Midline Guidance

The aim of the proposal is to provide possibility to Dr. Tirin to spend 24 months in the laboratory of Dr. Dixon at a leading basic biomedical research centre the IMP in Vienna. The scientific goal of the research project is the better understanding of basic processes required for the development of the nervous system. We will study the mechanism of axon pathfinding in a well characterized model system: the Drosophila midline. Growth cones are the highly motile and sensitive structures that guide axons to appropriate synaptic partners. One critical decision for axons of the central nervous system is to cross or not to cross the midline. Though several axon guidance molecules were identified during the past years, the cell biology of axon crossing in vivo is largely unknown. The aim of my proposal is to understand critical events that take place as growth cones guide axons towards, across and beyond the midline. Since axonal protein synthesis is a recent finding virtually nothing is known how protein molecules are sorted in axons navigating to their synaptic partners. We will study the localization of the protein sorting machinery in the growth cones with tagged forms of proteins present in different membrane components of the protein sorting machinery expressed in specific neurons. In the second set of experiments we will study the expression and subcellular localization of guidance molecules that control midline crossing using fluorescent tags, biosensors and photo-activation and -recovery experiments. For the better understanding of the cell biological mechanisms that control midline crossing we will test the current hypotheses by expressing guidance molecules in single neurons both in living Drosophila embryos and primary neurons.