Dominant negative expression of a cytoplasmically deleted mutant of XB/U-cadherin disturbs mesoderm migration during gastrulation in Xenopus laevis

Abstract

XB/U-cadherin is a maternal Xenopus cadherin which mediates interblastomere adhesion in early embryogenesis. In order to explore its role in gastrulation, we expressed a cytoplasmic deletion mutant of XB/U-cadherin (XB delta c38) under the control of the CMV promoter in Xenopus embryos. This truncated XB-cadherin fails to form complexes with catenins and does not mediate cell-cell aggregation as shown by transfection of mouse Ltk- cells. Injections of the deletion for XB/U-cadherin into the dorsal-marginal region of four cell stage embryos resulted in a dominant negative expression of the cadherin mutant after MBT. Two different phenotypes were observed in a dose dependent manner: high doses (125-250 pg DNA) led to severe distortions of the gastrulation movement. Involution of the mesoderm was impaired, posterior mesoderm migrated laterally around the blastopore and formed two bands of axial tissue. Low doses (up to 50 pg DNA) resulted in embryos of a posteriorized phenotype with disorganized neural structures. Both phenotypes could be rescued by coinjection of cDNA constructs containing wild-type XB/U-cadherin. Injections of constructs encoding a XB/U-cadherin protein truncated both in its extracellular and cytoplasmic domains yielded normal phenotypes. These results suggest that a proper function of XB/U-cadherin is essential for mesoderm movements during gastrulation.

Regulated adhesion as a driving force of gastrulation movements

“…Introductionfrom flies to mice (Babb and Marrs, 2004;Ciruna and Rossant, 2001;Kühl et al, 1996;Lee and Gumbiner, 1995;Wang et al, 2004). However, as already postulated in 1976 by Albert Harris (Harris, 1976) and theoretically demonstrated by G. Wayne Brodland (Brodland, 2003), recent experimental evidence indicates that, in addition to cell adhesion, cell affinity is influenced by intracellular mechanics and cell surface tension (Krieg et al, 2008;Ninomiya and Winklbauer, 2008).…”

“…2). Both their extra-and intracellular domains are required for proper gastrulation movements (Kühl et al, 1996;Lee and Gumbiner, 1995). During Xenopus gastrulation, adherens junctions (AJs) formed by E-cadherin/catenin complexes are restricted to the outer ectodermal layer and contribute to the apical constriction of bottle cells (Merzdorf et al, 1998;Schneider et al, 1993).…”

“…Epithelialization of blastoderm; AJ and monolayer maintenance in ectoderm during gastrulation; delamination of NBs during neurogenesis (Tepass et al, 1996;Wang et al, 2004); segregation and internalization of amnioserosa (Laplante and Nilson, 2006). C/XB-cadherin Xenopus Ectoderm and mesoderm morphogenesis (Kühl et al, 1996;Lee and Gumbiner, 1995;Winklbauer et al, 1992). N-cadherin (also known as Cadherin 2) Zebrafish CE of mesoderm (Warga and Kane, 2007); dispensable for gastrulation in Drosophila and mouse (Derycke and Bracke, 2004 (Abe and Takeichi, 2008;Drees et al, 2005;Weis and Nelson, 2006).…”

Shield formation at the onset of zebrafish gastrulation

“…During Xenopus and zebrafish gastrulation, the over or underexpression of paraxial protocadherin (papc) leads to defects in convergence and extension of the forming embryonic body axis (Hukriede et al, 2003;Kim et al, 1998;Yamamoto et al, 1998). Furthermore, when XB/U-or EP/C-Cadherin function is blocked at the onset of Xenopus gastrulation, both mesodermal progenitor cell involution and migration, as well as germ layer separation, are affected (Kuhl et al, 1996;Lee and Gumbiner, 1995;Wacker et al, 2000). Finally, inactivating E-Cadherin in Xenopus and zebrafish embryos causes variable defects before and during gastrulation, including impaired prechordal plate formation and migration in zebrafish and ectodermal lesions in Xenopus (Babb and Marrs, 2004;Levine et al, 1994).…”

receptor tyrosine phosphataseψ is required for Delta/Notch signalling and cyclic gene expression in the presomitic mesoderm

“…How Wnt signalling is translated into convergent extension movements during gastrulation is poorly understood, but it clearly involves changes in the adhesive properties of cells, e.g. via regulated decreases in the activity of cell adhesion molecules such as cadherins (Kuhl et al, 1996;Marsden and deSimone, 2003). Non-canonical Wnt signalling seems not to be required for the segmentation clock, as we have shown that oscillator behaviour is normal in kny mutants (Fig.…”