On the turning of Xenopus retinal axons induced by ephrin-A5 (original) (raw)

The Eph family of receptor tyrosine kinases and their ligands, the ephrins,play important roles during development of the nervous system. Frequently they exert their functions through a repellent mechanism, so that, for example, an axon expressing an Eph receptor does not invade a territory in which an ephrin is expressed. Eph receptor activation requires membrane-associated ligands. This feature discriminates ephrins from other molecules sculpturing the nervous system such as netrins, slits and class 3 semaphorins, which are secreted molecules. While the ability of secreted molecules to guide axons,i.e. to change their growth direction, is well established in vitro, little is known about this for the membrane-bound ephrins. Here we set out to investigate – using Xenopus laevis retinal axons – the properties of substratum-bound and (artificially) soluble forms of ephrin-A5(ephrin-A5-Fc) to guide axons. We find – as expected on the basis of chick experiments – that,when immobilised i...