1/1/2024 0 Comments Define dendrite pruningMicrotubule dynamics in dendrites are increased during the early pupal stage by fine-tuned activation of the kinase Par-1 ( Bu et al., 2022 Herzmann et al., 2017). These pruning factors lead to disassembly of actin ( Kirilly et al., 2009 Wolterhoff et al., 2020) and microtubules ( Herzmann et al., 2017 Lee et al., 2009 Williams and Truman, 2005) as well as locally increased endocytosis ( Kanamori et al., 2015) in proximal dendrites. Dendrite pruning is induced by an ecdysone pulse at the onset of metamorphosis that induces the expression of pruning factors such as the transcription factor Sox14 and the actin severing enzyme Mical in a cell autonomous manner ( Kirilly et al., 2009). The peripheral sensory class IV dendritic arborization (c4da) neurons of Drosophila larvae specifically prune their dendrites during metamorphosis through proximal severing close to the cell body ( Kuo et al., 2005 Williams and Truman, 2005). Neurite pruning, the regulated loss of axons or dendrites during development without loss of the parent neuron, serves to specify neuronal connections and to remove developmental intermediates during neuronal development ( Riccomagno and Kolodkin, 2015 Yu and Schuldiner, 2014) and often involves apparent neurite breaking or fragmentation. Thus, our data establish mechanical tearing as a novel mechanism during neurite pruning. Tissue movements and dendrite severing peak during pupal ecdysis, a period of strong abdominal contractions, and abolishing ecdysis causes non-cell autonomous dendrite pruning defects. Severing occurs during periods of increased pupal morphogenetic tissue movements, which exert mechanical forces on the destabilized dendrites. We found that ecdysone signaling causes the dendrites to become mechanically fragile. Subsequently, dendrites are severed at positions close to the soma by an unknown mechanism. Pruning of Drosophila sensory neuron dendrites during metamorphosis is triggered by the hormone ecdysone, which induces local disassembly of the dendritic cytoskeleton. Developmental neurite pruning, a critical circuit specification mechanism, often involves neurite abscission at predetermined sites by unknown mechanisms. Mechanical forces actively shape cells during development, but little is known about their roles during neuronal morphogenesis.
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