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PubMed2000

Gangliosides affect membrane-channel activities dependent on ambient temperature.

1. The functional properties of biological membranes depend on their molecular composition. In regard to this, charged glycosphingolipids play an outstanding role in the functional adaptation of membranes to different temperatures. 2. In order to shed some light on the respective functional properties of complex membraneous glycosphingolipids, the effects of altered temperatures (5-40 degrees C) on planar lipid bilayers made from diphytanoylphosphatidylcholine (DPPC) and alamethicin as an ion channel was analyzed in the presence of either a sialoglycosphingolipid (less polar disialoganglioside GD1a or highly polar tetrasialoganglioside GQ1b) or phosphatidylserine (PS; as control). 3. Different to the control bilayers made from DPPC or DPPC + PS, the bilayers containing gangliosides had specific maxima in alamethicin conductance and stabile life times. Changes in pore-state conductances indicate structural effects based on an interaction of the large (negatively charged) ganglioside headgroups with the alamethicin pores. 4. The results concerning open time and closed time of channels seem to be based on the gangliosides changing the viscosity of the bilayer and possibly introducing phase transitions. 5. Thus, the findings suggest that gangliosides (1) directly affect channel molecules via their headgroups and (2) may additionally affect the fluidity of membranes in order to maintain membrane homeoviscosity in areas surrounding ion channels independent from the environmental temperature. 6. The effects of gangliosides may be of special interest in describing the ability of neuronal adaptation of vertebrates to temperature and more general regarding the functional adaptation of neurons.

Alamethicin↗
PubMed2000

Ganglioside expression during differentiation of chick retinal cells in vitro.

The neural retina has been widely used to study the developmental patterns of ganglioside metabolism. Recent findings about in vitro differentiating chick embryo retina cells showed that: a) GD3 and GD1a ganglioside patterns undergo the most dramatic changes; b) when the cells emit neurites, GD3 ganglioside and a group of complex gangliotetraosylgangliosides (GTOG) are transiently coexpressed; c) synchronized developmental phenomena are dissociated by anti-GM1 antibodies; d) GD3 remains as a major ganglioside in differentiated neurons, though it is almost not immunoexpressed; e) GTOG affect antibody binding to GD3; f) the content of gangliosides involved in neural differentiation modifies their immunostain localization on cell membrane; g) after exogenous GTOG uptake, immature neurons mimic GD3 immunofluorescent localization of mature cells; h) a subset of purified retinal ganglion cells express GTOG characteristic of mature neurons.

Animals↗
PubMed1992

A cell-type specific ganglioside of glomerular podocytes in rat kidney: an O-acetylated GD3.

We recently described a monoclonal antibody (clone 27A) that detected a membrane antigen specific for glomerular podocytes in adult rat kidney. After binding in vivo, the antibodies induced rapid changes in the foot processes. Here we show that in other rat tissues the antigen is detectable only in cells of adrenal medulla, in some cells of neural or neural crest origin, and in 1 to 5% of the cells of a rat pheochromocytoma cell line PC-12. Attempts to isolate the antigen revealed that it is an acidic, sialic acid containing lipid, as shown by thin layer chromatography and immuno-overlay techniques. Further characterization of the gangliosides extracted from rat glomeruli, bovine kidney, rat adrenal glands, or from PC-12 cells by ion exchange, thin layer, and gas liquid chromatography identified the antigenic lipid as a modified disialosyllactosylceramide (GD3). The results of mild alkaline treatment or periodate oxidation of the antigenic ganglioside, as well as chemical O-acetylation studies of standard gangliosides, showed that the modified ganglioside is O-acetylated, most probably at the 9-carbon of its terminal sialic acid residue. To our knowledge this is the first report of cell-type specific expression of gangliosides in the kidney.

Animals↗
PubMed2001

Modulation of epidermal growth factor receptor phosphorylation by endogenously expressed gangliosides.

