Highlights
- •Prediction of human appearance from DNA is a useful tool to identify unknown persons.
- •Genetic variants in MC1R, IRF4, ASIP and BNC2 contribute to freckling in Spain.
- •A preliminary DNA-based prediction model for the presence of ephelides is developed.
- •Accuracy of the newly-generated freckle prediction model is reasonably high.
- •Further research is needed before practical use in forensics of the newly-generated freckle model.
Abstract
Prediction of human pigmentation traits, one of the most differentiable externally
visible characteristics among individuals, from biological samples represents a useful
tool in the field of forensic DNA phenotyping. In spite of freckling being a relatively
common pigmentation characteristic in Europeans, little is known about the genetic
basis of this largely genetically determined phenotype in southern European populations.
In this work, we explored the predictive capacity of eight freckle and sunlight sensitivity-related
genes in 458 individuals (266 non-freckled controls and 192 freckled cases) from Spain.
Four loci were associated with freckling (MC1R, IRF4, ASIP and BNC2), and female sex was also found to be a predictive factor for having a freckling
phenotype in our population. After identifying the most informative genetic variants
responsible for human ephelides occurrence in our sample set, we developed a DNA-based
freckle prediction model using a multivariate regression approach. Once developed,
the capabilities of the prediction model were tested by a repeated 10-fold cross-validation
approach. The proportion of correctly predicted individuals using the DNA-based freckle
prediction model was 74.13%. The implementation of sex into the DNA-based freckle
prediction model slightly improved the overall prediction accuracy by 2.19% (76.32%).
Further evaluation of the newly-generated prediction model was performed by assessing
the model’s performance in a new cohort of 212 Spanish individuals, reaching a classification
success rate of 74.61%. Validation of this prediction model may be carried out in
larger populations, including samples from different European populations. Further
research to validate and improve this newly-generated freckle prediction model will
be needed before its forensic application. Together with DNA tests already validated
for eye and hair colour prediction, this freckle prediction model may lead to a substantially
more detailed physical description of unknown individuals from DNA found at the crime
scene.
Keywords
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Article info
Publication history
Published online: November 23, 2017
Accepted:
November 22,
2017
Received in revised form:
November 13,
2017
Received:
June 27,
2017
Identification
Copyright
© 2017 Elsevier B.V. All rights reserved.
