PROJECT SUMMARY Targeted cell ablation is a powerful approach for investigating cellular functions, tissue regeneration, developmental processes and disease pathogenesis. Several genetic methods are available for cell ablation, but the ablation process is relatively slow, requiring at least several hours. This can be a disadvantage when examining relatively rapid cellular events (ranging from seconds to minutes) during development or in physiology. This proposal tests the feasibility of a novel genetic cell ablation technology established in mammals for mediating rapid cell ablation in zebrafish. Preliminary data indicate that the system works very well in vitro with cultured zebrafish neurons. These studies will optimize the conditions for effective and rapid cell ablation in vivo, in gastrulating embryos to swimming larvae.