Biomedical Engineering Reference
In-Depth Information
(
Bayly & Axelrod, 2011; Ganner et al., 2009; Guirao et al., 2010; Park,
Mitchell, Abitua, Kintner, & Wallingford, 2008
).
Several recent studies have suggested that the cilium regulates Wnt path-
way usage and PCP. This is an extremely complicated issue that cannot be
dealt with appropriately here (for a more detailed discussion, see
Wallingford
&Mitchell, 2011
). However, we briefly discuss this issue here, as it is an im-
portant topic.
Mice carrying mutations in genes that are necessary for ciliogenesis show
pathologies that have been linked to PCP defects including cystic kidney
tubules (
Hildebrandt, Attanasio, & Otto, 2009; Lin et al., 2003; Patel,
Chowdhury, & Igarashi, 2009; Sattar & Gleeson, 2011; Sharma, Berbari,
& Yoder, 2008; Waters & Beales, 2011
). Although there is strong
evidence that PCP signaling is necessary for the planar-polarized location
of the cilia and the polarized beating of the cilia in some tissues, neither
of these situations appears to be relevant to the mammalian kidney.
Kidney cilia are nonmotile and do not show obvious planar polarization.
Ciliary signaling has been linked to oriented cell divisions, a form of
PCP, and activation of the noncanonical Wnt pathway. However, at this
point, the mechanisms connecting the cilia, Wnt signaling, and PCP signal-
ing (if there is such a connection) are still unclear. It is important to point out
that the mere presence of a defect in PCP in a mutant background does not
necessarily indicate that the mutated gene or structure plays a role in PCP.
It may simply be necessary for the cell type-specific effect of PCP. Further,
characterization will be required to gain a greater understanding of the cilia
to Wnt signaling and PCP.
2.5. Junctional remodeling
One of the processes affected by PCP are directed cell movements that occur
during morphogenesis (
Aigouy et al., 2010; Carreira-Barbosa et al., 2009;
Phillips, Murdoch, Chaudhry, Copp, & Henderson, 2005; Shnitsar &
Borchers, 2008; Skoglund & Keller, 2010; Takeuchi et al., 2003; Ulrich
et al., 2003; Veeman, Slusarski, Kaykas, Louie, & Moon, 2003;
Wallingford & Harland, 2002
). Although such movements take place
during axis elongation in Drosophila, they do not appear to be dependent
on any of the “canonical” PCP determinants discussed above. Instead,
these cell movements appear to be regulated by the spatial expression of
factors along the anterior/posterior axis of the embryo (
Blankenship,
Backovic, Sanny, Weitz, & Zallen, 2006; Zallen & Blankenship, 2008
).
