Cleavage stage mouse embryos share a common cell adhesion system with teratocarcinoma cells

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.

Epithelial E- and P-cadherins: role and clinical significance in cancer

E-cadherin and P-cadherin are major contributors to cell-cell adhesion in epithelial tissues, playing pivotal roles in important morphogenetic and differentiation processes during development, and in maintaining integrity and homeostasis in adult tissues. It is now generally accepted that alterations in these two molecules are observed during tumour progression of most carcinomas. Genetic or epigenetic alterations in E- and P-cadherin-encoding genes (CDH1 and CDH3, respectively), or alterations in their proteins expression, often result in tissue disorder, cellular de-differentiation, increased invasiveness of tumour cells and ultimately in metastasis. In this review, we will discuss the major properties of E- and P-cadherin molecules, its regulation in normal tissue, and their alterations and role in cancer, with a specific focus on gastric and breast cancer models.

Constitutive PtdIns(3,4,5)P3 synthesis promotes the development and survival of early mammalian embryos

Mammalian preimplantation embryos develop in the oviduct as individual entities, and can develop and survive in vitro, in defined culture media lacking exogenous growth factors or serum. Therefore, early embryos must generate intrinsic signals that promote their development and survival. In other cells, activation of class I phosphoinositide 3-kinase (PI3K) is a universal mechanism to promote cell proliferation and survival. Here, we examined whether PI3K is intrinsically activated during preimplantation development. Using GFP-tagged pleckstrin homology domains to monitor PtdIns(3,4,5)P(3) synthesis, we show that PI3K is constitutively activated in mouse preimplantation embryos. E-cadherin ligation promotes PtdIns(3,4,5)P(3) synthesis at sites of blastomere adhesion at all cleavage stages. In addition, in culture conditions that promote autocrine signalling, a second pool of PtdIns(3,4,5)P(3) is generated in the apical membrane of early stage blastomeres. We show that constitutive PtdIns(3,4,5)P(3) synthesis is necessary for optimal development to blastocyst and to prevent large-scale apoptosis at the time of cavitation.

Profiling of E-cadherin, β-catenin and Ca2+in embryo-uterine interactions at implantation

Establishment of early pregnancy is promoted by a complex network of signalling molecules that mediate cell-to-cell and cell-to-extracellular matrix communications between the receptive endometrium and the invasive trophectoderm. In this study, we have attempted to evaluate the expression profiles of cadherin and catenin during embryo implantation in the mouse. Western blotting studies along with immunocytochemical analysis revealed that E-cadherin is expressed rather ubiquitously in the uterine epithelial cells, distinct enrichment is observed on the apical membrane in the endometrium of peri-implantation uterus specifically at the implantation sites and not at the inter-implanation sites. beta-Catenin also is upregulated and is specifically restricted to apical membrane of epithelial cells of implantation sites. Progesterone induced expression of E-cadherin and 17beta-estradiol regulated the expression of catenin in implantation-delayed uteri. Interestingly, estradiol imparted negative modulation on cadherin expression when co-administered with progesterone. On the contrary, trophoblast exhibits a striking down regulation of cadherin, catenin and Ca(2+) at peri implanting stage. These observations suggest that the trophoblasts exhibited an invasive phenotype while the endometrial epithelium displayed an adhesive phenotype during the window of implantation. Thus, embryo implantation presents an instance where two interacting surfaces showed mutually complementing interaction phenotypes.

