Revealing the Biophysics of Lamina-Associated Domain Formation by Integrating Theoretical Modeling and...

Area of Science:

• Cell Biology
• Epigenetics
• Genomics

Background:

• Lamina-associated domains (LADs) are crucial for maintaining cell identity through gene repression by interacting with the nuclear lamina.
• The precise strength and environmental dependence of chromatin-nuclear lamina interactions remain poorly understood.

Purpose of the Study:

• To develop a theoretical framework predicting peripheral heterochromatin domain size and shape.
• To investigate the impact of the cellular microenvironment on chromatin-nuclear lamina interactions and LAD structure.

Main Methods:

• Developed a theory integrating chromatin interaction energetics, lamina affinity, and epigenetic modification kinetics.
• Analyzed super-resolution images of peripheral heterochromatin domains in human mesenchymal stem cells (hMSCs).
• Correlated LAD thickness with substrate stiffness, cellular contractility, histone deacetylase 3 (HDAC3) localization, and histone methylation levels.

Main Results:

• Determined a spatially heterogeneous, bimodal distribution of chromatin-nuclear lamina affinities.
• Observed increased LAD thickness on softer substrates, linked to HDAC3 nuclear translocation and elevated histone methylation.
• Found similar chromatin organization changes in tendinosis patient cells compared to cells on soft substrates.

Conclusions:

• The cellular microenvironment plays a pivotal role in shaping genome organization at the nuclear periphery.
• Environmental cues, such as substrate stiffness, can modulate chromatin-nuclear lamina interactions and gene regulation.
• These findings have implications for understanding genome organization in both normal cellular function and pathological conditions like tendinosis.