Polarization and migration in the zebrafish posterior lateral line system
Left: A sketch of the PLLP showing side and top-down views, with leading (red) and trailing (green) cells on a stripe of CXCL12a. Right: A schematic diagram of signalling in the PLLP, showing the mutual inhibition between FGFR and WntR signalling. (Black text denotes model components, white text aides in interpretation of experiments.) FGF signaling inhibits Wnt signaling by determining expression of Dkk1; Wnt signaling cells express the gene sef that inhibits FGF signaling. WntR active cells are sources of both FGF and Wnt ligands. Experimentally, pea3 and lef1 expression levels are used to identify FGF and Wnt signalling, respectively. The WntR-FGFR activity polarization sets up chemokine polarization (CXCR4b vs CXCR7b). In our model, this leads to the creation of a gradient of CXCL12a that enables directed migration of the PLLP.