A MODEL FOR CENTRAL SYNAPTIC JUNCTIONAL COMPLEX-FORMATION BASED ON THE DIFFERENTIAL ADHESIVE SPECIFICITIES OF THE CADHERINS

Cadherins control critical developmental events through well-documente d hemophilic interactions. In epithelia, they are hallmark constituent s of junctions that mediate intercellular adhesion. Brain tissue expre sses several cadherins, and we now show that two of these, neural (N)- and epithelial (E)-cadherin, are localized to synaptic complexes in m utually exclusive distributions. In cerebellum, N-cadherin is frequent ly found associated with synapses, some of which are perforated, and i n hippocampus, N- and E-cadherin-containing synapses are found aligned along dendritic shafts within the stratum lucidum of CA3. We propose that the cadherins function as primary adhesive moieties between pre- and postsynaptic membranes in the synaptic complex. According to this model, once neurites have been guided to the vicinity of their cognate targets, it is the differential distribution of cadherins along the a xonal and dendritic plasma membranes, and ultimately cadherin self-ass ociation, that ''locks in'' nascent synaptic connections.