Cadherins regulate aggregation of pancreatic beta-cells in vivo

Development ◽  
1996 ◽  
Vol 122 (9) ◽  
pp. 2895-2902 ◽  
Author(s):  
U. Dahl ◽  
A. Sjodin ◽  
H. Semb
Keyword(s):  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Endocrine Cells ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Beta Catenin ◽  
Adhesive Properties ◽  
Pancreatic Islets Of Langerhans ◽  
E Cadherin

It is thought that the cadherin protein family of cell adhesion molecules regulates morphogenetic events in multicellular organisms. In this study we have investigated the importance of beta-cell cadherins for cell-cell interactions mediating the organization of endocrine cells into pancreatic islets of Langerhans. To interfere with endogenous cadherin activity in beta-cells during pancreatic development, we overexpressed a dominant negative mutant of mouse E-cadherin, lacking nearly all extracellular amino acids, in pancreatic beta-cells in transgenic mice. Expression of the truncated E-cadherin receptor displaced both E- and N-cadherin from pancreatic beta-cells. As a result, the initial clustering of beta-cells, which normally begins at 13.5-14.5 days postcoitum, was perturbed. Consequently, the clustering of endocrine cells into islets, which normally begins at 17.5-18 days postcoitum, was abrogated. Instead, transgenic beta-cells were found dispersed in the tissue as individual cells, while alpha-cells selectively aggregated into islet-like clusters devoid of beta-cells. Furthermore, expression of truncated E-cadherin in beta-cells resulted in an accumulation of beta-catenin in the cytoplasm. Thus, we have for the first time shown in vivo that cadherins regulate adhesive properties of beta-cells which are essential for the aggregation of endocrine cells into islets.

Selective disruption of E-cadherin function in early Xenopus embryos by a dominant negative mutant

Development ◽  
1994 ◽  
Vol 120 (4) ◽  
pp. 901-909 ◽  
Author(s):  
E. Levine ◽  
C.H. Lee ◽  
C. Kintner ◽  
B.M. Gumbiner
Keyword(s):  
Early Embryo ◽  
Dominant Negative ◽  
Full Length ◽  
Dominant Negative Mutant ◽  
Wild Type ◽  
Truncated Form ◽  
Adhesive Properties ◽  
Negative Mutant ◽  
E Cadherin

E-cadherin function was disrupted in vivo in developing Xenopus laevis embryos through the expression of a mutant E-cadherin protein lacking its cytoplasmic tail. This truncated form of E-cadherin was designed to act as a dominant negative mutant by competing with the extracellular interactions of wild-type endogenous E-cadherin. Expression of truncated E-cadherin in the early embryo causes lesions to develop in the ectoderm during gastrulation. In contrast, expression of a similarly truncated N-cadherin protein failed to cause the lesions. The ectodermal defect caused by the truncated E-cadherin is rescued by overexpression of wild-type E-cadherin, by co-injection of full-length E-cadherin RNA along with the RNA for the truncated form. Overexpression of full-length C-cadherin, however, is unable to compensate for the disruption of E-cadherin function and can actually cause similar ectodermal lesions when injected alone, suggesting that there is a specific requirement for E-cadherin. Therefore, E-cadherin seems to be specifically required for maintaining the integrity of the ectoderm during epiboly in the gastrulating Xenopus embryo. Differential cadherin expression reflects, therefore, the requirement for distinct adhesive properties during different morphogenetic cell behaviors.

Expression of a dominant negative cadherin mutant inhibits proliferation and stimulates terminal differentiation of human epidermal keratinocytes

1996 ◽  
Vol 109 (13) ◽  
pp. 3013-3023 ◽  
Author(s):  
A.J. Zhu ◽  
F.M. Watt
Keyword(s):  
Cell Adhesion ◽  
Terminal Differentiation ◽  
Intercellular Adhesion ◽  
Dominant Negative ◽  
Epidermal Keratinocytes ◽  
Dominant Negative Mutant ◽  
Beta Catenin ◽  
Human Epidermal Keratinocytes ◽  
Negative Mutant ◽  
E Cadherin

Cell adhesion molecules are not only required for maintenance of tissue integrity, but also regulate many aspects of cell behaviour, including growth and differentiation. While the regulatory functions of integrin extracellular matrix receptors in keratinocytes are well established, such functions have not been investigated for the primary receptors that mediate keratinocyte intercellular adhesion, the cadherins. To examine cadherin function in normal human epidermal keratinocytes we used a retroviral vector to introduce a dominant negative E-cadherin mutant, consisting of the extracellular domain of H-2Kd and the transmembrane and cytoplasmic domains of E-cadherin. As a control a vector containing the same construct, but with the catenin binding site destroyed, was prepared. High levels of expression of the constructs were achieved; the dominant negative mutant, but not the control, formed complexes with alpha-, beta- and gamma-catenin. In cells expressing the dominant negative mutant there was a 5-fold decrease in the level of endogenous cadherins and a 3-fold increase in the level of beta-catenin. Cell-cell adhesion and stratification were inhibited by the dominant negative mutant and desmosome formation was reduced. Expression of the mutant resulted in reduced levels of the alpha 2 beta 1 and alpha 3 beta 1 integrins and increased cell motility, providing further evidence for cross-talk between cadherins and the beta 1 integrins. In view of the widely documented loss of E-cadherin in keratinocyte tumours it was surprising that the dominant negative mutant had an inhibitory effect on keratinocyte proliferation and stimulated terminal differentiation even under conditions in which intercellular adhesion was prevented. These results establish a role for cadherins in regulating keratinocyte growth and differentiation and raise interesting questions as to the relative importance of cell adhesion-dependent and -independent mechanisms.

