Research Highlight: Floor-plate-derived netrin-1 is dispensable for commissural axon guidance
The prevailing model of axon guidance relies on chemotactic cues that permit or prevent axon growth. The extra cellular matrix protein Netrin-1 expressed by Floor Plate (FP) cells in the CNS midline is indeed believed to attract commissural axons to the midline : among other supporting data, commissural axons fail to cross the FP in Netrin-1 loss of function in the mouse.
Here, ENP team leader Alain Chédotal and coll. using a conditional KO strategy that selectively ablates Netrin-1 expression in FP cells demonstrates 1) that FP-derived Netrin-1 is dispensable for commissural axon guidance, 2) that commissural axons do respond to Netrin-1 produced dorsally by neural progenitors from the Ventricular Zone and 3) that rather than a long-distance chemoattractant, Netrin-1 acts locally by promoting growth cone adhesion by providing a haptotactic scaffold for growth.
In conclusion, Netrin-1 accumulation on commissural neurons « creates a permissive pathway for follower neurons », a model of axon guidance different from the classical attractive gradient of FP-derived Netrin-1.
Check out the article:
Floor-plate-derived netrin-1 is dispensable for commissural axon guidance. Dominici C, Moreno-Bravo JA, Puiggros SR, Rappeneau Q, Rama N, Vieugue P, Bernet A, Mehlen P, Chédotal A.
Nature. 2017 May 18;545(7654):350-354.
doi: 10.1038/nature22331. Epub 2017 Apr 26. PMID: 28445456