Conserved nucleocytoplasmic density homeostasis drives cellular organization across eukaryotes

Area of Science:

• Cellular biochemistry
• Biophysics
• Systems biology

Background:

• Macromolecular confinement shapes cellular environments, influencing diffusion, crowding, and reaction rates.
• The mechanisms generating intracellular density distributions and their physiological impact remain poorly understood.

Purpose of the Study:

• To investigate the emergence and physiological relevance of intracellular density distributions.
• To determine the relationship between nuclear and cytoplasmic densities and their role in cellular organization.

Main Methods:

• Quantitative phase imaging to measure cellular densities.
• Mathematical modeling to analyze pressure balance across the nuclear envelope.
• Live imaging in C. elegans during development.

Main Results:

• The nucleus is consistently less dense than the cytoplasm in living systems.
• A conserved nuclear-to-cytoplasmic density ratio is maintained via pressure balance across the nuclear envelope.
• This ratio remains stable during development despite changes in nuclear-to-cytoplasmic volume ratios.

Conclusions:

• Intracellular density distributions are actively regulated and coupled to cellular organization and function.
• Deviations from density homeostasis correlate with altered cellular functions, such as senescence.
• Nuclear-to-cytoplasmic density ratios represent key markers in pathophysiology.