Transparent Mice

I'm currently taking a course on "Multi-Modality Molecular Imaging in Living Subjects" which covers MRI, CT, Optical, and PET imaging. The first topic was optical (fluorescence and bioluminescence) imaging which, in a way, is easiest. Certain molecules give off light, either when exposed to specific other molecules or when excited with light. You then look for this light to see where the molecule of interest is. The problem is, tissue isn't transparent to light. Red light gets through the easiest, which can be seen by shining a flashlight through your hand.



Optical imaging is nice since it doesn't require complicated measurement devices (like MRI or PET) and doesn't expose the subject to radiation (like CT and PET). Optical techniques do get used in vivo, though it is easier in smaller animals and the resolution is poor. Wouldn't it be great if they were transparent? In fact, optical techniques are used extensively to study zebrafish embryos during development since they are transparent. Then genetically modified zebrafish were made that were transparent, event as adults.

Zebrafish are great for developmental biology studies, but aren't as good for cancer. They are used for cancer studies, but are less like humans than the mice that we usually study. And their smaller size would make radiotherapy much harder! But it would be nice to be able to do precise optical studies of cancer, since methods like CT uses radiation that affects tumors. What if we could make mice transparent?

Yes! Mark Oldham's Group of Duke University can make transparent mice. Unfortunately this is a chemical process that requires them to be dead first, rather than a genetic modification that makes them transparent from birth. Then again, how many dystopian stories have been written that begin with scientists making invisible mice? Well... perhaps I'll write that one.