Planar Cell Polarity

Global Influence

Science Signaling  16 Dec 2008:
Vol. 1, Issue 50, pp. ec434
DOI: 10.1126/scisignal.150ec434

The planar cell polarity (PCP) pathway is required for convergent extension (CE), a morphogenetic process during which cells simultaneously migrate and intercalate to elongate the chordate body axis. Core PCP components are required cell-autonomously to establish and maintain polarity in cells undergoing CE, but the non–cell-autonomous signal that initially polarizes the cells has not yet been identified. New evidence from Shi et al. suggests that fibroblast growth factor 3 (FGF3) is the global signal that polarizes cells of the notochord during CE in the ascidian Ciona intestinalis. Signaling through the FGF receptor (FGFR) was required for CE in Ciona; expression of a dominant-negative form of FGFR in cells that give rise to the notochord resulted in a reduced number of lamellopodia, impaired polarization of lamellopodia, and failure of notochord cells to intercalate. The ligand FGF3 was expressed in the floorplate, ventral neural tube tissue dorsal to the forming notochord. Antisense morpholino-mediated disruption of FGF3 in the floorplate prevented CE and abolished polarization in notochord cells. Misexpression of FGF3 in neighboring tissues, including in the notochord itself, prevented normal cell intercalation, which suggests that FGF3 acted as an instructional, rather than permissive, signal in establishing polarity. The requirement for FGF signaling in CE extended to vertebrates, because inhibiting FGF signaling with a pharmacological agent prevented normal CE and prevented membrane localization of the core PCP component Dishevelled in Xenopus laevis mesoderm explants. These results are consistent with FGF signaling being an important part of the global polarity cue that initiates PCP pathway–mediated coordination of polarity during CE.

W. Shi, S. M. Peyrot, E. Munro, M. Levine, FGF3 in the floor plate directs notochord convergent extension in the Ciona tadpole. Development 136, 23–28 (2009). [Abstract] [Full Text]