U.S. flag

An official website of the United States government, Department of Justice.

Naturally-occurring DNA fragment termini correlate with methylation at CpG sites in hair and blood plasma cell-free DNA

NCJ Number
311622
Journal
BMC Genomics Dated: 2026
Date Published
February 2026
Abstract

Background
CpG methylation is an important epigenetic regulator in growth, development, and disease and a biomarker of age. It was recently shown that CpG methylation influences nuclease activity in the natural process that generates blood plasma cell-free DNA fragments. This results in a correlation between fragmentation sites and methylation that can be used to estimate methylation levels at CpG sites.

Results
We find methylation-dependent fragmentation is also present in the process that generates the cell-free DNA fragments found in hair shafts and urine. Analysis of DNA fragments that includes accurate 5’ and 3’ termini and local sequence context improves modelling of CpG methylation from sequence data.

Conclusions
We demonstrate the existence of methylation-sensitive DNA fragmentation in rootless hair. We develop a model for estimating CpG methylation using both 5-prime and 3-prime native termini of these naturally occurring DNA fragments. This approach enables genotype and epigenetic inference from that same input data. It is applicable for samples that are prevalent in the field of liquid biopsy, forensics and ancient DNA and likely in other keratinized tissues where nuclease digestion of DNA occurs as part of regular development.

(Publisher abstract provided.)

Date Published: February 1, 2026