Centre for Developmental Neurobiology, King's College London, London, United Kingdom; King’s-NUS Joint Studentship Program, King's College London, London, United Kingdom
Amrita Mukherjee
Centre for Developmental Neurobiology, King's College London, London, United Kingdom
Yvette E Fisher
Department of Neurobiology, Stanford University, Stanford, United States; Department of Neurobiology, Harvard Medical School, Boston, United States
Department of Biological Sciences, National University of Singapore, Singapore, Singapore; Temasek Life Sciences Laboratory, Singapore, Singapore; Mechanobiology Institute, National University of Singapore, Singapore, Singapore
Building arborisations of the right size and shape is fundamental for neural network function. Live imaging in vertebrate brains strongly suggests that nascent synapses are critical for branch growth during development. The molecular mechanisms underlying this are largely unknown. Here we present a novel system in Drosophila for studying the development of complex arborisations live, in vivo during metamorphosis. In growing arborisations we see branch dynamics and localisations of presynaptic proteins very similar to the ‘synaptotropic growth’ described in fish/frogs. These accumulations of presynaptic proteins do not appear to be presynaptic release sites and are not paired with neurotransmitter receptors. Knockdowns of either evoked or spontaneous neurotransmission do not impact arbor growth. Instead, we find that axonal branch growth is regulated by dynamic, focal localisations of Neurexin and Neuroligin. These adhesion complexes provide stability for filopodia by a ‘stick-and-grow’ based mechanism wholly independent of synaptic activity.
