The long-term goal of this research program is to elucidate the cellular and molecular mechanisms that participate in the formation and function of a synaptic contact. The present proposal focuses on the role of cell adhesion in the formation of three major synaptic specializations: presynaptic terminals, active zones, and somatic spines. The primary hypothesis is that the development of adhesive linkages mediated by cell-cell and cell-matrix interactions are required for the structural organization and function of the synapse. In addition, a precise control of surface adhesion is needed for the structural modification of the synaptic junction in response to physiological stimuli. Utilizing the calyx-type synapse of the chick ciliary ganglion as an experimental model system and a retroviral system to induce molecular perturbations during development, this study will focus on the role of two families of adhesion molecules, namely the cadherins and the integrins. These molecules have been selected because of their prominent adhesive activity and expression pattern in the ciliary ganglion. The role of N-cadherin and integrins (beta1 and beta4) in the structural organization of the synapse will be investigated by perturbing their adhesive properties with wild type and mutated molecules that exert dominant negative effects. The consequences of interfering with cell adhesion will be evaluated morphologically, by analyzing the structure of the synapse at the light confocal and electron microscopic level, and functionally by assessing electrophysiologically the efficacy of synaptic transmission and the properties of the electrical currents of the ciliary neurons. The information gained from this study will lead to a better understanding of synaptogenesis and the structural requirements for synaptic function. As a variety of psychiatric and neurological disorders are believed to arise from synaptic malfunction, these studies will contribute basic knowledge toward elucidation of cellular and molecular mechanisms underlying neuropathological conditions.
