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Phase Separation and Scaling in Biology�An Dynamical Systems Perspective

MCB137/237 – Spring 2025

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The Usual Story About Cell Organization�Through Membrane-Bound Organelles

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P Granule Localization

  • Movie shows P granule localization in GFP::PGL-1 embryo (same embryo as in Fig. 1A). DIC images have been colored red and overlaid over GFP::PGL-1 image (green).

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Some Signatures of Phase Separation

P granules

“dripping”

isolated nucleoli

fusion

aminoacid chain bleaching

Brangynne, et al., Science 2009

Brangwynne et al., PNAS 2011

Boeynaems et al., Bio-Protocol, 2017.

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Liquid-Like Phenomenon in the Context of Nuclear Bodies

Nucleation, coarsening and coalescence of induced nuclear bodies. A novel type of nuclear body first described in Ref. [16] is induced to nucleate and grow upon gentle mechanical pressure applied to the nucleus of drosophila oocytes (t = 0 s). Large liquid-like nuclear bodies grow and coalesce upon contact with one another (courtesy Brangwynne, unpublished). The nucleus is approximately 40 mm in diameter.

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The Nucleolus Is an Example That Has Been Studies With Beautiful Effect

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Fluid-Like Behavior of Nucleoli

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Phase Diagram for Nucleolus Formation

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Size Scale of Organelles in Eukaryotic Cells

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Cell Size Can Vary Dramatically, Even In the Same Organism

Molecular Biology

of the Cell

understanding these scaling relations

demands a quantitative model

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Organelles Scale With Cell Size

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C. elegans development�

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More and Smaller Cells as Development Progresses

Fabio Piano

2 cell embryo

4 cell embryo

16 cell embryo

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The Nucleolus Scales With Nuclear Volume

Weber and Brangwynne (2015)

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Synthetic Biology: Creating Embryos With Varying Cell Sizes

Weber and Brangwynne (2015)

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Simple Model of Nucleolar Formation