A multivalent lacto-N-fucopentaose III-lysyllysine conjugate decompacts preimplantation mouse embryos, while the free oligosaccharide is ineffective

Structural Analysis of Oligosaccharides and Glycoconjugates Using NMR

Carbohydrate chains play critical roles in cellular recognition and subsequent signal transduction in the nervous system. Furthermore, gangliosides are targets for various amyloidogenic proteins associated with neurodegenerative disorders. To better understand the molecular mechanisms underlying these biological phenomena, atomic views are essential to delineate dynamic biomolecular interactions. Nuclear magnetic resonance (NMR) spectroscopy provides powerful tools for studying structures, dynamics, and interactions of biomolecules at the atomic level. This chapter describes the basics of solution NMR techniques and their applications to the analysis of 3D structures and interactions of glycoconjugates in the nervous system.

Fucosyltransferase gene expression in goat endometrium during the estrous cycle and early pregnancy

Regulation of the expression of the alpha(1,2)fucosyltransferase (FUT) genes and their enzymatic products, including the H-type 1 antigen (HT1), on the luminal surface of the uterus is believed to be critical for establishment of pregnancy in mammals. The FUT1 gene is a marker for conception rates in dairy cows and HT1 is a marker for uterine receptivity in rodents. To determine the spatiotemporal expression patterns of FUT1 and FUT2 genes in goats, endometrial tissues were obtained on six days spanning the estrous cycle (Days 5, 11, 13, 15, 17 and 19) and seven days spanning early pregnancy (Days 5, 11, 13, 15, 17, 19 and 25). In all data, we found no effect of status (cyclic or pregnant; P > 0.1) and pooled data where appropriate. We cloned FUT1 cDNA from goat endometrium and made probes from it for Northern and slot blot analyses. The analyses indicated that FUT1 gene expression was high until Day 13, and then declined. In situ hybridization revealed a change in the cell-specificity of FUT1 gene expression over the estrous cycle and early pregnancy. In situ hybridization signal intensity scores indicated that FUT1 expression by uterine epithelium was high on Day 5, moderate on Day 11, and minimal on subsequent days. In situ hybridization signals in uterine glandular epithelial cells remained high from Day 5 to Day 13, with weaker signals thereafter. Quantitative reverse transcription-PCR (RT-qPCR) assays were used for quantitation of FUT1 and FUT2 mRNAs. Quantitative RT-qPCR data were generated from endometrium collected from cyclic and pregnant animals on Days 5, 11 and 17. Relative levels of FUT1 mRNA were high on Days 5 and 11, but then fell 5-fold by Day 17 (P < 0.01). FUT2 mRNA concentrations were below the accurate detectable limit of the assay. High levels of HT1 were observed on the apical surface of uterine luminal epithelia on Days 5, 15, 17 and 19, with much lower levels on Days 11 and 13. Thus, data suggests that FUT1 is the primary enzyme responsible for the high levels of HT1 antigen present on the uterine luminal epithelium between Days 5 and 11 of the estrous cycle and early pregnancy. But changes in the expression of the FUT1 gene does not directly correlate to HT1 staining, which increased from Day 13-15. Future studies are required to understand the regulation of the HT1 antigen on the luminal surface of endometrium.

Glycans and glycosaminoglycans in neurobiology: key regulators of neuronal cell function and fate

The aim of the present study was to examine the roles of l-fucose and the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin sulfate/dermatan sulfate (CS/DS) with selected functional molecules in neural tissues. Cell surface glycans and GAGs have evolved over millions of years to become cellular mediators which regulate fundamental aspects of cellular survival. The glycocalyx, which surrounds all cells, actuates responses to growth factors, cytokines and morphogens at the cellular boundary, silencing or activating downstream signaling pathways and gene expression. In this review, we have focused on interactions mediated by l-fucose, KS and CS/DS in the central and peripheral nervous systems. Fucose makes critical contributions in the area of molecular recognition and information transfer in the blood group substances, cytotoxic immunoglobulins, cell fate-mediated Notch-1 interactions, regulation of selectin-mediated neutrophil extravasation in innate immunity and CD-34-mediated new blood vessel development, and the targeting of neuroprogenitor cells to damaged neural tissue. Fucosylated glycoproteins regulate delivery of synaptic neurotransmitters and neural function. Neural KS proteoglycans (PGs) were examined in terms of cellular regulation and their interactive properties with neuroregulatory molecules. The paradoxical properties of CS/DS isomers decorating matrix and transmembrane PGs and the positive and negative regulatory cues they provide to neurons are also discussed.

Distinct human α(1,3)-fucosyltransferases drive Lewis-X/sialyl Lewis-X assembly in human cells

In humans, six α(1,3)-fucosyltransferases (α(1,3)-FTs: FT3/FT4/FT5/FT6/FT7/FT9) reportedly fucosylate terminal lactosaminyl glycans yielding Lewis-X (LeX; CD15) and/or sialyl Lewis-X (sLeX; CD15s), structures that play key functions in cell migration, development, and immunity. Prior studies analyzing α(1,3)-FT specificities utilized either purified and/or recombinant enzymes to modify synthetic substrates under nonphysiological reaction conditions or molecular biology approaches wherein α(1,3)-FTs were expressed in mammalian cell lines, notably excluding investigations using primary human cells. Accordingly, although significant insights into α(1,3)-FT catalytic properties have been obtained, uncertainty persists regarding their human LeX/sLeX biosynthetic range across various glycoconjugates. Here, we undertook a comprehensive evaluation of the lactosaminyl product specificities of intracellularly expressed α(1,3)-FTs using a clinically relevant primary human cell type, mesenchymal stem cells. Cells were transfected with modified mRNA encoding each human α(1,3)-FT, and the resultant α(1,3)-fucosylated lactosaminyl glycoconjugates were analyzed using a combination of flow cytometry and MS. The data show that biosynthesis of sLeX is driven by FTs-3, -5, -6, and -7, with FT6 and FT7 having highest potency. FT4 and FT9 dominantly biosynthesize LeX, and, among all FTs, FT6 holds a unique capacity in creating sLeX and LeX determinants across protein and lipid glycoconjugates. Surprisingly, FT4 does not generate sLeX on glycolipids, and neither FT4, FT6, nor FT9 synthesizes the internally fucosylated sialyllactosamine VIM-2 (CD65s). These results unveil the relevant human lactosaminyl glycans created by human α(1,3)-FTs, providing novel insights on how these isoenzymes stereoselectively shape biosynthesis of vital glycoconjugates, thereby biochemically programming human cell migration and tuning human immunologic and developmental processes.