Glucose-dependent expansion of pancreatic beta-cells by the protein p8 in vitro and in vivo

2007 ◽  
Vol 115 (S 1) ◽  
Author(s):  
G Päth ◽  
A Opel ◽  
M Gehlen ◽  
V Rothhammer ◽  
X Niu ◽  
...  
Keyword(s):  
Beta Cells ◽  
Pancreatic Beta Cells

scholarly journals Role of Nectin in Formation of E-Cadherin–based Adherens Junctions in Keratinocytes: Analysis with the N-Cadherin Dominant Negative Mutant

2003 ◽  
Vol 14 (4) ◽  
pp. 1597-1609 ◽  
Author(s):  
Yoshinari Tanaka ◽  
Hiroyuki Nakanishi ◽  
Shigeki Kakunaga ◽  
Noriko Okabe ◽  
Tomomi Kawakatsu ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Cell Adhesion Molecule ◽  
Adherens Junctions ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Adhesion Activity ◽  
Negative Mutant ◽  
E Cadherin ◽  
Cell Cell

E-Cadherin is a Ca2+-dependent cell-cell adhesion molecule at adherens junctions (AJs) of epithelial cells. A fragment of N-cadherin lacking its extracellular region serves as a dominant negative mutant (DN) and inhibits cell-cell adhesion activity of E-cadherin, but its mode of action remains to be elucidated. Nectin is a Ca2+-independent immunoglobulin-like cell-cell adhesion molecule at AJs and is associated with E-cadherin through their respective peripheral membrane proteins, afadin and catenins, which connect nectin and cadherin to the actin cytoskeleton, respectively. We showed here that overexpression of nectin capable of binding afadin, but not a mutant incapable of binding afadin, reduced the inhibitory effect of N-cadherin DN on the cell-cell adhesion activity of E-cadherin in keratinocytes. Overexpressed nectin recruited N-cadherin DN to the nectin-based cell-cell adhesion sites in an afadin-dependent manner. Moreover, overexpression of nectin enhanced the E-cadherin–based cell-cell adhesion activity. These results suggest that N-cadherin DN competitively inhibits the association of the endogenous nectin-afadin system with the endogenous E-cadherin-catenin system and thereby reduces the cell-cell adhesion activity of E-cadherin. Thus, nectin plays a role in the formation of E-cadherin–based AJs in keratinocytes.

scholarly journals Nuclear Import of IκBα Is Accomplished by a Ran-Independent Transport Pathway

2000 ◽  
Vol 20 (5) ◽  
pp. 1571-1582 ◽  
Author(s):  
Shrikesh Sachdev ◽  
Sriparna Bagchi ◽  
Donna D. Zhang ◽  
Angela C. Mings ◽  
Mark Hannink
Keyword(s):  
Nuclear Import ◽  
Nuclear Export ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Nuclear Pore ◽  
Transport Pathway ◽  
Repeat Domain ◽  
Nuclear Export Receptor

ABSTRACT The inhibitor of kappa B alpha (IκBα) protein is able to shuttle between the cytoplasm and the nucleus. We have utilized a combination of in vivo and in vitro approaches to provide mechanistic insight into nucleocytoplasmic shuttling by IκBα. IκBα contains multiple functional domains that contribute to shuttling of IκBα between the cytoplasm and the nucleus. Nuclear import of IκBα is mediated by the central ankyrin repeat domain. Similar to previously described nuclear import pathways, nuclear import of IκBα is temperature and ATP dependent and is blocked by a dominant-negative mutant of importin β. However, in contrast to classical nuclear import pathways, nuclear import of IκBα is independent of soluble cytosolic factors and is not blocked by the dominant-negative RanQ69L protein. Nuclear export of IκBα is mediated by an N-terminal nuclear export sequence. Nuclear export of IκBα requires the CRM1 nuclear export receptor and is blocked by the dominant-negative RanQ69L protein. Our results are consistent with a model in which nuclear import of IκBα is mediated through direct interactions with components of the nuclear pore complex, while nuclear export of IκBα is mediated via a CRM1-dependent pathway.

