N-CADHERIN REDISTRIBUTION DURING SYNAPTOGENESIS IN HIPPOCAMPAL-NEURONS

Cadherins are hemophilic adhesion molecules that, together with their intracellular binding partners the catenins, mediate adhesion and sign aling at a variety of intercellular junctions. This study shows that n eural (N)-cadherin and beta-catenin, an intracellular binding partner for the classic cadherins, are present in axons and dendrites before s ynapse formation and then cluster at developing synapses between hippo campal neurons. N-cadherin is expressed initially at all synaptic site s but rapidly becomes restricted to a subpopulation of excitatory syna ptic sites. Sites of GABAergic, inhibitory synapses in mature cultures therefore lack N-cadherin but are associated with clusters of beta-ca tenin, implying that they contain a different classic cadherin. These findings indicate that N-cadherin adhesion may stabilize early synapse s that can then be remodeled to express a different cadherin and that cadherins systematically differentiate between functionally (excitator y and inhibitory) and spatially distinct synaptic sites on single neur ons. These results suggest that differential cadherin expression may o rchestrate the point-to-point specificity displayed by developing syna pses.