The effect of changing the ganglioside composition of Chinese hamster ovary K1 cells on the function of the epidermal growth factor receptor (EGFr) was examined by studying the signalling pathway generated after the binding of epidermal growth factor (EGF) both in cells depleted of glycosphingolipids by inhibiting glucosylceramide synthase activity and in cell lines expressing different gangliosides as the result of stable transfection of appropriate ganglioside glycosyltransferases. After stimulation with EGF, cells depleted of glycolipids showed EGFr phosphorylation and extracellular signal-regulated protein kinase 2 (ERK2) activity as parental cells expressing GM3 [ganglioside nomenclature follows Svennerholm (1963) J. Neurochem. 10, 613-623] or as transfected cells expressing mostly GM2 and GD1a as the result of stable transfection of UDP-GalNAc:LacCer/GM3/GD3 N-acetylgalactosaminyltransferase. However, cells stably transfected with CMP-NeuAc:GM3 sialyltransferase and expressing GD3 at the cell surface showed both decreased EGFr phosphorylation and ERK2 activation after stimulation with EGF. Results suggest that changes in the ganglioside composition of cell membranes might be important in the regulation of the EGF signal transduction.

Animals↗
PubMed1994

Cultured cerebellar granule cells, but not astrocytes, produce an ester of ganglioside GD1b, presumably GD1b monolactone, from exogenous GD1b.

Granule cells and astrocytes from rat cerebellum were fed in culture with 2 microM ganglioside [Gal-3H]GD1b and then analysed for the presence of carboxyl esters of that ganglioside. Before extraction and purification of gangliosides, cells were treated with NaBH4 under conditions that would allow complete reductive cleavage of carboxyl ester linkages, [Gal-3H]GD1b monolactone and dilactone being used as reference esters of GD1b. These conditions, established by adding harvested cells (250 micrograms of protein) with 0.01-2 nmol of standard [Gal-3H]GD1b monolactone or dilactone and [Gal-3H]GD1b-1ol or -2ol formed respectively, consisted of an NaBH4/cell protein ratio of 2:1 (w/w). Cerebellar granule cells, but not astrocytes, were able to produce a radioactive compound which was identified as GD1b-1ol. The formation of this compound increased with pulse (up to 4 h) and chase (up to 3 h) time after a 2 h pulse and also occurred when ganglioside endocytosis was blocked. It can be concluded that cerebellar granule cells are able to convert ganglioside GD1b into a carboxyl ester form, presumably GD1b monolactone. The natural occurrence of the same GD1b carboxyl ester in cerebellar granule cells was also demonstrated.

Animals↗
PubMed2001

Gangliosides GD1b, GT1b, and GQ1b suppress the growth of human melanoma by inhibiting interleukin-8 production: the inhibition of adenylate cyclase.

We studied the effects of various gangliosides on in vitro growth of human metastatic melanoma WM266-4. GD1b, GT1b, and GQ1b inhibited 3H-thymidine uptake and growth rate of WM266-4 whereas the other gangliosides were ineffective. The growth inhibition by GD1b, GT1b, and GQ1b was counteracted by interleukin-8 but not by the other growth factors. The growth inhibition by gangliosides was not detected in the presence of anti-interleukin-8 antibody. GD1b, GT1b, and GQ1b reduced the constitutive interleukin-8 secretion and mRNA levels in WM266-4. Transient transfection showed that GD1b, GT1b, and GQ1b inhibited the constitutive chloramphenicol acetyltransferase expression driven by interleukin-8 promoter in WM266-4. Transfection with a series of 5'-deleted mutants demonstrated that the sequences between -98 and -62 bp on interleukin-8 promoter may be involved in the transcriptional repression by these gangliosides. Cyclic AMP analog dibutyryl cAMP counteracted GD1b, GT1b, and GQ1b-induced inhibition of interleukin-8 production at the levels of protein secretion, mRNA expression, and promoter activity. GD1b, GT1b, and GQ1b reduced cAMP level and protein kinase A activity in WM266-4. These gangliosides suppressed adenylate cyclase activity without altering that of cyclic nucleotide phosphodiesterase in WM266-4. The data indicate that GD1b, GT1b, and GQ1b may suppress the growth of melanoma by inhibiting interleukin-8 production via the inhibition of adenylate cyclase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2000

Phase variation of a beta-1,3 galactosyltransferase involved in generation of the ganglioside GM1-like lipo-oligosaccharide of Campylobacter jejuni.

