-attached CSPGs were able to exert such inhibitory effects. Only brain-type CSPGs, not a cartilage-derived CSPG (PGH) or a hyaluronate-binding PGH, had such inhibitory effects. Furthermore, these inhibitory activities were associated only with the core proteins of brain-derived CSPGs, and not with polysaccharide chains from brain-derived CSPGs. Incorporation of [3H]thymidine into DNA did not decrease for at least the first 12 h. Consequently, the amount of DNA per cell after 48 h of culture was about twofold higher in cells treated with brain CSPGs than in nontreated cells after exposure to the medium with CSPGs. Microspectrophotometry revealed that the population of cells with a high DNA content was greater in the culture treated with brain-derived CSPGs than in the control culture. These findings indicate that purified soluble brain CSPGs block the cell cycle of PC12D cells at the G2 phase with resultant cessation of cell proliferation and the inhibition of neurite outgrowth.

Microvascular and cellular defects of the periosteum of osteogenesis imperfecta

Periosteum stripped from fragments of diaphyseal long bones from osteogenesis imperfecta (OI) patients was examined both in vivo and in vitro. The OI periosteum was thickened and characteristic finding was a defective microvascular system. The vascular walls of arterioles and capillaries were thick and the lumina of many of these vessels were narrowed or occluded by hypertrophic endothelial cells and multiplication of smooth muscle cell layers. Circulatory deficiency in the OI periosteum might be regarded as one of the causes of the slender, osteopenic diaphyseal bone characteristic of the disorder. A higher proliferative activity was observed in cultured OI periosteal cells, but the cytoplasmic structure showed increased myelinoid bodies and smooth endoplasmic reticulum and decreased lysosomes and rough endoplasmic reticulum. These findings may be related to the abnormal metabolic activity of OI periosteal cells.

Biochemical comparison of brain glycosaminoglycans between normal and reeler mutant mice

Glycosaminoglycans (GAGs) were isolated from the brains of reeler and normal mice on postnatal days 13 and 20. The GAG content of the reeler mouse brain, based upon the amount of DNA, was about 150% that of the normal mouse brain on both days. The GAGs consisted of chondroitin sulfate (CS), heparan sulfate (HS), hyaluronic acid (HA) and polysialosyl glycopeptides. There was no significant difference in the composition of GAGs isolated from either reeler or normal brain. Repeating disaccharide compositions of CS and HS were also similar in reeler and normal brains. Core proteins of brain chondroitin sulfate proteoglycans (CSPGs), solubilized with phosphate buffered saline, were prepared by digesting purified CSPGs with chondroitinase ABC, and were analyzed by SDS-polyacrylamide slab gel electrophoresis. There was no difference in the composition of core proteins from either reeler or normal brain. These results indicate that, although the GAG content of the reeler mouse brain is higher than the normal, all structural parameters of GAGs/CSPGs so far examined were normal. The rate of synthesis and/or degradation of brain GAGs may be affected in the mutant mouse brain.

Effects of anti-mouse EGF antiserum on prenatal lung development in fetal mice

To clarify the precise role of epidermal growth factor (EGF) on fetal lung development, rabbit anti-mouse EGF (anti-mEGF) antiserum was administered to pregnant mice from days 10 to 17 during late gestation. Control mice were administered either normal rabbit serum (NRS) or physiological saline (PS). Serum EGF was not detected in fetuses from anti-mEGF antiserum treated mothers, but the level in NRS treated control animals was 4.73 +/- 0.66 ng/mL. One day prior to birth, the fetuses were removed and their body and lung weights were measured. There was no difference between body weights and lung weights of anti-mEGF antiserum treated animals and NRS-treated control animals. On light microscopic morphometry, there was no obvious difference between pulmonary architecture of anti-mEGF antiserum treated animals and NRS treated control animals. On transmission electron microscopy, osmiophillic lamellar inclusion bodies were less prominent in the type II epithelial cells in anti-mEGF antiserum treated animals. Electron microscopic morphometric study revealed that the osmiophillic lamellar inclusion bodies in type II epithelial cells of anti-mEGF antiserum treated animals were fewer in number and had decreased area fraction. These findings support the previous finding that EGF promotes epithelial cell differentiation of the fetal lung without affecting body weight and lung weight.