- BDNF is a secreted protein that regulates neuronal development and plasticity - Vesicular exocytosis of BDNF is driven by SNAREs, Syb2, SNAP25, and SNAP47 - Unlike Syb2 and SNAP25, SNAP47 appears to be unnecessary for neurotransmission - Loss of BDNF or SNAP47 in callosal neurons diminishes branching of their axons