During brain development, neural circuits are refined in a process that involves the elimination - or 'pruning' - of dendritic spines and the maturation of surviving spines. Yu and colleagues now cast light on the mechanisms that coordinate this process, showing that competition between neighbouring spines for cadherin-catenin complexes determines which spines are eliminated and which mature.Spine pruning and maturation in the cortex are regulated by sensory experience. Here, the authors showed that, in mice, provision of environmental enrichment accelerated spine pruning and maturation in excitatory neurons in the sensory cortices, whereas sensory deprivation (whisker trimming) eliminated both processes. They hypothesized that the coordinated regulation of spine pruning and maturation might involve activity-dependent changes in the distribution of a particular factor in neighbouring spines. The cadherin-catenin complex, consisting of N-cadherin, (3-catenin and aN-catenin, appeared to be a good candidate for such a role: N-cadherins located within the membranes of presynaptic terminals and dendritic spines can stabilize synapses through trans-synaptic homophilic interactions and also regulate synaptic function through the formation of complexes with intracellular partners, including beta-catenin.
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