Defining the roles of beta-catenin and plakoglobin in cell-cell adhesion: isolation of beta-catenin/plakoglobin-deficient F9 cells

F9 teratocarcinoma cells in which beta-catenin and/or plakoglobin genes are knocked-out were generated and investigated in an effort to define the role of beta-catenin and plakoglobin in cell adhesion. Loss of beta-catenin expression only did not affect cadherin-mediated cell adhesion activity. Loss of both beta-catenin and plakoglobin expression, however, severely affected the strong cell adhesion activity of cadherin. In beta-catenin-deficient cells, the amount of plakoglobin associated with E-cadherin dramatically increased. In beta-catenin/plakoglobin-deficient cells, the level of E-cadherin and alpha-catenin markedly decreased. In these cells, E-cadherin formed large aggregates in cytoplasm and membrane localization of alpha-catenin was barely detected. These data confirmed that beta-catenin or plakoglobin is required for alpha-catenin to form complex with E-cadherin. It was also demonstrated that plakoglobin can compensate for the absence of beta-catenin. Moreover it was suggested that beta-catenin or plakoglobin is required not only for the cell adhesion activity but also for the stable expression and cell surface localization of E-cadherin.

In the first extracellular domain of E-cadherin, heterophilic interactions, but not the conserved His-Ala-Val motif, are required for adhesion

The classical cadherins, definitive proteins of the cadherin superfamily, are characterized functionally by their ability to mediate calcium-dependent cell aggregation in vitro. To test hypothetical mechanisms of adhesion, we have constructed two mutants of the chicken E-cadherin protein, one with the highly conserved His-Ala-Val (HAV) sequence motif reversed to Val-Ala-His (VAH), the other lacking the first extracellular domain (EC1). The inversion of HAV to VAH has no effect on the capacity of E-cadherin to mediate adhesion. Deletion of EC1 completely eliminates the ability of E-cadherin to mediate homophilic adhesion, but the deletion mutant is capable of adhering heterophilically to both unmutated E-cadherin and to the HAV/VAH mutant. These results demonstrate that the conserved HAV sequence motif is not involved in cadherin-mediated adhesion as has been suggested previously and supports the idea that in the context of the cell surface, cadherin-mediated cell-cell adhesion involves an interaction of EC1 with other domains of the cadherin extracellular moiety and not the "linear zipper" model, which posits trans interactions only between EC1 on apposing cell surfaces.

Maternal hyperglycemia alters glucose transport and utilization in mouse preimplantation embryos

Glucose utilization was studied in preimplantation embryos from normal and diabetic mice. With use of ultramicrofluorometric enzyme assays, intraembryonic free glucose in single embryos recovered from control and streptozotocin-induced hyperglycemic mice was measured at 24, 48, 72, and 96 h after mating. Free glucose concentrations dropped significantly in diabetics at 48 and 96 h, corresponding to the two-cell and blastocyst stages (48 h: diabetic 0.23 +/- 0.09 vs. control 2.30 +/- 0.43 mmol/kg wet wt; P < 0.001; 96 h: diabetic 0.31 +/- 0.29 vs. control 5.12 +/- 0.17 mmol/kg wet wt; P < 0.001). Hexokinase activity was not significantly different in the same groups. Transport was then compared using nonradioactive 2-deoxyglucose uptake and microfluorometric enzyme assays. The 2-deoxyglucose uptake was significantly lower at both 48 and 96 h in embryos from diabetic vs. control mice (48 h diabetic, 0.037 +/- 0. 003; control, 0.091 +/- 0.021 mmol . kg wet wt-1 . 10 min-1, P < 0. 05; 96 h diabetic, 0.249 +/- 0.008; control, 0.389 +/- 0.007 mmol . kg wet wt-1 . 10 min-1, P < 0.02). When competitive quantitative reverse transcription-polymerase chain reaction was used, there was 44 and 68% reduction in the GLUT-1 mRNA at 48 h (P < 0.001) and 96 h (P < 0.05), respectively, in diabetic vs. control mice. GLUT-2 and GLUT-3 mRNA values were decreased 63 and 77%, respectively (P < 0.01, P < 0.01) at 96 h. Quantitative immunofluorescence microscopy demonstrated 49 +/- 6 and 66 +/- 4% less GLUT-1 protein at 48 and 96 h and 90 +/- 5 and 84 +/- 6% less GLUT-2 and -3 protein, respectively, at 96 h in diabetic embryos. These findings suggest that, in response to a maternal diabetic state, preimplantation mouse embryos experience a decrease in glucose utilization directly related to a decrease in glucose transport at both the mRNA and protein levels.

