Of interest, Drosophila dendritic arborization (da) neurons, which are part of the peripheral nervous system (PNS), undergo either apoptosis or pruning to generate adult‐specific processes. In Drosophila, large‐scale remodeling of nervous systems takes place during metamorphosis, a transition stage between larval and adult stages (Yu & Schuldiner, 2014 Kanamori et al, 2015). Neuronal pruning is also essential for the development of invertebrate nervous systems. Impaired neuronal pruning is associated with autism spectrum disorder (ASD) with increased dendritic spine density in layer V pyramidal neurons (Tang et al, 2014). In mammalian brains, some developing neurons remove their long axonal bundles and re‐establish functional circuits. Selective removal of their unwanted or redundant dendrites or axons without causing neuronal death, referred to as pruning, is a fundamental strategy to ensure proper wiring in the developing nervous systems (Luo & O'Leary, 2005 Riccomagno & Kolodkin, 2015 Schuldiner & Yaron, 2015). Neurons often extend their exuberant processes and connections at early developmental stages. Thus, we demonstrate that the MT polymerase Msps is required to form dendritic minus‐end‐out MTs and thereby promotes dendrite pruning in Drosophila sensory neurons. Excessive MT depolymerization, which is induced by pharmacological treatment and katanin overexpression, also perturbs dendritic MT orientation and dendrite pruning, phenocopying msps mutants. We further show that the functions of msps in dendritic MT orientation and dendrite pruning are antagonized by the kinesin‐13 MT depolymerase Klp10A. Moreover, Msps and TACC are required to orient minus‐end‐out MTs in dendrites. Msps associates with another MT‐associated protein TACC, and both stabilize each other in ddaC neurons. Here, we identify an unexpected role of Mini spindles (Msps), a conserved MT polymerase, in governing dendrite pruning. During dendrite pruning, severing of proximal dendrites is preceded by local microtubule (MT) disassembly. Drosophila class IV ddaC neurons selectively prune all larval dendrites to refine the nervous system during metamorphosis.
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