Growth cone navigation in substrate-bound ephrin gradients.
Graded distributions of ephrin ligands are involved in the formation of topographic maps. However, it is still poorly understood how growth cones read gradients of membrane-bound guidance molecules. We used microcontact printing to produce discontinuous gradients of substrate-bound ephrinA5. These consist of submicron-sized protein-covered spots, which vary with respect to their sizes and spacings. Growth cones of chick temporal retinal axons are able to integrate these discontinuous ephrin distributions and stop at a distinct zone in the gradient while still undergoing filopodial activity. The position of this stop zone depends on both the steepness of the gradient and on the amount of substrate-bound ephrin per unit surface area. Quantitative analysis of axon outgrowth shows that the stop reaction is controlled by a combination of the local ephrin concentration and the total amount of encountered ephrin, but cannot be attributed to one of these parameters alone.
von Philipsborn
Anne C
AC
Max-Planck-Institut für Entwicklungsbiologie, Spemannstrasse 35, 72076 Tuebingen, Germany.
Lang
Susanne
S
Loeschinger
Jürgen
J
Bernard
André
A
David
Christian
C
Lehnert
Dirk
D
Bonhoeffer
Friedrich
F
Bastmeyer
Martin
M
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002642:Chick Embryo; D047108:Embryonic Development; D036386:Ephrin-A5 / Q000502:physiology*; D036342:Ephrins / Q000494:pharmacology / Q000502:physiology*; D020439:Growth Cones / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000502:physiology*
D036386:Ephrin-A5; D036342:Ephrins