UC Irvine

Cell-cell contacts are crucial in a myriad of biological settings including cancer progression,

embryonic development, and immune system function. Understanding such processes requires

examining cellular communication in its native context. Optical imaging tools are ideally suited

for this purpose.

The most commonly employed optical imaging technology is fluorescence. While

fluorescent tools are useful at the microscopic level, issues of autofluorescence and the

requirement for incident light limit their utility at larger length scales. This leaves a gap in our

ability to “see” at the macroscopic level.

A complementary strategy, bioluminescence, circumvents these issues allowing chemically

generated light from a luciferase enzyme to illuminate cellular movement. Bioluminescence has

been employed to monitor both intracellular and extracelluar events, from gene expression to

protein secretion.

Despite its versatility, bioluminescence has not easily transitioned to monitoring direct cell

contacts. This is due, in part, to a lack of tools that can illuminate celllular interactions at the

microscopic level. Moreover, there are a limited number of luciferase probes useful for cell

xiii

tracking. My work was aimed at filling this gap by developing new bioluminescent tools for

studying cell populations.

To enable visualization of cell contacts, I employed a split-reporter strategy wherein the

luciferase halves were tethered to separate cells. This method enabled light emission to be linked

with the microscopic process of cell contacts. It could be used to monitor immune and cancer

cell interactions during disease progression.

To develop new cell tracking tools, I exploited an enzymatic chemical attachment method to

append bioluminescent enzymes to small molecules and proteins. Furthermore, this method was

used to directly label cell surfaces with luciferases. Such tools will facilitate the monitoring cells

recalcitrant to genetic manipulation, including stem cells and primary cells, as well as tracking

endogenous cell populations, such as metastatic tumor cells.

My work will enable the study of cellular contacts as well as non-genetically encodable cell

populations in vivo and noninvasively. Future work from our lab will use these methodologies to

further diversify bioluminescent imaging techniques and use the tools I have developed to

monitor stem cell and cancer cell migration in mouse models.