Inverse Size Scaling of the Nucleolus by a Concentration-Dependent Phase Transition

Details

• Alternative Title:
  Curr Biol
• Personal Author:
  Weber, Stephanie C. ; Brangwynne, Clifford P.
• Description:
  Just as organ size typically increases with body size, the size of intracellular structures changes as cells grow and divide. Indeed, many organelles, such as the nucleus [1, 2], mitochondria [3], mitotic spindle [4, 5], and centrosome [6], exhibit size scaling, a phenomenon in which organelle size depends linearly on cell size. However, the mechanisms of organelle size scaling remain unclear. Here, we show that the size of the nucleolus, a membraneless organelle important for cell-size homeostasis [7], is coupled to cell size by an intracellular phase transition. We find that nucleolar size directly scales with cell size in early C. elegans embryos. Surprisingly, however, when embryo size is altered, we observe inverse scaling: nucleolar size increases in small cells and decreases in large cells. We demonstrate that this seemingly contradictory result arises from maternal loading of a fixed number rather than a fixed concentration of nucleolar components, which condense into nucleoli only above a threshold concentration. Our results suggest that the physics of phase transitions can dictate whether an organelle assembles, and, if so, its size, providing a mechanistic link between organelle assembly and cell size. Since the nucleolus is known to play a key role in cell growth, this biophysical readout of cell size could provide a novel feedback mechanism for growth control.
• Subjects:
  Animals Article Caenorhabditis Elegans Cell Nucleolus Cell Size Feedback, Physiological Fluorescence Image Processing, Computer-Assisted Microscopy, Confocal Models, Biological RNA Interference

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• Source:
  Curr Biol. 2015; 25(5):641-646.
• Pubmed ID:
  25702583
• Pubmed Central ID:
  PMC4348177
• Document Type:
  Journal Article
• Funding:
  1DP2GM105437-01/DP/NCCDPHP CDC HHS/United States ; DP2 GM105437/GM/NIGMS NIH HHS/United States ; P40 OD010440/OD/NIH HHS/United States
• Volume:
  25
• Issue:
  5
• Collection(s):
  CDC Public Access
• Main Document Checksum:
  urn:sha256:7a7fedd2f87d163fbca6322a64d7645910ec855b254b6b44f6b30ee4c135f067
• Download URL:
  https://stacks.cdc.gov/view/cdc/30519/cdc_30519_DS1.pdf
• File Type:
  [PDF - 1.31 MB ]