Con-nectin axons and dendrites

Abstract

Unlike adherens junctions, synapses are asymmetric connections, usually between axons and dendrites, that rely on various cell adhesion molecules for structural stability and function. Two cell types of adhesion molecules found at adherens junctions, cadherins and nectins, are thought to mediate homophilic interaction between neighboring cells. In this issue, Togashi et al. (see p. 141) demonstrate that the differential localization of two heterophilic interacting nectins mediates the selective attraction of axons and dendrites in cooperation with cadherins.

Figure 1.

Cellular and molecular role of cadherins and nectins in the hippocampus. (A) Simplified schematic diagram of the hippocampus depicting the major divisions, including the dentate gyrus, CA1 field, and CA3 field, and the major three-cell circuit. CA3 and CA1 pyramidal cell bodies are located within the stratum pyramidale (SP). A dentate gyrus granule cell extends an axon and synapses (area in yellow) onto a CA3 pyramidal neuron's proximal, apical dendrite within the stratum lucidum (SL). A CA3 pyramidal neuron extends an axon through the stratum oriens (SO) and synapses onto dendrites of a CA1 pyramidal neuron within the stratum radiatum (SR). Based on Togashi et al. (2006), axons, likely nectin-1⁺, are colored red, and dendrites, likely nectin-3⁺, are colored green. (B) A dentate gyrus (DG) granule cell synapses onto a CA3 pyramidal spine with puncta adherentia junctions (circled in blue) on the CA3 dendrite on either side. (C) Cadherin and nectin interactions at adherens junctions and puncta adherentia junctions are described in more detail in the text.