Clustered cytoneme interactions contribute to peripheral nervous system patterning in Drosophila.

The formation of patterned adult tissues requires precise spatiotemporal communication between cells that comprise the tissue during development. Organization of the dorsal thoracic sensory bristles of the fruit fly Drosophila melanogaster relies in part on the activity of cell protrusions called cytonemes. Experimental studies have identified several of the mechanisms that govern individual cytoneme dynamics in the patterning PNS, and theoretical studies have considered the effects of their collective activity. Here, using in vivo and ex vivo imaging strategies combined with fly genetics, we show that cytonemes form clusters along the basal surface and that association with clusters promotes the dynamics of individual cytonemes. Clusters are dynamic and transient organizations of cytonemes, and we show that when their movement is perturbed ex vivo through locally aligned nanofibers, PNS patterning is disrupted. We show evidence that cytoneme interactions via clusters is supported by the cell adhesion molecule E-cadherin, as reducing E-cadherin expression leads to changes in cluster dynamics, ability to promote cytoneme length, and overall patterning of the PNS. Taken together, our results support a model in which complex cytoneme interactions promote the dynamics of individual cytonemes. We propose that the enhanced dynamics and stability provided by increased cell-cell interactions may support both the range and strength of local signaling events.