Difference between axon and dendrite series#

It remains unclear whether Dronc is required for initial dendrite cleavage or only once the severing event has occurred. Caspases are a crucial component of the apoptotic machinery, and in Drosophila the initiator caspase Dronc (Nedd2-like caspase - FlyBase)is required for the pruning of da neuron dendrites during metamorphosis( Kuo et al., 2006 Williams et al., 2006). What accounts for this localized action in the dendrites? Dendritic pruning shares morphological features with apoptosis - in particular, the fragmentation of arbors and their clearing by phagocytes( Williams and Truman, 2005),prompting the examination of apoptotic machinery during remodeling( Kuo et al., 2006 Williams et al., 2006). Remarkably, in many cells that prune their dendrites, the axon remains fully intact. Some dendritic trees and axons are pruned under the control of the steroid hormone ecdysone, acting through the B1 isoform of the Ecdysone receptor (EcR), as well as by matrix metalloproteases and the ubiquitin-proteasome system( Kuo et al., 2005 Kuo et al., 2006 Lee et al., 2000 Marin et al., 2005 Watts et al., 2003 Williams and Truman, 2005 Zheng et al., 2003).

The dendrites and axons of insect neurons can undergo dramatic remodeling during the metamorphic transition from larva to adult to match the stark behavioral differences between these stages. Likewise, rat hippocampal neurons transfected with Sar1 siRNA show strongly reduced dendritic length but normal axon growth( Ye et al., 2007), indicating that these distinct cell types utilize evolutionarily conserved mechanisms of dendritic secretory trafficking. Axons are not as strongly affected in these mutants and show only a reduction in small terminal fibers ( Ye et al.,2007). Sar1 is required to initiate vesicle formation for trafficking from the ER to Golgi,and clones mutant for sar1 show reduced dendrite growth and diffuse Golgi outposts ( Fig. A forward genetic screen for mutations that affect dendrite and axon morphology using Drosophila class IV dendritic arborization (da) neurons (see Glossary, Box 2), recovered mutations in several genes that encode proteins involved in ER-to-Golgi transport,including sar1, sec23 and Rab1( Ye et al., 2007). The dependence of dendrite growth on Golgi outposts is also conserved in Drosophila. In cultured rat hippocampal neurons, Golgi outposts are found in longer and more highly branched dendrites, and manipulations that disrupt Golgi trafficking lead to defects in dendritic growth and maintenance( Horton et al., 2005). Isolated Golgi compartments, termed Golgi outposts,are a component of the secretory pathway found in dendrites of some vertebrate and invertebrate neurons, indicating that local secretory trafficking occurs in dendrites and is a conserved process( Fig. The growth and specialized functions of dendritic arbors can require large investments of dendritic plasma membrane and proteins during development, and,indeed, the polarized trafficking of cargoes to dendritic branches and the incorporation of new membrane are fundamental processes for proper arbor branching and expansion. Genetic insights into the cell biology of dendrite growth and branching We focus on several key questions, including: what are the cell biological mechanisms that specify the distribution of dendritic branches along an arbor? How do dendrites achieve type-specific branching patterns? How is specific dendritic targeting controlled in different neurons? How are dendrites instructed when to stop branching and growing? How does activity impact dendrite development in Drosophila? We refer readers to other reviews that cover topics that have thus far been studied primarily in vertebrate systems, including dendritic spine morphogenesis and activity-dependent dendrite growth ( Alvarez and Sabatini, 2007 Chen and Ghosh, 2005 Flavell and Greenberg, 2008 Lippman and Dunaevsky, 2005 Redmond,2008).

1)and refer to known or emerging areas of conservation in vertebrate systems where appropriate. We focus primarily on studies carried out in Drosophila ( Fig. In this review, we highlight recent advances in understanding the molecules and mechanisms that function during these key stages of dendrite morphogenesis. Each process is under extensive genetic regulation and has been the subject of intensive study in recent years.

Difference between axon and dendrite series#

Dendrite morphogenesis consists of a series of interrelated steps, which include outgrowth and branching, guidance and targeting, cessation of growth and, in some cases, arbor remodeling (see Box 1).