Ganglioside changes in the chicken optic lobes as biochemical indicators of brain development and maturation

Effect of HFE variants on sphingolipid expression by SH-SY5Y human neuroblastoma cells

C282Y and H63D are two common variants of the hemochromatosis protein HFE. SH-SY5Y human neuroblastoma cells stably transfected to express either wild type HFE (WT-HFE), or the C282Y or H63D allele were analyzed for effect of expression of the mutant proteins on transcription of 14 enzymes involved in sphingolipid metabolism. Cells expressing the C282Y variant showed significant increases (>2-fold) in transcription of five genes and decreases in two compared to that seen for cells expressing WT-HFE, while cells expressing the H63D variant showed an elevation in transcription of one gene and a decrease in two. These changes were seen as alterations in ganglioside composition, cell surface binding by the binding subunit of cholera toxin, expression of sphingosine-kinase-1 and synthesis of sphingosine-1-phosphate. These changes may explain why C282Y-HFE is a risk factor for colon and breast cancer and possibly protective against Alzheimer's disease while H63D-HFE is a risk factor for neurodegenerative diseases.

Novel method for chase analysis of oligosaccharide metabolic error caused by xenobiotics

Saccharide primers, such as dodecyl beta-lactoside (Lac-C12), are unique artificial precursors of glycolipid synthesis. In culture media supplemented with saccharide primers, they are taken up by the cells in the culture media and glycosylated by cellular glycosyltransferases in the Golgi apparatus to form pseudo-glycolipids. In this study, we examine the effects of various xenobiotics on glycolipid synthesis by implementing a novel method to analyze pseudo-glycolipids, mainly gangliosides, produced by ONS-76 medulloblastoma cells in a culture medium containing various xenobiotics. The ganglioside group of pseudo-glycolipids was effectively purified by using strong anion-exchange cartridges. The production of pseudo-gangliosides was stimulated by N-(n-butyl)deoxygalactonojirimycin (NB-DGJ), but was inhibited by castanospermine, 2-deoxy-2-fluoro-d-galactose, tunicamycin, and brefeldin A. Because the cells in the culture medium are exposed to the saccharide primers and xenobiotics at the same time, and are secreted in the culture medium in their glycosylated form, our method can be used to effectively analyze the direct effects of xenobiotics on ganglioside synthesis.

Expression of ganglioside GT1b in mouse embryos at different developmental stages after cryopreservation

Gangliosides are a family of sialic acid-containing glycosphingolipids that are abundant in neurons and have a variety of functions in developing and mature tissues. We examined the expression of ganglioside GT1b in the embryonic preimplantation stage after freezing and thawing processes to determine the regulatory roles of ganglioside GT1b in early embryonic development. ICR mouse embryos at the two-cell stage obtained by flushing the oviducts were frozen by two cryopreservation procedures, slow freezing using a programmable freezer or vitrification by direct plunging into liquid nitrogen. Slow freezing was conducted with equilibration in 1.5 M 1,2-propanediol or 5% equilibration glycerol. Vitrification was applied with a 10-15 min equilibration in 7.5% ethylene glycol (EG), 7.5% dimethylsulfoxide (DMSO), and 30 sec in a solution of 15% EG, 15% DMSO and 0.5 M sucrose. Immediately after thawing, the survival rate of the embryos was assessed by their morphology and ability to develop to blastocysts in culture. The survival rate of vitrified and thawed embryos (92%) was significantly higher than that of slow frozen and thawed embryos (76%) (P<0.05). A tendency of higher blastocyst rate was found in the vitrified and thawed embryos compared to that of the slow frozen and thawed embryos. Confocal immunofluorescence staining confirmed that surviving embryos expressed ganglioside GT1b, with the strongest expression at the compacted eight-cell or later stage embryos. Ganglioside GT1b was not observed in the TUNEL-positive, apoptotic embryos, suggesting that cryopreservation had induced DNA breaks in them. These results suggest that ganglioside GT1b may play an important role in embryo survival or development.

Adult retinal neuronal cell culture

Despite a relatively long history, general knowledge is not widespread that adult neurons can be maintained in cell culture for fairly extended periods of time. Within the central nervous system, this capacity seems to be particularly well developed in the retina, although it is still not clear whether this property is due to physical reasons (spatial configuration, simple connections) or to more fundamental differences (molecular composition, physiological function). Irrespective of the reasons, in vitro model systems are useful for investigating physiological and pathological processes occurring in mature retina. The authors argue that the numerous molecular changes undergone during maturation (modifications in ion channels and receptors, apoptotic pathways and growth factor effects) should be taken into account when using in vitro approaches to study processes involved in photoreceptor and ganglion cell degeneration, and hence that more classical methods relying on embryonic or newborn tissue should be interpreted with caution. A number of examples are given where the use of adult retinal neuronal culture may be especially informative: neurite regeneration, neuroprotection assays and pathogenic mechanisms; and areas of further research that should be explored: cell transplantation.

The role of sphingolipids in neuronal development: lessons from models of sphingolipid storage diseases

The study of sphingolipids has undergone a renaissance over the past decade due to the realization that these lipids are involved in a variety a biological processes, such as differentiation, apoptosis, cell growth, and cell migration. In the nervous system, sphingolipids, particularly gangliosides, have attracted particular attention as they occur at high levels and their levels change in a developmentally regulated program. Despite the fact that a large body of data has accumulated on the expression and metabolism of individual gangliosides within specific brain regions, the role of individual gangliosides in neuronal development is still poorly understood, and their specific functions are only now beginning to be elucidated. In the present article, we discuss various aspects of our current knowledge concerning the involvement of sphingolipids and gangliosides in neuronal development, and then discuss some recent findings that shed light on the role of sphingolipids and gangliosides obtained with animal models of sphingolipid and other lysosomal storage diseases.

Glycosyltransferases in different brain regions during chick embryo development

Glycosphingolipids, in particular gangliosides, play a crucial role in neuronal development and are known to change dramatically in total content and distribution in different brain areas during embryogenesis. In the present work we analyzed the activity of enzymes involved in the metabolism of gangliosides, at different periods of functional maturation in different regions of chick embryo brain. Our data demonstrate differences in the enzymatic activities in the examined areas; these differences might be correlated with the functional lateralization occurring in the brain during development. Significative differences were found in glycosphingolipid composition between controlateral cerebral hemispheres and optic lobes; these results together with previous data we found, contribute to reinforce our hypothesis on the occurrence of biochemical lateralization during early brain development.

