Extensive Heterogeneity and Intrinsic Variation in Spatial Genome Organization

Area of Science:

• Genomics and Molecular Biology
• Cell Biology
• Epigenetics

Background:

• Established principles of 3D genome organization include non-random chromosome positioning, chromatin compartments, and topologically associating domains (TADs).
• However, cell-to-cell and cell-intrinsic variability in genome architecture remains poorly understood.

Purpose of the Study:

• To systematically investigate and characterize the heterogeneity in 3D genome organization at the single-cell level.
• To understand the extent and nature of variability in genome architecture within a population of human fibroblasts.

Main Methods:

• Employed high-throughput optical mapping to analyze several hundred intra-chromosomal interactions in individual human fibroblasts.
• Utilized single-cell analysis to examine the behavior of individual alleles within single nuclei.

Main Results:

• Demonstrated low intra-chromosomal association frequencies, influenced by genomic distance, higher-order chromatin structure, and chromatin environment.
• Revealed variability in the structure of topologically associating domains (TADs) between individual cells, with common inter-TAD associations.
• Showcased independent behavior of individual alleles within single nuclei, highlighting significant heterogeneity.

Conclusions:

• The study reveals extensive variability and heterogeneity in 3D genome organization at the individual allele level.
• A broad spectrum of genome configurations coexist within a cell population, challenging the notion of a static genome architecture.