Speaker: Matthew Smart (University of Toronto)
Title: Cell fate specification and transitions in multicellular systems
Multicellular organisms comprise a diverse collection of stable tissues built from different cell types. It remains unclear how large numbers of interacting cells can precisely coordinate their gene expression during tissue self-organization. In this talk, I will introduce and characterize an attractor landscape model of single-cell gene expression based on Hopfield networks. I will then extend this single-cell picture to a general model of multicellular transcription that includes intracellular and intercellular gene interactions in tissue-like collectives. Tuning the intercellular signaling strength results in a cascade of transitions from single-cell autonomy towards different self-organized collective states. Despite an enormous number of possible tissue states, disordered signaling tends to stabilize a surprisingly small number of compositionally simple tissue types. Statistical properties of the stable phenotypes are preserved for different interaction networks and initial conditions. These results may explain how collections of cells in distinct organisms robustly self-organize into relatively simple tissues even for complex interaction networks mediated by large numbers of different molecules, and how different stable tissues emerge during development.