TARGETED NEURONAL ABLATION - THE ROLE OF PIONEER NEURONS IN GUIDANCE AND FASCICULATION IN THE CNS OF DROSOPHILA

Although pioneer neurons are the first to delineate the axon pathways, it is uncertain whether they have unique pathfinding abilities. As a first step in defining the role of pioneer neurons in the Drosophila e mbryonic CNS, we describe the temporal profile and trajectory of the a xons of four pioneer neurons and show that they differ from previously published reports. We show, by targeted ablation of one, two, three o r four pioneer neurons at a time, that (1) no single pioneer neuron is essential for axon tract formation, (2) the interaction between two p ioneers is necessary for the establishment of each fascicle and (3) pi oneer neurons function synergistically to establish the longitudinal a xon tracts, to guide the fasciculation of follower neurons along speci fic fascicles and to prevent axons from crossing the midline.