NrCAM, also known as Bravo, belongs to the L1 family of cell adhesion molecules which also includes L1CAM, Neurofascin, and CHL-1/L1CAM-2 (1). These molecules are type I transmembrane proteins that have 6 Ig-like domains and 4-5 fibronectin type III-like domains in their extracellular domain. L1 family cell adhesion molecules are expressed primarily in the nervous system where they share overlapping functions in controlling axonal growth and guidance (2). Mature mouse NrCAM is an approximately 200 kDa molecule that consists of a 1090 amino acid (aa) extracellular domain (ECD) with 6 Ig-like domains followed by 4 fibronectin type III domains; a 23 aa transmembrane segment, and a 114 aa cytoplasmic domain. Within the region of Ig-like domains, mouse NrCAM shares 91% and 96% aa sequence identity with human and rat NrCAM, respectively. Alternative splicing generates an additional isoform with short deletions in the sixth Ig-like domain and in the juxtamembrane region of the ECD. A 140 kDa soluble fragment of the ECD can be released by proteolytic cleavage (3, 4). NrCAM is expressed on cerebellar granule neurons, retinal ganglion cells (RGC), star pyramidal cells in visual cortex, thalamocortical axons, and glial cells (3, 5-10). It is found on both axons and dendritic spines (6, 8). NrCAM mediates homophilic adhesion as well as heterophilic adhesion with Contactin, Contactin-2/TAG1, Neurofascin, PTP beta zeta, and Integrin alpha 4 beta 1 (4, 11-14) and also interacts with Neuropilin-2, Plexin A3, and EphB2 (7-9). Depending on its interacting partners, NrCAM can promote or inhibit axon and neurite extension (5, 6, 10, 14) and mediate Semaphorin 3F induced neuronal growth cone collapse (8, 9). NrCAM plays an important role in the development of normal vision by regulating RGC axon pathfinding and mapping to the visual cortex (6, 7, 9). It is upregulated in papillary thyroid carcinomas and the shed form can promote tumorigenesis (4, 15).