AI Insight
FIRE is a new long-read sequencing method that maps chromatin accessibility along individual DNA molecules from each parent chromosome, providing detailed views of the diploid epigenome. The technique identified the HLA locus as having the highest density of haplotype-specific chromatin in immune cells and revealed mechanisms by which some genes escape X chromosome inactivation. Importantly, the study discovered widespread somatic epimutations—stable chromatin changes that occur during cell division but are not caused by DNA sequence changes—which limit the extent to which genetics alone determines the epigenome.
Why it matters
This work demonstrates that epigenetic states are not purely determined by DNA sequence, as somatic epimutations introduce variability that persists across cell divisions. The findings have implications for understanding disease susceptibility, cellular diversity within individuals, and why genetically identical cells can have different functional states.
Understand the Science
FIRE is a long-read Fiber-seq method that resolves chromatin accessibility along individual DNA molecules on each parental chromosome, enabling a comprehensive assessment of the diploid epigenome. FIRE reveals that the HLA locus harbors the densest haplotype-selective chromatin in immune cells and resolves regulatory principles of escape from X inactivation. It also uncovers pervasive somatic epimutations, mitotically stable and non-genetically mediated chromatin changes that cap genetic determinism in the human epigenome.
Source: Somatic epimutations cap genetic determinism in the human diploid chromatin epigenome