Optimization of an age estimation model for semen samples based on DNA methylation using SNaPshot technique.

Identifier:  TFM:313

Handle: https://hdl.handle.net/20.500.11797/TFM313

Authors:  Català Blanco, Marc

Abstract:
Epigenetic interest for age estimation in the forensic context has risen noticeably during last few years. DNA methylation analysis in CpG dinucleotides has turned into be the reference biomarker for age estimation of individuals. Many articles have provided valuable information for body fluids such as blood or saliva samples; nevertheless, few has been reported about semen body fluid. A recent report by Lee et al. was able to develop two age prediction regression models by using only 3 very informative CpG sites (cg06304190 in TTC7B gene, cg12837463, and cg06979108 in NOX4 gene) according to DNA methylation patterns in semen samples. During the present project, 50 μL and 300 μL semen samples from 5 individuals have been bisulfite-converted and analysed by methylation SNaPshot technique for the CpGs selected in the reference paper. Thus, by following the regression models described in Lee et al., an age approach has been achieved successfully with an average absolute difference (MAD) of approximately 5 years between the predicted age and the chronological age in 4 out of 5 individuals. This way, the accuracy and the adaptability of these initial regression models has been verified meaning that, the MAD obtained for original samples in Lee et al. is maintained in other samples from individuals with distinct geographical precedence and subjected to different environmental conditions. However, the limited number of samples considered in this project has not enabled statistical treatment of data, therefore the development of a new regression model has not been possible. That is why further large-scale studies may be developed in order to implement new age estimation models which can aid to solve forensic relevant cases such as sexual assaults or rapes, in which semen is a biological fluid frequently found as an evidence in the crime scene.