Transgenic mice expressing a cameleon fluorescent Ca super(2+) indicator in astrocytes and Schwann cells allow study of glial cell Ca super(2+) signals in situ and in vivo

Glial cell Ca super(2+) signals play a key role in glial-neuronal and glial-glial network communication. Numerous studies have thus far utilized cell-permeant and injected Ca super(2+) indicator dyes to investigate glial Ca super(2+) signals in vitro and in situ. Genetically encoded fluorescent Ca super(2+) indicators have emerged as novel probes for investigating cellular Ca super(2+) signals. We have expressed one such indicator protein, the YC 3.60 cameleon, under the control of the S100 beta promoter and directed its expression predominantly in astrocytes and Schwann cells. Expression of YC 3.60 extended into the entire cellular cytoplasmic compartment and the fine terminal processes of protoplasmic astrocytes and Schwann cell Cajal bands. In the brain, all the cells known to express S100 beta in the adult or during development, expressed YC 3.60. While expression was most extensive in astrocytes, other glial cell types that express S100 beta , such as NG2 and CNP-positive oligodendrocyte progenitor cells (OP cells), microglia, and some of the large motor neurons in the brain stem, also contained YC 3.60 fluorescence. Using a variety of known in situ and in vivo assays, we found that stimuli known to elicit Ca super(2+) signals in astrocytes caused substantial and rapid Ca super(2+) signals in the YC 3.60-expressing astrocytes. In addition, forepaw stimulation while imaging astrocytes through a cranial window in the somatosensory cortex in live mice, revealed robust evoked and spontaneous Ca super(2+) signals. These results, for the first time, show that genetically encoded reporter is capable of recording activity-dependent Ca super(2+) signals in the astrocyte processes, and networks.