Changes of glycoconjugate expression profiles during early development

A variety of glycoconjugates, including glycosphingolipids (GSLs), expressed in mammalian tissues and cells were isolated and characterized in early biochemical studies. Later studies of virus-transformed fibroblasts demonstrated the association of GSL expression profiles with cell phenotypes. Changes of GSL expression profile were observed during mammalian embryogenesis. Cell surface molecules expressed on embryos in a stage-specific manner appeared to play key roles in regulation of cell-cell interaction and cell sorting during early development. Many mAbs showing stage-specific reactivity with mouse embryos were shown to recognize carbohydrate epitopes. Among various stage-specific embryonic antigens (SSEAs), SSEA-1 was found to react with neolacto-series GSL Le^x, while SSEA-3 and SSEA-4 reacted with globo-series Gb5 and monosialyl-Gb5, respectively. GSL expression during mouse early development was shown to shift rapidly from globo-series to neolacto/lacto-series, and then to ganglio-series. We found that multivalent Le^x caused decompaction of mouse embryos, indicating a functional role of Le^x epitope in the compaction process. Autoaggregation of mouse embryonal carcinoma (EC) F9 cells provided a useful model of the compaction process. We showed that Le^x-Le^x interaction, a novel type of molecular interavction termed carbohydrate-carbohydrate interaction (CCI), was involved in cell aggregation. Similar shifting of GSL expression profiles from globo-series and neolacto/lacto-series to ganglio-series was observed during differentiation of human EC cells and embryonic stem (ES) cells, reflecting the essential role of cell surface glycoconjugates in early development.

Embryoglycan: a highly branched poly-N-acetyllactosamine in pluripotent stem cells and early embryonic cells

Embryonal carcinoma cells, stem cells of teratocarcinomas, are pluripotent stem cells and also prototypes of embryonic stem cells. Embryonal carcinoma cells contain large amounts of a highly branched poly-N-acetyllactosamine called embryoglycan, which has a molecular weight of approximately 10,000 or greater, and is asparagine-linked. This glycan was found by analyses of fucose-labeled glycopeptides, and its characteristics were established by biochemical analyses. The content of embryoglycan progressively decreases during the in vitro differentiation of embryonal carcinoma cells. Embryoglycan is also abundant in mouse embryonic stem cells and preimplantation mouse embryos, and decreases during embryogenesis. Embryoglycan carries a number of carbohydrate markers of murine pluripotent stem cells. Lewis x markers, such as SSEA-1, 4C9 antigen, and binding sites for Lotus tetragonolobus agglutinin are of particular importance. 4C9 antigenicity requires clustering of Lewis x, best accomplished by poly-N-acetyllactosamine branching, whereas SSEA-1 does not. Although in vivo evidence is lacking, these epitopes have been suggested to participate in cell-to-cell and cell-to-substratum adhesion. Other markers on embryoglycan include α-galactosyl antigens such as ECMA-2, and binding sites for Dolichos biflorus agglutinin, the epitope of which is considered to be identical to Sd^a antigen, namely, GalNAcβ1-4(NeuAcα2-3)Galβ1-4GlcNAc. While embryoglycan is also present in human teratocarcinoma cells, the carbohydrate markers characterized in human pluripotent stem cells to date are largely carried by glycolipids and keratan sulfate. Information on embryoglycan and markers carried by it may assist in the development of new markers of human pluripotent stem cells and their progenies.

Characterization of embryonic stem cell model of polycystic ovary syndrome

The aims of this study are to establish an embryonic stem (ES) cell model of polycystic ovary syndrome and to characterize this ES cell line. ES cells were isolated and cultured from 322 wasted fertilized embryos from polycystic ovary syndrome (PCOS) patients in vitro. They were also characterized by development and differential markers. ES cells from PCOS subject present normal development profile with ES-specific markers such as OCT-4 and SSEA-4. These ES cells can also differentiate into three germ layer derivatives and form teratomas in vivo. ES cells from PCOS patients pose development and differentiation potentials as you would expect of cells from non-PCOS patients; therefore, they can be used as a cellular model to study the pathology of PCOS.

What Have We Learned from Glycosyltransferase Knockouts in Mice?

There are five major classes of glycan including N- and O-glycans, glycosaminoglycans, glycosphingolipids, and glycophosphatidylinositol anchors, all expressed at the molecular frontier of each mammalian cell. Numerous biological consequences of altering the expression of mammalian glycans are understood at a mechanistic level, but many more remain to be characterized. Mouse mutants with deleted, defective, or misexpressed genes that encode activities necessary for glycosylation have led the way to identifying key functions of glycans in biology. However, with the advent of exome sequencing, humans with mutations in genes involved in glycosylation are also revealing specific requirements for glycans in mammalian development. The aim of this review is to summarize glycosylation genes that are necessary for mouse embryonic development, pathway-specific glycosylation genes whose deletion leads to postnatal morbidity, and glycosylation genes for which effects are mild, but perturbation of the organism may reveal functional consequences. General strategies for generating and interpreting the phenotype of mice with glycosylation defects are discussed in relation to human congenital disorders of glycosylation (CDG).

Role of Glycans in Cancer Cells Undergoing Epithelial-Mesenchymal Transition

The term “cancer” refers to a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. Epithelial–mesenchymal transition (EMT), a process whereby epithelial cells lose their cell polarity and cell–cell adhesion ability, and acquire migratory and invasive properties to gain mesenchymal phenotype, is an important step leading to tumor metastasis. Glycans, such as N-glycans, O-glycans, and glycosphingolipids, are involved in numerous biological processes, including inflammation, virus/bacteria–host interactions, cell–cell interactions, morphogenesis, and cancer development and progression. Aberrant expression of glycans has been observed in several EMT models, and the functional roles of such glycans in cancer development and progression has been investigated. We summarize here recent research progress regarding the functions of glycans in cancer cells undergoing EMT. Better understanding of the mechanisms underlying aberrant glycan patterns in EMT and cancer will facilitate the development of such glycans as cancer biomarkers or as targets in design and synthesis of anti-tumor drugs.

