Non-Invasive In Vivo Imaging of Calcium Signaling in Mice

Abstract

Rapid and transient elevations of Ca2+ within cellular microdomains play a critical role in the regulation of many signal transduction pathways. Described here is a genetic approach for non-invasive detection of localized Ca2+ concentration ([Ca2+]) rises in live animals using bioluminescence imaging (BLI). Transgenic mice conditionally expressing the Ca2+-sensitive bioluminescent reporter GFP-aequorin targeted to the mitochondrial matrix were studied in several experimental paradigms. Rapid [Ca2+] rises inside the mitochondrial matrix could be readily detected during single-twitch muscle contractions. Whole body patterns of [Ca2+] were monitored in freely moving mice and during epileptic seizures. Furthermore, variations in mitochondrial [Ca2+] correlated to behavioral components of the sleep/wake cycle were observed during prolonged whole body recordings of newborn mice. This non-invasive imaging technique opens new avenues for the analysis of Ca2+ signaling whenever whole body information in freely moving animals is desired, in particular during behavioral and developmental studies.

Interactions between sarco-endoplasmic reticulum and mitochondria in cardiac and skeletal muscle – pivotal roles in Ca2+ and reactive oxygen species signaling

“…On the basis of these data, it was concluded that enhancement of the Ca 2+ permeability by the overexpressed VDAC is needed to optimize the local transfer of the brief high- [Ca 2+ ] c microdomains during RyR-mediated [Ca 2+ ] m transients (Rapizzi et al, 2002). In vivo recording in skeletal muscle confirmed that mitochondria display increases in [Ca 2+ ] m that closely follow [Ca 2+ ] c transients under both single twitch and tetanic stimulation (Rudolf et al, 2004;Rogers et al, 2007). Another elegant study identified a subset of mitochondria that displayed a rise in [Ca 2+ ] m upon caffeine stimulation even when global [Ca 2+ ] c transients were buffered by BAPTA, further supporting a local SR-mitochondrial Ca 2+ transfer (Shkryl and Shirokova, 2006).…”

Calcium imaging in single neurons from brain slices using bioluminescent reporters

“…Nonetheless, it has been hypothesized that obelin could be a better reporter of rapid Ca 21 signals than aequorin because of faster response kinetics (Illarionov et al, 2000;Markova et al, 2002). Recently, a GFP-aequorin (GA) fusion protein has been described that allows fluorescence labeling of expressing cells and bioluminescence Ca 21 imaging of single cultured cells, of tissue slices and in vivo (Baubet et al, 2000;Rogers et al, 2005Rogers et al, , 2007Martin et al, 2007). A GFP-obelin (GO) fusion protein has also been described but has not been used as a reporter of Ca 21 signals (Gorokhovatsky et al, 2004).…”

In vivo functional calcium imaging of induced or spontaneous activity in the fly brain using a GFP-apoaequorin-based bioluminescent approach

“…Importantly, there is also an increase in total light emission [15]. A variety of transgenic organisms including mice [19] and Drosophila [20] have been generated using this new chimeric gene.…”