Cadherin-dependent differential cell adhesion in Xenopus causes cell sorting in vitro, but not in the embryo

Abstract

SummaryAdhesion differences between cell populations are in principle a source of strong morphogenetic forces promoting cell sorting, boundary formation and tissue positioning, and cadherins are main mediators of cell adhesion. However, a direct link between cadherin expression, differential adhesion and morphogenesis has not yet been determined for a specific process in vivo. To identify such a connection, we modulated the expression of C-cadherin in the Xenopus laevis gastrula, and combined this with direct measurements of cell adhesion-related parameters. Our results show that gastrulation is surprisingly tolerant of overall changes in adhesion. Also, as expected, experimentally generated, cadherin-based adhesion differences promote cell sorting in vitro. Importantly, however, such differences do not lead to the sorting of cells in the embryo, showing that differential adhesion is not sufficient to drive morphogenesis in this system. Compensatory recruitment of cadherin protein to contacts between cadherin-deprived and -overexpressing cells could contribute to the prevention of sorting in vivo.

The cellular basis of tissue separation

“…The effect of manipulating cadherin levels and functions in normal embryonic tissues has been studied in the Xenopus gastrula, and the results did not support DAH: interference with cadherin adhesion did not affect normal tissue separation, while the artificial creation of adhesive differences failed to induce separation (Ninomiya et al, 2012). Sorting at the notochord boundary was found to be astonishingly resistant to the manipulation of cell adhesion (Reintsch et al, 2005;Fagotto et al, 2013).…”

“…The reconstitution of the separation process in mixed aggregates remains a simple and powerful assay with which to study the underlying mechanisms (e.g. Chen et al, 2009;Ninomiya et al, 2012). It is however crucial to remember that mere sorting into distinct clusters cannot be equated to separation (Fig.…”

“…The expression of a truncated paraxial protocadherin [PAPC; also known as protocadherin 8 (PCDH8)], for example, typically produces strikingly sharp interfaces (e.g. Chen et al, 2009), whereas a difference in cadherin levels does not (Foty and Steinberg, 2004;Ninomiya et al, 2012), suggesting that cells can cluster without necessarily forming a boundary.…”

Embryoids, organoids and gastruloids: new approaches to understanding embryogenesis

“…More recent efforts, however, have challenged this notion. Indeed, in some cases, the differential expression of cadherins does not lead to cell sorting in vivo or in embryoid bodies (Moore et al, 2009(Moore et al, , 2014Ninomiya et al, 2012). Taking into account that cells undergo active processes such as polarization, the in vivo and in vitro results can be reconciled.…”

Understanding Early Organogenesis Using a Simplified <em>In Situ</em> Hybridization Protocol in <em>Xenopus</em>

“…In Xenopus, as in most early embryos, the most commonly used assay for detecting the expression of a gene is whole mount in situ hybridization using labeled antisense RNA probes. The use of antibody staining to assess expression of a gene in Xenopus is becoming more common as researchers discover antibodies, usually raised against mammalian proteins, that cross react to the Xenopus homologue or generate their own [1][2][3] . However, the vast majority of studies on Xenopus organogenesis still utilize antisense RNA probes.…”