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Neural cell adhesion molecule (N-CAM) is required for cell type segregation and normal ultrastructure in pancreatic islets.

Esni F, Täljedal IB, Perl AK, Cremer H, Christofori G, Semb H - J. Cell Biol. (1999)

Bottom Line: These data together with the polarized distribution of islet cell nuclei and Na+/K+-ATPase indicate that islet cell polarity is also affected.Finally, degranulation of beta cells suggests that N-CAM is required for normal turnover of insulin-containing secretory granules.Taken together, our results confirm in vivo the hypothesis that a cell adhesion molecule, in this case N-CAM, is required for cell type segregation during organogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Umeå University, S-901 87 Umeå, Sweden.

ABSTRACT
Classical cell dissociation/reaggregation experiments with embryonic tissue and cultured cells have established that cellular cohesiveness, mediated by cell adhesion molecules, is important in determining the organization of cells within tissue and organs. We have employed N-CAM-deficient mice to determine whether N-CAM plays a functional role in the proper segregation of cells during the development of islets of Langerhans. In N-CAM-deficient mice the normal localization of glucagon-producing alpha cells in the periphery of pancreatic islets is lost, resulting in a more randomized cell distribution. In contrast to the expected reduction of cell-cell adhesion in N-CAM-deficient mice, a significant increase in the clustering of cadherins, F-actin, and cell-cell junctions is observed suggesting enhanced cadherin-mediated adhesion in the absence of proper N-CAM function. These data together with the polarized distribution of islet cell nuclei and Na+/K+-ATPase indicate that islet cell polarity is also affected. Finally, degranulation of beta cells suggests that N-CAM is required for normal turnover of insulin-containing secretory granules. Taken together, our results confirm in vivo the hypothesis that a cell adhesion molecule, in this case N-CAM, is required for cell type segregation during organogenesis. Possible mechanisms underlying this phenomenon may include changes in cadherin-mediated adhesion and cell polarity.

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N-CAM affects the  epithelial cell morphology of  cadherin-expressing L cells.  Parental L cells and L cells  transfected with cDNAs for  murine E-cadherin (LE;  Nose et al., 1988) and N-cadherin (LN; Miyatani et al.,  1989) were transiently transfected with cDNAs encoding  murine N-CAM-120, N-CAM-140, and N-CAM-180. Except for N-CAM-120, which  did not localize to the cell  surface, all N-CAM isoforms  exhibited similar effects on L  cell morphology, independent  of cadherin expression. Results from parental L cells  and LE cells transfected with  N-CAM-140 are shown. (a  and b) Phase-contrast images  of L cells (a) and LE cells  (b). (c and d) Fluorescence  of eGFP in L cells (c) and LE  cells (d) transfected with  eGFP alone. No change in  cell morphology was observed. (e and f) Immunofluorescence staining of L cells  (e) and LE cells (f) transfected with N-CAM-140. Expression of N-CAM conferred similar effects on cell  morphology independently of  whether the transfected cells  exhibited a fibroblast-like or  epithelial-like cellular phenotype. N-CAM induced extensive neurite-like extensions or filopodia on the cells,  regardless of the mesenchymal or epithelial phenotype  of the cell lines. In LE cells  the majority of the transfected cells left the monolayer and migrated on top  of      neighboring cells. (g–j)  Double immunofluorescence stainings of N-CAM-140 transfected LE cells with  anti-N-CAM polyclonal antibody (g and i) and anti-E-cadherin mAb (h and j).  The majority of the transfected cells lost their typical  epithelial phenotype upon  N-CAM expression (g and h),  however, occasionally, transfected cells remained within  the monolayer (i and j).  While the polar distribution  of E-cadherin was lost in the  former cells, it remained unchanged in the latter cells.  Bars, 20 μm.
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Figure 7: N-CAM affects the epithelial cell morphology of cadherin-expressing L cells. Parental L cells and L cells transfected with cDNAs for murine E-cadherin (LE; Nose et al., 1988) and N-cadherin (LN; Miyatani et al., 1989) were transiently transfected with cDNAs encoding murine N-CAM-120, N-CAM-140, and N-CAM-180. Except for N-CAM-120, which did not localize to the cell surface, all N-CAM isoforms exhibited similar effects on L cell morphology, independent of cadherin expression. Results from parental L cells and LE cells transfected with N-CAM-140 are shown. (a and b) Phase-contrast images of L cells (a) and LE cells (b). (c and d) Fluorescence of eGFP in L cells (c) and LE cells (d) transfected with eGFP alone. No change in cell morphology was observed. (e and f) Immunofluorescence staining of L cells (e) and LE cells (f) transfected with N-CAM-140. Expression of N-CAM conferred similar effects on cell morphology independently of whether the transfected cells exhibited a fibroblast-like or epithelial-like cellular phenotype. N-CAM induced extensive neurite-like extensions or filopodia on the cells, regardless of the mesenchymal or epithelial phenotype of the cell lines. In LE cells the majority of the transfected cells left the monolayer and migrated on top of      neighboring cells. (g–j) Double immunofluorescence stainings of N-CAM-140 transfected LE cells with anti-N-CAM polyclonal antibody (g and i) and anti-E-cadherin mAb (h and j). The majority of the transfected cells lost their typical epithelial phenotype upon N-CAM expression (g and h), however, occasionally, transfected cells remained within the monolayer (i and j). While the polar distribution of E-cadherin was lost in the former cells, it remained unchanged in the latter cells. Bars, 20 μm.

