(665e) An Optimal Regulatory Grammar for Dynamic Gene Control in Space and Time

Proper gene control across space and time is crucial for the seamless execution of various cellular functions, as too much or too little gene expression in the wrong place or time leads to developmental defects and disease phenotypes. While the importance of gene regulation is well acknowledged, systematic characterization of dynamic gene control is lacking. What is the “normal” range of gene expression, and how does transcriptional kinetics play a role? We employ quantitative live imaging and mathematical modeling to examine the governing equation of dynamic gene control for normal development by perturbing regulatory DNAs. Through systematically modulating 3 Dorsal and 1 Twist transcription factor binding sites in the snail enhancer, we found that the mutations in these binding sites caused a drastic reduction in the maximum intensity, resulting in a reduction in total mRNA production. Using an equilibrium binding model, we characterized the synergistic capabilities of each binding site by quantifying the contribution of each binding site to the total mRNA production. Moreover, we implemented the Hidden Markov Model and determined the time each cell spent in the on and off states of transcription. Through this, we identified distinct mechanisms by which transcription factors regulate proper gene expression during development.