Imaging In Mice With Fluorescent Proteins: From Macro To Subcellular
Received: 15 January 2008 / Accepted: 19 February 2008 / Published: 22 February 2008
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Whole-body imaging with fluorescent proteins has been shown to be a powerfultechnology with many applications in small animals. Brighter, red-shifted proteins can makewhole-body imaging even more sensitive due to reduced absorption by tissues and less scatter.For example, a new protein called Katushka
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Whole-body imaging with fluorescent proteins has been shown to be a powerfultechnology with many applications in small animals. Brighter, red-shifted proteins can makewhole-body imaging even more sensitive due to reduced absorption by tissues and less scatter.For example, a new protein called Katushka has been isolated that is the brightest known proteinwith emission at wavelengths longer than 620 nm. This new protein offers potential for non-invasive whole-body macro imaging such as of tumor growth. For subcellular imaging, toobserve cytoplasmic and nuclear dynamics in the living mouse, cancer cells were labeled in thenucleus with green fluorescent protein and with red fluorescent protein in the cytoplasm. Thenuclear and cytoplasmic behavior of cancer cells in real time in blood vessels was imaged as theytrafficked by various means or adhered to the vessel surface in the abdominal skin flap. Duringextravasation, real-time dual-color imaging showed that cytoplasmic processes of the cancer cellsexited the vessels first, with nuclei following along the cytoplasmic projections. Both cytoplasmand nuclei underwent deformation during extravasation. Cancer cells trafficking in lymphaticvessels was also imaged. To noninvasively image cancer cell/stromal cell interaction in the tumormicroenvironment as well as drug response at the cellular level in live animals in real time, wedeveloped a new imageable three-color animal model. The model consists of GFP-expressingmice transplanted with the dual-color cancer cells. With the dual-color cancer cells and a highlysensitive small animal imaging system, subcellular dynamics can now be observed in live mice inreal time. Fluorescent proteins thus enable both macro and micro imaging technology and thereby provide the basis for the new field of in vivo cell biology.