Planar Cell Polarity in Coordinated and Directed Movements - Current Topics in Developmental Biology - page 94

caudally by preventing from their ectopic migration ( Stockinger et al.,
2011 ). To clarify the issue of cell-non-autonomous function of PCP
during FMB neuron migration, a genetic-based conditional

loss-of-

function approach in time and in space will be required in future.

4.3. Collective migration of a group of epithelial
cells Mice AVE

Epithelial cells of the mouse AVE migrate as a group from the distal tip of the
mouse cylinder proximally and orient the future body axis prior to gastru-
lation. AVE cells migrate actively with basal protrusions to the direction of
their migration while undergoing cell intercalation both among themselves
and with the surrounding cells ( Migeotte et al., 2010; Srinivas et al., 2004;
Trichas et al., 2011 ). This directional migration is mediated by the formation
of rosette, which is defined by five cells or more meeting at the point/vertex
( Trichas et al., 2012 ). As AVE cells migrate anteriorly, the mean rosette
density increases in the visceral endoderm, although there is no
correlation between the spatial localization of rosettes and the direction of
their migration. Based on a mathematical model, the potential role for
the rosettes is proposed to ensure the coherent interaction between the
AVE cells. Importantly, embryos with disrupted PCP signaling show a
reduction in the rosette density, thereby exhibiting defective AVE
migration ( Trichas et al., 2012 ). Consistent with the notion that AVE
migration is a PCP-dependent process, Dvl2 is enriched in the lateral
membrane of migrating AVE cells ( Trichas et al., 2011 ). Despite the fact
that this strategy is similar to cells undergoing CE during Drosophila
germband extension ( Bertet et al., 2004; Blankenship et al., 2006 ), there
are differences between the two systems. While mouse AVE cells utilize
the rosettes by means of their coordination and coherence rather than
being related to their directionality, cells undergoing CE during
germband extension mediate to form and resolve the rosettes in a
directional manner, thereby being associated with the force generation
process underlying directionality. Further, CE during germband
extension is a PCP-independent process ( Zallen & Wieschaus, 2004 ).

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4.4. PCP mediating CE in tube elongation Cochlea

Epithelial cells of the mouse cochlear also undergo CE, contributing to the
elongation of the cochlear duct in the organ of Corti. This process involves
junctional remodeling reminiscent of rosette formation during Drosophila
germband extension ( Bertet et al., 2004; Blankenship et al., 2006 ).

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