A novel heptasialosyl c-series ganglioside in embryonic chicken brain: its structure and stage-specific expression

A ganglioside of unknown structure (ganglioside X) was purified from chicken brain at embryonic day 12 (E12) and characterized for its structure. Ganglioside X was reactive with a monoclonal antibody A2B5 and migrated below GH1c on thin-layer chromatography (TLC). Extensive treatment of ganglioside X with Clostridium perfringens sialidase produced a single ganglioside product. This ganglioside was identified as GM1 based upon its chromatographic mobility and reactivity to cholera toxin B subunit and anti-GM1 antibody. Partial hydrolysis of ganglioside X by sialidase generated several degradation products including GH1c, GP1c, and GQ1c. Electrospray ionization (ESI)-mass spectrometry (MS) of the permethylated derivative of ganglioside X produced a triple-charged parent ion peak at m/z 1355, which corresponded with the gangliotetraose oligosaccharide structure having seven sialic acids and ceramide with the molecular mass of 566 (as non-methylated form). Collision-induced dissociation (CID)-MS(2) showed fragment ions including those at m/z 1066 and 1931; these two ions matched the structures of (NeuAc)(3)-Gal-Glc-Cer and (NeuAc)(4)-Gal-GalNAc, respectively. These structures were confirmed by CID-MS(3) of the corresponding peaks. Based upon these findings, the structure of ganglioside X was identified as NeuAc-NeuAc-NeuAc-NeuAc-Galbeta1-3GalNAcbeta1-4(NeuAc-NeuAc-NeuAcalpha2-3)Galbeta1-4Glcbeta1-1'Cer. This ganglioside was designated as GS1c. A developmental study demonstrated that GS1c was expressed in chicken brain during a period from E6 to E13 and thereafter decreased rapidly in its concentration. The present study suggests that GS1c may play a specific role in early development of chicken brain.

GM3 as a novel growth regulator for human gliomas

The simple ganglioside GM3 inhibits proliferation and induces apoptosis in proliferating immature rodent CNS cells. To determine whether GM3 influenced the expansion of human neural tumors the effects of GM3 treatment on primary human brain tumors were assayed. Here we demonstrate that GM3 treatment dramatically reduces cell numbers in primary cultures of high-grade human glioblastoma multiforme (GBM) tumors and the rat 9L cell gliosarcoma cell line. By contrast, GM3 treatment had little effect on cell number in cultures of normal human brain. A single injection of GM3 3 days after intracranial implantation of 9L tumor cells in a murine xenograft model system resulted in a significant increase in the symptom-free survival period of host animals. The effects of GM3 were not restricted to GBMs and 9L cells. Cultures of high-grade ependymomas, mixed gliomas, astrocytomas, oligodendrogliomas, and gangliogliomas were all susceptible to GM3 treatment. These results suggest that GM3 may have considerable value as a selectively toxic chemotherapeutic agent for human high-grade gliomas.

Significance of gangliosides in neuronal differentiation of neuroblastoma cells and neurite growth in tissue culture

Addition of DL-threo-1-phenyl-2-decanolylamine-3-morpholino-1-propanol HCl (PDMP; 7-24 microM) or Fumonisin B1 (FB1; 30-50 microM) to SH-SY5Ytrk-A human neuroblastoma cells results within 4 days in a 40% decrease of the ganglioside content and in a reduction of nerve-growth-factor (NGF)-induced outgrowth of neuritic processes. NGF-induced enhancement of GAP-43 expression was not affected. However, unlike controls, immunostained GAP-43 appeared concentrated in defined areas of cell perikarya and mostly absent from cell processes. Presence of 20-microM exogenous GM1 for 4 days in NGF and PDMP containing cell cultures led to an increase of cell-associated GM1(15-fold), GM2 (10-fold), GM3 (15 fold), GD1a (4-fold), GD2, GD1b, and GT1b (all 3-fold), and partially reversed the PDMP (and FB1) effects on neurite growth and GAP-43 distribution. In a newly developed neuronal tissue culture system, PDMP and FB1 led to a comparable dose-dependent inhibition of neurite outgrowth from embryonic chicken spinal cord explants, which had been embedded into a fibrin matrix. In this system, addition of GM1 led to a further inhibition of neurite growth, probably due to an interaction with growth-promoting components present in the surrounding fibrin matrix.

Ganglioside GM1 alters neuronal morphology by modulating the association of MAP2 with microtubules and actin filaments

In previous studies, we demonstrated that the exogenous ganglioside GM1 increased the complexity of the microtubular network and level of tubulin, selectively changed the distribution of microtubule associated protein-2 (MAP2) immunoreactivity from the perikarya to distal neuritic processes and increased immunogold label of MAP2 in the subplasmalemmal cytoplasm, neuritic filopodia and growth cones of Neuro-2a neuroblastoma cells. Since these areas are rich in actin filaments, our data suggested that MAP2 may be associated with microfilaments in the early stages of ganglioside-induced neuritogenesis. To determine if GM1 alters neuronal morphology by facilitating the interaction of actin and MAP2, we examined the immunolocalization of these two proteins with confocal and electron microscopy. We found that along with the redistribution of MAP2 from perikaryal to neuritic regions, there was parallel redistribution of actin. The uniform subplasmalemmal actin meshwork was disrupted in areas of processes and filopodia with a redistribution of actin to these areas in close association with MAP2. Our present results suggest that gangliosides enhance neuritogenesis by redistributing actin as well as MAP2 to processes and filopodia thereby facilitating their interaction. The association of MAP2 with actin filaments is likely to be an early step in ganglioside-mediated filopodia formation.

A synthetic approach to the c-series gangliosides containing sialyl-alpha(2-->8)sialyl-alpha(2-->8)sialic acid: synthesis of ganglioside GT4, alpha(2-->6) GT4 and GT3

Trimeric sialic acid [Neu5Ac alpha(2-->8)Neu5Ac alpha(2-->8)Neu5Ac, 1] residue-containing gangliosides, GT4, alpha(2-->6)GT4 and GT3, have been synthesized for the first time. Methyl [phenyl] 5-acetamido-8-O-[5-acetamido-8-O-(5-acetamido-4, 7, 8, 9-tetra-O-acetyl-3, 5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylono-1", 9'-lactone)-4,7-di-O-acetyl-3,5-dideoxy-D- glycero-alpha-D-galacto-2-nonulopyranosylono-1',9-lactone]-4,7-di- O-acetyl -3,5-dideoxy-2-thio-D- glycero-D-galacto-2-nonulopyranosid]onate (3) was prepared from 1, via lactonization, methyl esterification of the carboxyl group at the reducting end, O-acetylation and conversion of the anomeric acetoxy group into a phenylthio group. Iodonium-promoted glycosylation of 3 with 2-(trimethylsilyl)ethyl 2,6-di-O-benzyl-beta-D-galactopyranoside (5), 2-(trimethylsilyl)ethyl 3-O-benzyl-beta-D-galactopyranoside (6), 2-(trimethylsilyl)ethyl 2-O-benzoyl-3-O-benzyl-beta-D-galactopyranoside (9), and 2-(trimethylsilyl)ethyl 2, 3-di-O-benzyl-beta-D-galactopyranoside (11) gave the corresponding tetrasaccharides (13-15, 17) having the (Neu5Ac)3-Gal structure. The peracylated oligosaccharides 18 and 24 derived from 13 and 17, and the previously reported lactose derivative 29 were converted into the alpha-trichloroacetimidates 20, 26 and 31, and coupled with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (21) to afford the corresponding beta-glycosides 22, 27 and 32. These protected azidosphingosine derivatives were each transformed into the target gangliosides GT4, alpha(2-->6)GT4 and GT3 via selective reduction of the azido group, subsequent coupling with octadecanoic acid, O-deacylation and saponification of the methyl ester and lactone groups.