Ganglioside mimicry by Campylobacter jejuni lipo-oligosaccharide (LOS) is thought to be a critical factor in the triggering of the Guillain-Barré and Miller-Fisher syndrome neuropathies after C. jejuni infection. The combination of a completed genome sequence and a ganglioside GM1-like LOS structure makes C. jejuni NCTC 11168 a useful model strain for the identification and characterization of the genes involved in the biosynthesis of ganglioside-mimicking LOS. Genome analysis identified a putative LOS biosynthetic cluster and, from this, we describe a putative gene (ORF Cj1139c), which we have termed wlaN, with a significant level of similarity to a number of bacterial glycosyltransferases. Mutation of this gene in C. jejuni NCTC 11168 resulted in a LOS molecule of increased electrophoretic mobility, which also failed to bind cholera toxin. Comparison of LOS structural data from wild type and the mutant strain indicated lack of a terminal beta-1,3-linked galactose residue in the latter. The wlaN gene product was demonstrated unambiguously as a beta-1,3 galactosyltransferase responsible for converting GM2-like LOS structures to GM1-like by in vitro expression. We also show that the presence of an intragenic homopolymeric tract renders the expression of a functional wlaN gene product phase variable, resulting in distinct C. jejuni NCTC 11168 cell populations with alternate GM1 or GM2 ganglioside-mimicking LOS structures. The distribution of wlaN among a number of C. jejuni strains with known LOS structure was determined and, for C. jejuni NCTC 12500, similar wlaN gene phase variation was shown to occur, so that this strain has the potential to synthesize a GM1-like LOS structure as well as the ganglioside GM2-like LOS structure proposed in the literature.

Amino Acid Sequence↗
PubMed2000

Analysis of mutants of tetanus toxin Hc fragment: ganglioside binding, cell binding and retrograde axonal transport properties.

Tetanus toxin binds neuronal tissue prior to internalization and trafficking to the central nervous system. Binding of the carboxy-terminal 50 kDa HC fragment of tetanus toxin to polysialogangliosides is important for this initial cell binding step. Using the three-dimensional structure of HC, mutants were designed to investigate the role of individual residues in ganglioside binding. Mutant proteins were tested for binding to GT1b gangliosides, to primary motoneurons and for their ability to undergo retrograde transport in mice. Two classes of mutant were obtained: (i) those containing deletions in loop regions within the C-terminal beta-trefoil domain which showed greatly reduced ganglioside and cell binding and did not undergo retrograde transport and (ii) those that showed reduced ganglioside binding, but retained primary neuronal cell binding and retrograde transport. The second class included point mutants of Histidine-1293, previously implicated in GT1b binding. Our deletion analysis is entirely consistent with recent structural studies which have identified sugar-binding sites in the immediate vicinity of the residues identified by mutagenesis. These results demonstrate that ganglioside binding can be severely impaired without abolishing cell binding and intracellular trafficking of tetanus toxin.

Animals↗
PubMed1994

Regulation of ganglioside composition and synthesis is different in developing chick retinal pigment epithelium and neural retina.

We examined the immunocytochemical expression of GM3 and GD3 in 3-day-old chick embryo retinal pigment epithelium (RPE) and neural retina (NR). We also compared the composition of gangliosides and the activities of key ganglioside glycosyltransferases of the RPE and NR of 8-, 12-, and 15-day old embryos. The immunocytochemical studies in 3-day-old embryos showed heavy expression of GM3 and GD3 at the inner and outer layers of the optic vesicle that are the precursors of the RPE and NR, respectively. The compositional and enzymatic studies showed pronounced differences between RPE and NR of 8-day and older embryos. HPTLC showed that at 8 days the major species were GM3 and GD3 in RPE and GD3 and GT3 in NR. As development proceeded, GD3 decreased in both tissues, GM3 became the major ganglioside in RPE, and ganglio-series gangliosides (mainly GD1a) became the major species in NR. At 15 days the major species were GD1a in NR and GM3 in RPE. Enzyme determinations showed that whereas in RPE from 12-day-old embryos GM2 synthase was under the limit of detection and GD3 synthase activity was about sixfold lower than GM3 synthase, in NR the activities of GM3 and GD3 synthases were similar and both six- to ninefold lower than GM2 synthase. These results evidence a markedly different modulation of the ganglioside glycosylating system in cells of a common origin that through distinct differentiation pathways originate two closely related tissues of the optic system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

N -butyldeoxynojirimycin reduces growth and ganglioside content of experimental mouse brain tumours.

