Planar cell polarity meets membrane trafficking

In an interesting new finding, Rab23 - a presumed regulator of membrane traffic - is required for planar cell polarity in Drosophila. Rab23 has a 'multiple wing hair' type phenotype and affects the polarized distribution of protiens such as Vang and Prickle.

Genetics. 2010 Feb 1. [Epub ahead of print]

Drosophila Rab23 is Involved in the Regulation of the Number and Planar Polarization of the Adult Cuticular Hairs.

Pataki C, Matusek T, Kurucz E, Andó I, Jenny A, Mihály J.

HAS: BRC Institute of Genetics.

The planar coordination of cellular polarization is an important, yet not well understood aspect of animal development. In a screen for genes regulating planar cell polarization in Drosophila, we identified Rab23, encoding a putative vesicular trafficking protein. Mutations in the Drosophila Rab23 orthologue result in abnormal trichome orientation and the formation of multiple hairs on the wing, leg and abdomen. We show that Rab23 impairs hexagonal packing of the wing cells, and that it plays a role in cortical polarization of the polarity proteins. We found that Rab23 is able to associate with the proximally accumulated Prickle protein, although Rab23 itself does not appear to display a polarized subcellular distribution in wing cells. The absence of Rab23 leads to increased actin accumulation in the sub-apical region of the pupal wing cells that fail to restrict prehair initiation to a single site. Rab23 acts as a dominant enhancer of the weak multiple hair phenotype exhibited by the core polarity mutations, whereas the Rab23 homozygous mutant phenotype is sensitive to the gene dose of the planar polarity effector genes. Together, our data suggest that Rab23 contributes to the mechanism that inhibits hair formation at positions outside of the distal vertex by activating the planar polarity effector system.