Cholera toxin binds to differentiating neurons in the developing murine basal ganglia

Cell-surface expression of gangliosides in the developing mammalian central nervous system is temporally-regulated in a cell-type and regionally specific fashion. Gangliosides may be involved in cell-cell and cell-matrix interactions, and can act synergystically with several growth factors or growth factor receptors. Thus, a role for gangliosides in the regulation of neuronal stem cell proliferation and differentiation has been suggested. We have previously shown that cholera toxin B subunit (CTB), which binds to the ganglioside GM1, binds heterogeneously to dissociated neuroepithelial cells from the developing mouse telencephalon. We stained fixed sections of the ganglionic eminences (GE) of fetal mouse brains and found that CTB labels regions which contain differentiating neurons, but does not stain the rapidly dividing neuroepithelial cells in the ventricular zone. We dissociated cells from the GE on day 14 of gestation (E14), labeled the cells with CTB-FITC, and separated them by flow cytometry. We found the highest level of CTB binding in postmitotic cells which had begun to express markers of neuronal differentiation. When CTB-sorted cells were placed into short-term (48 h) cell culture, high CTB binding continued to correlate with fewer numbers of proliferating cells and larger numbers of differentiating neurons. CTB binding and fluorescence activated cell sorting appear to be useful for separating populations of differentiating neurons from immature, proliferating cells. These studies further lead us to suggest that GM1 plays a role in the differentiation of neurons in the basal ganglia.

Ontogenic development of membrane lipids in the chick optic lobe

The developmental profiles of the lipid composition and their de novo synthesis and remodelling in the optic lobe of the chicken were studied. The 32P incorporation to phospholipids showed an active de novo synthesis mainly of phosphatidylinositol and of a particular fraction of phosphatidylcholine during the early stages of the embryo development, concomitantly with the beginning of synaptogenesis. This de novo synthesis of phospholipids strongly increased at hatching. On the other hand, phosphatidylinositol presented an active lipid exchange (acylation-deacylation) in the early stages of embryogenesis, indicating a strong incorporation of 14C-arachidonic acid during this period, followed by a fast drop in specific activity. Two different fractions of phosphatidylcholine were isolated by high-performance thin-layer chromatography with a different profile of fatty acid composition, disclosing their different physicochemical behavior, metabolic activities and evolution during embryogenesis. 32P incorporation into phosphatidylethanolamine remained very low during the earliest stages of embryogenesis, showing an increase when the process of synaptogenesis began, until hatching, when radioactivity reached a plateau. 14C-arachidonic acid incorporation into phosphatidylethanolamine was minimal. Furthermore, the phosphatidylethanolamine pool was progressively enriched in its ethanolamine plasmalogen throughout the development. Chromatographic analysis of lipid extracts showed the presence of cerebroside traces after 16 days of embryo incubation. At hatching, a remarkable increase in non-hydroxylated cerebrosides was observed concurrently with the appearance of hydroxylated ones. These glycosphingolipids, as well as the sulfatides, were markedly increased in the lipid extracts of optic lobes of adult animals, indicating the progressive development and maturity of the myelin sheath.

Gangliosides are neuronal ligands for myelin-associated glycoprotein

Nerve cells depend on specific interactions with glial cells for proper function. Myelinating glial cells are thought to associate with neuronal axons, in part, via the cell-surface adhesion protein, myelin-associated glycoprotein (MAG). MAG is also thought to be a major inhibitor of neurite outgrowth (axon regeneration) in the adult central nervous system. Primary structure and in vitro function place MAG in an immunoglobulin-related family of sialic acid-binding lactins. We report that a limited set of structurally related gangliosides, known to be expressed on myelinated neurons in vivo, are ligands for MAG. When major brain gangliosides were adsorbed as artificial membranes on plastic microwells, only GT1b and GD1a supported cell adhesion of MAG-transfected COS-1 cells. Furthermore, a quantitatively minor ganglioside expressed on cholinergic neurons, GQ1b alpha (also known as Chol-1 alpha-b), was much more potent than GT1b or GD1a in supporting MAG-mediated cell adhesion. Adhesion to either GT1b or GQ1b alpha was abolished by pretreatment of the adsorbed gangliosides with neuraminidase. On the basis of structure-function studies of 19 test glycosphingolipids, an alpha 2,3-N-acetylneuraminic acid residue on the terminal galactose of a gangliotetraose core is necessary for MAG binding, and additional sialic acid residues linked to the other neutral core saccharides [Gal(II) and GalNAc(III)] contribute significantly to binding affinity. MAG-mediated adhesion to gangliosides was blocked by pretreatment of the MAG-transfected COS-1 cells with anti-MAG monoclonal antibody 513, which is known to inhibit oligodendrocyte-neuron binding. These data are consistent with the conclusion that MAG-mediated cell-cell interactions involve MAG-ganglioside recognition and binding.

Complex gangliosides affect GD3 accessibility to antibody in developing neuronal cells

Ganglioside expression of embryonic chick retina cells developed in vitro was analyzed by indirect immunofluorescence. Immature neurons were GD3 positive cells and the labeling was chiefly distributed all over their cell membrane. Mature neurons became GD3 negative and expressed complex gangliosides of the a- and b-pathways; nevertheless, the content of GD3 accounted for approximately 40% of the total gangliosides in these cells. Neuraminidase hydrolysis pointed out that GD3 was located in membrane of differentiated cells. The frequency of cells with the GD3 immunostain localized in restricted area of membrane of undifferentiated neurons increased significantly after adding a mixture of bovine brain gangliosides (largely complex gangliosides). Antibody binding to immobilized GD3 showed a dose-dependent inhibition by adding a mixture of bovine brain gangliosides, GM1, GD1a or asialo-GM1. Glycosphingolipids with shorter oligosaccharide chains, as cerebrosides or sulfatides, did not affect this binding. These results suggest that, concomitant with the accretion of content of complex gangliosides, a rearrangement in the membrane would occur, which progressively masks GD3 to its antibody. This rearrangement might affect putative ganglioside functions involved in neuronal differentiation.

Phylogenetic conservation of ganglioside GD3 expression during early vertebrate ontogeny

Gangliosides were investigated in adult brains and in 5-vesicle stage embryos of representatives belonging to the four vertebrate classes: Chondrichthyes, Amphibia, Aves and Mammalia. Considerable variability in brain ganglioside composition and concentration was observed among the adult vertebrates. The ganglioside patterns of the developmentally matched vertebrate embryos were similar in that each comprised GD3 as the predominant ganglioside. The phylogenetic conservation of abundant GD3 expression during early vertebrate ontogeny is interpreted as biochemical evidence consistent with von Baer's theory of increasing differentiation and suggests that GD3 is of critical importance for normal vertebrate development.