Abnormalities in glycosphingolipid (GSL) biosynthesis have been implicated in the oncogenesis and malignancy of brain tumours. GSLs comprise the gangliosides and the neutral GSLs and are major components of the cell surface glycocalyx. N -butyldeoxynojirimycin (N B-DNJ) is an imino sugar that inhibits the glucosyltransferase catalysing the first step in GSL biosynthesis. The influence of N B-DNJ was studied on the growth and ganglioside composition of two 20-methylcholanthrene-induced experimental mouse brain tumours, EPEN and CT-2A, which were grown in vitro and in vivo. N B-DNJ (200 microM) inhibited the proliferation of the EPEN and CT-2A cells by 50%, but did not reduce cell viability. The drug, administered in the diet (2400 mg kg(-1)) to adult syngeneic C57BL/6 mice, reduced the growth and ganglioside content of subcutaneous and intracerebral EPEN and CT-2A tumours by at least 50% compared to the untreated controls. N B-DNJ treatment also shifted the relative distribution of tumour gangliosides in accordance with the depletion of metabolic substrates. Side effects of N B-DNJ treatment were generally mild and included reductions in body and spleen weights and intestinal distension. We conclude that N B-DNJ may inhibit tumour growth through an effect on ganglioside biosynthesis and may be useful as a new chemotherapy for brain tumours.

1-Deoxynojirimycin↗
PubMed2002

Gangliosides are functional nerve cell ligands for myelin-associated glycoprotein (MAG), an inhibitor of nerve regeneration.

Myelin-associated glycoprotein (MAG) binds to the nerve cell surface and inhibits nerve regeneration. The nerve cell surface ligand(s) for MAG are not established, although sialic acid-bearing glycans have been implicated. We identify the nerve cell surface gangliosides GD1a and GT1b as specific functional ligands for MAG-mediated inhibition of neurite outgrowth from primary rat cerebellar granule neurons. MAG-mediated neurite outgrowth inhibition is attenuated by (i) neuraminidase treatment of the neurons; (ii) blocking neuronal ganglioside biosynthesis; (iii) genetically modifying the terminal structures of nerve cell surface gangliosides; and (iv) adding highly specific IgG-class antiganglioside mAbs. Furthermore, neurite outgrowth inhibition is mimicked by highly multivalent clustering of GD1a or GT1b by using precomplexed antiganglioside Abs. These data implicate the nerve cell surface gangliosides GD1a and GT1b as functional MAG ligands and suggest that the first step in MAG inhibition is multivalent ganglioside clustering.

Animals↗
PubMed1970

Enzymatic block in the synthesis of gangliosides in DNA virus-transformed tumorigenic mouse cell lines.

The ganglioside pattern of both SV40- and polyoma virus-transformed mouse cell lines differs from that of the parent cell lines or of cell lines that have transformed spontaneously in tissue culture. This is manifested by a dramatic decrease of gangliosides with an oligosaccharide chain larger than sialyllactose. Present investigations indicate that this change probably cannot be attributed to excessive catabolism of gangliosides, but is caused by impaired synthesis of tri- and tetrahexosyl gangliosides in the virus-transformed cell lines. We present evidence for the block of a required step for the biosynthesis of these ganglioside homologs. The block involves the enzyme catalyzing the transfer of N-acetylgalactosamine from uridine diphosphate N-acetylgalactosamine to hematosides (N-glycolylneuraminyl or N-acetylneuraminylgalactosylglucosyl ceramide). This well-defined enzymatic change opens the way for studies of the biochemical mechanism of the alteration of cell membranes which occurs after transformation by the tumorigenic DNA viruses polyoma and SV40.

Animals↗
PubMed1981

Reevaluation of the role of gangliosides in the binding and action of thyrotropin.

