A requirement for filopodia extension toward Slit during Robo-mediated axon repulsion

J Cell Biol. 2016 Apr 25;213(2):261-74. doi: 10.1083/jcb.201509062. Epub 2016 Apr 18.

Abstract

Axons navigate long distances through complex 3D environments to interconnect the nervous system during development. Although the precise spatiotemporal effects of most axon guidance cues remain poorly characterized, a prevailing model posits that attractive guidance cues stimulate actin polymerization in neuronal growth cones whereas repulsive cues induce actin disassembly. Contrary to this model, we find that the repulsive guidance cue Slit stimulates the formation and elongation of actin-based filopodia from mouse dorsal root ganglion growth cones. Surprisingly, filopodia form and elongate toward sources of Slit, a response that we find is required for subsequent axonal repulsion away from Slit. Mechanistically, Slit evokes changes in filopodium dynamics by increasing direct binding of its receptor, Robo, to members of the actin-regulatory Ena/VASP family. Perturbing filopodium dynamics pharmacologically or genetically disrupts Slit-mediated repulsion and produces severe axon guidance defects in vivo. Thus, Slit locally stimulates directional filopodial extension, a process that is required for subsequent axonal repulsion downstream of the Robo receptor.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Axons / metabolism*
  • Axons / ultrastructure
  • Chemotaxis
  • Embryonic Development
  • Glycoproteins / metabolism
  • Glycoproteins / physiology*
  • Growth Cones / metabolism
  • Growth Cones / ultrastructure
  • HEK293 Cells
  • Humans
  • Mice
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Nerve Tissue Proteins / physiology*
  • Pseudopodia / metabolism
  • Pseudopodia / physiology*
  • Pseudopodia / ultrastructure
  • Receptors, Immunologic / genetics
  • Receptors, Immunologic / metabolism
  • Receptors, Immunologic / physiology*
  • Roundabout Proteins
  • Signal Transduction

Substances

  • Glycoproteins
  • Nerve Tissue Proteins
  • Receptors, Immunologic
  • slit protein, vertebrate