Adult rat retina interneurons synthesize GD3: GD3 expression by these cells is regulated by cell-cell interactions

GD3, a ganglioside of the lactosyl series, is prevalent in rat retina neuronal cells. We studied here whether rat retina neurons synthesize their own surface GD3 or if they acquire it from Müller glia cells. We analyzed the activity of GD3 synthase and the in vivo labeling of gangliosides from N-[3H]acetylmannosamine in adult rat retinas after selective destruction of Müller glia cells with the gliotoxic alpha-D,L-aminoadipate (AAA). Immunostaining of rat retina sections and western blot analysis with an antivimentin antibody confirmed the gliotoxic effect of AAA. Neither GD3 synthase activity nor the in vivo labeling of GD3 and other gangliosides was significantly affected by AAA, indicating that neuronal cells synthesize their own GD3. We next analyzed the regulation of the expression of GD3 by these neurons in culture. About 80% of freshly dissociated cells from retina of 4-day-old rats (R4) immunoexpress surface GD3. After 3 days in dispersed cell culture conditions, GD3 expression was under the limit of detection in 80% of neuronal cells, indicating a failure of these cells to maintain the expression of surface GD3 in these experimental conditions. Most flat Müller glia-derived cells present in these cultures were GD3 positive. Surface GD3 was detected in approximately 60% of neuronal cells dissociated from R4 tissue that was developed in vitro as an organ culture for 3 days. Likewise, approximately 50% of neurites that had grown out from R4 retinal explants within 3 days in culture and whose neuronal character was indicated by immunoexpression of growth-associated protein GAP-43 were GD3 positive. These findings suggest that the tissue organization and/or specific interactions modulate GD3 expression in neuronal cells. Under dispersed-cell culture conditions, c-pathway gangliosides (GQ1c and GT1c), which are built up from the sialylation of GD3 and later completion of the oligosaccharide backbone, were detected in approximately 60% of neuronal cells, suggesting a maintenance of production of GD3 as an intermediate for gangliotetraosyl gangliosides.

Tangential neuronal migration in the avian tectum: cell type identification and mapping of regional differences with quail/chick homotopic transplants

This paper is a sequel to a previous report, using quail/chick chimeras with partial tectal transplants, in which a tangential invasion of host (chick) tectal territories by cells originating in the quail graft was demonstrated. The cells displaying this secondary tangential migration appeared restricted to two strata (stratum griseum centrale (SGC) and stratum griseum et fibrosum superficiale (SGFS)). Here we describe the morphology of the tangentially displaced neurons, as well as their overall distribution in the host tectal lobe, by means of an antibody that specifically recognizes quail cells, staining them in a Golgi-like manner. Neurons that migrated into the SGC are identified as multipolar projection neurons, typical of this stratum. The majority of cells that migrated into the SGFS correspond to horizontal neurons, as was also corroborated by observations in Golgi-impregnated material. These horizontal cells are concentrated in laminae b, d and f, where their processes form well delimited axonal plexuses. In confirmation of previous results, SGC neurons have a limited range of migration, whereas SGFS cells translocate across much longer distances. In reconstructions of appropriate cases, a remarkable polarity was noted. Significant invasion of chick tectum by quail cells mostly occurred in the rostral half of the host tectum. The long-range migration of superficial horizontal cells frequently reached, but did not cross, the rostral tectal boundary. Conversely, tangential migration in the caudal half of the host tectum was scarce and coincided with a typical arrangement of quail-derived radial columns interdigited with chick-derived columns. These findings are discussed in relation to existing data on immature neuronal populations, molecular marker distribution and polarity of the avian optic tectum.

Gangliosides and neuronal differentiation

Using the GD3-specific mAb R24 we demonstrate by immunohistochemistry that the first embryonic cells of chicken expressing GD3 represent heavily proliferating cells of mesodermal origin (mesenchymal stem and endothelial cells). At this developmental stage (E1-1.5) neuroectodermal cells of the forming neural tube are not stained by R24 or any other available anti-ganglioside antibodies. These cells of the neural tube start to express GD3 at around E1.5 in parallel with increasing proliferative activity. Likewise proliferating and migrating neuronal crest derivates as well as undifferentiated retinal cells, the forming lens and otic placodes increasingly express GD3 in an organ-specific pattern following the spatiotemporal increase in mitotic activity. Immunostaining of GD1b (mAb D21b) or c-pathway polysialogangliosides (mAb Q211) is not obtained before E2.5, is nervous tissue specific and restricted to "new-born" neurons, which start to migrate and form first neurites. This striking change in ganglioside synthesis and expression also occurs in primary cell cultures (after or without previous Q211-mediated complement kill of neurons) during differentiation of mitotic progenitor cells to neurons (neurogenesis). In cell culture, the fluorescence staining is evenly distributed over the whole neuronal surface including filopodia at the growth cones. Monensin (10(-8) M) prevents expression of GD1b and c-polysialogangliosides and simultaneously differentiation of neuronal morphology (neurogenesis). The presence of exogenous gangliosides from bovine brain leads to a decrease of the monensin effect or even abolishes it.

Cell surface distribution of endogenous and effects of exogenous gangliosides on neuronal survival, cell shape and growth in vitro

In vitro immunostaining of neurons from spinal cord or brain of embryonic chicken by means of monoclonal anti-ganglioside antibodies (Q211, D21b) revealed a fluorescence-labeling of c-polysialogangliosides and GD1b evenly distributed over the entire neuronal surface including filopodia at the growth cones. On electronmicroscopical level the gold-stained ganglioside-antigens were found more or less densely packed in small adjacent areas suggesting a concentration in local "domains". Survival in serum-free or serum-containing medium of embryonic spinal cord motoneurons, which normally died if not cultivated in muscle conditioned medium or in contact to myotubes, was remarkably improved in the presence of a ganglioside mixture (10 microM) from bovine brain. If embryonic neurons from optic lobes were cultivated at low Ca(2+)-concentration (< 20 microM) they developed flat, broad cell bodies with many filopodia and only a few flat-shaped short processes. A very weak cytoskeleton-staining by means of rhodamine-linked phalloidine indicated that polymerization of actin was impaired in these neurons. At the same low Ca(2+)-concentration of < 20 microM but in the presence of ganglioside GM1 (up to 100 microM) most of the neurons developed a "normal" cell shape with rounded perikarya and thin neurites with "normal" shaped growth cones. In this case rhodamine-linked phalloidine revealed a much more intense staining mainly concentrated within the growing tips. The morphology and growth of the ganglioside-treated neurons resembled that of neurons cultivated at a higher Ca(2+)-concentration of at least 600 microM.

