Calcium/Calmodulin-Dependent Protein Kinase II Alters Structural Plasticity and Cytoskeletal Dynamics inDrosophila

Abstract

Drosophila dendritic arborization (da) neurons contain subclasses of neurons with distinct dendritic morphologies. We investigated calcium/calmodulin-dependent protein kinase II (CaMKII) regulation of dendritic structure and dynamics in vivo using optically transparent Drosophila larvae. CaMKII increases the dynamic nature and formation of dendritic filopodia throughout larval development but only affects neurons that normally contain dendritic filopodia. In parallel, we examined the effects of Rac1 activity on dendritic structure to explore signaling specificity. In contrast to CaMKII activity, Rac1 does not alter filopodia stability but instead causes de novo filopodia formation on all da neurons. Although both mediators increase cytoskeletal turnover, measured by fluorescence recovery after photobleaching experiments, only CaMKII increases the dynamic nature of dendritic filopodia. CaMKII signaling thus appears to use mechanisms and machinery distinct from Rac1 signaling. This study illustrates a molecular means of uncoupling cytoskeletal regulation from morphological regulation. Our results suggest that Drosophila dendritic filopodia may share some cytoskeletal regulatory mechanisms with mammalian dendritic filopodia. Furthermore, general dendrite cytoskeletal compartmentalization is conserved in multipolar neurons.

spineless provides a little backbone for dendritic morphogenesis: Figure 1.

“…It is particularly important to identify sensory cell target genes of Ss and other transcription factors; ideally, it would be useful to profile the complement of target genes specific for each sensory neuron. Additionally, generating complex dendritic patterns will also require localizing RNAs and proteins at specific defined sites along processes, and understanding how their functions can be modified at these defined sites (Andersen et al 2005). Connecting molecular genetics with dendrite morphology will require a strong dose of cell biology.…”

A Screen for Modifiers of Notch Signaling Uncovers Amun, a Protein With a Critical Role in Sensory Organ Development

“…Achaete is a bHLH transcription factor required for SOP specification within proneural equivalence groups (see Introduction). We compared the pattern of Achaete expression in sr.AmunTRFP nota with that in control nota using sr.mRFP (a myristylated monomeric RFP; Andersen et al 2005). Achaete-positive cells are detected in regions of control nota expressing mRFP at 9 hr APF ( Figure 8A).…”

A Novel Forward Genetic Screen for Identifying Mutations Affecting Larval Neuronal Dendrite Development in Drosophila melanogaster

“…In mammalian development, following dendrite outgrowth and branching, numerous F-actin-rich structures, including dendritic spines and dendritic filopodia (Fifkova and Delay 1982), form and continuously emerge and retract on dendrites. Previously, we demonstrated that actin-rich dendritic filopodia can also be found on Drosophila dendrites during larval stages and that these structures also continuously emerge and retract on dendrites (Andersen et al 2005). Forward genetic analysis of late stages of dendrite development have been limited because many assay systems used to analyze dendrite development examine neurons that lack actin-rich dendritic filopodia or dendritic spines on mature dendrites (Wu and Cline 1998).…”