Guidance of circumferentially growing axons by netrin-dependent and -independent floor plate chemotropism in the vertebrate brain.
Netrin-1, a diffusible signal secreted by floor plate cells at the ventral midline of the vertebrate CNS, can attract ventrally migrating axons and repel a subset of dorsally migrating axons in the spinal cord and rostral hindbrain in vitro. Whether netrin-1 can act as a global cue to guide all circumferentially migrating axons is, however, unknown. Here, we show that netrin-1 can attract alar plate axons that cross the floor plate along its entire rostrocaudal axis. Dorsally directed axons forming the posterior commissure are, however, repelled by the floor plate by a netrin-independent mechanism. These results suggest that netrin-1 functions as a global guidance cue for attraction to the midline. Moreover, floor plate-mediated chemorepulsion may also operate generally to direct dorsal migrations, but its molecular basis may involve both netrin-dependent and -independent mechanisms.
Shirasaki
R
R
Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University, Japan.
Mirzayan
C
C
Tessier-Lavigne
M
M
Murakami
F
F
D000818:Animals; D001369:Axons / Q000502:physiology*; D002630:Chemotactic Factors / Q000502:physiology*; D005314:Embryonic and Fetal Development; D008526:Medulla Oblongata / Q000196:embryology / Q000648:ultrastructure; D008636:Mesencephalon / Q000196:embryology* / Q000648:ultrastructure; D009414:Nerve Growth Factors / Q000502:physiology*; D000075388:Netrin-1; D000075385:Netrins; D009434:Neural Pathways / Q000196:embryology; D051381:Rats / Q000196:embryology; D017208:Rats, Wistar; D025521:Tumor Suppressor Proteins
D002630:Chemotactic Factors; D009414:Nerve Growth Factors; D000075385:Netrins; C000617354:Ntn1 protein, rat; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; C088894:netrin-2