Biochemical correlates of epilepsy in the E1 mouse: analysis of glial fibrillary acidic protein and gangliosides

The E1 (epileptic) mouse is considered a model for complex partial seizures in humans. Seizures in E1 mice begin around 7-8 weeks of age and persist throughout life. To determine if astrocytic gliosis was present in adult seizing E1 mice, the distribution of glial fibrillary acidic protein (GFAP) was studied in the hippocampus using an antibody to GFAP. The mean number of GFAP-positive cells per square millimeter of hippocampus was approximately 15- to 40-fold higher in adult E1 mice than in nonseizing control C57BL/6J (B6) mice or in young nonseizing E1 mice. Relative GFAP concentration (expressed per milligram of total tissue protein) in hippocampus and cerebellum was estimated by densitometric scanning of peroxidase-stained western blots. GFAP concentration was 2.7-fold greater in hippocampus of adult seizing E1 mice than in the control B6 mice. No differences in GFAP content were detected between the strains in the cerebellum. Because gangliosides can serve as cell surface markers for changes in neuronal cytoarchitecture, they were analyzed to determine if the gliotic response in E1 mice was associated with changes in neural composition. Although the total ganglioside concentration of hippocampus, cerebral cortex, and cerebellum was similar in adult E1 and control B6 mice, a synaptic membrane enriched ganglioside, GD1a, was elevated in the adult E1 cerebral cortex and hippocampus. The findings indicate that E1 mice express a type of gliosis that is not accompanied by obvious neuronal loss.

Developmental changes in the activity of membrane-bound gamma-glutamyl transpeptidase and in the sialylation of synaptosomal membranes from the chick embryonic brain

gamma-Glutamyl transpeptidase (GGT) is a membrane-bound sialoglycoprotein. The developmental changes in GGT activity and in sialic acid content were determined in a crude synaptosomal membrane fraction from the cerebral hemispheres of the chick embryo between days 11 and 19 of incubation. The GGT activity increased almost eightfold during the examined developmental period, while sialic acid content rose significantly only between days 11 and 15. Cortical administered on day 13 significantly increased GGT activity. On the other hand, the content of membrane bound sialic acid was not substantially affected. The value of the GGT apparent Michaelis constant (Kmapp) for gamma-glutamyl-p-nitroanilide in the presence of 20 mmol.l-1 glycylglycine was 1.5 mmol.l-1 and cortisol did not influence it. However, Vmax was increased by this hormone. The affinity of GGT to concanavalin A (ConA) did not change during development. Neither the administration of cortisol nor neuroaminidase treatment had any effect on the interaction of GGT with ConA. Desialylation of crude synaptosomal fraction did not change GGT activity. The results presented here suggest no developmental nor functional relationship between the activity of GGT and the level of sialylation in synaptosomal membranes from the cerebral hemispheres of the chick embryo.

Immunohistochemical localisation of monoclonal antibody R 24-recognized ganglioside Glac2 in early chick embryos

The spatio-temporal cellular expression and biosynthesis of ganglioside Glac2 was investigated in early chick embryogenesis. For demonstration of embryonic Glac2-biosynthesis, chick embryos of stage 0 and of stages 4-5 were incubated in vitro in the presence of radioactive sugar precursors. It was found that chick embryos synthesize Glac2 as early as at the blastula stage as well as at the gastrula stage, both within the area pellucida and the area opaca. In contrast to the biosynthetical findings immunohistochemical staining of the chick embryos at various stages by aid of the mouse monoclonal antibody (mAb) R 24, specific for the immunoepitope NeuAc alpha, 8NeuAc alpha, 3Gal beta less than, as present on the ganglioside Glac2, revealed a spatio-temporal cellular pattern of expression of this ganglioside in early chick embryos. Immunohistochemical staining of the chick embryo at stage 0 shows that all cells of the embryo, the extraembryonic epiblast and the yolk endoderm included, are mAb R 24-positive. At the intermediate streak stage (stage 3), the cranial part of the deep layer, the so-called endophyll, is strongly mAb R 24-positive, whereas at the end of gastrulation (stage 5), mAb R 24-recognized epitopes appear to be restricted to a narrow band of deep-layer cells in the endophyllic crescent and to the yolk endoderm of the area opaca. At this stage, no labelling by the antibody is observed in cell layers of the future embryo. The beginning of neurulation (stage 7) is characterized by the expression of the mAb R 24-recognized epitope in the notochord, whilst the deep layer in the cranial part of the neural fold still expresses this epitope. No ecto- or mesodermal structures are stained by the antibody at this developmental stage. During further development (stage 12 and 13), mAb R 24-reactivity is restricted to the cranial part of the embryo with a preferential staining of cells of endodermal origin. At these stages, the notochord expresses mAb R 24 binding sites only in its cranial region. The spatial and temporal correlation between the presence of mAb R 24-recognized epitopes and the morphogenetic positioning of tissues may be indicative for a possible role of the ganglioside Glac2 in corresponding cellular interactions.

Age-related alteration of brain gangliosides in senescence-accelerated mouse (SAM)-P/8

The senescence-accelerated mouse (SAM)-P/8 was examined with respect to changes in the content and composition of brain gangliosides during aging from juvenile to senescence. The gangliosides were compared with those of control mice, senescence-accelerated resistant mouse (SAM)-R/1. The ganglioside contents in the whole brains of SAM-P/8 and -R/1 were at almost constant level from 0.5 to 6 months, but decreased thereafter until senescence to about 80% of the levels reached at the younger ages. Upon aging, the ganglioside compositions changed with an increase of GM1, and decreases of GD1a, GD1b and GT1b in both strains (GT1b greater than GD1a greater than GD1b). A minor component, GM3 was two to four fold higher in the molecular distributions of the whole brain gangliosides of SAM-P/8 than those of -R/1 at any age examined throughout the life span. The regional gangliosides in olfactory bulb, cerebral cortex, hippocampus, hypothalamus, cerebellum, corpora quadrigemina region, brain stem and medulla oblongata were compared between the two strains at the age of three months. The ganglioside contents in the brain stem and medulla oblongata were lower in SAM-P/8 than -R/1, but there was no significant difference between the two strains in the other regions. As a minor component, GM3 was found to occur in a higher concentration in SAM-P/8 than -R/1 in all brain regions examined, except in the olfactory bulb where GM3 was detected as a major component with no difference in the distribution level between the two strains.

Migration and aggregation of embryonic chicken neurons in vitro: possible functional implication of polysialogangliosides

The presented study reports a primary culture system of embryonic chicken optic lobe neurons, which turned out to be a suitable model for cell migration and aggregation: Freshly dissociated neurons developed short processes, contacted one another and formed fasciculated bundles, on which neurons migrated as long-shaped cells, similar to migrating neurons in vivo. We used this system to study the possible involvement of c-pathway polysialogangliosides for neuronal migration and aggregation. These highly negative charged glycosphingolipids are the predominant gangliosides of migrating and outgrowing neurons in vivo. Addition of a purified ganglioside mixture (50 microM), extracted from brains of the corresponding embryonic stage, strongly enhanced neuronal migration and aggregation, while incubation of the cells with monoclonal antibody Q211, specifically binding c-polysialogangliosides, reduced aggregate formation in a dose-dependent manner. Cultures treated with 10 micrograms/ml Q211, instead, displayed a more divergent growth, leading to the formation of a fine network of single neuronal processes. These results suggest a functional implication of c-polysialogangliosides in neuronal fasciculation, migration and aggregation.

