Highlights
- •We optimized an assay based on pyrosequencing of 7 CpG sites in the ELOVL2 gene.
- •The linear regression model based on ELOVL2 enabled age prediction with R2 = 0.859.
- •Age prediction based on ELOVL2 is possible in bloodstains.
- •ELOVL2 provides a very good source of information about human chronological age.
Abstract
Age estimation in forensic investigations may complement the prediction of externally
visible characteristics and the inference of biogeographical ancestry, thus allowing
a better description of an unknown individual. Multiple CpG sites that show linear
correlation between age and degree of DNA methylation have been identified in the
human genome, providing a selection of candidates for age prediction. In this study,
we optimized an assay based on bisulfite conversion and pyrosequencing of 7 CpG sites
located in the ELOVL2 gene. Examination of 303 blood samples collected from individuals aged 2–75 years
allowed selection of the most informative site, explaining 83% of variation in age.
The final linear regression model included two CpG sites in ELOVL2 and enabled age prediction with R2 = 0.859, prediction error = 6.85 and mean absolute deviation MAD = 5.03. Examination of a testing set of 124 blood samples (MAD = 5.75) showed that 68.5% of samples were correctly predicted, assuming that chronological
and predicted ages matched ±7 years. It was found that the ELOVL2 methylation status in bloodstains had not changed significantly after 4 weeks of
storage in room temperature conditions. Analysis of 45 bloodstains deposited on tissue
paper after 5, 10 and 15 years of storage in room conditions indicated that although
a gradual decrease of positive PCR results was observed, the general age prediction
success rate remained similar and equaled 60–78%. The obtained results show that the
ELOVL2 locus provides a very good source of information about human chronological age based
on analysis of blood, including bloodstains, and it may constitute a powerful and
reliable predictor in future forensic age estimation models.
Keywords
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Article info
Publication history
Published online: October 13, 2014
Accepted:
October 1,
2014
Received in revised form:
September 12,
2014
Received:
May 29,
2014
Identification
Copyright
© 2014 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.
