Nuclear repulsion enables division autonomy in a single cytoplasm.

Area of Science:

• Cell Biology
• Mycology
• Genetics

Background:

• Classic cell-cycle models predict synchronous nuclear division in shared cytoplasm.
• Naturally occurring syncytia, like in Ashbya gossypii, exhibit asynchronous nuclear division.
• This raises questions about how nuclei maintain timing differences in a common cellular environment.

Purpose of the Study:

• Investigate the mechanisms maintaining nuclear asynchrony in syncytia.
• Determine how nuclei manage cell-cycle timing within a shared cytoplasm.
• Explore the role of nuclear spacing and territoriality in cell-cycle regulation.

Main Methods:

• Observation of nuclear behavior and division cycles in Ashbya gossypii.
• Analysis of nuclear spacing, territoriality, and microtubule regulation.
• Correlation of territory size and proximity with cell-cycle duration.

Main Results:

• Nuclei exhibit variable division-cycle durations and repel neighbors to form distinct territories.
• Territory size influences nuclear cycling rates, with larger territories correlating with longer cycles.
• Microtubule-regulated nuclear spacing is crucial for asynchrony; close proximity can induce partial synchrony.
• Sister nuclei, though not persistent neighbors, retain similar division times, suggesting a 'birth state' memory.

Conclusions:

• Nuclei utilize cytoplasmic microtubules to establish dynamic, individual compartments or "cells within cells."
• These compartments compete for cytoplasmic space, insulating individual division cycles.
• This spatial organization mechanism allows syncytial nuclei to manage cell-cycle signaling and size control without physical barriers.