Tiling among stereotyped dendritic branches in an identified Drosophila motoneuron

Abstract

Different types of neurons can be distinguished by the specific targeting locations and branching patterns of their dendrites, which form the blueprint for wiring the brain. Unraveling which specific signals control different aspects of dendritic architecture, such as branching and elongation, pruning and cessation of growth, territory formation, tiling, and self-avoidance requires a quantitative comparison in control and genetically manipulated neurons. The highly conserved shapes of individually identified Drosophila neurons make them well suited for the analysis of dendritic architecture principles. However, to date it remains unclear how tightly dendritic architecture principles of identified central neurons are regulated. This study uses quantitative reconstructions of dendritic architecture of an identified Drosophila flight motoneuron (MN5) with a complex dendritic tree, comprising more than 4,000 dendritic branches and 6 mm total length. MN5 contains a fixed number of 23 dendritic subtrees, which tile into distinct, nonoverlapping volumes of the diffuse motor neuropil. Across-animal comparison and quantitative analysis suggest that tiling of the different dendritic subtrees of the same neuron is caused by competitive and repulsive interactions among subtrees, perhaps allowing different dendritic compartments to be connected to different circuit elements. We also show that dendritic architecture is similar among different wildtype and GAL4 driver fly lines. Metric and topological dendritic architecture features are sufficiently constant to allow for studies of the underlying control mechanisms by genetic manipulations. Dendritic territory and certain topological measures, such as tree compactness, are most constant, suggesting that these reflect the intrinsic molecular identity of the neuron.

Mutations in KATNB1 Cause Complex Cerebral Malformations by Disrupting Asymmetrically Dividing Neural Progenitors

“…Among all singly identifiable flight motoneurons, MN5 serves as a paradigm of dendritic architecture (Consoulas et al, 2002; Vonhoff and Duch, 2010). Using D42-Gal4 to express kat80-IR primarily in adult flight motoneurons (Vonhoff and Duch, 2010) resulted in reduced dendritic arborization of MN5 (Fig. 8C–D).…”

Intra-neuronal Competition for Synaptic Partners Conserves the Amount of Dendritic Building Material

“…First, MN5 displays a stereotyped dendritic morphology (Figure 1A) with metric and topological features that are sufficiently constant across animals to allow statistical comparison of measurements between control and genetic manipulation. MN5 contains a fixed number of 23 dendritic subtrees that all arise from the primary neurite, tile the input space, and, on average, comprise 4,000 ± 577 dendritic branches with a total length of 6,716 ± 731 μm (means ± SD) (Vonhoff and Duch, 2010). Second, MN5 receives synaptic input of different transmitter classes.…”

“…We test this hypothesis by combining genetic manipulation with quantitative three-dimensional dendritic architecture analysis of an identified Drosophila flight motoneuron, named MN5. MN5 shows a stereotypical overall dendritic morphology, but fine branching structure differs between animals (Vonhoff and Duch, 2010). The complex MN5 dendritic arbor with more than 6mmtotal length and more than 4,000 branches covers a diffuse motor neuropil with intermingled terminals of GABAergic and cholinergic synaptic terminals.…”

MECP2 impairs neuronal structure by regulating KIBRA

“…We expressed hMECP2 in an identified motoneuron (MN5), which displays a stereotyped and well described dendritic morphology, thus allowing for quantitative in vivo dendritic structure analysis following genetic interaction experiments (Duch et al, 2008; Hutchinson et al, 2014; Vonhoff and Duch, 2010; Vonhoff et al, 2013; Vonhoff et al, 2012). As previously reported, expression of full length hMECP2 in MN5 reduced total dendritic length and the number of dendritic branches by 50% compared to controls (Fig.…”

“…Adult Drosophila (1–2 days old) were dissected and dye filled with Neurobiotin solution (7% Neurobiotin (Vector Labs) and lysine fixable rhodamine-dextran 3000 (Life Technologies) in 2Mpotassium acetate) using sharp electrodes as described previously (Vonhoff and Duch, 2010; Vonhoff et al, 2012). After staining, ganglia were fixed in 4% paraformaldehyde (PFA) in PBS for 1 h and washed in PBS.…”