Molecular and cellular mechanisms of synaptic development and plasticity

Synapses are the places where neurons speak to each other, and changing synapses seemingly underlies information storage in the nervous system. The Max Planck group "Neuroplasticity" focuses on the cellular and molecular mechanisms of synapse assembly and plasticity, using neuromuscular synapses of Drosophila as a model system. Apart from combining genetic approaches typical for Drosophila with electrophysiological analysis we have developed protocols, which allow to follow identified synapses over extended time periods in the intact animal. The team of Stephan Sigrist particularly concentrate on the glutamate receptors which receive the acitivity signal from the presynaptic neuron. We find that new glutamate receptor fields form exclusively de novo and usually grow to their characteristic mature size within about 24 hours. The mobility of glutamate receptors at individual receptor fields was analyzed in photo-bleaching and photo-activation experiments. While mature receptor fields are stable because both glutamate receptor entry and exit are low, the entry of glutamate receptors directly controls receptor field growth. Consistently, we find that glutamate receptors are directly needed for postsynaptic assembly independent of their ionic conductance. The in vivo imaging is currently used to illuminate how pre- and postsynaptic site interact within synapse assembly as well as to study the interplay of glutamate receptor dynamics glutamate receptor binding partners and postsynaptic assembly. In this context, the working group find that the Drosophila glutamate receptor binding protein homologue surprisingly controls muscle cell guidance.