Characteristics of actin fibers and ultrastructure of the contact regions involved in the separation of blastomeres of two-cell mouse embryos, frozen-thawed without the zona pellucida

Freezing of embryos deprived of the zona pellucida (ZP) decreases their survival rate immediately after thawing, and gives rise to the separation of their blastomeres in a high percentage of cases. We have studied the ultrastructure and the characteristics of actin fibers in the cell-to-cell contact region in mouse embryos frozen-thawed without the ZP at the two-cell stage. Our results indicate that most of the embryos that retain their blastomeres united after freezing and thawing show either the presence of a midbody, or a contact region with a close apposition of the plasma membranes but without an organized actin cortex in their contact region. Only a small percentage of embryos that retain their blastomeres united after freezing and thawing show a contact region with widely separated plasma membranes and an organized actin cytocortex.

Experimental manipulations of compaction and their effects on the phosphorylation of uvomorulin

Compaction of the eight-cell stage mouse embryo is a critical event in the generation of different cell types within the preimplantation embryo. Uvomorulin, a member of the cadherin family of cell adhesion molecules, is important during compaction and its phosphorylation increases early in the eight-cell stage, suggesting that this posttranslational modification may be important for compaction to proceed. We have assessed the importance of the phosphorylation of uvomorulin during compaction by preventing, reversing, or inducing adhesion prematurely. The only condition that affected the overall level of uvomorulin phosphorylation was the prevention of compaction through prolonged exposure of four-cell embryos to low Ca2+. This treatment reduced the level of uvomorulin phosphorylation in eight-cell embryos, and perturbed its localization to regions of cell-cell contact. Thus, whilst the phosphorylation of uvomorulin does not appear to regulate directly uvomorulin's adhesive function, it may be associated with the redistribution of uvomorulin during compaction.

The cytoskeleton and associated proteins during cleavage, compaction and blastocyst differentiation in the pig

The organization of the cytoskeleton during early pig embryogenesis was investigated by using fluorescence and electron microscopy. The early morphogenesis of the pig embryo differed from that of the mouse, the standard model of the early mammalian development. In the pig, both compaction and polarization were gradual, and definitive polarization of cell surface microville occurred first shortly before blastocyst formation; the compaction and polarization of the mouse embryo are completed as early as at the 8 cell stage. Furthermore, the pig morula undergoes cycles of compaction and decompaction throughout its development. Distinct changes in the distribution of actin and the actin-associated proteins alpha-fodrin, vinculin and E-cadherin coincided with these events. In the pig, all these molecules were evenly distributed at all aspects of the blastomeres during early cleavage and then gradually accumulated in regions of intercellular contacts toward the blastocyst stage; microfilaments in trophectoderm cells formed a cortical meshwork associated with apical microvilli and adherent junctions (zonula adherens). In the mouse, the corresponding changes occur earlier, at the 8 cell stage. Microtubules formed a network-like cortical layer beneath the microvilli at the free outer surfaces of pig blastomeres. Cytokeratin bundles were not observed until the early blastocyst, where they characteristically associated with newly formed desmosomes. In both species a close correlation between morphologically defined developmental stages and the organization of the cytoskeleton: actin and actin-associated proteins are involved in polarization and compaction, whereas the appearance of intermediate filament bundles coincides with the building of the first epithelium, the trophectoderm; it is in the timing of events that a contrast between species is observed.

