![]() Such large-scale pruning is thus achieved in a compartmentalized manner within the entire neuronal processes. In the refinement processes, a substantial portion of neuronal branches is often eliminated by local degeneration, in which a group of neuronal branches distal from a boundary point in a neuron is degenerated simultaneously 2, 5. Likewise, mitral and tufted cells in the olfactory bulb of rats initially have multiple primary dendrites that contact adjacent glomeruli however, they eventually lose all but one dendritic branch that remains in contact with a single glomerulus 4. For example, layer V neurons in the visual cortex of rats degenerate the distal compartment of the primary axons that is initially formed during early development and extends to the spinal cord 3. In the developing brain of vertebrates and invertebrates, after axon/dendrite outgrowth and synapse formation, neurons prune their axons and dendrites to eliminate excessive or inappropriate connections that initially formed during early development 1, 2. Further genetic analyses suggest that local endocytosis in proximal dendrites functions cooperatively with global endocytosis-mediated protein degradation pathways to promote dendrite pruning. Two GTPases, Rab5 and dynamin, are required for both the increased endocytic activity and compartmentalized Ca 2+ transients. In vivo imaging of single dendrites reveals an increase of endocytosis in proximal dendrites that spatially and temporally correlates with dendrite thinning, an early step in pruning tightly coupled with compartmentalized Ca 2+ transients. Here we report that local elevation of endocytic activity contributes to defining dendrites that generate Ca 2+ transients, triggering pruning. In Drosophila sensory neurons, compartmentalized calcium (Ca 2+) transients in dendrites act as spatiotemporal cues to trigger pruning, yet how neurons define the dendrites with Ca 2+ transients remains elusive. ![]() The refinement of neural circuits involves dendrite pruning, a process that removes inappropriate projections that are formed during development. ![]()
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