Aim: To test whether DNA samples stored for a prolonged period (20 years) under various storage conditions could be used for comparative methylation studies using reduced representation bisulfite sequencing.
Patients & methods: Five groups of human blood DNA samples (n = 5-6/group) were compared. The groupings were based on the anticoagulant used and storage temperature and duration.
Results: Methylation profiles of defined genomic regions in the DNA or blood samples archived for 20 years were similar across all storage temperatures, including 4°C. The level of intersample similarity in archived samples was not significantly different than that in recently collected samples.
Conclusion: Archived samples, including DNA stored at 4°C for 20 years, are suitable for comparative studies of DNA methylation.
Keywords: methylation profiles; stability; storage conditions.