Similar responses to pharmacological agents of 1,2-OAG-induced compaction-like adhesion of two-cell mouse embryo to physiological compaction

A comparison was made of responses to pharmacological agents between cell adhesion induced by an activator of Ca(2+)-phospholipid-dependent protein kinase (PKC) and physiological compaction in mouse embryos. An activator of PKC, 1-oleoyl-2-acetyl-sn-glycerol (1,2-OAG) induced the compaction-like adhesion of cells in two-cell embryos within 5-10 min and the adhesion lasted during the course of treatment for 1 h. W-7 and W-5 (calmodulin antagonists) and cytochalasin B and cytochalasin D (inhibitors of the polymerization of microfilaments) each completely interfered with the 1,2-OAG-induced adhesion of cells. Two-cell embryos having once shown evidence of cell adhesion in response to 1,2-OAG were decompacted when they were transferred to a medium that contained 1,2-OAG and any one of the agents described above. Colchicine and colcemid (inhibitors of the polymerization of microtubules) and tunicamycin (an inhibitor of N-linked protein glycosylation) each had no effect on the 1,2-OAG-induced adhesion of cells. In Ca(2+)-free medium, treatment with 1,2-OAG failed to induce any cell adhesion. These results are very similar to those reported for physiological compaction at the late eight-cell stage. Thus, the compaction-like adhesion of cells in mouse embryos at the two-cell stage appears to be a calmodulin-dependent process, requiring assembled microfilaments and extracellular Ca2+ ions but not microtubules or N-linked glycoproteins as is the case for the physiological compaction.

Cadherin-mediated cell-cell adhesion is perturbed by v-src tyrosine phosphorylation in metastatic fibroblasts

Rat 3Y1 cells acquire metastatic potential when transformed with v-src, and this potential is enhanced by double transformation with v-src and v-fos (Taniguchi, S., T. Kawano, T. Mitsudomi, G. Kimura, and T. Baba. 1986. Jpn. J. Cancer Res. 77:1193-1197). We compared the activity of cadherin cell adhesion molecules of normal 3Y1 cells with that of v-src transformed (SR3Y1) and v-src and v-fos double transformed (fosSR3Y1) 3Y1 cells. These cells expressed similar amounts of P-cadherin, and showed similar rates of cadherin-mediated aggregation under suspended conditions. However, the aggregates or colonies of these cells were morphologically distinct. Normal 3Y1 cells formed compacted aggregates in which cells are firmly connected with each other, whereas the transformed cells were more loosely associated, and could freely migrate out of the colonies. Overexpression of exogenous E-cadherin in these transformed cells had no significant effect on their adhesive properties. We then found that herbimycin A, a tyrosine kinase inhibitor, induced tighter cell-cell associations in the aggregates of the transformed cells. In contrast, vanadate, a tyrosine phosphatase inhibitor, inhibited the cadherin-mediated aggregation of SR3Y1 and fosSR3Y1 cells but had little effect on that of normal 3Y1 cells. These results suggest that v-src-mediated tyrosine phosphorylation perturbs cadherin function directly or indirectly, and the inhibition of tyrosine phosphorylation restores cadherin action to the normal state. We next studied tyrosine phosphorylation on cadherins and the cadherin-associated proteins, catenins. While similar amounts of catenins were expressed in all of these cells, the 98-kD catenin was strongly tyrosine phosphorylated only in SR3Y1 and fosSR3Y1 cells. Cadherins were also weakly tyrosine phosphorylated only in the transformed cells. The tyrosine phosphorylation of these proteins was enhanced by vanadate, and inhibited by herbimycin A. Thus, the tyrosine phosphorylation of the cadherin-catenin system itself might affect its function, causing instable cell-cell adhesion.

Injection of Antisense RNA specific for E-cadherin demonstrates that E-cadherin facilitates compaction, the first differentiative step of the mammalian embryo

We have investigated the effect of antisense E-cadherin RNA in the preimplantation mouse embryo. Antisense RNA was injected into each cell of two-cell embryos that were cultured for 2 days until the normal time of compaction and scored for abnormalities. Embryos injected with the antisense RNA showed delayed compaction compared to the embryos injected with control, or sense, RNA. Delayed cleavage was not the cause because nuclear staining with Hoechst dye 33258 showed about the same number of nuclei in both uncompacted embryos injected with antisense RNA compared with compacted embryos injected with sense RNA at the same hours post human chorionic gonadotropin (hCG). Immunofluorescence with a monoclonal antibody to E-cadherin was markedly diminished in embryos injected with antisense RNA compared with control, injected embryos, suggesting that the observed delayed compaction is due to the inhibition of E-cadherin gene expression by antisense RNA. Embryos injected with antisense RNA eventually compacted and then expressed E-cadherin, but at lower apparent levels than controls. Injection of a single blastomere at the two-cell stage created half-embryo abnormalities.