Major glycan structure underlying expression of the Lewis X epitope in the developing brain is O-mannose-linked glycans on phosphacan/RPTPβ

Glycosylation is a major protein modification. Although proteins are glycosylated/further modulated by several glycosyltransferases during trafficking from the endoplasmic reticulum to the Golgi apparatus, a certain glycan epitope has only been detected on a limited number of proteins. Of these glycan epitopes, Lewis X is highly expressed in the early stage of a developing brain and plays important roles in cell-cell interaction. The Lewis X epitope is comprised of a trisaccharide (Galβ1-4 (Fucα1-3) GlcNAc), and a key enzyme for the expression of this epitope is α1,3-fucosyltransferase 9. However, the scaffolding glycan structure responsible for the formation of the Lewis X epitope as well as its major carrier protein has not been fully characterized in the nervous system. Here we showed that the Lewis X epitope was mainly expressed on phosphacan/receptor protein tyrosine phosphatase β (RPTPβ) in the developing mouse brain. Expression of the Lewis X epitope was markedly reduced in β1,4-galactosyltransferase 2 (β4GalT2) gene-deficient mice, which indicated that β4GalT2 is a major galactosyltransferase required for the Lewis X epitope. We also showed that the Lewis X epitope almost disappeared due to the knockout of protein O-mannose β1,2-N-acetylglucosaminyltransferase 1, an N-acetylglucosaminyltransferase essential for the synthesis of O-mannosylated glycans, which indicated that the O-mannosylated glycan is responsible for presenting the Lewis X epitope. Since O-mannosylated glycans on phosphacan/RPTPβ could also present human natural killer-1, another glycan epitope specifically expressed in the nervous system, our results revealed the importance of O-mannosylated glycan chains in the presentation of functional glycan epitopes in the brain.

Equilibrium-fluctuation-analysis of single liposome binding events reveals how cholesterol and Ca2+ modulate glycosphingolipid trans-interactions

Carbohydrate-carbohydrate interactions (CCIs) are of central importance for several biological processes. However, the ultra-weak nature of CCIs generates difficulties in studying this interaction, thus only little is known about CCIs. Here we present a highly sensitive equilibrium-fluctuation-analysis of single liposome binding events to supported lipid bilayers (SLBs) based on total internal reflection fluorescence (TIRF) microscopy that allows us to determine apparent kinetic rate constants of CCIs. The liposomes and SLBs both contained natural Le(x) glycosphingolipids (Galβ4(Fucα3)GlcNAcβ3Galβ4Glcβ1Cer), which were employed to mimic cell-cell contacts. The kinetic parameters of the self-interaction between Le(x)-containing liposomes and SLBs were measured and found to be modulated by bivalent cations. Even more interestingly, upon addition of cholesterol, the strength of the CCIs increases, suggesting that this interaction is strongly influenced by a cholesterol-dependent presentation and/or spatial organization of glycosphingolipids in cell membranes.

Self-recognition of high-mannose type glycans mediating adhesion of embryonal fibroblasts

High-mannose type N-linked glycan with 6 mannosyl residues, termed "M6Gn2", displayed clear binding to the same M6Gn2, conjugated with ceramide mimetic (cer-m) and incorporated in liposome, or coated on polystyrene plates. However, the conjugate of M6Gn2-cer-m did not interact with complex-type N-linked glycan with various structures having multiple GlcNAc termini, conjugated with cer-m. The following observations indicate that hamster embryonic fibroblast NIL-2 K cells display homotypic autoadhesion, mediated through the self-recognition capability of high-mannose type glycans expressed on these cells: (i) NIL-2 K cells display clear binding to lectins capable of binding to high-mannose type glycans (e.g., ConA), but not to other lectins capable of binding to other carbohydrates (e.g. GS-II). (ii) NIL-2 K cells adhere strongly to plates coated with M6Gn2-cer-m, but not to plates coated with complex-type N-linked glycans having multiple GlcNAc termini, conjugated with cer-m; (iii) degree of NIL-2 K cell adhesion to plates coated with M6Gn2-cer-m showed a clear dose-dependence on the amount of M6Gn2-cer-m; and (iv) the degree of NIL-2 K adhesion to plates coated with M6Gn2-cer-m was inhibited in a dose-dependent manner by α1,4-L-mannonolactone, the specific inhibitor in high-mannose type glycans addition. These data indicate that adhesion of NIL-2 K is mediated by self-aggregation of high mannose type glycan. Further studies are to be addressed on auto-adhesion of other types of cells based on self interaction of high mannose type glycans.

Carbohydrate to carbohydrate interaction in development process and cancer progression

Two types of carbohydrate to carbohydrate interaction (CCI) have been known to be involved in biological processes. One is the CCI between molecules expressed on interfacing cell membranes of different cells to mediate cell to cell adhesion, and subsequently induce cell signaling, and is termed trans-CCI. It has been indicated that the Le(x) to Le(x) interaction at the morula stage in mouse embryos plays an important role in the compaction process in embryonic development. GM3 to Gg3 or GM3 to LacCer interaction has been suggested to be involved in adhesion of tumor cells to endothelial cells, which is considered a crucial step in tumor metastasis. The other is the CCI between molecules expressed within the same microdomain of the cell surface membrane, and is termed cis-CCI. The interaction between ganglioside GM3, and multi (>3) GlcNAc termini of N-linked glycans of epidermal growth factor receptor (EGFR), has been indicated as the molecular mechanism for the inhibitory effect of GM3 on EGFR activation. Also, the complex with GM3 and GM2 has been shown to inhibit the activation of hepatocyte growth factor (HGF) receptor, cMet, through its association with tetraspanin CD82, and results in the inhibition of cell motility. Since CCI research is still limited, more examples of CCI in biological processes in development, and cancer progression will be revealed in the future.

Combinatorial glycoarray

Glycolipid-protein interactions are increasingly recognised as critical to numerous and diverse biological processes, including immune recognition, cell-cell signalling, pathogen adherence, and virulence factor binding. Previously, such carbohydrate-lectin interactions have been assessed in vitro largely by assaying protein binding against purified preparations of single glycolipids. Recent observations show that certain disease-associated autoantibodies and other lectins bind only to complexes formed by two different gangliosides. However, investigating such 1:1 glycolipid complexes can prove technically arduous. To address this problem, we have developed a semi-automated system for assaying lectin binding to large numbers of glycolipid complexes simultaneously. This employs an automated thin-layer chromatography sampler. Single glycolipids and their heterodimeric complexes are prepared in microvials. The autosampler is then used to print reproducible arrays of glycolipid complexes onto polyvinylidene difluoride membranes affixed to glass slides. A printing density of 300 antigen spots per slide is achievable. Following overnight drying, these arrays can then be probed with the lectin(s) of interest. Detection of binding is by way of a horseradish peroxidase-linked secondary antibody driving a chemiluminescent reaction rendered on radiographic film. Image analysis software can then be used to measure signal intensity for quantification.

