Synthetic circuits for cell ratio control

Recent advances in genetic engineering have provided diverse tools for artificially diversifying both prokaryotic and eukaryotic cell populations1–6. However, achieving precise control over the ratios of multiple cell types within a population derived from a single founder remains a major challenge. Here we introduce a suite of recombinase-mediated genetic devices designed to accurately control population ratios, enabling the distribution of distinct functionalities across multiple cell types. We systematically evaluated key parameters that influence recombination efficiency and developed data-driven models to reliably predict binary differentiation outcomes. Using these devices, we constructed parallel and series circuit topologies to implement user-defined, multistep cell-fate branching programs. The branching devices facilitated the autonomous differentiation of precision fermentation consortia from a single founder yeast strain, optimizing cell-type ratios for applications such as pigmentation and cellulose degradation. Similar effects were obtained with mammalian cells. We also engineered multicellular aggregates with genetically encoded morphologies by coordinating self-organization through cell adhesion molecules. Our work provides a comprehensive characterization of recombinase-based cell-fate branching mechanisms and introduces an approach for constructing synthetic consortia and multicellular assemblies. A synthetic genetic circuit made up of recombinase-based cell-fate branching devices enables precise control over the ratios of cell types in an offspring population derived from one founder strain, and could be used to build user-defined multicellular aggregates.