Validation study of age estimation methods based on blood DNA methylation rates using artificially degraded DNA

Age estimation based on DNA methylation rates can provide useful information on unknown suspects and victims of crimes from biological materials like blood. We have previously shown the accuracy and effectiveness of the age estimation methods using a pyrosequencing approach on Japanese blood and aged bloodstain samples. However, the DNA quality required for an accurate age estimation is not known: effects of DNA degradation on the methylation rate-based age estimation methods are not clear. In the present study, we evaluated the effect of DNA degradation on the three age estimation methods by using artificially degraded DNA samples. When we used a default amount (50 ng) of DNA for age estimation, enzymatically degraded samples ranging 1.12–4.54 in the degradation index by QuantifilerTM HP DNA Quantification Kit predicted age accurately with a comparable level to undegraded DNA. On the other hand, in case of using a less amount (<50 ng) of DNA, degraded samples caused an unignorable level of difference in the methylation rates of ELOVL2 markers and age predictions by the three estimation models between undegraded control DNA. These results indicate the importance of using a sufficient DNA to ensure an accurate age estimation on forensic samples.