Multicellular Circuit Design in Mammalian Cells

Citation

Zhu, Ronghui (2023) Multicellular Circuit Design in Mammalian Cells. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/p0fn-qa56. https://resolver.caltech.edu/CaltechTHESIS:07252022-061122576

Abstract

Multicellular circuits control the development of multicellular organisms, through programming processes such as cell proliferation, cell differentiation, cell movement, and cell signaling. A fundamental goal of biology is to understand the design principles of these multicellular circuits, and use these principles to design synthetic multicellular systems for therapeutic purposes. Top-down approaches, for example analyzing embryos bearing genetic mutations, have identified key genes in many multicellular circuits, but are challenging to study these circuits in an isolated context and in a quantitative and systematic manner. An alternative, complementary approach is to engineer or reconstitute multicellular circuits from bottom-up, which allows us to overcome the limitations of top-down approach and gain quantitative insights into multicellular circuit design. In this thesis, we use this bottom-up approach to explore the design principles of two multicellular circuits. In the first project, we took inspiration from two prevalent features from natural multistable circuits, namely competitive protein-protein interactions and positive autoregulation, to design a synthetic multistable circuit architecture called MultiFate. Both in the model and in the experiment, MultiFate circuits generate multiple cellular states, each stable for weeks, allow control over state-switching and state stability, and can be easily expanded to generate more states. In the second project, we use a gradient reconstitution system to systematically analyze a gradient modulation circuit consisting of BMP4 and its modulators, Chordin, Twsg and BMP-1. We found that the circuit can give rise to diverse gradient modulation capabilities. In particular, the full circuit is sufficient for active ligand shuttling and generation of non-monotonic displaced gradient. These multicellular circuits could provide a foundation for engineering synthetic multicellular systems in mammalian cells.

Thesis Files