Local translation and mRNA trafficking in axon pathfinding.

Axons and their growth cones are specialized neuronal sub-compartments that possess translation machinery and have distinct messenger RNAs (mRNAs). Several classes of mRNAs have been identified using candidate-based, as well as unbiased genome-wide-based approaches. Axonal mRNA localization serves to regulate spatially the protein synthesis; thereby, providing axons with a high degree of functional autonomy from the soma during axon pathfinding. Importantly, de novo protein synthesis in navigating axonal growth cones is necessary for chemotropic responses to various axon guidance cues. This chapter discusses the molecular components involved in regulating axonal mRNA trafficking, targeting, and translation, and focuses on RNA binding proteins (RNBPs) and microRNAs. The functional significance of local mRNA translation in the directional response of growth cones to a gradient is highlighted along with the downstream signaling events that mediate local protein synthesis. The view that emerges is that local translation is tightly coupled to extracellular cues, enabling growth cones to respond to new signals with exquisite adaptability and spatiotemporal control.