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Fig. 2. Evolutionarily conserved planar cell polarity (PCP) signaling pathway
controls diverse cellular behaviors during invertebrate and vertebrate
development. (A) Convergence and extension can be achieved during gastrulation
via distinct cellular activities: (a) in X. laevis mesoderm by
mediolateral intercalation; (b) in X. laevis neuroectoderm by
dorsally directed intercalation; and (c) in zebrafish lateral mesoderm by
combined anterior and dorsally directed migration. (B) The D.
melanogaster PCP pathway (shown in blue) mediates cell polarity in the
plane of epithelia (epithelial cells also exhibit apical-basal polarization,
shown in C). The vertebrate equivalent of this pathway, the non-canonical Wnt
signaling pathway (shown in red), is required for the mediolateral elongation
of mesenchymal mesodermal and epithelial neuroectodermal cells, which exhibit
such diverse behaviors as directed migration, and mediolateral and dorsal
intercalation (as shown in A). Modified, with permission, from Myers et al.
(Myers et al., 2002 ).
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