Three AMIGOs grow a brain

Amphoterin, a heparin-binding protein isolated from perinatal rat brain, has the intriguing ability to promote neurite outgrowth, but its mechanism of action remains unknown. On page 963, Kuja-Panula et al. use mRNA differential display to identify an amphoterin-induced gene called AMIGO, leading to the discovery of a small family of similar proteins that may mediate extracellular interactions in both neurite outgrowth and other types of cell movement.

After cloning the AMIGO gene, the authors identified two related genes, AMIGO-2 and AMIGO-3, by sequence homology. All three appear to encode type I transmembrane receptors, each with six leucine-rich repeats (LRRs) and one immunoglobulin-like domain. AMIGO is expressed at high levels in the nervous system, while AMIGO-2 and AMIGO-3 are distributed in a variety of tissues. Chimeric AMIGO bound to a surface can act as a substrate for neurite...