Novel insight into the function and regulation of αN-catenin by Snail2 during chick neural crest cell migration

Abstract

The neural crest is a transient population of migratory cells that differentiates to form a variety of cell types in the vertebrate embryo, including melanocytes, the craniofacial skeleton, and portions of the peripheral nervous system. These cells initially exist as adherent epithelial cells in the dorsal aspect of the neural tube and only later become migratory after an epithelial-to-mesenchymal transition (EMT). Snail2 plays a critical role in mediating chick neural crest cell EMT and migration due to its expression by both premigratory and migratory cranial neural crest cells and its ability to down-regulate intercellular junctions components. In an attempt to delineate the role of cellular junction components in the neural crest, we have identified the adherens junction molecule neural alpha-catenin (αN-catenin) as a Snail2 target gene whose repression is critical for chick neural crest cell migration. Knock-down and overexpression of αN-catenin enhances and inhibits neural crest cell migration, respectively. Furthermore, our results reveal that αN-catenin regulates the appropriate movement of neural crest cells away from the neural tube into the embryo. Collectively, our data point to a novel function of an adherens junction protein in facilitating the proper migration of neural crest cells during the development of the vertebrate embryo.

The tight junction protein claudin-1 influences cranial neural crest cell emigration

“…HNK-1, a protein found on the surface of migratory neural crest cells (Bronner-Fraser, 1986), was increased on the electroporated side of 3/4 embryos electroporated with Claudin-1 MO but not in 5/5 controls (Fig 2i,j; yellow arrowhead in i). We also observed no change in cell proliferation via phospho-histone H3 (PH3) immunostaining (Fig 2k,l, 3/3 embryos)(Coles et al, 2007; Jhingory et al, 2010; Wu et al, 2011) or in cell death through a TUNEL assay (Fig 2m,n, 4/4 embryos)(Coles et al, 2007; Jhingory et al, 2010; Wu et al, 2011) or caspase 3 immunostaining (data not shown) in the neural tube and migratory neural crest cell population upon depletion of claudin-1.…”

“…A five base pair mismatch fluorescein-labeled claudin-1 control MO, 5’-AgACcGGAcCACAACCAAgAcCGC-3’, was used that does not target claudin-1 mRNA (mutated bases are in lower case, GeneTools, L.L.C). The MOs were introduced into chick embryos using a modified version of in ovo electroporation (Itasaki et al, 1999; Jhingory et al, 2010). Briefly, the MOs were electroporated at concentrations ranging from 0.5mM-1mM into the neural tube lumen at the midbrain axial level, and 2, 25V, 30 mSec pulses were applied across the embryo.…”

Resolving Time and Space Constraints During Neural Crest Formation and Delamination

“…Thus, all these data concur with the idea of transcriptional repression of cadherin-6B being a major triggering event at onset of EMT. This view is further supported by the observation that αN-catenin, a cytoskeleton-associated partner of cadherins, present in adherens junctions in premigratory NCC is also transcriptionally repressed by Snail-2 upon delamination and that manipulating its expression leads to the same outcomes as for cadherin-6B ( Jhingory, Wu, & Taneyhill, 2010). Interestingly, other studies suggest that, in addition to transcriptional regulation, the timing of NCC delamination is also defined by posttranscriptional regulation of cadherin-6B activity (Fairchild & Gammill, 2013).…”

Otic Mesenchyme Cells Regulate Spiral Ganglion Axon Fasciculation through a Pou3f4/EphA4 Signaling Pathway

“…ChIP was performed as described previously (Jhingory et al, 2010), but with minor modification. E15.5 cochleae were isolated in chilled PBS and then fixed for 20 minutes using 4% paraformaldehyde.…”