Neuronal plasticity accompanying development and experience-dependent processes facilitates the establishment and refinement of the nervous system, while presenting significant challenges to the functional stability of the neural networks. The nervous system uses a variety of compensatory mechanisms to cope with perturbations. Recent studies suggested that structural plasticity serves as a major component for neuronal homeostasis. Our previous studies have demonstrated experience-dependent plasticity in the developing Drosophila larval visual circuit, in which ventral lateral neurons (LNvs), the postsynaptic targets of larval photoreceptors, exhibit robust structural plasticity of their dendritic arbors when animals are subjected to different visual experience. These observations also established a genetically tractable model system for mechanistic studies on the activity-dependent regulation of developmental plasticity. To analyze the change of neuronal morphology with high spatial and temporal resolutions, we carried out two-photon live imaging of LNvs in the developing larval brain. We observed fast structural dynamics of dendritic arbors, which was strongly influenced by the visual experience of the animals and their developmental stages. In addition, to investigate the contributions of genetic factors in the activity-dependent regulation of dendrite morphology, we carried out forward genetic screens and cell type specific manipulations. We identified candidate synaptic cell adhesion molecule as critical components involved in the regulation of dendrite dynamics and activity-dependent structural plasticity. These findings provided novel insights into the cellular and molecular mechanisms underlying homeostatic structural plasticity in the developing neural circuit.
