E-cadherin is required for cranial neural crest migration in Xenopus laevis

Abstract

The cranial neural crest (CNC) is a highly motile and multipotent embryonic cell population, which migrates directionally on defined routes throughout the embryo, contributing to facial structures including cartilage, bone and ganglia. Cadherin-mediated cell-cell adhesion is known to play a crucial role in the directional migration of CNC cells. However, migrating CNC co-express different cadherin subtypes, and their individual roles have yet to be fully explored. In previous studies, the expression of individual cadherin subtypes has been analysed using different methods with varying sensitivities, preventing the direct comparison of expression levels. Here, we provide the first comprehensive and comparative analysis of the expression of six cadherin superfamily members during different phases of CNC cell migration in Xenopus. By applying a quantitative RT-qPCR approach, we can determine the copy number and abundance of each expressed cadherin through different phases of CNC migration. Using this approach, we show for the first time expression of E-cadherin and XB/C-cadherin in CNC cells, adding them as two new members of cadherins co-expressed during CNC migration. Cadherin co-expression during CNC migration in Xenopus, in particular the constant expression of E-cadherin, contradicts the classical epithelial-mesenchymal transition (EMT) model postulating a switch in cadherin expression. Loss-of-function experiments further show that E-cadherin is required for proper CNC cell migration in vivo and also for cell protrusion formation in vitro. Knockdown of E-cadherin is not rescued by co-injection of other classical cadherins, pointing to a specific function of E-cadherin in mediating CNC cell migration. Finally, through reconstitution experiments with different E-cadherin deletion mutants in E-cadherin morphant embryos, we demonstrate that the extracellular domain, but not the cytoplasmic domain, of E-cadherin is sufficient to rescue CNC cell migration in vivo.

Cadherins function during the collective cell migration of Xenopus Cranial Neural Crest cells: revisiting the role of E-cadherin

“…This allows the isolation of a population of CNC free of any neural, placodal, ectodermal or mesodermal contaminants hours before they migrate. The purity of these explants has been ascertained by in situ hybridization (Alfandari et al, 2003) and qRT-PCR (Huang et al, 2016). Incidentally, these explants can also be performed at the post-migratory stage (Huang et al, 2016) (H. Cousin, unpublished observations).…”

“…The purity of these explants has been ascertained by in situ hybridization (Alfandari et al, 2003) and qRT-PCR (Huang et al, 2016). Incidentally, these explants can also be performed at the post-migratory stage (Huang et al, 2016) (H. Cousin, unpublished observations). Another advantage of the Xenopus system is that the geometry of their embryos makes them amenable to time-lapse imaging in vivo .…”

“…While the downregulation of E-cadherin and the up-regulation of N-cadherin is often used as an indicator of EMT, data are accumulating showing that this downregulation may not be strictly required for the acquisition of cell motility, at least in some instances such as mesoderm ingression or the metastasis of certain types of cancer (discussed below). New findings by Huang and colleagues show that in CNC, E-cadherin protein function may in fact be required for cell migration and we will discuss their results in the last section of this review (Huang et al, 2016). …”

“…The neural crest studies done so far, performed in majority on trunk neural crest inferred that the “swap” between E and N-cadherin is employed to initiate their migration. However, the data recently accumulated on the CNC in chick, mouse and now Xenopus seems to indicate that a remnant of E-cadherin is still present in these CNC and may have a physiological role to play during their migration (Dady et al, 2012; Huang et al, 2016; Lee et al, 2013). It implies that the cadherin switch in that case fit with the model of a rheostat.…”

“…This is understandable as the authors did not expect to have any expression of E-cadherin in migrating CNC and were therefore using the gain of function approach in the migrating CNC stages. Huang and colleagues have furthered the investigation of E-cadherin role during CNC migration (Huang et al, 2016). …”