DISTRIBUTION AND CHARACTERISTICS OF A 90 KDA PROTEIN, KG-CAM, IN THE RAT CNS

The distribution of a 90 kDa protein, termed KG-CAM, was examined in t he developing and adult rat central nervous system (CNS) using the mon oclonal antibody 11-59. The amino acid sequence of this protein reveal ed a sequence homology with a group of chick cell adhesion molecules f rom the immunoglobulin superfamily: DM-GRASP; SC1; and BEN. Immunolabe ling of cells cultured from the embryonic and neonatal rat brain demon strates that the protein recognized by 11-59 is on the external surfac e of a subpopulation of neurons and a limited population of glial cell s. When the 11-59 antibody was used to stain sections of the adult bra in and spinal cord, a number of different structures were labeled. The most intense immunoreactivity was found in the somatosensory system, the basal ganglia, the cortex, the olfactory system, and the circumven tricular organs. One of the more interesting aspects of KG-CAM is the spatially and temporally regulated patterns of expression observed dur ing the development of the CNS. For example, the dendrites of layer II pyramidal cells in the granular retrosplenial cortex are immunopositi ve for 11-59 while the dendrites are in the process of bundling in lay er I, but not before bundling begins or after the process is completed . These findings reveal the varied roles of this adhesion molecule in the developing brain and spinal cord, as well as its potential role in the maintenance of the structural integrity of the adult CNS.