Soft-matter properties of multilayer chromosomes

Area of Science:

• Biophysics
• Soft Matter Physics
• Molecular Biology

Background:

• Chromosomes condense into micrometer-scale cylinders during mitosis.
• Previous studies suggest metaphase chromosomes possess a multilayered structure composed of mononucleosome sheets.

Purpose of the Study:

• To explore the relationship between the structural and dynamic properties of chromosomes and soft-matter systems.
• To understand the self-organization principles governing chromosome structure.

Main Methods:

• Transmission electron microscopy (TEM)
• Atomic force microscopy (AFM)
• Cryo-electron tomography

Main Results:

• Metaphase chromosomes exhibit self-organized hydrogel properties with internal liquid-crystal order.
• Chromosome self-organization is attributed to weak interactions between nucleosome building blocks and thermal fluctuations.
• Chromosomes demonstrate properties of soft matter, including easy deformability and phase transitions.

Conclusions:

• Metaphase chromosomes can be viewed as self-organized hydrogels, akin to soft-matter systems.
• The observed properties are consistent with principles governing spontaneous assembly in soft matter.
• Phase transitions, influenced by factors like Mg2+ concentration, facilitate chromosome decondensation and gene expression during interphase.