Synaptic remodeling has been postulated as a mechanism underlying synaptic plasticity, and cadherin adhesion molecules are thought to be a regulator of such a process. We examined the effects of cadherin blockage on synaptogenesis in cultured hippocampal neurons. This blockade resulted in alterations of dendritic spine morphology, such as filopodia-like elongation of the spine and bifurcation of its head structure, along with concomitant disruption of the distribution of postsynaptic proteins. The accumulation of synapsin at presynaptic sites and synaptic vesicle recycling were also perturbed, although these synaptic responses to the cadherin blockade became less evident upon the maturation of the synapses. These findings suggest that cadherin regulates dendritic spine morphogenesis and related synaptic functions, presumably cooperating with cadherin-independent adhesive mechanisms to maintain spine-axon contacts.

In the auditory epithelium of the cochlea, the sensory hair cells and supporting cells are arranged in a checkerboard-like fashion, but the mechanism underlying this cellular patterning is unclear. We found that mouse hair cells and supporting cells express the immunoglobulin-like adhesion molecules nectin-1 and -3, respectively, and that their interaction mediates the heterotypic adhesion between these two cell types. Genetic removal of nectin-1 or -3 disrupted the checkerboard-like pattern, inducing aberrant attachment between hair cells. When cells expressing either nectin-1 or -3 were cocultured, they arranged themselves into a mosaic pattern. Thus, nectin-1 and -3 promote the formation of the checkerboard-like pattern of the auditory epithelia.

No abstract

Neurites recognize their specific partners during the formation of interneuronal connections. In hippocampal pyramidal neurons, axons attach to dendrites for their synaptogenesis, but the dendrites do not form stable contacts with each other, suggesting the presence of a mechanism to allow their selective associations. Nectin-1 (N1), an immunoglobulin domain adhesive protein, is preferentially localized in axons, and its heterophilic partner, N3, is present in both axons and dendrites; we tested their potential roles in interneurite recognition. The overexpression of N1, causing its mislocalization to dendrites, induced atypical dendrodendritic as well as excessive axodendritic associations. On the contrary, the genetic deletion of N1 loosened the contacts between axons and dendritic spines. Those actions of nectins required cadherin–catenin activities, but the overexpression of cadherin itself could not accelerate neurite attachment. These results suggest that the axon-biased localization of N1 and its trans-interaction with N3 in cooperation with the cadherin machinery is critical for the ordered association of axons and dendrites.

Cellular rearrangements between olfactory cells and supporting cells, driven by the different expression and distribution of nectins and cadherins, are required for mosaic cellular patterning in the olfactory epithelium.

Cell adhesion is the binding of a cell to another cell or to an extracellular matrix component. This process is essential in organ formation during embryonic development and in maintaining multicellular structure. Armstrong et al. (2006) [J. Theor. Biol. 243, pp. 98-113] proposed a nonlocal advection-diffusion system as a possible continuous mathematical model for cell-cell adhesion. Although the system is attractive and challenging, it gives biologically unrealistic numerical solutions under certain situations. We identify the problems and change underlying idea of cell movement from "cells move randomly" to "cells move from high to low pressure regions". Then we provide a modified continuous model for cell-cell adhesion. Numerical experiments illustrate that the modified model is able to replicate not only Steinberg׳s cell sorting experiments but also some phenomena which cannot be captured at all by Armstrong-Painter-Sherratt model.

Cell-cell adhesion molecules play key roles at the intercellular junctions of a wide variety of cells, including interneuronal synapses and neuron-glia contacts. Functional studies suggest that adhesion molecules are implicated in many aspects of neural network formation, such as axon-guidance, synapse formation, regulation of synaptic structure and astrocyte-synapse contacts. Some basic cell biological aspects of the assembly of junctional complexes of neurons and glial cells resemble those of epithelial cells. However, the neuron specific junctional machineries are required to exert neuronal functions, such as synaptic transmission and plasticity. In this review, we describe the distribution and function of cell adhesion molecules at synapses and at contacts between synapses and astrocytes.

The stable N isotopic composition of individual amino acids (SIAA) has recently been used to estimate trophic positions (TPs) of animals in several simple food chain systems. However, it is unknown whether the SIAA is applicable to more complex food web analysis. In this study we measured the SIAA of stream macroinvertebrates, fishes, and their potential food sources (periphyton and leaf litter of terrestrial C3 plants) collected from upper and lower sites in two streams having contrasting riparian landscapes. The stable N isotope ratios of glutamic acid and phenylalanine confirmed that for primary producers (periphyton and C3 litter) the TP was 1, and for primary consumers (e.g., mayfly and caddisfly larvae) it was 2. We built a two-source mixing model to estimate the relative contributions of aquatic and terrestrial sources to secondary and higher consumers (e.g., stonefly larva and fishes) prior to the TP calculation. The estimated TPs (2.3-3.5) roughly corresponded to their omnivorous and carnivorous feeding habits, respectively. We found that the SIAA method offers substantial advantages over traditional bulk method for food web analysis because it defines the food web structure based on the metabolic pathway of amino groups, and can be used to estimate food web structure under conditions where the bulk method cannot be used. Our result provides evidence that the SIAA method is applicable to the analysis of complex food webs, where heterogeneous resources are mixed.