# Nascent dendrite branches initiated by a localized burst of Spire-dependent actin polymerization

## TL;DR

This study shows how Spire and Rab11 work together to create new dendrite branches by linking actin polymerization with endosome trafficking in neurons.

## Contribution

The paper reveals a novel mechanism where Spire and Rab11 cooperate to initiate dendrite branching through localized actin polymerization and endosome trafficking.

## Key findings

- Spire localizes to new branch initiation sites and triggers a burst of actin polymerization before filopodial outgrowth.
- Spire interacts with Rab11 to link actin dynamics with endosome trafficking for dendrite arborization.
- Intact structural domains of Spire are required for actin nucleation and targeting the secretory network.

## Abstract

Dendrites form arbors whose size, shape and complexity define how neurons cover their receptive territories. Actin dynamics contribute to growth and remodeling of dendrite arbors. Here, we have examined how Spire, a conserved actin nucleation factor, promotes the formation of new branches in vivo. In live imaging of Drosophila class IV dendritic arborization (c4da) neurons, Spire was observed at new sites of branch initiation, where it assembled new actin polymer in a burst immediately before filopodial outgrowth. For dendrite arborization, Spire required intact structural domains to nucleate actin and target the secretory network, and interacted with Rab11 GTPase, a key regulator of recycling endosomes. Together, these findings support a model in which Spire cooperates with Rab11 to promote new dendrite branches by linking localized actin dynamics with intracellular trafficking of endosomes that deliver lipids and cargoes to fuel protrusive outgrowth of nascent dendrites.

Highlighted Article:
Spire and Rab11 cooperate to promote new dendrite branches by linking actin dynamics with endosome trafficking, facilitating the growth and remodeling of dendritic arbors in neurons.