Cancer vaccines and carbohydrate epitopes

Tumor-associated carbohydrate antigens (TACA) result from the aberrant glycosylation that is seen with transformation to a tumor cell. The carbohydrate antigens that have been found to be tumor-associated include the mucin related Tn, Sialyl Tn, and Thomsen-Friedenreich antigens, the blood group Lewis related Lewis(Y), Sialyl Lewis(X) and Sialyl Lewis(A), and Lewis(X) (also known as stage-specific embryonic antigen-1, SSEA-1), the glycosphingolipids Globo H and stage-specific embryonic antigen-3 (SSEA-3), the sialic acid containing glycosphingolipids, the gangliosides GD2, GD3, GM2, fucosyl GM1, and Neu5GcGM3, and polysialic acid. Recent developments have furthered our understanding of the T-independent type II response that is seen in response to carbohydrate antigens. The selection of a vaccine target antigen is based on not only the presence of the antigen in a variety of tumor tissues but also on the role this antigen plays in tumor growth and metastasis. These roles for TACAs are being elucidated. Newly acquired knowledge in understanding the T-independent immune response and in understanding the key roles that carbohydrates play in metastasis are being applied in attempts to develop an effective vaccine response to TACAs. The role of each of the above mentioned carbohydrate antigens in cancer growth and metastasis and vaccine attempts using these antigens will be described.

Structurally distinct LewisX glycans distinguish subpopulations of neural stem/progenitor cells

There is increasing evidence that the stem and progenitor cell population that builds the central nervous system is very heterogeneous. Stem cell markers with the potential to divide this cell pool into subpopulations with distinct characteristics are sparse. We were looking for new cell type-specific antigens to further subdivide the progenitor pool. Here, we introduce the novel monoclonal antibody clone 5750. We show that it specifically labels cell surfaces of neural stem and progenitor cells. When 5750-expressing cells were isolated by fluorescence-activated cell sorting from embryonic mouse brains, the sorted population showed increased neurosphere forming capacity and multipotency. Neurospheres generated from 5750-positive cells could self-renew and remained multipotent even after prolonged passaging. Carbohydrate binding assays revealed that the 5750 antibody specifically binds to LewisX-related carbohydrates. Interestingly, we found that the LewisX epitope recognized by clone 5750 differs from those detected by other anti-LewisX antibody clones like 487(LeX), SSEA-1(LeX), and MMA(LeX). Our data further reveal that individual anti-LewisX clones can be successfully used to label and deplete different subpopulations of neural cells in vivo and in vitro. In conclusion, we present a new tool for the isolation and characterization of neural subpopulations and provide insights into the complexity of cell surface glycosylation.

Lipid rafts: keys to sperm maturation, fertilization, and early embryogenesis

Cell membranes are composed of many different lipids and protein receptors, which are important for regulating intracellular functions and cell signaling. To orchestrate these activities, the cell membrane is compartmentalized into microdomains that are stably or transiently formed. These compartments are called "lipid rafts". In gamete cells that lack gene transcription, distribution of lipids and proteins on these lipid rafts is focused during changes in their structure and functions such as starting flagella movement and membrane fusion. In this paper, we describe the role of lipid rafts in gamete maturation, fertilization, and early embryogenesis.

Functional role of gangliotetraosylceramide in epithelial-to-mesenchymal transition process induced by hypoxia and by TGF-{beta}

The epithelial-to-mesenchymal transition (EMT) is a basic cellular process that plays a key role in normal embryonic development and in cancer progression/metastasis. Our previous study indicated that EMT processes of mouse and human epithelial cells induced by TGF-β display clear reduction of gangliotetraosylceramide (Gg4) and ganglioside GM2, suggesting a close association of glycosphingolipids (GSLs) with EMT. In the present study, using normal murine mammary gland (NMuMG) cells, we found that levels of Gg4 and of mRNA for the UDP-Gal:β1-3galactosyltransferase-4 (β3GalT4) gene, responsible for reduction of Gg4, were reduced in EMT induced by hypoxia (∼1% O(2)) or CoCl(2) (hypoxia mimic), similarly to that for TGF-β-induced EMT. An increase in the Gg4 level by its exogenous addition or by transfection of the β3GalT4 gene inhibited the hypoxia-induced or TGF-β-induced EMT process, including changes in epithelial cell morphology, enhanced motility, and associated changes in epithelial vs. mesenchymal molecules. We also found that Gg4 is closely associated with E-cadherin and β-catenin. These results suggest that the β3GalT4 gene, responsible for Gg4 expression, is down-regulated in EMT; and Gg4 has a regulatory function in the EMT process in NMuMG cells, possibly through interaction with epithelial molecules important to maintain epithelial cell membrane organization.

The role of mucin-type O-glycans in eukaryotic development

Newly emerging genetic studies have revealed that a subset of the family of glycosyltransferases responsible for the formation of mucin-type O glycans is essential for normal development. As additional genetic, biochemical and physical tools are developed to interrogate the complex structure and surface location of this under-studied class of carbohydrate, no doubt additional roles will be elucidated.

Structures and application of oligosaccharides in human milk

Comparative study of the oligosaccharide profiles of individual human milk revealed the presence of three different patterns. Four oligosaccharides containing the Fucalpha1-2Gal group were missing in the milk of non-secretor, and three oligosaccharides containing the Fucalpha1-4GlcNAc group were missing in the milk of Lewis negative individuals. Disappearance of some major oligosaccharides in these samples led to the finding of five novel minor oligosaccharides, which were hidden under the missing oligosaccharides. Following these studies, structures of many novel milk oligosaccharides were elucidated. At least 13 core oligosaccharides were found in these oligosaccharides. By adding alpha-fucosyl residues and sialic acid residues to these core oligosaccharides, more than one hundred oligosaccharides were formed. All these oligosaccharides contain lactose at their reducing termini. This evidence, together with the deletion phenomena found in the milk oligosaccharides of non-secretor and Lewis negative individuals, suggested that the oligosaccharides are formed from lactose by the concerted action of glycosyltransferases, which are responsible for elongation and branching of the Galbeta1-4GlcNAc group in the sugar chains of glycoconjugates on the surface of epithelial cells. Therefore, oligosaccharides in human milk could include many structures, starting from the Galbeta1-4GlcNAc group in the sugar chains of various glycoconjugates. Many lines of evidence recently indicated that virulent enteric bacteria and viruses start their infection by binding to particular sugar chains of glycoconjugates on the target cell surfaces. Therefore, milk oligosaccharides could be useful for developing drugs, which inhibit the infection of bacteria and viruses.

