Brain Imaging with New GCaMPs
○Akira Muto、Koichi Kawakami
Division of Molecular and Developmental Biology, National Institute of Genetics
Why we behave as we do, or why animals behave as they do? To
answer this fascinating question, we have chosen zebrafish as a
model system. It is the brain activity that creates behaviors.
Therefore, visualization of the brain function can be the first step to
understanding of the brain-behavior connection. Neuronal activity
can be monitored by measuring calcium influx that is coupled with generation of electrical
signals in the neurons. Calcium imaging with DNA-encoded calcium indicators, such as
GCaMP, is a powerful means because it allows us to monitor the activity of genetically
identified neurons. Recently we developed an improved GCaMP, GCaMPHS, and demonstrated
visualization of the activity in the spinal neurons during a motor behavior (Muto et al., 2011).
Here we have further modified the GCaMP and generated UAS:GCaMP transgenicfish. To
observe neuronal activities in a visual behavior, the UAS:GCaMP was expressed in GAL4
enhancer/gene trap lines with specific expression patterns. Our imaging study using artificial
visual stimuli revealed a functional retinotopic map in accordance with the well established
retinotectal projection. Next, we asked how natural visual stimuli are represented in the brain.
One of the vision-guided behaviors in zebrafish larvae is feeding with paramecia. We observed
that the neuronal activity driven by the visual input of a moving paramecium also moved around
on the neuropil showing the functional retinotopy. We also observed spontaneous activities in
the forebrain, habenula and cerebellum, although their roles remain to be elucidated. The
improved GCaMPs, in combination with the Gal4-UAS system will be an excellent tool to
study brain functions in animal behavior, from sensory perception, cognition, to motor outputs.
Muto A, Ohkura M, Kotani T, Higashijima S, Nakai J, Kawakami K. Genetic visualization with
an improved GCaMP calcium indicator reveals spatiotemporal activation of the spinal motor
neurons in zebrafish. Proc Natl Acad Sci U S A. 2011 Mar 29;108(13):5425-30.