Glowing from Within
A new fluorescent marker illuminates tissue deep within living animals

SOURCE: “Bright Far-Red Fluorescent Protein for Whole-Body Imaging”
Dmitriy Chudakov et al.
Nature Methods 4: 741-746

RESULTS: Using genetic-­engineering techniques, scientists have altered a red protein found in sea anemones to create a fluorescent marker that can be used to study living tissue deep in the body.

WHY IT MATTERS: The light from existing fluorescent markers is difficult to detect through layers of tissue, so the use of such markers has been limited to dissected or surface tissue or to transparent animals, such as worms. This new marker emits light in the far-red part of the spectrum, which can better pass through living tissue. That means the marker can be used in live animals to help researchers track molecular and cellular activity, such as the rapid division of cancer cells, in real time.

METHODS: By inducing both random and directed mutations in the anemone protein, scientists altered it to create new compounds that are brighter than the original one. They then tested the new proteins both in frogs and in human cells, showing that they shine much more brightly than those previously available.

NEXT STEPS: Collaborators of the scientists will soon begin testing the proteins in mice. Although the markers aren’t bright enough for whole-body imaging of humans, they might eventually be used to image human tumors that are near the surface of the skin, such as melanoma and breast cancer.