title: Growth cone navigation in substrate-bound ephrin gradients.
abstract: 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.
authors.affiliation: Max-Planck-Institut für Entwicklungsbiologie, Spemannstrasse 35, 72076 Tuebingen, Germany.
authors.forename: Anne C
authors.initials: AC
authors.lastname: von Philipsborn
authors.forename: Susanne
authors.initials: S
authors.lastname: Lang
authors.forename: Jürgen
authors.initials: J
authors.lastname: Loeschinger
authors.forename: André
authors.initials: A
authors.lastname: Bernard
authors.forename: Christian
authors.initials: C
authors.lastname: David
authors.forename: Dirk
authors.initials: D
authors.lastname: Lehnert
authors.forename: Friedrich
authors.initials: F
authors.lastname: Bonhoeffer
authors.forename: Martin
authors.initials: M
authors.lastname: Bastmeyer
mesh_terms: 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*
chemical_list: D036386:Ephrin-A5; D036342:Ephrins