Opto-genetic control of gene regulation in living fly embryos*

Gene regulation is a hallmark of most processes in biology, in particular for cell fate decisions and patterning during early development of an organism. Precise and highly coordinated dynamic gene activity dictates the functional output in the context of complex genetic networks. In order to construct causal relationships in the programs underlying gene regulatory networks and transcription, we developed a light-inducible system to directly interfere with these programs and to quantitatively measure the cellular response in living fly embryos. Our approach allows us to precisely control transcription factor (TF) levels and their immediate response in gene expression. We show how nuclear concentration and TF residence times affect the kinetic rates and expression levels of downstream gene targets, and we test the limits of natural expression patterns by altering the shapes and strengths of the input patterns and measuring their genetic responses. The following questions will be asked: How cells utilize the differential levels of TF to make cell fate decisions? How do downstream genes respond to spatially and temporally modulated doses of TF input concentration?