The N-glycome of human embryonic stem cells

Background

Complex carbohydrate structures, glycans, are essential components of glycoproteins, glycolipids, and proteoglycans. While individual glycan structures including the SSEA and Tra antigens are already used to define undifferentiated human embryonic stem cells (hESC), the whole spectrum of stem cell glycans has remained unknown. We undertook a global study of the asparagine-linked glycoprotein glycans (N-glycans) of hESC and their differentiated progeny using MALDI-TOF mass spectrometric and NMR spectroscopic profiling. Structural analyses were performed by specific glycosidase enzymes and mass spectrometric fragmentation analyses.

Results

The data demonstrated that hESC have a characteristic N-glycome which consists of both a constant part and a variable part that changes during hESC differentiation. hESC-associated N-glycans were downregulated and new structures emerged in the differentiated cells. Previously mouse embryonic stem cells have been associated with complex fucosylation by use of SSEA-1 antibody. In the present study we found that complex fucosylation was the most characteristic glycosylation feature also in undifferentiated hESC. The most abundant complex fucosylated structures were Le^x and H type 2 antennae in sialylated complex-type N-glycans.

Conclusion

The N-glycan phenotype of hESC was shown to reflect their differentiation stage. During differentiation, hESC-associated N-glycan features were replaced by differentiated cell-associated structures. The results indicated that hESC differentiation stage can be determined by direct analysis of the N-glycan profile. These results provide the first overview of the N-glycan profile of hESC and form the basis for future strategies to target stem cell glycans.

Specific glycosphingolipids mediate epithelial-to-mesenchymal transition of human and mouse epithelial cell lines

Epithelial-to-mesenchymal cell transition (EMT) is a basic process in embryonic development and cancer progression. The present study demonstrates involvement of glycosphingolipids (GSLs) in the EMT process by using normal murine mammary gland NMuMG, human normal bladder HCV29, and human mammary carcinoma MCF7 cells. Treatment of these cells with D-threo-1-(3',4'-ethylenedioxy)phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (EtDO-P4), the glucosylceramide (GlcCer) synthase inhibitor, which depletes all GSLs derived from GlcCer, (i) down-regulated expression of a major epithelial cell marker, E-cadherin; (ii) up-regulated expression of mesenchymal cell markers vimentin, fibronectin, and N-cadherin; (iii) enhanced haptotactic cell motility; and (iv) converted epithelial to fibroblastic morphology. These changes also were induced in these cell lines with TGF-beta, which is a well-documented EMT inducer. A close association between specific GSL changes and EMT processes induced by EtDO-P4 or TGF-beta is indicated by the following findings: (i) The enhanced cell motility of EtDO-P4-treated cells was abrogated by exogenous addition of GM2 or Gg4, but not GM1 or GM3, in all 3 cell lines. (ii) TGF-beta treatment caused changes in the GSL composition of cells. Notably, Gg4 or GM2 was depleted or reduced in NMuMG, and GM2 was reduced in HCV29. (iii) Exogenous addition of Gg4 inhibited TGF-beta-induced changes of morphology, motility, and levels of epithelial and mesenchymal markers. These observations indicate that specific GSLs play key roles in defining phenotypes associated with EMT and its reverse process (i.e., mesenchymal-to-epithelial transition).

Surface marker antigens in the characterization of human embryonic stem cells

The use of cell surface antigens to characterise embryonic stem (ES) cells, and to monitor their differentiation, has had a long history, stretching back to the early studies of differentiation antigens in the haematopoietic system, and their application to teratocarcinomas and embryonal carcinoma (EC) cells in the laboratory mouse. A wide series of such antigens, which include both glycolipids and glycoproteins are now extensively used in studies of human ES cells. Many of these were first identified using both mouse and human EC cells, although the cell surface antigen phenotype of human EC and ES cells has proved to be significantly different from that of murine EC and ES cells.

The Lc3-synthase gene B3gnt5 is essential to pre-implantation development of the murine embryo

Background

Glycosphingolipids (GSL) are integral components of mammalian cell membranes that are involved in cell adhesion and cell signaling processes. GSL are subdivided into structural series, like ganglio-, lacto/neolacto-, globo- and isoglo-series, which are defined by distinct trisaccharide cores. The β1,3 N-acetylglucosaminyltransferase-V (B3gnt5) enzyme catalyzes the formation of the Lc3 structure, which is the core of lactoseries derived GSL.

Results

The biological significance of the glycoconjugates produced by the B3gnt5 enzyme was investigated by inactivating the B3gnt5 gene in the mouse germline. The disruption of the B3gnt5 protein-coding region in mouse embryonic stem cells resulted in reduced Lc3-synthase activity, supporting its specific contribution to lactoseries derived GSL synthesis. Breeding of heterozygous mutant mice failed to produce any viable progeny homozygous for the B3gnt5-null allele. The genotypic examination of embryos from heterozygous crosses showed that the disruption of the B3gnt5 gene leads to pre-implantation lethality. This finding was compatible with the expression pattern of the B3gnt5 gene in the pre-implantation embryo as shown by in situ hybridization. The analysis of GSL profiles in embryonic stem cells heterozygous for the B3gnt5-null allele confirmed the reduced levels of lactoseries derived GSL levels and of other GSL species.

Conclusion

The disruption of the B3gnt5 gene in mice affected the expression of lactoseries derived GLS and possibly of protein-bound β3GlcNAc-linked glycans, thereby demonstrating an essential contribution of these glycoconjugates in early embryonic development, and supporting the importance of these glycoconjugates in cell differentiation and adhesion processes.

