Defining a Role and Mechanism for Igcam Function in Vertebrate Axon Guidance

The past two decades of research on vertebrate neural adhesion molecules of the immunoglobulin superfamily class (IgCAMs) have produced an bewildering maze of molecules and potential binding activities (for review, see Sonderegger 1998). If one takes at equivalent face value the full range of these interactions that might influence even a particular aspect of neural development, such as axonal pathfinding, the complexity is daunting (Fig. 1). This issue of JCB contains an article describing a set of studies that helps to break through this dilemma by relating the molecular and cellular properties of three interacting IgCAMs (indicated in red in Fig. 1) to a specific pathway choice (Fig. 2 A) made by vertebrate CNS commissural axons in vivo (Fitzli et al. 2000). Not only does the new information focus attention on a...