Biomedical Engineering Reference
In-Depth Information
of oriented cell division, acting as a global cue in the
Drosophila
wing (
Mao
et al., 2011; Rogulja et al., 2008
). Thus, both Wnt/PCP and Fat-Ds
pathways can contribute to tissue elongation. Despite its requirement for
this process, Wnt/PCP-mediated orientated cell division does not
account for the elongation of the body axis, reemphasizing a primary role
of theWnt/PCP pathway in regulating cell intercalation during gastrulation.
Likewise, other processes, in which Wnt/PCP signal has been proposed
to mediate CE or collective migration, require reassessment as to whether or
not Wnt/PCP signal mediates oriented cell division, accounting for tissue
elongation or directionality. For example, during cochlear tube elongation,
it appears that significant tissue growth contributes to the elongation and that
the Fat-Ds pathway is involved in this process as well as the Wnt/PCP path-
way. Therefore, it requires assessment for new regulators as to what is a pri-
mary cause and which pathway to interact rather than judging by the
terminal phenotype. Similarly, it is plausible that oriented cell division
mediated by the Wnt/PCP pathway may in part account for collective mi-
gration of mouse AVE cells as significant tissue growth is occurring during
their migration.
6. CONCLUDING REMARKS
A variety of different developmental processes underlying collective
cell migration and cell intercalation utilize the Wnt/PCP pathway as a con-
served genetic module, regardless of the size of cell populations in both mes-
enchymal and epithelial tissues. The concept of planar polarization applies to
understanding of how cells communicate and coordinate in the plane of the
tissue. Despite the enormous progress in identification of the modulators of
the PCP pathway and of the biological processes involving the PCP path-
way, little is known about the cell-nonautonomous mechanisms by which
the cells know where they are within the tissue and propagate the signal(s) to
their neighbors. Further identification of novel cellular and developmental
processes utilizing the PCP pathway and of genetic pathway(s) that interact
or counteract with the PCP pathway will provide us with the clues to
understanding of the cell-nonautonomous mechanisms underlying the co-
ordination and directionality of cells.
ACKNOWLEDGMENTS
We thank Roberto Mayor and Shankar Srinivas for critical reading of the manuscript. MT is
supported by the MRC and Royal Society. MK is supported by KAKENHI 12640066.