Complex N-glycans or core 1-derived O-glycans are not required for the expression of stage-specific antigens SSEA-1, SSEA-3, SSEA-4, or Le(Y) in the preimplantation mouse embryo

The glycan epitopes termed stage-specific embryonic antigens (SSEA) occur on glycoproteins and glycolipids in mammals. However, it is not known whether these epitopes are attached to N- or O-glycans on glycoproteins and/or on glycolipids in the developing mouse embryo. In this paper the expression of the antigens SSEA-1, SSEA-3, SSEA-4 and Le(Y) was examined on ovulated eggs, early embryos and blastocysts lacking either complex and hybrid N-glycans or core-1 derived O-glycans. In all cases, antigen expression determined by fluorescence microscopy of bound monoclonal antibodies to embryos at the stage of development of maximal expression was similar in mutant and control embryos. Thus, none of these developmental antigens are expressed solely on either complex N- or core 1-derived O-glycans attached to glycoproteins in the preimplantation mouse embryo. Furthermore, neither of these classes of glycan is essential for the expression of SSEA-1, SSEA-3, SSEA-4 or Le(Y) on mouse embryos.

Membrane microdomains from early gastrula embryos of medaka, Oryzias latipes, are a platform of E-cadherin- and carbohydrate-mediated cell-cell interactions during epiboly

Formation of membrane microdomain is critical for cell migration (epiboly) during gastrulation of medaka fish [Adachi et al. (Biochem. Biophys. Res. Commun. 358:848-853, 2007)]. In this study, we characterized membrane microdomain from gastrula embryos to understand its roles in epiboly. A cell adhesion molecule (E-cadherin), its associated protein (beta-catenin), transducer proteins (PLCgamma, cSrc), and a cytoskeleton protein (beta-actin) were enriched in the membrane microdomain. Le(X)-containing glycolipids and glycoproteins (Le(X)-gp) were exclusively enriched in the membrane microdomain. Interestingly, the isolated membrane microdomain had the ability to bind to each other in the presence of Ca(2+). This membrane microdomain binding was achieved through the E-cadherin homophilic and the Le(X)-glycan-mediated interactions. E-cadherin and Le(X)-gp were co-localized on the same membrane microdomain, suggesting that these two interactions are operative at the same time. Thus, the membrane microdomain functions as a platform of the E-cadherin- and Le(X)-glycan-mediated cell adhesion and signal transduction.

Functional role of glycosphingolipids and gangliosides in control of cell adhesion, motility, and growth, through glycosynaptic microdomains

At cell surface microdomains, glycosyl epitopes, carried either by glycosphingolipids, N- or O-linked oligosaccharides, are recognized by carbohydrate-binding proteins or complementary carbohydrates. In both cases, the carbohydrate epitopes may be clustered with specific signal transducers, tetraspanins, adhesion receptors or growth factor receptors. Through this framework, carbohydrates can mediate cell signaling leading to changes in cellular phenotype. Microdomains involved in carbohydrate-dependent cell adhesion inducing cell activation, motility, and growth are termed "glycosynapse". In this review a historical synopsis of glycosphingolipids-enriched microdomains study leading to the concept of glycosynapse is presented. Examples of glycosynapse as signaling unit controlling the tumor cell phenotype are discussed in three contexts: (i) Cell-to-cell adhesion mediated by glycosphingolipids-to-glycosphingolipids interaction between interfacing glycosynaptic domains, through head-to-head (trans) carbohydrate-to-carbohydrate interaction. (ii) Functional role of GM3 complexed with tetraspanin CD9, and interaction of such complex with integrins, or with fibroblast growth factor receptor, to control tumor cell phenotype and its reversion to normal cell phenotype. (iii) Inhibition of integrin-dependent Met kinase activity by GM2/tetraspanin CD82 complex in glycosynaptic microdomain. Data present here suggest that the organizational status of glycosynapse strongly affects cellular phenotype influencing tumor cell malignancy.

Carbohydrate recognition in neuronal development: structure and expression of surface oligosaccharides and beta-galactoside-binding lectins

The differentiation and development of vertebrate neurons is controlled in part by interactions with cell surface and extracellular matrix molecules, many of which are glycoproteins that mediate their developmental actions by homophilic or heterophilic binding to other glycoproteins. In addition there is increasing evidence that cell recognition and adhesion in some embryonic cell types involve interactions between cell surface oligosaccharides and complementary carbohydrate-binding proteins. Although a role for carbohydrate recognition in neuronal development has been proposed, the precise function of complex carbohydrate structures on neural cells has not been defined. To approach this problem, we have examined the structure and expression of cell surface oligosaccharides and carbohydrate-binding proteins by primary sensory neurons in the rat dorsal root ganglion (DRG). There are several functionally distinct subsets of DRG neurons, each of which conveys a different sensory modality to distinct target domains in the spinal cord. Monoclonal antibodies against defined oligosaccharide structures identify each of the major subsets of DRG neurons on the basis of their expression of a distinct set of complex oligosaccharides, derived from lacto-, globo- and ganglioseries backbone structures. In particular, small diameter DRG neurons involved in pain processing express beta-galactoside-based lactoseries oligosaccharides. DRG and spinal cord neurons also express two soluble beta-galactoside-binding proteins of relative molecular masses 14,500 and 29,000, termed RL-14.5 and RL-29, which represent potential ligands for lactoseries oligosaccharides. RL-14.5 is expressed by the majority of DRG neurons whereas RL-29 is restricted to the subset of small DRG neurons that express surface N-acetyllactosamine structures. RL-14.5 and RL-29 are expressed soon after the differentiation of DRG neurons and appear to be released from cultured DRG neurons. Rat brain cDNA clones encoding RL-14.5 have been isolated. The nucleotide and predicted amino acid sequence of RL-14.5 has confirmed that this lectin is highly homologous to soluble beta-galactoside-binding proteins in other vertebrate species. Northern blot analysis and in situ hybridization indicate that RL-14.5 mRNA is selectively expressed in sensory and motor neurons in the rat nervous system. The selective expression of lactoseries oligosaccharides and complementary beta-galactoside-binding lectins may contribute to the differentiation and/or development of these two classes of neurons.

Structure and function of glycosphingolipids and sphingolipids: recollections and future trends

Based on development of various methodologies for isolation and characterization of glycosphingolipids (GSLs), we have identified a number of GSLs with globo-series or lacto-series structure. Many of them are tumor-associated or developmentally regulated antigens. The major question arose, what are their functions in cells and tissues? Various approaches to answer this question were undertaken. While the method is different for each approach, we have continuously studied GSL or glycosyl epitope interaction with functional membrane components, which include tetraspanins, growth factor receptors, integrins, and signal transducer molecules. Often, GSLs were found to interact with other carbohydrates within a specific membrane microdomain termed "glycosynapse", which mediates cell adhesion with concurrent signal transduction. Future trends in GSL and glycosyl epitope research are considered, including stem cell biology and epithelial-mesenchymal transition (EMT) process.

