Syndapin is dispensable for synaptic vesicle endocytosis at the Drosophila larval neuromuscular junction

Syndapin is a conserved dynamin-binding protein, with predicted function in synaptic-vesicle endocytosis. Here, we combine genetic mutational analysis with in vivo cell biological assays to ask whether Drosophila syndapin (Synd) is an essential component of synaptic-vesicle recycling. The only isoform of Drosophila syndapin (synd) is broadly expressed and at high levels in the nervous system. synd mutants are late-larval lethals, but fertile adult “escapers” frequently emerge. Contrary to expectation, we report that the Synd protein is predominantly postsynaptic, undetectable at presynaptic varicosities at Drosophila third-instar larval neuromuscular junctions. Electrophysiological and synaptopHluorin imaging in control, synd-deficient or synd-overexpressing motor neurons reveals that synd is dispensable for synaptic-vesicle endocytosis. Our work in Drosophila leads to the suggestion that syndapin may not be a general or essential component in dynamin-dependent synaptic-vesicle endocytosis.