Genome architecture plasticity underlies DNA replication timing dynamics in cell differentiation

Area of Science:

• Genomics
• Epigenetics
• Cell Biology

Background:

• DNA replication timing (RT) is ordered, with active genes replicating early and inactive genes late.
• Sequencing advances enable exploration of RT, histone modifications, and 3D chromatin structure.
• Cell differentiation involves dynamic changes in gene expression and genome organization.

Purpose of the Study:

• To characterize the dynamics of replication timing during human cell differentiation.
• To compare RT, epigenetic features, and 3D chromatin structure across cell types.
• To uncover the coordinated regulation of RT and genome architecture during pluripotency loss and lineage commitment.

Main Methods:

• Collected sequencing data for human embryonic stem cells and four differentiated cell types.
• Compared replication timing (RT) and its conservation before and after germ layer specification.
• Partitioned the human genome into categories based on RT and analyzed genomic, epigenetic, and 3D structural features.

Main Results:

• Constitutive early and late replication regions showed active and inactive features, respectively.
• Dynamic RT regions exhibited intermediate features and distinct 3D structural preferences.
• Early-to-late and late-to-early replication regions had opposite structural preferences in human embryonic stem cells, despite similar histone modifications.

Conclusions:

• Replication timing and 3D genome structure are coordinately regulated during cell differentiation.
• Genome architecture plays a crucial role in the loss of pluripotency and lineage commitment.
• Dynamic changes in RT and 3D structure are key to developmental processes.