Developmental profiles of gangliosides in trisomy 19 mice

The ganglioside composition of the cerebrum, cerebellum, brainstem, liver, heart, and spleen was analyzed quantitatively in trisomy 19 (Ts19) mice aged 4 to 12 days postpartum. The developmental profiles of cerebral gangliosides were similar in Ts19 mice and control littermates: Total ganglioside-sialic acid as well as the proportions of the individual gangliosides GD1a and GM1 increased with age, while the percentages of GQ1b and GT1b decreased during development. Both the accretion of the total ganglioside content and the development of the individual ganglioside fractions were delayed by 2-3 days in the Ts19 telencephalon. Likewise, the shift from the b- to the a-pathway of ganglioside synthesis was retarded. Ganglioside development was equally delayed in the cerebellum and the brainstem of Ts19 mice. Since in Ts19 mice, morphogenesis of several brain regions is similarly delayed by 2 days, these results confirm the usefulness of gangliosides as biochemical markers for brain maturation. In contrast to brain gangliosides, the ganglioside composition of the Ts19 livers was clearly distinguished from that of control livers. Total ganglioside-bound sialic acid was increased by 35-50% in Ts19 livers. This elevation in ganglioside content not explicable by a simple delay in development was mainly due to an increase in GD3 and fraction 2, which is likely to contain GD1a and GD1b. In contrast, GM2 which increased considerably with age in control mice persisted on a low level in Ts19 livers. Comparable alterations of the ganglioside pattern were neither observed in the spleen nor in the heart of Ts19 mice. The data presented give additional evidence that ganglioside synthesis in the liver is under a different regulation mechanism than that in the brain, heart, and spleen.

GD3 ganglioside is prevalent in fully differentiated neurons from rat retina

Adult mammalian retinas contain unusually high amounts of GD3, a ganglioside of the lactosylceramide series. In this respect, they differ from adult avian retina and other regions of the adult avian and mammalian brain, where GD3 is a minor ganglioside and gangliosides of the gangliotetraosylceramide series (GM1, GD1a, GD1b, GT1b) are the predominant ones. We compare here the ganglioside patterns of rat, human, horse, and guinea pig retinas, which are known to differ in the degree of vascularization and astrocytic cell content. All these retinas showed a prevalence of pathway "b" gangliosides over pathway "a" gangliosides but showed no correlation between GD3 content and the degree of vascularization and astrocytic cell content. Immunostaining of rat retina sections showed the presence of GD3 in the inner and outer plexiform layers and also in the ganglion cell and inner nuclear layers. About 60% of the cells dissociated from rat retina showed immuno-colocalization of GD3 and the neuronal marker class III beta tubulin isotype or cholera toxin binding. All morphologically identifiable glial Muller cells coexpress GD3 and gangliotetraosylgangliosides. GD3 was a minor ganglioside among these axonally transported by ganglion cells in rats and guinea pigs, suggesting that it is either not synthesized by ganglion cells or, if so, it is restricted to the cell soma and/or dendritic tree. Our results demonstrate that, unlike neurons from avian retina and other regions of avian and mammalian brain, neurons from mammalian retina not only contain gangliosides of the gangliotetraosylceramide series but also keep a prevalence of gangliosides of the lactosylceramide series (GD3) when they are fully differentiated.

c-pathway polysialogangliosides in the nervous tissue of vertebrates, reacting with the monoclonal antibody Q211

The mouse monoclonal antibody Q211, previously shown to recognize a common epitope of chicken brain GP1c and of two other polysialogangliosides containing 4 and 6 sialic acid residues respectively, is demonstrated to bind to gangliosides with identical thin-layer chromatography (TLC) migration in the brain of representatives of boney fish, rays, reptiles and mammals, including man. In the boney fish brains, the Q211 binding gangliosides were found to be alkali-labile, the Q211 epitope, however, is alkali-stable. After alkaline treatment, the cichlid fish contained at least 4 Q211-binding gangliosides, migrating as GT1c, GQ1c, GP1c and 'GH'. In the trout brain only one Q211 antigenic fraction was found, migrating as GQ1c. In the brains of ray, turtle and embryonic chicken an identical pattern of Q211-binding gangliosides (GQ1c, GP1c, 'GH') occurred. In the embryonic rat and human brain, the content of Q211-binding gangliosides was much lower as compared to the other vertebrate species. The epitope was found in two fractions, migrating like GQ1c (human and rat) and GP1c (rat). The presence of Q211 epitope in all species was confirmed by immunohistochemistry. These data confirm that the Q211-epitope contains a complete c-ganglio-tetraose structure, carrying 3 sialic residues at the inner galactose. They furthermore demonstrate that the expression of c-pathway polysialogangliosides is a general feature of the vertebrate nervous tissue, either during whole life (fish, reptiles) or more or less transient during embryonic development (birds, mammals).

Further studies on the changes of chicken brain gangliosides during prenatal and postnatal life

The developmental profiles of the gangliosides and those of the fatty acids and long-chain bases of the total ganglioside mixture of the brain of chicken were followed from the 10th day of incubation to the 63rd posthatching day. One O-acetylated polysialoganglioside that seems specific of the earlier embryonic stage and up to 21 alkali-stable components could be recognized by high-resolution two-dimensional TLC procedures and quantified by computer-assisted two-dimensional TLC densitometry. Besides a number of gangliosides identified by co-chromatography with reference standards, 10 were of unidentified structure, and within these 4 did not belong to the gangliotetrahexosyl series. Throughout embryonic life, the ceramide portion of gangliosides was found to contain the long-chain base species with 18 carbons. Those with 20 carbons, approximately 10% of the total, were found to be present only after hatching.

Gangliosides in lesion-induced synaptogenesis: studies in the hippocampus of the rat brain

Changes in ganglioside composition, biosynthesis and individual distribution were studied in hippocampal regions after unilateral destruction of the entorhinal cortex. After 1 and 3 days postlesion (dpl), a decrease in ganglioside content was detected in area dentata (AD) and pyramidal cell regions CA1-CA3 (CA), both ipsilateral and contralateral to the lesion. By 5 dpl all the values had returned to control values, except in AD which showed a dramatic increase in total ganglioside content reaching a maximum at 12 dpl. By 30 dpl this area also showed control content. A significant increase in biosynthesis of gangliosides was observed at 5 and 8 dpl in the hippocampus ipsilateral to the lesion without changes in the contralateral counterpart. Individual ganglioside distribution showed a pronounced change in GM1 and GQ1b with small changes in the other major gangliosides. Significant differences were observed in the distribution of gangliosides between the two hippocampal regions studied in unoperated control animals. GD1a was more concentrated in AD, whereas GQ1b, GT1b and GD1b predominated in CA. The data presented here indicate that important modifications in ganglioside content as well as pattern occur in the deafferented hippocampus a phenomenon that could be related with the known effect of gangliosides on neuritogenesis observed in cell culture studies.