A cloned line of normal rat thyroid cells, FRTL, contained a small number of high-affinity binding sites for thyrotropin (TSH) when measured under physiological conditions. The cells also bound small amounts of cholera toxin, and both hormone and toxin stimulated cyclic AMP production by the cells. The major ganglioside of FRTL cells was N-acetylneuraminylgalactosylglucosylceramide (GM3), with minor amounts of gangliosides corresponding to galactosyl-N-acetylgalactosaminyl-[N-acetyl-neuraminyl]-galactosylglucosylceramide (GM1) and N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (GD1a). Treatment of these cells with neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) converted most of the GD1a to GM1. After neuraminidase treatment, the binding of cholera toxin, which binds to GM1, was increased, but there was no change in the binding of TSH. Preincubation of neuraminidase-treated FRTL cells with the B (binding) component of cholera toxin completely prevented cholera toxin binding but had no effect on the binding of TSH. Neuraminidase treatment also somewhat enhanced, rather than decreased, the cyclic AMP response to TSH. Pretreatment of FRTL cells with mixed brain gangliosides resulted in a 10-fold increase in cholera toxin binding. Again there was no enhancement of TSH binding or adenylate cyclase stimulation. Finally, prolonged exposure of FRTL cells to TSH induced down-regulation of TSH receptors but had no effect on gangliosides or cholera toxin receptors. The results indicate that more complex gangliosides do not serve as a component of the TSH receptor nor are they involved in the transmission of the hormone signal across the cell membrane of these cultured rat thyroid cells.

Animals↗
PubMed1988

Gangliosides prevent glutamate and kainate neurotoxicity in primary neuronal cultures of neonatal rat cerebellum and cortex.

Using a sensitive histofluorescence staining method that allows for a quantitation of neuronal death, we compared the protective effects of gangliosides (a group of naturally occurring glycosphingolipids), phencyclidine (PCP), and MK-801 (dibenzocyclohepteneimine) on glutamate- and kainate-induced neuronal death in primary cultures of cortical and cerebellar neurons prepared from neonatal rats. PCP and MK-801 block neurotoxicity induced by glutamate doses 50 times higher than the LD50 (LD50 in Mg2+-free medium, 10 microM) but only partially block the kainate neurotoxicity (LD50 in presence of Mg2+, 100 microM). In contrast, pretreatment with gangliosides (GT1b greater than GD1b greater than GM1) results in complete and insurmountable protection against the neurotoxicity elicited by glutamate or kainate. In primary cultures of cerebellar granule cells gangliosides, unlike PCP and MK-801, fail to block glutamate-gated cationic currents and the glutamate-evoked increase of (i) inositol phospholipid hydrolysis (ii) c-fos mRNA content, and (iii) nuclear accumulation of c-fos protein. Protection of glutamate neurotoxicity by gangliosides does not require their presence in the incubation medium; however, it is proportional to the amount of glycosphingolipid accumulated in the neuronal membranes. The ganglioside concentration (30-60 microM) that blocks glutamate-elicited neuronal death also prevents glutamate- and kainate-induced protein kinase C translocation from cytosol to neuronal membranes.

Animals↗
PubMed1995

Identification of gangliosides as inhibitors of ADP-ribosyltransferases of pertussis toxin and exoenzyme C3 from Clostridium botulinum.

We have previously reported the presence of an endogenous inhibitory activity in bovine brain for the ADP-ribosylation of GTP-binding proteins catalyzed by pertussis toxin (PT) (Hara-Yokoyama, M., and Furuyama, S. (1989) Biochem. Biophys. Res. Commun. 160, 67-71). In the present study, we identified the inhibitor as a ganglioside. The screening of various gangliosides revealed that GQ1b alpha most effectively inhibited the ADP-ribosyltransferase activities of both the holoenzyme and the catalytic subunit of PT. GQ1b alpha is a ganglioside newly identified as one of the antigens recognized by the cholinergic neuron-specific antibody, anti-Chol-1 alpha (Hirabayashi, Y., Nakao, T., Irie, F., Whittaker, V.P., Kon, K., and Ando, S. (1992) J. Biol. Chem. 267, 12973-12978). GQ1b alpha also inhibited the PT-catalyzed NAD+ glycohydrolysis. Unlike PT activity, the ADP-ribosylation and the NAD+ glycohydrolysis catalyzed by the C3 exoenzyme from Clostridium botulinum type C were inhibited by GT1b and GQ1b. The ADP-ribosylation catalyzed by either PT or the C3 exoenzyme was not inhibited by ceramide, galactocerebroside, or sialic acid. In addition to the inhibitory action of gangliosides on ADP-ribosylation, the importance of gangliosides as regulators of NAD+ metabolism is discussed.

