Cadherin switch marks germ layer formation in the diploblastic sea anemone Nematostella vectensis

Abstract

Morphogenesis is a shape-building process during development of multicellular organisms. During this process the establishment and modulation of cell-cell contacts play an important role. Cadherins, the major cell adhesion molecules, form adherens junctions connecting ephithelial cells. Numerous studies in Bilateria have shown that cadherins are associated with the regulation of cell differentiation, cell shape changes, cell migration and tissue morphogenesis. To date, the role of Cadherins in nonbilaterians is unknown. Here, we study the expression and the function of two paralogous classical cadherins, cadherin1 and cadherin3, in the diploblastic animal, the sea anemone Nematostella vectensis. We show that a cadherin switch is accompanying the formation of germ layers. Using specific antibodies, we show that both cadherins are localized to adherens junctions at apical and basal positions in ectoderm and endoderm. During gastrulation, partial EMT of endodermal cells is marked by a step-wise downregulation of cadherin3 and upregulation of cadherin1. Knockdown experiments show that both cadherins are required for maintenance of tissue integrity and tissue morphogenesis. This demonstrates that cnidarians convergently use cadherins to differentially control morphogenetic events during development.

Diverse cell junctions with unique molecular composition in tissues of a sponge (Porifera)

“…As we begin to examine cell adhesion in non-bilaterian lineages, there appears to be more mechanistic diversity than anticipated. For example, the cnidarian Nematostella vectensis has a conserved classical cadherin/catenin complex [16], but β-catenin is not always detected at cadherin-positive cell–cell adhesions in tissues [15, 61]. Likewise, sequence analyses of ctenophores indicate that they lack conserved cadherin/β-catenin interaction motifs [52], and a recent study indicates that β-catenin is altogether absent at cell–cell contacts in Mnemiopsis leidyi [62].…”

Neuronal and non-neuronal functions of the synaptic cell adhesion molecule, neurexin, inNematostella vectensis

“…Cortical F-actin staining showed that by the planula stage, ectoderm and endoderm layers were not properly attached to each other (Figure 4d,e, Supplementary Figure 12). On the other hand, staining of Cadherin 1 (NvCdh1), located in the apical and basal junctions of both ectoderm and endoderm layers of N. vectensis planula larva (Pukhlyakova et al 2019), suggested that homophilic cell-cell adhesion in the epithelial layers remains intact (Supplementary Figure 13). The detachment between ectoderm and endoderm caused by NvNrxnα3-1 knockdown became more pronounced at the polyp stage, and an abnormal "blister" appearance of the tentacles was observed (Figure 4f-h).…”

“…Antibodies against N. vectensis Cadherin1 (Cdh1) (v1g244010) were graciously shared by Prof. Ulrich Technau (University of Vienna). Planula larvae (3 dpf) were fixed and stained with Cdh1 antibody following (Pukhlyakova et al 2019) with few modifications. Samples were fixed for 1 h at 4°C with Lavdovsky's fixative (3.7% formaldehyde (FA), 50% ethanol, 4% acetic acid).…”

Muscular hydraulics drive larva-polyp morphogenesis

“…Animals were anesthetized in 7% MgCl 2 prior to fixation. Fixation was performed for 1 hour at room temperature either with 4% paraformaldehyde (EMS, E15710) in PBS with 0.1% Tween (PTw 0.1%, Sigma, P1379) for phosphorylated histone 3 antibody staining 85 (pH3, Sigma # 05-806, 1:100), or with Lavdovsky's fixative following the described protocol 42 (3.7% formaldehyde, 50% ethanol, 4% acetic acid) for Cadherin3 antibody detection (gift from Technau lab, 42 1:500). Animals were permeabilized in 10% DMSO (Thermo Fisher, 85190) in PBS for 20 minutes and washed with PBS with 0.2% Triton (Sigma, T8787) (PTx 0.2%), followed by 1-hour incubation in blocking buffer containing PTx 0.1%, 0.1% DMSO, 1% BSA (Sigma, A2153), and 5% Goat serum (Sigma, G9023).…”