Non-equilibrium fluctuations as drivers of tissue fluidization during embryonic development – N-EDEV

Embryonic development depends keenly on the dynamics of the underlying biological tissues, which itself arises from cellular attributes such as: cell-cell adhesion, cortical tension, osmotic pressure, elasticity, and viscosity. While physical models exist that describe how tissue dynamics emerge from such cellular attributes, there is no consensus on how to treat the fact that these systems continuously consume energy, and are therefore far from equilibrium.

While the global distribution of tension in the embryo directs tissue flow, it has recently been theoretically proposed that fluctuations in local tension at cell-cell contacts are required for cells to rearrange, allowing the tissue to act as a viscous fluid instead of an elastic solid. However, there have been few experimental studies to quantify such fluctuations in biological tissue and relate them to cell rearrangements and tissue dynamics. Further, it is unknown how these energetically-costly fluctuations relate to non-equilibrium effects resulting from energy-consumption in the cells.

In this project, I will perform live imaging of Drosophila embryogenesis to quantify cell-scale shape and tension fluctuations, and correlate them to cell rearrangements and tissue flow speeds. I will use experimental techniques to modify tissue flow speed (using temperature), and the energy consumption of cells (by manipulating metabolism) to (1) uncover what role cell-scale tension fluctuations play in tissue fluidization, (2) measure how these fluctuations depend on energy consumption within the cell, and (3) reveal the relative roles of non-equilibrium effects on cell-scale fluctuations, tissue-scale dynamics, and organism-scale developmental rates.