Keeping wing cells in line

Cell polarity in fly wing cells is set with extraordinary precision. Out of the distal end of each cell grows an actin-rich protrusion known as a wing hair. Although the wing contains over 30,000 epidermal cells, it produces this distal-specific hair pattern without error. Dali Ma, Jeffrey Axelrod (Stanford University, Stanford, CA), and colleagues report that this precision is achieved through cooperation between two pathways. They find that wide-ranging gradients and locally acting signaling molecules work together to ensure high fidelity throughout the wing.

The local signaling is based on an intercellular feedback loop that has been shown to put Frizzled (Fz) on one side of the cell and keep it from the adjacent side of the neighboring cell. Fz localization is thus propagated from one wing cell...