LEONARDO, A DROSOPHILA 14-3-3 PROTEIN INVOLVED IN LEARNING, REGULATESPRESYNAPTIC FUNCTION

The leonardo gene encodes a conserved member of the 14-3-3 protein fam ily, which plays a role in Drosophila teaming. Immunological localizat ion of the protein shows that it is expressed at synaptic connections and enriched in presynaptic boutons of the neuromuscular junction (NMJ ). Null leonardo mutants die as mature embryos. Electrophysiological a ssays of the mutant NMJ demonstrate that basal synaptic transmission i s reduced by 30% and that transmission amplitude, fidelity, and fatigu e resistance properties are reduced at elevated stimulation frequencie s and in low external [Ca2+]. Moreover, transmission augmentation and post-tetanic potentiation (PTP) are disrupted in the mutant. These res ults suggest that Leonardo plays a role in the regulation of synaptic vesicle dynamics, a function which may underlie synaptic modulation pr operties enabling learning.