Weak self-association in a carbohydrate system

The physiological importance of weak interactions between biological macromolecules (molar dissociation constants >10 microM) is now well recognized, particularly with regard to cell adhesion and immunological phenomena, and many weak interactions have been measured for proteins. The concomitant importance of carbohydrate-carbohydrate interactions has also been identified, although no weak interaction between pure carbohydrate systems has ever been measured. We now demonstrate for the first time to our knowledge using a powerful probe for weak interactions--sedimentation velocity in the analytical ultracentrifuge--that at least some carbohydrates (from the class of polysaccharides known as heteroxylans and demonstrated here to be biologically active) can show well-defined weak self-interactions of the "monomer-dimer" type frequently found in protein systems. The weak interaction between the heteroxylans is shown from a temperature dependence study to be likely to be hydrophobic in nature.

Membrane microdomain formation is crucial in epiboly during gastrulation of medaka

Membrane microdomain (microdomain) was isolated from early gastrula embryos. The isolated microdomain was characterized by enrichment of cholesterol and sphingomyelin, and by the presence of huge glycoproteins containing Lewis X structure. Importance of the microdomain in the progress of epiboly was assessed using methyl beta-cyclodextrin (MBCD) and C2-ceramide that disrupt microdomains through different mechanisms. Both reagents efficiently disrupted the microdomain structure and concomitantly impaired epiboly. Interestingly, when embryos pretreated with MBCD, a cholesterol-binding molecule, were exogenously supplemented with cholesterol, the embryos underwent not only reconstitution of the microdomain, but also complete restoration to the normal epiboly. Thus, normal or impaired development is reversibly controlled by the cholesterol-dependent formation or disruption of microdomains. The most typical phenotype of the microdomain-disrupted embryos is detachment of cells from the blastoderm, suggesting that a major contribution of microdomains to epiboly is cell adhesion of blastodermal cells.

Le(x) glycan mediates homotypic adhesion of embryonal cells independently from E-cadherin: a preliminary note

Le(x) glycan and E-cadherin (Ecad) are co-expressed at embryonal stem (ES) cells and embryonal carcinoma (EC) cells. While the structure and function of Ecad mediating homotypic adhesion of these cells have been well established, evidence that Le(x) glycan also mediates such adhesion is weak, despite the fact that Le(x) oligosaccharide inhibits the compaction process. To provide stronger evidence, we knocked out Ecad gene in EC and ES cells to establish F9 Ecad (-/-) and D3M Ecad (-/-) cells, which highly express Le(x) glycan but do not express Ecad at all. Both F9 Ecad (-/-) and D3M Ecad (-/-) cells displayed strong autoaggregation in the presence of Ca(2+), while PYS-2 cells, which express trace amount of Ecad and undetectable level of Le(x) glycan, did not display autoaggregation. In addition, F9 Ecad (-/-) and D3M Ecad (-/-) cells displayed strong adhesion to plates coated with Le(x) glycosphingolipid (III(3)FucnLc4Cer), in dose-dependent manner, in the presence of Ca(2+). Thus, ES or EC cells display autoaggregation and strong adhesion to Le(x)-coated plates in the absence of Ecad, further supporting the notion of Le(x) self-recognition (i.e., Le(x)-to-Le(x) interaction) in cell adhesion.

Increased apoptosis and skewed differentiation in mouse embryonic stem cells lacking the histone methyltransferase Mll2

Epigenetic regulation by histone methyltransferases provides transcriptional memory and inheritable propagation of gene expression patterns. Potentially, the transition from a pluripotent state to lineage commitment also includes epigenetic instructions. The histone 3 lysine 4 methyltransferase Mll2/Wbp7 is essential for embryonic development. Here, we used embryonic stem (ES) cell lines deficient for Mll2 to examine its function more accurately. Mll2-/- ES cells are viable and retain pluripotency, but they display cell proliferation defects due to an enhanced rate of apoptosis. Apoptosis was not relieved by caspase inhibition and correlated with decreased Bcl2 expression. Concordantly, Mll2 binds to the Bcl2 gene and H3K4me(3) levels are reduced at the binding site when Mll2 is absent. In vitro differentiation showed delays along representative pathways for all three germ layers. Although ectodermal delays were severe and mesodermal delays persisted at about three days, endodermal differentiation seemed to recover and overshoot, concomitant with prolonged Oct4 gene expression. Hence, Mll2 is not required for ES cell self-renewal or the complex changes in gene expression involved in lineage commitment, but it contributes to the coordination and timing of early differentiation decisions.

The expression and functions of glycoconjugates in neural stem cells

The mammalian central nervous system is organized by a variety of cells such as neurons and glial cells. These cells are generated from a common progenitor, the neural stem cell (NSC). NSCs are defined as undifferentiated neural cells that are characterized by their high proliferative potential while retaining the capacity for self-renewal and multipotency. Glycoconjugates carrying carbohydrate antigens, including glycoproteins, glycolipids, and proteoglycans, are primarily localized on the plasma-membrane surface of cells and serve as excellent biomarkers at various stages of cellular differentiation. Moreover, they also play important functional roles in determining cell fate such as self-renewal, proliferation, and differentiation. In the present review, we discuss the expression pattern and possible functions of glycoconjugates and carbohydrate antigens in NSCs, with an emphasis on stage-specific embryonic antigen-1, human natural killer antigen-1, polysialic acid-neural cell-adhesion molecule, prominin-1, gp130, chondroitin sulfate proteoglycans, heparan sulfate proteoglycans, cystatin C, galectin-1, glycolipids, and Notch.

Substrate discrimination by the human GTP fucose pyrophosphorylase

GTP-l-fucose pyrophosphorylase (GFPP, E. C. 2.7.7.30) catalyzes the reversible condensation of guanosine triphosphate and beta-l-fucose-1-phosphate to form the nucleotide-sugar GDP-beta-l-fucose. The enzyme functions primarily in the mammalian liver and kidney to salvage free l-fucose during the breakdown of glycolipids and glycoproteins. The mechanism by which this protein discriminates between substrate and nonsubstrate molecules has been elucidated for the first time in this study. The ability of GFPP to form nucleotide-sugars from a series of base-, ribose-, phosphate-, and hexose-modified precursor molecules has revealed that the enzyme active site senses a series of substrate substituents that drive substrate/nonsubstrate discrimination. These substituents alter the ability of the precursor molecule to interact with the enzyme, as measured by either changes in the Michaelis constant, K(m), the binding affinity, K(a), or through changes in enzymatic turnover, k(cat). In this work, the combined substrate binding and enzyme analysis has revealed that the nature of the purine base is the major determinant in substrate specificity, followed by the nature of the hexose-1-P, and finally by the ribose moiety. Binding is enthalpy-driven and does not involve proton transfer. For the majority of nucleotide-sugar analogues, binding to GFPP is entropically unfavorable; however, surprisingly, a few of the substrate analogues tested bind to GFPP with a favorable entropic term.

