(105b) Development of a Recombinase-Based Genetic Oscillator

It has been shown that certain genes and proteins (e.g., p53, NF-kB, etc.) can oscillate in their level of expression or activity over time. However, it remains to be shown whether these fluctuations in gene expression have physiological relevance or whether they are simply a result of feedback regulation. We hypothesize that these fluctuations do play a role in deciding a cell's fate. We are developing a tool that will help answer this question. We have constructed a recombinase-based genetic oscillator designed to function in mammalian cells.

Previous synthetic oscillators have utilized systems where repressor proteins bind to promoters that drive transcription of repressor genes. The oscillations in these systems often dampen eventually. We have constructed an oscillator that can only exist in one of two possible states, and the inversion from one state to the other is catalyzed by site-specific recombinase enzymes. Using live cell imaging, we can follow the function of the oscillator in individual cells by tracking the expression of fluorescent proteins encoded on the oscillator construct. Here we present results showing the incorporation of the oscillator in NIH-3T3 mouse fibroblast cells and its activity upon introduction of recombinase genes.