#39 · Epigenomics

Single-cell data point to cooperative origin firing and position-dependent initiation

The common thread is a move from population-averaged descriptions of replication toward single-cell resolution. RepTile infers allele-resolved replication states in individual cells from multiplexed FISH and chromosome tracing, reporting locus-specific dependence of replication initiation on subnuclear position. A separate single-cell dynamics model proposes that genome replication requires cooperative activation of thousands of origins in each cell, explicitly superseding population-based models. A third preprint, on cohesin loop extrusion, bears on origin behaviour only indirectly: it fits ChIA-PET and HiChIP loop statistics and fountain anisotropy with kinetic theory incorporating roadblocks and crowding, favouring effective two-sided extrusion. What is new is direct single-cell access to replication states and the proposal that initiation is cooperative and position-dependent, while the cohesin work supplies only three-dimensional chromatin context.