Biology Reference
In-Depth Information
V. Conclusions
Living cells, tissues and whole organisms are essentially defined by their complex
spatial structures. Underlying such broad morphological characteristics are much
finer molecular assemblies, such as microdomains within the cytoskeleton, plasma
membrane, nucleus and cytoplasm. It is becoming clear that such microdomains are
the loci of many key signaling events, including those that involve Ca
2
þ
and as such,
they are becoming amajor area of interest for investigators in the Ca
2
þ
signaling field.
In recent years, researchers have made spectacular advances on the live-cell imaging
front, due in part to the development of techniques that combine breaking Ernst
Abbe's di
raction barrier (
Abbe, 1873
) being compatible with examining living
systems. Such techniques include stimulated emission depletion (STED) microscopy
(
Hell, 2007
), photoactivated localization microscopy (PALM) (
Betzig et al.,2006
),
and stochastic optical reconstruction microscopy (STORM) (
Rust et al.,2006
). It is
imperative, therefore, that Ca
2
þ
imaging also joins the super-resolution revolution,
and indeed significant progress has been made on this front with the development of
fluorescence-based techniques such as single channel Ca
2
þ
nanoscale resolution
(SCCaNR) microscopy (
Wiltgen et al.,2009
). The continued development of both
fluorescent and luminescent GET-CRs will undoubtedly also make a contribution to
this advancement, especially if, in the case of the latter, the intensity of the Ca
2
þ
-
mediated luminescent emission can be increased. We find ourselves, therefore, at a
most exciting and opportune time to extend our understanding of Ca
2
þ
signaling in
living cells from the microscopic to the nanoscopic level.
V
Acknowledgments
We thank Philippe Brˆ let, Marc Knight, and Jean-Ren´ Martin, who kindly gave us permission to
use their previously published work. Special thanks also to Osamu Shimomura for his generous support
of aequorin-based imaging over the years. We acknowledge financial support from Hong Kong RGC
GRF grants: HKUST-6241/04M,-6416/06M,-661707 and-662109.
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