Abstract
Following epithelial-mesenchymal transition, acquisition of avian trunk neural crest cell (NCC) polarity is prerequisite for directional delamination and migration, which in turn is essential for peripheral nervous system development. However, how this cell polarization is established and regulated remains unknown. Here we demonstrate that, using the RHOA biosensor in vivo and in vitro, the initiation of NCC polarization is accompanied by highly activated RHOA in the cytoplasm at the cell rear and its fluctuating activity at the front edge. This differential RHOA activity determines polarized NC morphology and motility, and is regulated by the asymmetrically localized RhoGAP Deleted in liver cancer (DLC1) in the cytoplasm at the cell front. Importantly, the association of DLC1 with NEDD9 is crucial for its asymmetric localization and differential RHOA activity. Moreover, NC specifiers, SOX9 and SOX10, regulate NEDD9 and DLC1 expression, respectively. These results present a SOX9/SOX10-NEDD9/DLC1-RHOA regulatory axis to govern NCC migratory polarization.
Highlights
Following epithelial-mesenchymal transition, acquisition of avian trunk neural crest cell (NCC) polarity is prerequisite for directional delamination and migration, which in turn is essential for peripheral nervous system development
Moderate level of RHOA activity is detected and uniformly distributed throughout neuroepithelial cells in the neural tube (Supplementary Fig. 1a, b). These results indicate that NCCs display differential RHOA activity in subcellular localization as they undergo directional delamination and migration
To further interrogate whether this differential RHOA activity is maintained as NCCs change in migratory direction, emigrating NCCs from neural tube explants were exposed to beads coated with stromal cell derived factor 1 (SDF-1), which is a chemoattractant for trunk NCCs16, to mimic the in vivo environment
Summary
Following epithelial-mesenchymal transition, acquisition of avian trunk neural crest cell (NCC) polarity is prerequisite for directional delamination and migration, which in turn is essential for peripheral nervous system development. In this study, using a fluorescence resonance energy transfer (FRET)-based biosensor for RHOA in chick embryos and live-cell imaging in vitro, we demonstrate that high RHOA activity in the cytoplasm defines the prospective rear of delaminating and migratory trunk NCCs while fluctuating RHOA activity in the membrane protrusion at the cell front. This differential RHOA activity is regulated by asymmetric localization of the RhoGAP Deleted in liver cancer 1 (DLC1) in the cytoplasm at the cell front. These results reveal a SOX9/SOX10NEDD9/DLC1-RHOA regulatory axis to orient trunk NCCs in the direction of movement
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