The role(s) of gangliosides in neural differentiation and repair: a perspective

Gangliosides, sialylated glycosphingolipids, are found in greatest concentration in the brain. While they were first characterized as a unique class of lipids almost 50 years ago, little is known regarding their actual function. It is known that (a) ganglioside composition changes during development, (b) different types of neural cells have specific gangliosides associated with them, (c) the accumulation of gangliosides in certain inborn errors of metabolism results in the formation of aberrant meganeurites, and (d) gangliosides appear to enhance recovery from certain neural traumas. Recent work suggests that it is the oligosaccharide portion of the ganglioside that carries much of the biological specificity. Coupled with observations that ganglioside-binding proteins are present on the plasma membranes of cells, it suggests the hypothesis that gangliosides present on the surface of one cell may interact with specific ganglioside-binding proteins, "receptors," on target cells. As a result of the ganglioside-binding protein interaction, a signal could be transmitted to the cell. This might occur via modulation of the effect of the endogenous ganglioside on the activity of a kinase(s) or by an alteration in ionic flux. The signal would initiate the appropriate cellular response.

Gangliosides in the brain in adult Down's syndrome and Alzheimer's disease

Quantitative analysis of total gangliosides and of ganglioside composition by HPTLC has been carried out on the gray matter of frontal cerebral cortex of six brains from Down's syndrome (DS) adults, six age-matched controls, six Alzheimer's disease (AD) adults, and six controls matched for age with the AD brains, as well as on three DS and six control cerebellum specimens. In addition, the analyses were carried out on specimens of corpus callosum of five adult DS and five control brains. No abnormalities were found in the gangliosides of DS corpus callosum. In DS frontal cortex, the concentration of total gangliosides was reduced, and there was a decrease in the fraction of GT1b and GD1b, and an increase in those of GT1a, GD3, GM1 and GM2; the ratio of total b-series to a-series gangliosides was decreased. Very similar abnormalities were found in the gangliosides of DS cerebellum. In AD frontal cortex, by contrast, the total gangliosides and their composition were normal by comparison with age-matched controls, with the minor exception of reductions in the fractions of GQ1b and GT1L. It is concluded that abnormalities in gangliosides exist in the brain in DS that are unrelated to AD-type pathology and may reflect developmental disturbances.

Developmental changes of plasma ganglioside concentration during the neonatal period

We investigated the developmental changes of plasma ganglioside concentration during the neonatal period. The mean plasma ganglioside concentration at birth was 8.22 +/- 3.70 nmol lipid-bound sialic acid (LBSA)/ml, significantly lower than the value in adults (12.05 +/- 1.36 nmol LBSA/ml, P less than 0.02). However, it increased rapidly early in the neonatal period and reached its maximum level at 14 days of age (16.25 +/- 6.04 nmol LBSA/ml), which was higher than that of adults (P less than 0.05); then it decreased slowly to the adult level at one month of age. The mean plasma ganglioside concentration in preterm infants (gestational age less than 37 weeks) was 6.65 +/- 3.35 nmol LBSA/ml, somewhat lower than that of fullterm infants (gestational age greater than or equal to 37 weeks, 9.90 +/- 3.39 nmol LBSA/ml, P less than 0.02) at birth. After birth, it increased much more rapidly in preterm infants and there was no significant difference between these two groups at 5 days of age. Plasma ganglioside concentration at birth increased gradually in correlation with gestational age. Our investigations show that plasma ganglioside concentration may reflect the development and maturation of the central nervous system to some degree, at least early in the neonatal period.

Changes of mouse brain gangliosides during aging from young adult until senescence

The brain gangliosides from young adult to senescent mice (BDF1 and C57BL/6) were studied. The total ganglioside concentrations of the whole brains were almost constant from young adulthood until the beginning of senescence, but decreased constant from young adulthood until the beginning of senescence, but decreased during senescence to about 80% of the constant level observed at the period before the beginning of senescence. In spite of the constancy of the ganglioside concentrations at the period before the beginning of senescence, the composition gradually changed, with an increase of GM1 and decreases of GD1b, GT1b and GQ1b. During the senescence, all of the gangliosides decreased in their concentrations, but GD1a, GT1b and GQ1b decreased to a markedly greater extent (GT1b greater than GD1a greater than GQ1b). The regional gangliosides in olfactory bulb, cerebrum cortex, cerebrum white matter, hippocampus, hypothalamus, cerebellum and medulla oblongata were compared between 3- and 30-month-old mice of both strains. Significant changes in ganglioside concentrations were observed in both strains in the cerebrum and the hippocampus. In the cerebrum white matter, cerebellum and medulla oblongata, GM1 and GM4 contents significantly increased in the senescent mice.

Human brain gangliosides: developmental changes from early fetal stage to advanced age

The developmental profiles of the four major brain gangliosides, GM1, GD1a, GD1b, and GT1b, were examined in human frontal lobe covering the period from 10 fetal weeks to 80 years of age. The ganglioside concentration increased approx. 3-fold from the 10th gestational week to the age of about 5 years. Gangliosides GM1 and GD1a increased 12-15-fold during the same period. The most rapid increase of GM1 and GD1a occurred around term, during the period for dendrite arborization, outgrowth of axons and synaptogenesis. GT1b showed a quite different developmental curve. It was the major ganglioside during the 3rd to 5th gestational month, whereafter its concentration dropped rapidly to term, from which time the concentration then increased up to 50 years of age. Similar curves were found for the other gangliosides of the b-series, GD3, GD2, GD1b and GQ1b. Ganglioside 3'-isoLM1 was a characteristic early fetal ganglioside which dropped rapidly to the 5th gestational month, reached a small peak around term and then disappeared during adulthood. The concentration of gangliosides of the neolacto series was larger than that of the lacto series during the whole developmental period. In the beginning of the second trimester, 3'-LM1 constituted 2% and LD1 10% of total ganglioside sialic acid. The new findings demonstrate more dynamic changes of the ganglioside patterns during development than noted in previous studies.

Ganglioside function in the development and repair of the nervous system. From basic science to clinical application

Gangliosides play important roles in the normal physiological operations of the nervous system, in particular that of the brain. Changes in ganglioside composition occur in the mammalian brain not only during development, but also in aging and in several neuropathological situations. Gangliosides may modulate the ability of the brain to modify its response to cues or signals from the microenvironment. For example, cultured neurons are known to respond to exogenous ganglioside with changes characteristic of cell differentiation. Gangliosides can amplify the responses of neurons to extrinsic protein factors (neuronotrophic factors) that are normal constituents of the neuron's environment. The systemic administration of monosialoganglioside also potentiates trophic actions in vivo and improves neural responses following various types of injury to the adult mammalian central nervous system. The possible molecular mechanism(s) underlying the ganglioside effects may reflect an action in modulating ligand-receptor linked transfer of information across the plasma membrane of the cell.

