Stability of global methylation profiles of whole blood and extracted DNA under different storage durations and conditions.

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.