latheo, a Drosophila gene involved in learning, regulates functional synaptic plasticity

Mutations in the latheo (laf) gene disrupt associative learning in Drosophi la, but a role for LAT in regulating neuronal function has not been demonst rated. Here, we report that LAT plays a central role in regulating Ca2+- an d activity-dependent synaptic plasticity. Immunological localization of the LAT protein indicates it is present at synaptic connections of the larval neuromuscular junction (NMJ) and is enriched in presynaptic boutons. Basal synaptic transmission amplitude at the laf mutant NMJ is elevated 3- to 4-f old, and Ca2+ dependence of transmission is significantly reduced. Multiple forms of synaptic facilitation and posttetanic potentiation (PTP) are stro ngly depressed or absent at the mutant synapse. Our results suggest that LA T is a novel presynaptic protein with a role in the Ca2+-dependent synaptic modulation mechanisms necessary for behavioral plasticity.