Sexing of rat embryos with antisera specific for male rats

Male-specific antigenicity (H-Y antigen) of rat embryos has been examined, and the feasibility of sexing rat embryos by use of H-Y antibodies has been studied. Rat H-Y antisera were produced by immunization of female Wistar rats with a homogenate of testes from male Wistar neonates. Male specificity of the antiserum (H-Y antibody) was determined by retention of cytotoxicity to male epidermal cells after absorption with female cells. After cultivation of rat embryos for 5 to 6 hr in the presence of antibody, half of the embryos were arrested at the morula stage. However, these embryos developed into blastocysts after removal of the antiserum, and then they grew into male young in recipient foster mothers. Eighty percent of the embryos that developed to blastocysts in the presence of the antiserum grew into female young.

Immunological evidence for the presence in sea urchin embryos of a cell adhesion protein similar to mouse uvomorulin (E-cadherin)

A tryptic fragment (88 kDa), obtained from external digestion of sea urchin embryos carried out in the presence of calcium, shows immunological cross-reactivity with polyclonal and monoclonal antibodies (DECMA-1) against mouse teratocarcinoma uvomorulin. Fab fragments obtained from anti-mouse terato-carcinoma uvomorulin mono- and polyclonal antibodies, and from polyclonal antibodies against the partially purified 88-kDa tryptic fragment, decompact early sea urchin embryos and block reaggregation of dissociated sea urchin blastula cells. These data indicate the presence of an uvomorulin-like protein in sea urchin embryos and suggest an important role for this protein in embryonic development.

Temporally specific involvement of cell surface beta-1,4 galactosyltransferase during mouse embryo morula compaction

Cell surface beta-1,4 galactosyltransferase (GalTase) is shown to mediate intercellular adhesions between embryonal carcinoma (EC) cells and specifically during late morula compaction in the preimplantation mouse embryo. Monospecific anti-GalTase IgG raised against affinity-purified bovine beta-1,4 GalTase recognizes F9 EC cell GalTase as judged by immunoprecipitation and inhibition of GalTase activity, as well as by immunoprecipitation of a single 52 kd metabolically labeled membrane protein. Anti-GalTase IgG inhibits cell adhesions between EC cells, dissociates compacted mouse morulae, and inhibits blastocyst formation. Anti-GalTase IgG specifically inhibits cell adhesions during late morula compaction, coincident with a peak of surface GalTase activity as determined by direct enzyme assay. On EC cells, GalTase activity can be proteolytically released from intact cells, and is localized by indirect immunofluorescence to areas of intercellular contact, consistent with its proposed role in cell adhesion. Beta-1,4 GalTase is the first cell adhesion molecule identified that participates during late morula compaction, subsequent to uvomorulin function.

Studies on cellular adhesion of Xenopus laevis melanophores: modulation of cell-cell and cell-substratum adhesion in vitro by endogenous Xenopus galactoside-binding lectin

We have investigated cell-cell and cell-substratum adhesion of Xenopus laevis neural crest cells at various stages of melanophore differentiation. Single-cell suspensions were obtained by trypsinization and aggregated in a cell-cell adhesion assay. Unpigmented cells did not adhere while the rate of adhesion of melanophores correlated with the degree of melanization. Melanophore cell-cell adhesion decreased significantly in the presence of beta-galactosidase, which suggests that cell-surface galactose is involved. Beta-galactoside-binding lectin has been isolated and purified from embryos at the stage of neural crest migration. When added to aggregating cells smaller, looser clusters formed compared to controls. When lectin was added to cells in stationary culture to test cell-substratum adhesion, melanophores spread more smoothly and formed more regular spacing patterns. These results suggest that this lectin can modulate receptors used in cell-cell and cell-substratum adhesion of melanophores.

