Filopodial dynamics and growth cone stabilization in Drosophila visual circuit development
Mehmet Neset Özel,
Marion Langen,
Bassem A Hassan,
P Robin Hiesinger
Affiliations
Mehmet Neset Özel
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States; Division of Neurobiology, Institute for Biology, Freie Universität Berlin, Berlin, Germany; NeuroCure Cluster of Excellence, Charite Universitätsmedizin Berlin, Berlin, Germany
Marion Langen
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States
Bassem A Hassan
Center for the Biology of Disease, Vlaams Instituut voor Biotechnologie, Leuven, Belgium; Center for Human Genetics, University of Leuven School of Medicine, Leuven, Belgium
P Robin Hiesinger
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States; Division of Neurobiology, Institute for Biology, Freie Universität Berlin, Berlin, Germany; NeuroCure Cluster of Excellence, Charite Universitätsmedizin Berlin, Berlin, Germany
Filopodial dynamics are thought to control growth cone guidance, but the types and roles of growth cone dynamics underlying neural circuit assembly in a living brain are largely unknown. To address this issue, we have developed long-term, continuous, fast and high-resolution imaging of growth cone dynamics from axon growth to synapse formation in cultured Drosophila brains. Using R7 photoreceptor neurons as a model we show that >90% of the growth cone filopodia exhibit fast, stochastic dynamics that persist despite ongoing stepwise layer formation. Correspondingly, R7 growth cones stabilize early and change their final position by passive dislocation. N-Cadherin controls both fast filopodial dynamics and growth cone stabilization. Surprisingly, loss of N-Cadherin causes no primary targeting defects, but destabilizes R7 growth cones to jump between correct and incorrect layers. Hence, growth cone dynamics can influence wiring specificity without a direct role in target recognition and implement simple rules during circuit assembly.
