Article

IrisPlex: A sensitive DNA tool for accurate prediction of blue and brown eye colour in the absence of ancestry information

Department of Forensic Molecular Biology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands.
Forensic Science International: Genetics (Impact Factor: 4.6). 03/2010; 5(3):170-80. DOI: 10.1016/j.fsigen.2010.02.004
Source: PubMed

ABSTRACT

A new era of 'DNA intelligence' is arriving in forensic biology, due to the impending ability to predict externally visible characteristics (EVCs) from biological material such as those found at crime scenes. EVC prediction from forensic samples, or from body parts, is expected to help concentrate police investigations towards finding unknown individuals, at times when conventional DNA profiling fails to provide informative leads. Here we present a robust and sensitive tool, termed IrisPlex, for the accurate prediction of blue and brown eye colour from DNA in future forensic applications. We used the six currently most eye colour-informative single nucleotide polymorphisms (SNPs) that previously revealed prevalence-adjusted prediction accuracies of over 90% for blue and brown eye colour in 6168 Dutch Europeans. The single multiplex assay, based on SNaPshot chemistry and capillary electrophoresis, both widely used in forensic laboratories, displays high levels of genotyping sensitivity with complete profiles generated from as little as 31pg of DNA, approximately six human diploid cell equivalents. We also present a prediction model to correctly classify an individual's eye colour, via probability estimation solely based on DNA data, and illustrate the accuracy of the developed prediction test on 40 individuals from various geographic origins. Moreover, we obtained insights into the worldwide allele distribution of these six SNPs using the HGDP-CEPH samples of 51 populations. Eye colour prediction analyses from HGDP-CEPH samples provide evidence that the test and model presented here perform reliably without prior ancestry information, although future worldwide genotype and phenotype data shall confirm this notion. As our IrisPlex eye colour prediction test is capable of immediate implementation in forensic casework, it represents one of the first steps forward in the creation of a fully individualised EVC prediction system for future use in forensic DNA intelligence.

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Available from: Fan Liu, Oct 01, 2014
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    • "We thank the authors of reference [1] for the use of the eye pictures (license number 3687520938055). "
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    • "); Snipper15 (those SNPs present in the HGDP-CEPH online data) and Snipper23* (all 23 SNPs studied by Ruiz).Erasmus6 (the 6 Irisplex SNPs analyzed with the Erasmus Irisplex Webtool) was additionally tested. It should be noted that the Erasmus Irisplex Webtool is based on a larger reference dataset [8] than the Excel calculator included in the original Irisplex publication [1] and gives improved MLR probabilities for a majority of SNP profiles. Supplementary Fig. S1 "
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    ABSTRACT: New DNA-based predictive tests for physical characteristics and inference of ancestry are highly informative tools that are being increasingly used in forensic genetic analysis. Two eye colour prediction models: a Bayesian classifier–Snipper and a multinomial logistic regression (MLR) system for theIrisplex assay, have been described for the analysis ofunadmixed European populations. Since multiple SNPs in combination contribute in varying degrees to eye colour predictability in Europeans, it is likely that these predictive tests will perform in different ways amongst admixed populations that have European co-ancestry, compared to unadmixed Europeans. In this study we examined 99 individuals from two admixed South American populations comparingeye colour versus ancestry in order to reveal a direct correlation of light eye colour phenotypes with European co-ancestry in admixed individuals. Additionally, eye colour prediction following six prediction models,using varying numbers of SNPs and based on Snipper and MLR,were applied to the study populations.Furthermore, patterns of eye colour prediction have been inferredfor a set of publicly available admixed and globally distributed populationsfrom the HGDP-CEPH panel and 1000 Genomes databases with a special emphasis on admixed American populations similar to those of the study samples.
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