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 investigate the contribution 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. In addition, we performed two-photon time-lapse imaging of LNvs in the developing larval brain and analyzed the dendrite morphogenesis with high spatial and temporal resolutions. We observed fast branch dynamics that were strongly influenced by the visual experience as well as the developmental stages, and identified specific molecules required for the regulation of the dendrite dynamics. These findings provided novel insights into the cellular and molecular mechanisms underlying homeostatic structural plasticity in the developing neural circuit.
