GFP expression in specific cells, tissues and organs by gene trapping and enhancer trapping. (upper, left) skeleton, (upper, right) cells on the skin, (lower, left) blood vessels, (lower, right) sensory neurons.

Zebrafish is an excellent model vertebrate because of high fecundity, rapid embryonic development, nsparency at the embryonic stages and inex¬pensive and easy breeding procedures. However, there had not been an efficient transgenesis ethod and a transposon technology. We identified an autonomous member from the medaka fish Tol2 transposable element, and veloped a highly efficient transgenesis method for the first time in zebrafish. Further, we successfully developed the gene trap nd enhancer trap methods and the Gal4-UAS method. By using these methods, we cre¬ated a large number of transgenic fish that express the GFP reporter gene or the yeast Gal4 transcription activator in specific cells, tissues and organs. These sgenic fish are valuable resources for studies of developmental biology and neuroscience. We have applied these methods to the udy of neuroscience. By using transgenic fish that express Gal4 in specific neural circuits and the Gal4-UAS system, we sualize structures of specific neural circuits, inhibit their functions and detect their activities by calcium imaging. Thus,studies that aim to understand molecular and cellular mechanisms underlying complex behaviors of a vertebrate are currently ongoing in our laboratory.