Genome-wide absolute quantification of chromatin looping

Area of Science:

• Genomics
• Molecular Biology
• Cell Biology

Background:

• Three-dimensional genomics techniques like Hi-C and Micro-C identify chromatin loops involved in gene regulation.
• Current methods measure chromatin interactions on a relative scale, lacking absolute probability quantification.

Purpose of the Study:

• To overcome the limitation of relative interaction probabilities in 3D genomics.
• To establish a method for genome-wide absolute loop quantification.
• To determine the absolute looping probabilities of chromatin loops.

Main Methods:

• Utilized live-imaging data to calibrate Micro-C in mouse embryonic stem cells.
• Quantified absolute looping probabilities for 65,929 Micro-C-identified chromatin loops.
• Extended findings to human cells under specific assumptions.

Main Results:

• The looped state is generally rare, with a mean pairwise looping probability of 1.2% and a maximum of 25%.
• CTCF-CTCF loops exhibit higher probabilities (2.2%) compared to cis-regulatory loops (<1%).
• Established a genome-wide approach for absolute loop quantification.

Conclusions:

• Chromatin loops generally occur with low absolute probabilities.
• The developed method provides a quantitative framework for understanding genome architecture.
• Findings generalize live-imaging observations to the entire genome.