Biology Reference
In-Depth Information
inhibiting them, suggesting that certain current approaches to cancer che-
motherapy should be modified.
32
7. METHOD OF CHOICE FOR WHOLE-BODY IMAGING
The features of fluorescent-protein-based imaging, such as a very strong
and stable signal, enable noninvasive whole-body imaging down to the subcel-
lular level,
19
especially with red-shifted proteins, and make it far superior to
luciferase-based imaging. Luciferase-based imaging,with its veryweak signal,
12
precluding image acquisition and allowing only photon counting with
pseudocolor-generated images, has very limited applications.
6
For example,
cellular imaging
in vivo
is not possible with luciferase. The dependence on cir-
culating luciferin makes the signal from luciferase imaging unstable.
6
The one
possible advantage of luciferase-based imaging is that no excitation light is nec-
essary. However, far-red absorbing proteins such as Katushka greatly reduce
problems with excitation, even in deep tissues, as shown by Shcherbo
et al.
33
8. CONCLUSIONS
With the imaging technologies described here, essentially any
in vivo
process can be imaged, enabling the new field of
in vivo
cell biology using
fluorescent proteins that act as visible
in vivo
genetic sensors.
34
Recent
applications of the technology described here include linking fluorescent
proteins with cell-cycle-specific proteins such that the cells change color
from red to green as they transit from G1 to S phases.
35
Another recent
application is the combinatorial expression of a series of four different color
fluorescent proteins, resulting in at least 90 different colors of cells in the
brain such that the lineage of each can be traced. The technique has been
called “Brainbow.”
36
The possibilities
seem limitless
for sensing any
phenomena
in vivo
with visible genetic reports.
REFERENCES
1. Chishima T, Miyagi Y, Wang X, Yamaoka H, Shimada H, Moossa AR, et al. Cancer
invasion and micrometastasis visualized in live tissue by green fluorescent protein expres-
sion.
Cancer Res
1997;
57
:2042-7.
2. Yang M, Baranov E, Jiang P, Sun F-X, Li X-M, Li L, et al. Whole-body optical imaging
of green fluorescent protein-expressing tumors and metastases.
Proc Natl Acad Sci USA
2000;
97
:1206-11.
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