FIGURE 2.

Schematic representation of different steps in trans-synaptic complex formation in excitatory synapse development. (A) Synaptogenesis is initiated at the points of contacts between dendritic filopodia and axons. At this stage, synaptic CAMs are distributed evenly at the contact point. (B) Contact point is stabilized by dimerization of the opposing CAM molecules that form trans-synaptic complexes spanning the partner cells and creating mechanical adhesion points. (C) Adhesion points develop into mature synapses that consist of presynaptic terminal with neurotransmitter vesicles and a postsynaptic density characterized by the presence of receptors. The molecular diversity of pre- and postsynaptic constituents is built upon C-terminal interactions of trans-synaptic complexes linking the trans-synaptic dimer to the scaffolding proteins and filamentous actin (McMahon and Díaz, 2011).