Mechanisms in dendrite pruning of drosophila dendritic arborization neurons

Abstract

The capability of neurons to remodel existing neuronal projections and connections confers great flexibility in response to activity-dependent processes, developmental regulated alterations, neuronal diseases and post-injury recoveries. Although a wide range of events lead to neuronal remodeling, the underlying mechanisms remain elusive. Among various types of neuronal remodeling, selective removal of dendrite branches, so called dendrite pruning, of Drosophila dendritic arborization (da) neurons occurs during metamorphosis, a developmental process that transforms a b worm-likeb larva into an adult fruit fly. To understand the mechanisms that regulate dendrite pruning of these peripheral neurons, a forward genetic screen was carried out and identified Mical (Molecule interacting with CasL) as a novel factor that promotes severing of dendrites at the initial stage of dendrite pruning. Further studies suggest that destabilization of cytoskeleton molecules, such as microtubules and actins, is suppressed in remodeling da neurons devoid of Mical. Mical functions in da neuron pruning downstream of the steroid nuclear hormone receptor complex EcR-B1/Ultraspirical during the larval-pupal transition; whereas Dronc (Drosophila Nedd2-like caspase) mediates cell-death of apoptotic da neurons and clearance of dendrite debris.