Developmental expression of opioid-binding cell adhesion molecule (OBCAM) in rat brain

Opioid-binding cell adhesion molecule (OBCAM), a neuron-specific protein, c onsists of three immunoglobulin (Ig)-like domains anchored to the membrane through a glycosylphosphatidylinositol (GPI)-tail. OBCAM has been presumed to play a role as a cell adhesion/recognition molecule, but its function ha s not been fully elucidated. We investigated the developmental expression o f OBCAM in rat brain by using a monoclonal anti-OBCAM peptide antibody (OBC 53). OBCAM was clearly detectable on embryonic day 16 (E16) as assessed by immunoblotting. The expression level increased by the second postnatal week and was maintained at a constant level until week 17. During the early dev elopmental period OBCAM was found to be expressed on postmitotic neurons an d to be strongly expressed in at the fiber tracts containing expanding axon s, in contrast to the adult brain, in which OBCAM is principally expressed in the gray matter. These findings suggest that the function of OBCAM invol ves axonal outgrowth. (C) 2000 Elsevier Science BN. All rights reserved.