MSC Seminar. 24/06/2024. Pierre Sens (Institut Curie): “Physical principles of cell volume and density regulation”

The size and density of living cells are the result of passive physical constraints and active biological processes. Their interplay leads to the appearance of robust and ubiquitous scaling laws relating linearly cell size, dry mass, and nuclear size. One remarkable feature is that the protein density within a cell remains constant during cell growth.

I will discuss how the different scaling laws can be explained quantitatively by a single model of size regulation based on three simple, yet generic, physical constraints – osmotic balance, hydrostatic balance, and electro-neutrality – defining the “the Pump-Leak model”. I will show how cell density homeostasis can be understood by coupling “the Pump-Leak model” with a simple model of gene expression. I will then extend this analysis to the cell nucleus and discuss factors that can influence to nuclear to cell volume ratio, and discuss how cell mechanics may modify the different scaling law. If time permits, I will end with the interesting case of fresh-water single celled organisms, which need specific mechanisms to deal with acute osmotic challenges.