Retinal axon growth cone responses to different environmental cues are mediated by different second-messenger systems.
Numerous studies have shown that the developing tip of a neurite, the growth cone, can respond to environmental cues with behaviors such as guidance or collapse. To assess whether a given cell type can use more than one second-messenger pathway for a single behavior, we compared the influence of two well-characterized guidance cues on growth cones of chick temporal retinal ganglion cells. The first cue was the repulsive activity derived from the posterior optic tectum (p-membranes), and the second was the collapse-inducing activity derived from oligodendrocytes known as NI35/NI250. p-Membranes caused permanent growth cone collapse with no recovery after several hours, while NI35 caused transient collapse followed by recovery after about 10 min. The p-membrane-induced collapse was found to be Ca2+ independent, as shown using the Ca2+-sensitive dye Fura-2 and by the persistence of collapse in Ca2+-free medium. Dantrolene, a blocker of the ryanodine receptor, had only a minor effect on the collapse frequency caused by p-membranes. In contrast, the NI35-induced collapse was clearly Ca2+ dependent. [Ca2+]i increased sevenfold preceding collapse, and both dantrolene and antibodies against NI35 significantly reduced both the Ca2+ increase and the collapse frequency. Thus, even in a single cell type, growth cone collapse induced by two different signals can be mediated by two different second-messenger systems.
Löschinger
J
J
Max-Planck Institut für Entwicklungsbiologie, Abteilung für Physikalische Biologie, Tübingen, Germany.
Bandtlow
C E
CE
Jung
J
J
Klostermann
S
S
Schwab
M E
ME
Bonhoeffer
F
F
Kater
S B
SB
D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002642:Chick Embryo; D003620:Dantrolene / Q000494:pharmacology; D016257:Fura-2; D019922:GAP-43 Protein / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D007476:Ionophores; D009185:Myelin Proteins / Q000378:metabolism; D051381:Rats; D012165:Retinal Ganglion Cells / Q000502:physiology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D015290:Second Messenger Systems / Q000502:physiology*; D040121:Semaphorin-3A
D019922:GAP-43 Protein; D006023:Glycoproteins; D007476:Ionophores; D009185:Myelin Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D040121:Semaphorin-3A; D003620:Dantrolene; D002118:Calcium; D016257:Fura-2