A monoclonal antibody disrupting calcium-dependent cell-cell adhesion of brain tissues: possible role of its target antigen in animal pattern formation

The Ca2+-dependent cell-cell adhesion system (CDS) is thought to be essential for the formation and maintenance of cell adhesion in a wide variety of tissues. Previous studies suggested that CDS has some cell-type specificity; for example, the monoclonal antibody ECCD-1 selectively recognizes CDS of certain epithelial tissues in mouse embryos but not nervous tissues. In the present study, we have obtained a monoclonal antibody, designated NCD-1, that disrupts connections between brain cells of mouse embryos. A series of experiments suggested that NCD-1 specifically recognizes CDS. We then determined the distribution of the NCD-1 antigen in various mouse tissues. NCD-1 reacted with cells of the following tissues and cell lines: nervous tissues from various sources, lens, striated muscle, cardiac muscle, glioma G26-20, adrenocortical tumor Y1, and melanoma B16. None of these cells reacted with ECCD-1, and the cells reactive with ECCD-1 did not react with NCD-1. There was also a class of cells that did not react with either ECCD-1 or NCD-1. These results suggest that cells in the body can be classified into at least three groups containing CDS of differing specificities. A map of the tissue localization of these different classes of CDS also suggests that the expression of cell-type-specific cell adhesion molecules in each tissue plays a crucial role in adhesion between the same cell types and segregation of different cell types in processes essential for animal morphogenesis.

Cell surface glycoproteins mediate compaction, trophoblast attachment, and endoderm formation during early mouse development

Early mouse embryos undergo several morphogenetic processes, such as compaction, trophoblast attachment, and endoderm formation that can be studied in vitro. Several polyspecific and monospecific antisera have been used to perturb these processes in a nontoxic, reversible fashion. One of the antibody-defined molecules, cell CAM 120/80, promotes epithelial cell adhesion, embryo compaction, and endoderm formation. The results suggest the presence of another such molecule(s) involved in these same processes. Evidence is also presented that another set of antibody-defined molecules, GP 140, involved in attachment of somatic cells to the substrate, mediates trophoblast attachment of the mouse blastocyst. The possible role of these molecules in governing the processes leading to cell lineages in the mouse embryo is discussed.

Aggregation-deficient embryonal carcinoma cells: defects in peanut agglutinin (PNA) receptors

The components involved in cell adhesion were studied using the H6 line of embryonal carcinoma cells. H6 cells are especially suitable for studies on cell interactions, since genetic mutants can be selected, and various processes of cell adhesion can be controlled by regulating the calcium concentration in the medium. Three aggregation-defective variants of H6 were isolated, all of which showed reduced binding of the lectin, peanut agglutinin (PNA). Quantitation of PNA receptors on the cell surface by immunoprecipitation of iodinated surface proteins indicated that these receptors were reduced on the variants by one-half to one-quarter. The separation of immunoprecipitated PNA receptors on sodium-dodecyl-sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that one type of receptor, with an apparent molecular weight of 94 kilodaltons, was reduced. Parental and variant cells bind similar quantities of concanavalin A and soybean agglutinin, suggesting that there is no generalized effect on major glycoproteins. Thus, the defect in aggregation and the defect in the 94-kilodalton protein may be correlated, and this glycoprotein may have a role in the mediation of H6 cell-cell adhesion.

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

A multivalent lacto-N-fucopentaose (LNFP) III-lysyllysine conjugate was observed to decompact preimplantation mouse embryos. Decompaction was not obtained with free oligosaccharides (LNFP II and III), nor with multivalent LNFP II-lysyllysine or chitotriose-lysyllysine conjugates. These results suggest a role for X hapten recognition during compaction and suggest further that X hapten valency may play a key role in modulating this developmental process.

