Chromosomal coordination and differential structure of asynchronous replicating regions

Area of Science:

• Epigenetics
• Genomics
• Developmental Biology

Background:

• Stochastic asynchronous replication timing (AS-RT) describes cell-to-cell variation in allele replication times.
• Understanding AS-RT is crucial for deciphering epigenetic regulation and cell fate determination.

Purpose of the Study:

• To map genome-wide AS-RT loci independently of genetic variation.
• To identify novel regulatory mechanisms coordinating AS-RT.
• To investigate the role of AS-RT in mono-allelic gene expression and cell identity.

Main Methods:

• Utilized stable clonal pre-B cell populations from C57BL6/Castaneous mice.
• Performed genome-wide mapping of AS-RT loci.
• Combined population-level mapping with single-cell Fluorescence In Situ Hybridization (FISH).

Main Results:

• Identified genome-wide AS-RT loci characterized by differential chromatin accessibility and mono-allelic expression.
• Discovered new gene families associated with cell identity specification within AS-RT regions.
• Revealed a novel regulatory program coordinating parallel and anti-parallel replication relationships between AS-RT loci on chromosomes.

Conclusions:

• AS-RT is a highly regulated epigenetic mark established during early embryogenesis.
• AS-RT may facilitate the programming of mono-allelic gene choice throughout development.
• This regulatory program offers insights into epigenetic control of cell identity and gene expression.