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Chemoaffinity in topographic mapping revisited--is it more about fiber-fiber than fiber-target interactions?

Abstract：

:Axonal projections between two populations of neurons, which preserve neighborhood relationships, are called topographic. They are ubiquitous in the brain. The development of the retinotectal projection, mapping the retinal output onto the roof of the midbrain, has been studied for decades as a model system. The rigid precision of normal retinotopic mapping has prompted the chemoaffinity hypothesis, positing axonal targeting to be based on fixed biochemical affinities between fibers and targets. In addition, however, abundant evidence has been gathered mainly in the 1970s and 80s that the mapping can adjust to variegated targets with stunning flexibility demonstrating the extraordinary robustness of the guidance process. The identification of ephrins and Eph-receptors as the underlying molecular cues has mostly been interpreted as supporting the fiber-target chemoaffinity hypothesis, while the evidence on mapping robustness has largely been neglected. By having a fresh look on the old data, we expound that they indicate, in addition to fiber-target chemoaffinity, the existence of a second autonomous guidance influence, which we call fiber-fiber chemoaffinity. Classical in vitro observations suggest both influences be composed of opposing monofunctional guidance activities. Based on the molecular evidence, we propose that those might be ephrin/Eph forward and reverse signaling, not only in fiber-target but also in fiber-fiber interactions. In fact, computational models based on this assumption can reconcile the seemingly conflicting findings on rigid and flexible topographic mapping. Supporting the suggested parsimonious and powerful mechanism, they contribute to an understanding of the evolutionary success of robust topographic mass wiring of axons.

journal_name

Semin Cell Dev Biol

journal_title

Seminars in cell & developmental biology

authors

Weth F,Fiederling F,Gebhardt C,Bastmeyer M

doi

10.1016/j.semcdb.2014.07.010

subject

Has Abstract

pub_date

2014-11-01 00:00:00

pages

126-35

eissn

1084-9521

issn

1096-3634

pii

S1084-9521(14)00221-3

journal_volume

pub_type

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Chemoaffinity in topographic mapping revisited--is it more about fiber-fiber than fiber-target interactions?