Mentions: To examine whether N-CAM's effects on pancreatic endocrine cell morphology also applies to other cell types, and to assess more directly whether N-CAM can influence cadherin function, we performed a series of cell transfection experiments. It has previously been demonstrated that expression of cadherins in fibroblast cell lines results in the transition from a mesenchymal to an epithelial cell morphology (Nose et al., 1988). To determine whether N-CAM affects the epithelial phenotype of cadherin- expressing L cells, we transiently transfected parental L cells and L cells that expressed either E-cadherin (LE; Nose et al., 1988) or N-cadherin (LN; Miyatani et al., 1989) with cDNA constructs encoding N-CAM-120, N-CAM-140, and N-CAM-180. Both N-CAM-140 and N-CAM-180, but not N-CAM-120, induced extensive neurite-like extensions or filopodia on the cells, regardless whether the L cells expressed cadherins or not (Fig. 7, e–g). Notably, the majority of the N-CAM-expressing cells left the monolayer and migrated on top of neighboring cells (Fig. 7, e and f). Furthermore, thick protrusions were observed on the dorsal side of N-CAM-expressing cells (data not shown).


Neural cell adhesion molecule (N-CAM) is required for cell type segregation and normal ultrastructure in pancreatic islets.

Esni F, Täljedal IB, Perl AK, Cremer H, Christofori G, Semb H - J. Cell Biol. (1999)

