Localized polarity protein translation in axons and epithelial cells. (a) In immature axons of sensory neurons, NGF or netrin-1 (green circles) can stimulate outgrowth, which depends on the localized translation of Par-3 mRNA. Signaling from the receptors might either release a translational repressor, or permit the association of a translational activator to increase protein expression. In nascent axons, Par-3 protein is transported to the growth cone by a kinesin, but it is not known if this also happens in DRG axons. Par-3 may interact with other polarity proteins such as aPKC to regulate outgrowth. (b) In fly embryonic epithelial cells, the transcripts for 2 polarity proteins, Crumbs (crb) and Stardust (Sdt) are transported by dynein to the apical region of the cell, where they are locally translated. A specific splice variant of Sdt is localized.