Modulates the structure and function of the apical ectodermal ridge (AER) that controls embryonic limb development (PubMed:21575622). Functions in cell-cell adhesion, cell migration and axon guidance, exerting an attractive or repulsive role depending on its interaction partners. Plays a role in the spatial organization of brain neurons. Plays a role in vascular development. Plays a role in cell-cell adhesion via its interaction with latrophilins that are expressed at the surface of adjacent cells. Mediates axon attraction towards cells expressing NTN1. Mediates axon growth cone collapse and plays a repulsive role in neuron guidance via its interaction with UNC-5 family members. Plays a role in the regulation of the density of glutamaergic synapses. Plays a role in fibroblast growth factor-mediated signaling cascades. Required for normal morphogenesis during embryonic development, but not for normal embryonic patterning (By similarity). Detected on dendritic punctae that colocalize in part with glutamaergic synapses, but not with GABAergic synapses. Proteolytic cleavage in the juxtamembrane region gives rise to a shedded ectodomain. Detected in distal ectodermal cells at Hamburger Hamilton stage 18 (18HH). Becomes restricted to the apical ectodermal ridge (AER) (at protein level). At stage 11HH, detected in neural ectoderm, developing optic placodes, the neural crest around the otic placodes, and along the anterior-posterior axis in somites. Detected in the ectoderm of the limb bud at 16HH to 18HH. Becomes restricted to the dermomyotome closer to the neural tube at stage 18HH. At 19HH and 23HH, detected in the apical ectodermal ridge, the developing eye and branchial arches. N-glycosylated. Proteolytic cleavage in the juxtamembrane region gives rise to a soluble ectodomain. Cleavage is probably effected by a metalloprotease.