First published online April 12, 2006
Development 133, 904e (2006)
© The Company of Biologists Limited
Planar polarity: novel functions and player
Two papers in this issue shed light on the establishment and functions of
planar cell polarity (PCP). The PCP pathway, which regulates cell orientation
within the plane of an epithelium, was first described in Drosophila:
activated Frizzled (Fz) receptors trigger the redistribution of core group PCP
proteins, which include Dishevelled (Dvl) and Flamingo (Fmi); these then
specify the orientation of cells and associated bristles. Frank Laski and
colleagues (see p.
1789) have identified
a new component of the PCP pathway - a Drosophila homologue of the
actin depolymerization factor cofilin called Twinstar (Tsr) - that they find
is required for Fz and Fmi redistribution during PCP establishment. What does
this tell us about the mechanisms that govern the redistribution of core
proteins? The authors propose that Tsr-dependent actin reorganisation is
triggered by a gradient of activated Fz across the cell, leading to the
asymmetric accumulation of Fz and other core proteins that might be either
stabilised by actin filaments or transported via an actin-dependent pathway.
Asymmetric Fz then signals further reorganisation of actin filaments into
future bristles. The authors discuss other factors that might be required for
actin cytoskeleton reorganisation in PCP, including the small GTPase Rho.
The PCP pathway is conserved, and homologous pathways have been described
in Xenopus (where it regulates convergent extension), in zebrafish,
and recently in the mouse (where it orientates cochlea sensory hairs). On p.
1767, Anthony
Wynshaw-Boris and colleagues show that in the mouse, Dvl homologues - Dvl1 and
Dvl2 - regulate a coordinated lengthening and narrowing of the neural plate,
which strongly resembles Xenopus convergent extension. Furthermore,
the authors introduced into the mouse a Dvl2 transgene carrying a
point mutation identical to the Dsh1 allele that abolishes the PCP
pathway in the fly. Following this, Dvl2 was no longer able to regulate
convergent extension or the polarity of cochlea sensory hair cells,
demonstrating remarkable conservation between PCP in the fly and convergent
extension in the mouse.
Related articles in Development:
- Dishevelled genes mediate a conserved mammalian PCP pathway to regulate convergent extension during neurulation
- Jianbo Wang, Natasha S. Hamblet, Sharayne Mark, Mary E. Dickinson, Brendan C. Brinkman, Neil Segil, Scott E. Fraser, Ping Chen, John B. Wallingford, and Anthony Wynshaw-Boris
Development 2006 133: 1767-1778.
[Abstract]
[Full Text]
- Twinstar, the Drosophila homolog of cofilin/ADF, is required for planar cell polarity patterning
- Adrienne Blair, Andrew Tomlinson, Hung Pham, Kristin C. Gunsalus, Michael L. Goldberg, and Frank A. Laski
Development 2006 133: 1789-1797.
[Abstract]
[Full Text]
