Liquid-fiber interactions– governed by the physical principle of elastocapillarity– are invoked when liquids adhere to flexible structures like membranes and microtubules. The liquid can influence the shape/structure of the fiber, and vice versa.
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Through simulations and experiments of a chromatin fiber networks and liquid-like condensates, we revealed that both chromatin-including, aspherical structures and chromatin-excluding, spherical structures seen in the mesoscale nucleus can be recreated through elastocapillarity
Elegantly, the variety of morphologies seen in nuclei can arise from varying just two parameters– condensate wetting and chromatin stiffness.
Nonwetting condensates in flexible networks cavitate and exclude fibers, while wetting condensates engulf and bundle them. Stiff networks inhibit growth.
We investigated the determinants of condensate wetting and chromatin stiffness in living cells.
Stiffness arises from chromatin density, while wetting is controlled by the strength and extent of chromatin binding, with heterochromatic protein HP1alpha’s chromodomain providing strong wetting
Multiple types of condensates coexist within one nucleus, potentially interacting mechanically through modulating the chromatin network– we found that wetting condensates bundle and stiffen chromatin, constraining the size of non-wetting condensates.
This work was a joint effort with Hongbo Zhao, with contributions from Jorine Eeftens, Mikko Haataja, Andrej Kosmrlj and Cliff Brangwynne. It was funded by Princeton University and through multiple federal sources. Please read the full story and write to your senators to support scientific funding.
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Nonwetting condensates in flexible networks cavitate and exclude fibers, while wetting condensates engulf and bundle them. Stiff networks inhibit growth.
Stiffness arises from chromatin density, while wetting is controlled by the strength and extent of chromatin binding, with heterochromatic protein HP1alpha’s chromodomain providing strong wetting
Surface tension and stiffness– not just binding affinity or location– shape genome structure.
Elastocapillarity offers a physical basis for mesoscale nuclear morphology, with implications for gene regulation and disease.