Measuring the Intracellular Dew Point: Phase Transitions in Cells

Measuring the Intracellular Dew Point: Phase Transitions in Cells
Cliff Brangwynne, Princeton University
Date and time: Tue, Sep 08, 2015 - 11:30am
Refreshments at 11:15am
Location: 201 LGRT
Category: Condensed Matter Seminar
Special notes: This seminar is co-hosted and co-sponsored with the Department of Chemical Engineering.
Abstract:
Increasing evidence suggests that phase transitions play an important role in the internal organization of living cells. We have shown that a number of membrane-less RNA and protein rich organelles, known as RNP bodies, represent condensed liquid phase droplets, which assemble by liquid-liquid phase separation. The nucleolus is a liquid-like nuclear body, which plays an important role in cell growth and size homeostasis. Using the reductive cell divisions of early C.elegans embryos, we show that a simple phase threshold model explains striking features of the intrinsic coupling of nucleolar assembly to cell size. Building on these findings, we develop a Cahn-Hilliard model for nucleolar liquid-liquid phase separation, which can quantitatively account for the dynamics of nucleolar assembly, for both an in vitro reconstituted system, and within living cells. We use a custom microfluidics platform to test these models in growing C.elegans worms, where we find that the nucleolus grows proportional to cell and organism growth. Concentration-dependent phase transitions allow the cell to read-out its size, and could provide a novel biophysical feedback mechanism for cell growth control.