Planar cell polarity (PCP) - asymmetry in the plane of epithelial tissues -controls the arrangement of structures such as insect hairs and ommatidia. The prevailing model for PCP establishment in Drosophila proposes that a morphogen gradient organizes the expression of two atypical cadherins,Dachsous (Ds) and Fat (Ft), and of the Golgi protein Four-jointed, to set up Ds system gradients. These then act via the Stan system - the cadherin receptor-like molecule Starry Night (Stan) and the Wnt receptor Frizzled (Fz)- to orientate hairs and ommatidia. On p. 4561, JoséCasal, Peter Lawrence and Gary Struhl challenge this model by reporting that the Ds and Stan systems act independently to orientate abdominal hairs. For example, they show that ectopic expression of ds repolarizes surrounding cells even in flies that lack both Stan and Fz. Other experiments indicate that cells that send polarity information need either Ds or Ft but responding cells need both proteins. From these findings, the researchers propose a radical new model that suggests how Ds-Ft bridges between cells might propagate PCP.

© 2006.
2006