N-CAM affects the  epithelial cell morphology of  cadherin-expressing L cells.  Parental L cells and L cells  transfected with cDNAs for  murine E-cadherin (LE;  Nose et al., 1988) and N-cadherin (LN; Miyatani et al.,  1989) were transiently transfected with cDNAs encoding  murine N-CAM-120, N-CAM-140, and N-CAM-180. Except for N-CAM-120, which  did not localize to the cell  surface, all N-CAM isoforms  exhibited similar effects on L  cell morphology, independent  of cadherin expression. Results from parental L cells  and LE cells transfected with  N-CAM-140 are shown. (a  and b) Phase-contrast images  of L cells (a) and LE cells  (b). (c and d) Fluorescence  of eGFP in L cells (c) and LE  cells (d) transfected with  eGFP alone. No change in  cell morphology was observed. (e and f) Immunofluorescence staining of L cells  (e) and LE cells (f) transfected with N-CAM-140. Expression of N-CAM conferred similar effects on cell  morphology independently of  whether the transfected cells  exhibited a fibroblast-like or  epithelial-like cellular phenotype. N-CAM induced extensive neurite-like extensions or filopodia on the cells,  regardless of the mesenchymal or epithelial phenotype  of the cell lines. In LE cells  the majority of the transfected cells left the monolayer and migrated on top  of      neighboring cells. (g–j)  Double immunofluorescence stainings of N-CAM-140 transfected LE cells with  anti-N-CAM polyclonal antibody (g and i) and anti-E-cadherin mAb (h and j).  The majority of the transfected cells lost their typical  epithelial phenotype upon  N-CAM expression (g and h),  however, occasionally, transfected cells remained within  the monolayer (i and j).  While the polar distribution  of E-cadherin was lost in the  former cells, it remained unchanged in the latter cells.  Bars, 20 μm.
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Figure 7: N-CAM affects the epithelial cell morphology of cadherin-expressing L cells. Parental L cells and L cells transfected with cDNAs for murine E-cadherin (LE; Nose et al., 1988) and N-cadherin (LN; Miyatani et al., 1989) were transiently transfected with cDNAs encoding murine N-CAM-120, N-CAM-140, and N-CAM-180. Except for N-CAM-120, which did not localize to the cell surface, all N-CAM isoforms exhibited similar effects on L cell morphology, independent of cadherin expression. Results from parental L cells and LE cells transfected with N-CAM-140 are shown. (a and b) Phase-contrast images of L cells (a) and LE cells (b). (c and d) Fluorescence of eGFP in L cells (c) and LE cells (d) transfected with eGFP alone. No change in cell morphology was observed. (e and f) Immunofluorescence staining of L cells (e) and LE cells (f) transfected with N-CAM-140. Expression of N-CAM conferred similar effects on cell morphology independently of whether the transfected cells exhibited a fibroblast-like or epithelial-like cellular phenotype. N-CAM induced extensive neurite-like extensions or filopodia on the cells, regardless of the mesenchymal or epithelial phenotype of the cell lines. In LE cells the majority of the transfected cells left the monolayer and migrated on top of      neighboring cells. (g–j) Double immunofluorescence stainings of N-CAM-140 transfected LE cells with anti-N-CAM polyclonal antibody (g and i) and anti-E-cadherin mAb (h and j). The majority of the transfected cells lost their typical epithelial phenotype upon N-CAM expression (g and h), however, occasionally, transfected cells remained within the monolayer (i and j). While the polar distribution of E-cadherin was lost in the former cells, it remained unchanged in the latter cells. Bars, 20 μm.
Mentions: To examine whether N-CAM's effects on pancreatic endocrine cell morphology also applies to other cell types, and to assess more directly whether N-CAM can influence cadherin function, we performed a series of cell transfection experiments. It has previously been demonstrated that expression of cadherins in fibroblast cell lines results in the transition from a mesenchymal to an epithelial cell morphology (Nose et al., 1988). To determine whether N-CAM affects the epithelial phenotype of cadherin- expressing L cells, we transiently transfected parental L cells and L cells that expressed either E-cadherin (LE; Nose et al., 1988) or N-cadherin (LN; Miyatani et al., 1989) with cDNA constructs encoding N-CAM-120, N-CAM-140, and N-CAM-180. Both N-CAM-140 and N-CAM-180, but not N-CAM-120, induced extensive neurite-like extensions or filopodia on the cells, regardless whether the L cells expressed cadherins or not (Fig. 7, e–g). Notably, the majority of the N-CAM-expressing cells left the monolayer and migrated on top of neighboring cells (Fig. 7, e and f). Furthermore, thick protrusions were observed on the dorsal side of N-CAM-expressing cells (data not shown).

Bottom Line: These data together with the polarized distribution of islet cell nuclei and Na+/K+-ATPase indicate that islet cell polarity is also affected.Finally, degranulation of beta cells suggests that N-CAM is required for normal turnover of insulin-containing secretory granules.Taken together, our results confirm in vivo the hypothesis that a cell adhesion molecule, in this case N-CAM, is required for cell type segregation during organogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Umeå University, S-901 87 Umeå, Sweden.

ABSTRACT
Classical cell dissociation/reaggregation experiments with embryonic tissue and cultured cells have established that cellular cohesiveness, mediated by cell adhesion molecules, is important in determining the organization of cells within tissue and organs. We have employed N-CAM-deficient mice to determine whether N-CAM plays a functional role in the proper segregation of cells during the development of islets of Langerhans. In N-CAM-deficient mice the normal localization of glucagon-producing alpha cells in the periphery of pancreatic islets is lost, resulting in a more randomized cell distribution. In contrast to the expected reduction of cell-cell adhesion in N-CAM-deficient mice, a significant increase in the clustering of cadherins, F-actin, and cell-cell junctions is observed suggesting enhanced cadherin-mediated adhesion in the absence of proper N-CAM function. These data together with the polarized distribution of islet cell nuclei and Na+/K+-ATPase indicate that islet cell polarity is also affected. Finally, degranulation of beta cells suggests that N-CAM is required for normal turnover of insulin-containing secretory granules. Taken together, our results confirm in vivo the hypothesis that a cell adhesion molecule, in this case N-CAM, is required for cell type segregation during organogenesis. Possible mechanisms underlying this phenomenon may include changes in cadherin-mediated adhesion and cell polarity.

Show MeSH
Related in: MedlinePlus