For long, lush cilia, try Par3

Aprotein that induces cells to create tight junctions also helps the primary cilium grow, as Sfakianos et al. show. Although the details remain murky, the protein, Par3, helps lengthen the structures by connecting a molecular motor that travels along the cilium to proteins that are embedded in the cilia membrane.

Researchers know that Par3 teams up with three other proteins, but they don't know all of its effects. Some studies suggest that Par3 helps induce adhesive tight junctions between epithelial cells. Other work indicates it sets up cell polarity in neurons by defining the axon. Sfakianos et al. have identified yet another function for Par3.

The team used RNAi to quash the protein. Although cells lacking Par3 still established tight junctions, they took extra time to form. The cells seemed to polarize normally, suggesting that...