PhD defence: Mechanical study of a morphogenesis process in a minimalist epithelium mode - Vladimir Misiak (MICROTISS)

Morphogenesis, the process of tissue formation and reorganization, is driven by dynamic changes in tissue properties such as stiffness and cell motility. Central to this process is the ability of cells to regulate their contacts with neighboring cells. Cell intercalation, a fundamental mechanism of cellcell rearrangement, plays a critical role in epithelial organization and embryo development. This thesis investigates the underlying mechanics of T1 transitions using a novel in vitro approach. The objective of this study is to explore how tension is distributed within epithelial structures and how these forces regulate cell reorganization during morphogenesis while maintaining tissue integrity. To achieve this, a quadruplet model of epithelial cells is developed using cell micro-patterning techniques to replicate the basic unit of tissue architecture. The thesis combines quantitative live imaging with traction force microscopy to examine the distribution of mechanical forces in these minimalistic epithelial models. Additionally, the study employs optogenetic tools to modulate cell contractility and induce morphological changes, providing insights into how changes in contractility impact cell intercalation and tissue dynamics. The findings offer new perspectives on the mechanical principles governing epithelial stability and highlight the potential of this approach for studying tissue morphogenesis at both microscopic and macroscopic scales. This work contributes to a deeper understanding of the mechanical and dynamic factors underlying epithelial organization and provides a foundation for future research into tissue development and remodeling.