Genetic visualization with an improved GCaMP calcium indicator reveals spatiotemporal activation of the spinal motor neurons in zebrafish. Press Release Proceedings of the National Academy of Sciences of the United States of America (PNAS) Kawakami Laboratory, Division of Molecular and Developmental Biology Genetic visualization with an improved GCaMP calcium indicator reveals spatiotemporal activation of the spinal motor neurons in zebrafish Akira Muto, Masamichi Ohkura, Tomoya Kotani, Shin-ichi Higashijima, Junichi Nakai, and Koichi Kawakami Proceedings of the National Academy of Sciences of the United States of America (PNAS) March 7, 2011 doi:10.1073/pnas.1000887108 To understand how a neuronal network works in an animal, we developed a genetic system that can visualize neuronal activities in zebrafish. In this study, we succeeded to record spatiotemporal patterns of the activity of the spinal motor neurons. First, we created an improved version of GCaMP, the DNA-encoded calcium indicator, and generated a transgenic fish that carried the GCaMP genedownstream of UAS. Second, we performed a gene trap screen and found transgenic fish that expressed Gal4FF in a subset of the spinal motor neurons. Then, we crossed the UAS:GCaMP fish with the Gal4FF fish and performed calcium imaging by using double transgenic embryos. The calcium imaging study successfully detected spatiotemporally coordinated neuronal activities in the zebrafish embryo. These technologies should be powerful tools to monitor other neuronal activities including the brain. 　 Visualization of the activity of a subset of the motor neurons in the spinal cord. Gray images show the fluorescence of the GCaMP. Color images show the neuronal activity (intracellular calcium ion concentration). Left panel: Neurons on the left side of the spinal cord are firing. Right panel: Neurons on the right side are firing. ←Back