It could complex or otherwise interact with other transmembrane proteins and modulate signaling pathways necessary for CNC migration

It could complex or otherwise interact with other transmembrane proteins and modulate signaling pathways necessary for CNC migration. a key role in immune defense through chemotactic responses of leukocytes and in tissue repair and regeneration. Surprisingly, many migrating cells start out as epithelial cells. These are immobile, highly polarized cells with strong cell-cell adhesions mediated by Adherens Junctions (intercellular junctions that join the actin cytoskeleton of each cell to the plasma membrane and form adhesive contacts between cells), and Tight Junctions (intercellular junctions that result in close juxtaposition of plasma membranes creating a permeability barrier). These adhesive properties, which result from interactions of cell-cell attachment proteins belonging to the cadherin family, give epithelia mechanical resilience and barrier function. Epithelial cells are ill equipped to perform cell migration, which typically requires a decrease in cell-cell adhesion, an increase in cell-extracellular matrix adhesions and activation of the actin-myosin based cytoskeleton (Ridley et al., PP1 2003). While epithelium can undergo collective cell migration during embryogenesis (Montell et al., 2012), often the acquisition of cell motility is usually associated with an epithelium to mesenchyme transition (EMT). This is achieved notably by modulating the expression and activity of cadherins, which mediate intercellular junctions. A comprehensive review of all the cellular changes occurring during EMT has been published elsewhere (Nieto et al., 2016). Note that the full conversion from epithelial to mesenchyme does not have to be complete for cells to migrate and a couple of metastable says of EMT have now been described where cells undergo efficient migration while maintaining strong cell-cell contact (Nieto et al., 2016). The cranial neural crest (CNC) migrates MIHC in such a way (Alfandari et al., 2003). The goal of this article is usually to review and revisit the role of some of the cadherins (namely E-cadherin, N-cadherin and cadherin-11) during the migration of Xenopus CNC. 2. Xenopus Cranial Neural Crest During early development of vertebrate embryos, the neural crest cells (NC) emerge from the sensory layer of the ectoderm, more specifically at the transition between the neural (future central nervous system) and non-neural (epidermis) ectoderm (Fig. 1A). Once induced, the CNC will stay stationary for a while, a phase called pre-migratory stage. Starting at the late neurula stage, these cells enter their migratory stage and acquire motility. The directionality of their migration depends on their antero/posterior origin: most cells will migrate ventrally but some, like the ones originating from the nuchal area or caudal area (called vagal and sacral crest), can also migrate antero/posteriorly. Once the cells reach their destination, they will differential into a variety of cell types and tissue (Le Douarin, 1980). The cranial neural crest (CNC) represents a subgroup of these cells that emerge at the most anterior part of the neural tissue. These cells distinguish themselves from the other NC in at least three ways. They are the first to emerge, segregating themselves from the neuroectoderm and emigrating well before the end of neurulation (Fig. 1A). Secondly, they undergo collective cell migration. Thirdly, they give rise to a wider array of derivatives than any other NC types, some of them specific of the cranial lineage (endothelial cells, chondrocytes and osteocytes of all of the viscerocranium and most of the neurocranium and odontoblasts). Open in a separate windows Fig. 1 Origin and migration of the cranial neural crest cells in ventrally). Once the placodes and CNC are separated, the Sdf1-based chemoattraction reasserts itself. This chase and run contributes to the proper migration of the each of the CNC segments while the placodes lying in the PP1 path of the CNC (Epibranchial placodes) reach their proper dorsoventral location and are shaped into narrow strips of tissues. Ot: Placode; NT, neural tube; n: notochord; psm: presomitic mesoderm, so: somites; LPM: lateral plate mesoderm, CG: cement gland; Op: optic vesicle. Wilhem His has discovered the neural crest in 1968 and their embryological origin and derivatives have been extensively studied in chicken and amphibian for the better part of the 20th century (H?rstadius, 1950; Le Douarin, 1980). The molecular underpinnings of NC development have been investigated more recently using a wider array of model PP1 systems including zebrafish and mouse. studies, while PP1 more recent, have made a sizable contribution to the CNC field. The development of classical embryological techniques (CNC grafts, explants and targeted injections), coupled to the well described strengths of the Xenopus model system (fertilization, development, strong biochemical tools) and the emergence of better molecular biology tools were instrumental in the rise of Xenopus as model system.