Oligosaccharides containing fucose linked alpha(1-3) and alpha(1-4) to N-acetylglucosamine cause decompaction of mouse morulae

Two- to four-cell and eight-cell mouse embryos were incubated in various fucosylated and unfucosylated oligosaccharides, fucose binding protein, and fucosylated BSA. Compaction at the eight-cell stage was reversed by a mixture containing the oligosaccharides lacto-N-fucopentaose II (80-90%), in which fucose is linked alpha(1-4) to N-acetylglucosamine, and lacto-N-fucopentaose III (10-20%), in which fucose is linked alpha(1-3) to N-acetylglucosamine. Pure lacto-N-fucopentaose III (LNFP III) and 3-fucosyl lactose (containing fucose alpha(1-3)glucose) had a similar effect. All three molecules affected blastocyst formation. Various closely related fucosylated and unfucosylated oligosaccharides did not induce decompaction or inhibit blastocyst formation. The proportion of embryos incubated from the two- to four-cell stage in LNFP II/III which reached the eight-cell stage and formed blastocysts was reduced. Those which formed compact morulae subsequently decompacted. Precompact or early compacting eight-cell embryos incubated in LNFP II/III compacted normally but subsequently decompacted and failed to form blastocysts. Decompaction of eight-cell embryos in LNFP II/III occurred during a specific period of development (80-90 hr post-hCG) and was reversible up to 84-86 hr post-hCG, but not by 92 hr post-hCG. The period of sensitivity to LNFP II/III was associated with the decrease in the ability of calcium-free medium to cause decompaction. It appears that LNFP II/III interferes with a later calcium-independent phase of compaction and we propose that LNFP III and II inhibit an endogenous lectin-saccharide interaction between membranes involved in the stabilization of compaction.

Molecular nature of the calcium-dependent cell-cell adhesion system in mouse teratocarcinoma and embryonic cells studied with a monoclonal antibody

The molecular nature of the Ca2+-dependent cell-cell adhesion system in mouse teratocarcinoma (t-CDS) was studied using a monoclonal antibody recognizing t-CDS. We isolated a hybridoma clone producing a monoclonal antibody (ECCD-1) able to disrupt cell-cell adhesion when added to monolayer cultures of teratocarcinoma cells. This antibody bound to the cells with intact t-CDS, resulting in an inhibition of their aggregation, but did not bind to cells from which t-CDS was removed by trypsin treatment in the absence of Ca2+. The binding of ECCD-1 to cell surfaces required Ca2+ but not other ions. Western blot analysis showed that ECCD-1 recognizes multiple cell surface proteins, the major one of which is a component with a molecular weight of 124,000. The binding of ECCD-1 to these antigens was Ca2+-dependent even in cell-free systems, suggesting that the molecules involved in t-CDS undergo conformational changes by binding with Ca2+, leading to conversion of their molecular structure into an active form. ECCD-1 also reacted with 8-cell stage mouse embryos and with certain types of epithelial cells (excluding fibroblastic cells) in various differentiated tissues collected from mouse fetuses, again affecting their cell-cell adhesion. We also showed that a monoclonal antibody (DE1) raised against gp84 (F. Hyafil et al., 1981, Cell 26, 447-454) recognizes the same antigens as ECCD-1.