Possible involvement of polysialogangliosides in nerve sprouting and cell contact formation: an ultracytochemical in vitro study

In Cichlid fish (Oreochromis mossambicus) primary cell cultures from whole brain and optic tectum, the differentiation-dependent distribution of polysialogangliosides on the outer cell surface has been followed on an ultrastructural level. For this, a two-step labeling technique with the monoclonal mouse antibody Q211, recognizing a polysialoganglioside-associated epitope, followed by a secondary IgM antibody, coupled to colloidal gold sols as an electron-dense marker, has been used. The gold grains are not uniformly distributed over the whole cell surface, but rather are clearly arranged clusters. In cells from freshly hatched larvae, both cell bodies and nerve fibers strongly exhibit the polysialoganglioside epitope on their surface. With progressing development, neuronal cell labeling is more and more restricted to nerve fibers and especially to cellular adhesion zones, including synaptic terminals, thus suggesting a functional involvement of polysialogangliosides in nerve sprouting and initiation of both cell-to-extracellular matrix and cell-to-cell contacts.

Coordinate regulation of ganglioside glycosyltransferases in differentiating NG108-15 neuroblastoma x glioma cells

The enzymatic basis for ganglioside regulation during differentiation of NG108-15 mouse neuroblastoma x rat glioma hybrid cells was studied. This cell line contains four gangliosides that lie along the same biosynthetic pathway: GM3, GM2, GM1, and GD1a. Chemically induced neuronal differentiation of NG108-15 cells led to an 80% drop in the steady-state level of their major ganglioside, GM3, a sixfold increase in the level of a minor ganglioside, GM2 (which became the predominant ganglioside of differentiated cells); and relatively little change in the levels of GM1 and GD1a, which lie further along the same biosynthetic pathway. The enzymatic basis for this selective change in ganglioside expression was investigated by measuring the activity of two glycosyltransferases involved in ganglioside biosynthesis. UDP-N-acetylgalactosamine: GM3 N-acetylgalactosaminyltransferase (GM2-synthetase) activity increased fivefold during butyrate-induced differentiation, whereas UDP-galactose: GM2 galactosyltransferase (GM1-synthetase) activity decreased to 10% of its control level. Coordinate regulation of these two glycosyltransferases appears to be primarily responsible for the selective increase of GM2 expression during NG108-15 differentiation.

In vivo and in vitro expression of gangliosides in chick retina Müeller cells

The expression of gangliosides of the lactosylceramide (LC) and of the gangliotetraosylceramide (GTC) series on the surface of cells from the chick neural retina was investigated by double-color indirect immunofluorescence. GD3 was assumed to be representative of LC and was detected using a specific monoclonal antibody. GM1 was assumed to be representative of GTC and was detected using the binding of cholera toxin followed by the binding of cholera toxin antibodies. The expression of polysialosylated GTC (polysialosyl-GTC) was detected using the cholera toxin-cholera toxin antibody experimental approach, after conversion of polysialosyl-GTC to GM1 by treatment of the cells with neuraminidase. In retinas from 6-day-old embryos (R6), most cells (approximately 80%) expressed GD3 but not GTC. After culturing for 7 days, (R6+7), the expression of GTC was found confined to neuron-like cells; flat cells derived from Müller cells expressed GD3 but were negative for GTC expression. On the other hand, postmitotic Müller cells obtained from 13-day-old embryo (R13) or 1-day-old hatched chick retina (RP1) expressed GD3, GM1, and polysialosyl-GTC but were unable to maintain the expression of these GTCs when kept in culture for several days. According to these results, retinal cells can be defined on the basis of their ganglioside expression as follows: (a) retinoblasts, by the expression of GD3; (b) postmitotic neuronal cells, by the expression of GTC; and (c) postmitotic Müller cells, by the expression of GD3 and GTC.(ABSTRACT TRUNCATED AT 250 WORDS)

Ganglioside composition of normal and mutant mouse embryos

The enrichment of gangliosides in neuronal membranes suggests that they play an important role in CNS development. We recently found a marked tetrasialoganglioside deficiency in twl/twl mutant mouse embryos at embryonic day (E)-11. The recessive twl/twl mutants die at embryonic ages E-9 to E-18 from failed neural differentiation in the ventral portion of the neural tube. In the present study, we examined the composition and distribution of gangliosides in twl/twl mutant mouse embryos at E-12. The total ganglioside sialic acid concentration was significantly lower in the mutants than in normal (+/-) embryos. The mutants also expressed significant deficiencies of gangliosides in the "b" metabolic pathway (GD3, GD1b, GT1b, and GQ1b) and elevations in levels of gangliosides in the "a" metabolic pathway (GM3, GM2, GM1, and GD1a). These findings suggest that the mutants have a partial deficiency in the activity of a specific sialyltransferase in the b pathway. Regional ganglioside distribution was also studied in E-12 normal mouse embryos. The ganglioside composition in heads and bodies was similar to each other and to whole embryos. Total ganglioside concentration and the distribution of b pathway gangliosides were significantly higher in neural tube regions than in nonneural tube regions. These findings suggest that b pathway gangliosides accumulate in differentiating neural cells and that the deficiency of these gangliosides in the twl/twl mutants is closely associated with failed neural differentiation.

Gangliosides of the mouse spinal cord: a comparison in in vivo and in vitro tissues

Ganglioside profiles in spinal cord from 13-day mouse fetuses, 21-day postnatal and adult mice were compared with those harvested from organotypic cross-sections of fetal mouse spinal cord grown for 28 days in vitro in a serum-free medium. All the major species of gangliosides reported for brain were present both in the in vivo tissue and cultured spinal cord, though not necessarily at each developmental stage examined. Fresh tissues showed increases and decreases in various gangliosides as have been reported for higher brain centers at similar stages of development in mammals and birds. However, qualitative and quantitative differences exist between fresh spinal cord and cultured cord explants as well as between galactose-grown and galactose-free cultures. Spinal cord explants grown in the presence of galactose showed measurable amounts of GM2 and GM3 which were not detected in the control-defined medium-grown cultures. The differences between the two culture groups may be related to interneuronal connectivity patterns.

Molecular differentiation of the otic vesicle and neural tube in the chick embryo demonstrated by monoclonal antibodies

Monoclonal antibodies (MAbs) were produced against membrane fractions of the chick neural tube and somite. These MAbs selectively stained the neural tube and neural crest cells; the antigens for some of these MAbs were identified as cell adhesion molecules or glycolipids. Histochemistry of the otic vesicle and its progeny in the chick embryo was performed with these MAbs and other MAbs obtained previously in our laboratory. It was demonstrated that differentiation of the otic placode and vesicle from the ectoderm, and development of the acoustic ganglion from the otic vesicle were accompanied by the appearance and disappearance of various molecules.