ADP Ribose Transferases↗
PubMed1995

Expression of de-N-acetyl-gangliosides in human melanoma cells is induced by genistein or nocodazole.

Neuraminic acid is the core structure of most known sialic acids. In natural systems, the amino group at the 5 position of neuraminic acid residues is usually assumed to be acylated. Previously, synthetic de-N-acetyl-gangliosides (with free amino groups at the 5 position of neuraminic acids) have been shown to modulate cellular proliferation and tyrosine phosphokinase reactions. While indirect evidence has suggested that traces of these molecules exist naturally in certain tumor cells, further exploration has been hampered by the lack of a system showing consistent expression at an easily detectable level. Using synthetic compounds as antigens, we have developed highly specific monoclonal antibodies against de-N-acetyl-GM3 and de-N-acetyl-GD3 that require both the free amino group and the exocyclic side chain of sialic acids for recognition. Cultured human melanoma cells showed low but variably detectable levels of reactivity with these antibodies. The ability of various biologically active molecules to stimulate this reactivity was explored. Of many compounds tested, only the tyrosine kinase inhibitor genistein induced reactivity in a dose-dependent manner. Antibody reactivity with ganglioside extracts from genistein-treated cells was abolished by chemical re-N-acetylation and/or truncation of sialic acid side chains by mild periodate oxidation. High performance thin layer chromatography immuno-overlay analysis confirmed the presence of the novel compound de-N-acetyl-GD3 in these extracts. Several other tyrosine kinase inhibitors tested did not give the same increase in de-N-acetyl-ganglioside expression. However, the microtubule inhibitor nocodazole caused a similar accumulation of these molecules, particularly in non-adherent cells expected to be arrested at metaphase. Thus, genistein may induce de-N-acetyl-ganglioside expression by virtue of its known ability to arrest cells in the G2M phase, rather than as a general consequence of tyrosine kinase inhibition. These studies also provide a system in which to analyze the enzymatic basis of de-N-acetyl-ganglioside expression and their potential roles as growth regulating molecules.

Antibodies, Monoclonal↗
PubMed1997

Acceleration of amyloid fibril formation by specific binding of Abeta-(1-40) peptide to ganglioside-containing membrane vesicles.

The interaction of Alzheimer's Abeta peptide and its fluorescent analogue with membrane vesicles was studied by spectrofluorometry, Congo Red binding, and electron microscopy. The peptide binds selectively to the membranes containing gangliosides with a binding affinity ranging from 10(-6) to 10(-7) M depending on the type of ganglioside sugar moiety. This interaction appears to be ganglioside-specific as under our experimental conditions (neutral pH, physiologically relevant ionic strength), no Abeta binding was observed to ganglioside-free membranes containing zwitterionic or acidic phospholipids. Importantly, the addition of ganglioside-containing vesicles to the peptide solution dramatically accelerates the rate of fibril formation as compared with that of the peptide alone. The present results strongly suggest that the membrane-bound form of the peptide may act as a specific "template" (seed) that catalyzes the fibrillogenesis process in vivo.

Alzheimer Disease↗
PubMed1998

Embryonic stem cells with a disrupted GD3 synthase gene undergo neuronal differentiation in the absence of b-series gangliosides.

The dramatic changes in the expression of GD3 and other b-series gangliosides during neuronal development and morphogenesis have led to a widely held belief that these gangliosides may be necessary for neuronal differentiation. To determine directly if GD3 and b-series gangliosides are required for neuronal differentiation, we have produced embryonic stem (ES) cells with both alleles of the GD3 synthase gene (GD3S) disrupted by successive rounds of gene targeting. The double-targeted ES cells were deficient in GD3 synthase activity and did not synthesize b-series gangliosides. Despite this deficit, the GD3S(-/-) ES cells could be induced to undergo neuronal differentiation. Neuronally differentiated wild-type and GD3S(-/-) ES cells formed a complex neurite network around the embryoid bodies. Both types of neuronal cells expressed the axon-specific cytoskeletal proteins, neurofilament-M, and growth-associated protein-43 as well as the dendrite-specific marker, microtubule-associated protein-2. Our results indicate that GD3 synthase and b-series gangliosides are not necessary for the neuronal differentiation of uncommitted precursor cells.

Animals↗