Abstract

We will first describe the development and application of a method to control at will the expression of a protein embedded in a complex gene network in a growing population of yeast cells. In order to achieve this goal, a control strategy has been designed to automatically regulate the administration of inducer molecules to the cells, by comparing the actual protein expression level in the cell population, with the desired expression level. We designed and implemented an integrated platform based on a microfluidic device, a time-lapse microscopy apparatus, and a set of motorized syringes, all controlled by a computer. We tested the platform to force yeast cells to express a desired time-varying amount of a reporter gene, part of a complex gene network, over thousands of minutes. We will then describe the construction and modeling of a transcriptional positive feedback loop in mammalian cells, which we show experimentally to be able to slow down the dynamics of the system; we will then show how adding a post-trascriptional negative feedback loop, via a microRNA, modifies the dynamics of the systems and protects from extrinsic noise in a cell population.