9 Eph Receptor Tyrosine Kinases
and Their Ligands in Development
U. Drescher
9.1
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. lSI
92
Receptor-Ligand Interactions in the Eph Family. . . . . . . . . . . . .. 152
9.3
The Retinotectal Projection .............................. 153
9.4
Formation of Lamina-Specific Synaptic Connections. . . . . . . . .. 159
9.5
Segmental Restriction of Motor Neuron Axons, Neural Crest,
and Hindbrain Segments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 160
9.6
Cardiovascular Development . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 161
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 162
9.1 Introduction
A current focus of interest in developmental neurobiology is the identification and characterization of mechanisms and molecules contributing
to the formation of neuronal connections. A number of gene families
playing a role in this process have recently been identified. They can be
classified tentatively according to the basic mechanisms by which axonal pathfinding to, and guidance in, the target area are thought to occur:
chemoattraction by Netrins, chemorepulsion by Netrins and secreted
Semaphorins; contact-mediated attraction by Ig domain-containing cell
adhesion molecules (Ig-CAMs), Cadherins, and extracellular matrix
proteins (ECM); and finally, contact-mediated repulsion by transmembrane Semaphorins, ECM proteins, and Ephrins (Tessier-Lavigne and
Goodman 1996; Muller 1999).