Can repulsion be induced by attraction: a role of ephrin-B1 in retinotectal mapping?

TL;DR

This paper investigates how ephrin-B1 influences retinotectal mapping, demonstrating that apparent repulsion can result from attraction combined with axonal competition, challenging previous notions of ephrin-B1 as solely a repellent.

Contribution

It shows that repulsive effects in retinotectal mapping can be explained by attraction and competition, providing a new perspective on ephrin-B1's role.

Findings

Repulsion can be mimicked by attraction and competition effects.

Ephrin-B1 may act as an attractant rather than a repellent.

Proposes an experimental test to distinguish true repulsion from attraction-based effects.

Abstract

We study a role of EphB receptors and their ligand ephrin-B1 in dorsal-ventral retinotopic mapping. Earlier studies suggested that ephrin-B1 acts as an attractant for EphB expressing axons. We address the results of the recent experiment in chick tectum (McLaughlin et al., 2003b) in which axons of retinal ganglion cells were shown to be repelled by high ephrin-B1 density. Thus it was proposed that ephrin-B1 might act as both attractant and repellent. We show that the same axonal behavior may follow from attraction to ephrin-B1 density and axonal competition for space. Therefore, we show how apparent repulsive interaction can be induced by a combination of attraction to the target and competitive interactions between axons. We suggest an experimental test that may distinguish repulsive interaction with the target from repulsion induced by attraction and competition.