Dendrites have a rapid program of injury-induced degeneration that is molecularly distinct from developmental pruning

Neurons have two types of processes: axons and dendrites. Axons have an active disassembly program activated by severing. It has not been tested whether dendrites have an analogous program. We sever Drosophila dendrites in vivo and find that they are cleared within 24 h. Morphologically, this clearance resembles developmental dendrite pruning and, to some extent, axon degeneration. Like axon degeneration, both injury-induced dendrite degeneration and pruning can be delayed by expression of Wld(s) or UBP2. We therefore hypothesized that they use common machinery. Surprisingly, comparison of dendrite pruning and degeneration in the same cell demonstrated that none of the specific machinery used to prune dendrites is required for injury-induced dendrite degeneration. In addition, we show that the rapid program of dendrite degeneration does not require mitochondria. Thus, dendrites do have a rapid program of degeneration, as do axons, but this program does not require the machinery used during developmental pruning.