Characterization of glycoconjugate antigens in mouse embryonic neural precursor cells

Neuronal and glial cells organizing the central nervous system (CNS) are generated from common neural precursor cells (NPCs) during neural development. However, the expression of cell-surface glycoconjugates that are crucial for determining the properties and biological function of these cells at different stages of development has not been clearly defined. In this study, we investigated the expression of several stage-specific glycoconjugate antigens, including several b-series gangliosides GD3, 9-O-acetyl GD3, GT1b and GQ1b, stage-specific embryonic antigen-1 (SSEA-1) and HNK-1, in mouse embryonic NPCs employing immunocytochemistry and flow cytometry. In addition, several of these antigens were positively identified by chemical means for the first time. We further showed that the SSEA-1 immunoreactivity was contributed by both glycoprotein and glycolipid antigens, and that of HNK-1 was contributed only by glycoproteins. Functionally, SSEA-1 may participate in migration of the cells from neurospheres in an NPC cell culture system, and the effect could be repressed by anti-SSEA-1 antibody. Based on this observation, we identified beta1 integrin as one of the SSEA-1 carrier glycoproteins. Our data thus provide insights into the functional role of certain glycoconjugate antigens in NPCs during neural development.

Photoswitchable cluster glycosides as tools to probe carbohydrate-protein interactions: synthesis and lectin-binding studies of azobenzene containing multivalent sugar ligands

Synthetic cluster glycosides have often been used to unravel mechanisms of carbohydrate-protein interactions. Although synthetic cluster glycosides are constituted on scaffolds to achieve high avidities in lectin binding, there have been no known attempts to modulate the orientations of the sugar clusters with the aid of a functional scaffold onto which the sugar units are linked. Herein, we describe synthesis, physical, and lectin-binding studies of a series of alpha-D-mannopyranoside and beta-D-galactopyranosyl-(1-->4)-beta-D-glucopyranoside glycoclusters that are attached to a photoswitchable azobenzenoid core. These glycoclusters were synthesized by the amidation of amine-tethered glycopyranosides with azobenzene carbonyl chlorides. From kinetic studies, the cis forms of the azobenzene-glycopyranoside derivative were found to be more stable in aqueous solutions than in organic solvents. Molecular modeling studies were performed to estimate the relative geometries of the photoswitchable glycoclusters in the trans- and cis-isomeric forms. Isothermal titration calorimetry (ITC) was employed to assess the binding of these glycoclusters to lectins peanut agglutinin (PNA) and concanavalin A (Con A). Although binding affinities were enhanced several orders higher as the valency of the sugar was increased, a biphasic-binding profile in ITC plots was observed during few glycoclusters lectin-binding processes. The biphasic-binding profile indicates a "cooperativity" in the binding process. An important outcome of this study is that in addition to inherent clustering of the sugar units as a molecular feature, an induced clustering emanates because of the isomerization of the trans form of the azobenzene scaffold to the cis-isomeric form.

Carbohydrate-carbohydrate interaction as a major force initiating cell-cell recognition

Sponges were the earliest multicellular organisms to evolve through the development of cell recognition and adhesion processes mediated by cell surface proteoglycans. Information on sponges has an extra added value because, as a group, they are the oldest Metazoans alive and contribute more to our understanding of life on earth than knowledge of other animal groups. Although the proteoglycans are emerging as key players in various physiological and pathophysiological cellular events, little is known about the carbohydrate moiety of the proteoglycan molecule. Until recently there was no evidence provided for the existence of specific and biologically significant carbohydrate-carbohydrate interaction. We show here that the interaction between single oligosaccharides of surface proteoglycans is relatively strong (in the 200-300 piconewtons range) and in the same range as other relevant biological interactions, like those between antibodies and antigens. This carbohydrate-carbohydrate recognition is highly species-specific and perfectly mimics specific cell-cell recognition. Both the strength and the species-specificity of the carbohydrate-carbohydrate interaction are guaranteed by polyvalency, by compositional and architectural differences between carbohydrates, and by the arrangement of the carbohydrate chain in a three-dimensional context. Ca(2+)-ions are essential and probably provide coordinating forces. Our findings confirm the existence and character of species-specific carbohydrate-carbohydrate recognition fundamental to cell recognition and adhesion events.

Carbohydrate antigens expressed on stem cells and early embryonic cells

Lewis X antigen (Le(X)) is a marker of embryonic stem cells, embryonal carcinoma cells and multipotential cells of early embryos in the mouse. Le(X) is carried by branched, high-molecular weight poly-N-acetyllactosamines (embryoglycan). While embryoglycan is present in human embryonal carcinoma cells, Le(X) is not expressed in human embryonic stem cells, embryonal carcinoma cells or inner cell mass cells. Instead, these cells express SSEA-3 and SSEA-4, both of which are carried by globo-series glycolipids. Le(X) is a marker of primordial germ cells or multipotential stem cells derived from primordial germ cells both in the mouse and human. In other species of vertebrates, Le(X) is widely expressed in early embryonic cells and primordial germ cells, but the mode of expression is not completely conserved among species. Le(X) is expressed in neural stem cells from both humans and mice. Hematopoietic stem cells are not reported to express the above carbohydrate markers. A marker of these cells is CD34, a membrane-bound sialomucin. Another sialomucin, CD164 (MGC-24v) is expressed in hemotopoietic progenitor cells. As a function of Le(X) in stem cells, the promotion of integrin action is proposed, based on analyses of glycoproteins with the marker, cDNA transfection experiments and the inhibitory effects of an anti-Le(X) antibody. Most probably, Le(X) antigen as well as poly-N-acetyllactosamines play roles in the interactions on the same membrane. On the other hand, O-linked oligosaccharides on CD34 and CD164 are probably involved in the regulation of cell adhesion and proliferation via intercellular recognition.