The calcium-dependent cell-cell adhesion system regulates inner cell mass formation and cell surface polarization in early mouse development

The monoclonal antibody ECCD-1 inhibits Ca2+-dependent cell-cell adhesion in teratocarcinoma cells, recognizing a cell surface component of MW 124,000. When mouse embryos at various preimplantation stages were cultured in the presence of ECCD-1, the compacted morphology of the 8- to 16-cell-stage embryos was destroyed. In these embryos, cell proliferation normally occurred and development of blastocyst-like vesicles was attained. However, these embryos did not contain inner cell mass (ICM). We found that ECCD-1 affects the pattern of polarization of the cell surface in late 8- and 16-cell-stage blastomeres, as detected by staining with fluorescence-labeled concanavalin A. In normal blastomeres, the pole was always apart from the cell-cell contact plane. In those cultured in ECCD-1, formation of the pole tended to be inhibited, and if observed, the pole was close to the cell-cell contact plane. We discuss the possible mechanisms for inhibition of ICM formation caused by blocking Ca2+-dependent cell-cell adhesion between blastomeres.

Calcium-induced compaction and its inhibition in embryonal carcinoma cell aggregates

H6 embryonal carcinoma cells form aggregates of cells in culture medium which contains 2 mM calcium. These aggregates are described as uncompacted, indicating that the individual cells of the aggregate are spherical and are in limited contact with each other. In contrast, compaction of the aggregate, induced by increasing the calcium concentration, results in a tight mass of cells flattened against one another and connected by intercellular junctions. At least 85-97% of the aggregates undergo compaction in 7 mM calcium and are subsequently decompacted if removed to 2 mM calcium. Since calcium ionophore A23187 does not induce compaction, extracellular rather than intracellular calcium seems to be the limiting factor. We have demonstrated that this calcium-induced morphogenetic change is sensitive to inhibition by agents which also prevent the calcium-dependent compaction of the 8-cell mouse embryo. The cytoskeletal-binding drugs tetracaine HCl, colcemid, vinblastine, colchicine, and cytochalasin B each inhibit compaction of H6 aggregates. Interference at surface molecule sites by exposure to the lectins wheat germ agglutinin or concanavalin A or by interruption of glycosylation with exposure to tunicamycin, or by reaction with anti-H6 Fab or anti-F9, also prevent compaction. Since the mouse embryo and embryonal carcinoma cells share certain processes which are involved in initiating and maintaining compaction, these processes and their subsequent roles in differentiation may be examined using embryonal carcinoma cell aggregates.

Calcium-dependent cell-cell adhesion molecules common to hepatocytes and teratocarcinoma stem cells

The molecules involved in Ca2+-dependent cell-cell adhesion systems (CDS) in mouse hepatocytes were characterized and compared with those in teratocarcinoma cells. Fab fragments of antibody raised against liver tissues (anti-liver) inhibited Ca2+-dependent aggregation of both liver and teratocarcinoma cells. A monoclonal antibody raised against teratocarcinoma CDS (ECCD-1) also inhibited the Ca2+-dependent aggregation of these two cell types equally. These antibodies induced disruption of cell-cell adhesion in monolayers of hepatocytes. Thus, CDS in these two cell types are not immunologically distinctive. Immunochemical analyses with these antibodies showed that CDS in both hepatocytes and teratocarcinoma cells involved at least two classes of cell surface proteins with molecular weights of 124,000 and 104,000. ECCD-1 selectively bound to hepatocytes but not to fibroblastic cells in liver cell cultures. Thus, the molecular constitution of CDS in hepatocytes and teratocarcinoma stem cells is identical. As ECCD-1 reacts with other classes of embryonic and fetal cells, the molecules identified here could have a major role in cell-cell adhesion in various tissues at any developmental stage of animals.

Teratocarcinoma stem cell adhesion: the role of divalent cations and a cell surface lectin

We describe two additive systems of intercellular adhesion in teratocarcinoma stem cells (Nulli cell line). One component is divalent cation-dependent (Ca++ or Mg++) and the other involves a cell surface fucan/mannan-specific lectin, previously identified on stem cells by an erythrocyte rosetting assay. The existence of these two systems is inferred from the observation that reaggregation of stem cells was partially inhibited by the removal of divalent cations or by the presence of lectin inhibitors such as fucoidan, but reaggregation was completely blocked when the two conditions were combined. Our results are related to recent work describing a calcium-dependent system of intercellular adhesion in teratocarcinoma stem cells.