Phenotypic consequences of gene expression driven by positive and negative feedback gene circuits.

Cellular processes such as metastasis or differentiation are governed by the network of dynamically interacting transcription factors (TFs) and their effectors. Prolonged or shortened expression of TFs can lead to aberrant network activity and in consequence affect the phenotype and phenotypic plasticity of living cells. Here, we investigate the influence of common network motifs, such as negative or positive feedback regulation, on the ectopic expression of the metastasis-related TF, Bach1. We use a site-specific integration strategy to introduce BACH1-controlling synthetic gene circuits into the genome of the MDA-MB-231 cell line. Constructs consisting of Bach1 co-expressed with eGFP and driven by repressor- or activator-dependent promoters generate negative and positive feedback, respectively. Using live cell imaging on single-cell arrays, we perform correlation analysis of Bach1 expression and relate it with the invasiveness of both engineered cell lines.