Transgenic Xenopus embryos from sperm nuclear transplantations reveal FGF signaling requirements during gastrulation

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3173-3183 ◽  
Author(s):  
K.L. Kroll ◽  
E. Amaya
Keyword(s):  
Large Scale ◽  
Neural Induction ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Mesoderm Induction ◽  
Fgf Signaling ◽  
Fgf Receptor ◽  
Transgenic Expression

We have developed a simple approach for large-scale transgenesis in Xenopus laevis embryos and have used this method to identify in vivo requirements for FGF signaling during gastrulation. Plasmids are introduced into decondensed sperm nuclei in vitro using restriction enzyme-mediated integration (REMI). Transplantation of these nuclei into unfertilized eggs yields hundreds of normal, diploid embryos per day which develop to advanced stages and express integrated plasmids nonmosaically. Transgenic expression of a dominant negative mutant of the FGF receptor (XFD) after the mid-blastula stage uncouples mesoderm induction, which is normal, from maintenance of mesodermal markers, which is lost during gastrulation. By contrast, embryos expressing XFD contain well-patterned nervous systems despite a putative role for FGF in neural induction.

beta-catenin signalling modulates proliferative potential of human epidermal keratinocytes independently of intercellular adhesion

Development ◽  
1999 ◽  
Vol 126 (10) ◽  
pp. 2285-2298 ◽  
Author(s):  
A.J. Zhu ◽  
F.M. Watt
Keyword(s):  
Stem Cells ◽  
Intercellular Adhesion ◽  
Dominant Negative ◽  
Full Length ◽  
Epidermal Keratinocytes ◽  
Dominant Negative Mutant ◽  
Proliferative Potential ◽  
Beta Catenin ◽  
Epidermal Stem Cells ◽  
Armadillo Repeats

We found that cultured human keratinocytes with high proliferative potential, the putative epidermal stem cells, expressed a higher level of noncadherin-associated beta-catenin than populations enriched for keratinocytes of lower proliferative potential. To investigate the physiological significance of this, a series of beta-catenin constructs was introduced into keratinocytes via retroviral infection. Full-length beta-catenin and a mutant containing only nine armadillo repeats had little effect on proliferative potential in culture, the full-length protein being rapidly degraded. However, expression of stabilised, N-terminally truncated beta-catenin increased the proportion of putative stem cells to almost 90% of the proliferative population in vitro without inducing malignant transformation, and relieved the differentiation stimulatory effect of overexpressing the E-cadherin cytoplasmic domain. Conversely, beta-catenin lacking armadillo repeats acted as a dominant negative mutant and stimulated exit from the stem cell compartment in culture. The positive and negative effects of the beta-catenin mutants on proliferative potential were independent of effects on cell-cycle kinetics, overt terminal differentiation or intercellular adhesion, and correlated with stimulation or inhibition of transactivation of a TCF/LEF reporter in basal keratinocytes. We conclude that the elevated level of cytoplasmic beta-catenin in those keratinocytes with characteristics of epidermal stem cells contributes to their high proliferative potential.

scholarly journals Keratin 18 is an integral part of the intermediate filament network in murine skeletal muscle

2020 ◽  
Vol 318 (1) ◽  
pp. C215-C224 ◽  
Author(s):  
Joaquin M. Muriel ◽  
Andrea O’Neill ◽  
Jaclyn P. Kerr ◽  
Emily Kleinhans-Welte ◽  
Richard M. Lovering ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Type I ◽  
Mrna Levels ◽  
Force Transmission ◽  
Keratin 18 ◽  
Murine Skeletal Muscle

Intermediate filaments (IFs) contribute to force transmission, cellular integrity, and signaling in skeletal muscle. We previously identified keratin 19 (Krt19) as a muscle IF protein. We now report the presence of a second type I muscle keratin, Krt18. Krt18 mRNA levels are about half those for Krt19 and only 1:1,000th those for desmin; the protein was nevertheless detectable in immunoblots. Muscle function, measured by maximal isometric force in vivo, was moderately compromised in Krt18-knockout ( Krt18-KO) or dominant-negative mutant mice ( Krt18 DN), but structure was unaltered. Exogenous Krt18, introduced by electroporation, was localized in a reticulum around the contractile apparatus in wild-type muscle and to a lesser extent in muscle lacking Krt19 or desmin or both proteins. Exogenous Krt19, which was either reticular or aggregated in controls, became reticular more frequently in Krt19-null than in Krt18-null, desmin-null, or double-null muscles. Desmin was assembled into the reticulum normally in all genotypes. Notably, all three IF proteins appeared in overlapping reticular structures. We assessed the effect of Krt18 on susceptibility to injury in vivo by electroporating siRNA into tibialis anterior (TA) muscles of control and Krt19-KO mice and testing 2 wk later. Results showed a 33% strength deficit (reduction in maximal torque after injury) compared with siRNA-treated controls. Conversely, electroporation of siRNA to Krt19 into Krt18-null TA yielded a strength deficit of 18% after injury compared with controls. Our results suggest that Krt18 plays a complementary role to Krt19 in skeletal muscle in both assembling keratin-based filaments and transducing contractile force.

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