Development of an epigenetic age predictor for costal cartilage with a simultaneous somatic tissue differentiation system

Age prediction from DNA has been a topic of interest in recent years due to the promising results obtained when using epigenetic markers. Since DNA methylation gradually changes across the individual's lifetime, prediction models have been developed accordingly for age estimation. The tissue-dependence for this biomarker usually necessitates the development of tissue-specific age prediction models, in this way, multiple models for age inference have been constructed for the most commonly encountered forensic tissues (blood, oral mucosa, semen). The analysis of skeletal remains has also been attempted and prediction models for bone have now been reported. Recently, the VISAGE Enhanced Tool was developed for the simultaneous DNA methylation analysis of 8 age-correlated loci using targeted high-throughput sequencing. It has been shown that this method is compatible with epigenetic age estimation models for blood, buccal cells, and bone. Since when dealing with decomposed cadavers or postmortem samples, cartilage samples are also an important biological source, an age prediction model for cartilage has been generated in the present study based on methylation data collected using the VISAGE Enhanced Tool. In this way, we have developed a forensic cartilage age prediction model using a training set composed of 109 samples (19-74 age range) based on DNA methylation levels from three CpGs in FHL2, TRIM59 and KLF14, using multivariate quantile regression which provides a mean absolute error (MAE) of ± 4.41 years. An independent testing set composed of 72 samples (19-75 age range) was also analyzed and provided an MAE of ± 4.26 years. In addition, we demonstrate that the 8 VISAGE markers, comprising EDARADD, TRIM59, ELOVL2, MIR29B2CHG, PDE4C, ASPA, FHL2 and KLF14, can be used as tissue prediction markers which provide reliable blood, buccal cells, bone, and cartilage differentiation using a developed multinomial logistic regression model. A training set composed of 392 samples (n = 87 blood, n = 86 buccal cells, n = 110 bone and n = 109 cartilage) was used for building the model (correct classifications: 98.72%, sensitivity: 0.988, specificity: 0.996) and validation was performed using a testing set composed of 192 samples (n = 38 blood, n = 36 buccal cells, n = 46 bone and n = 72 cartilage) showing similar predictive success to the training set (correct classifications: 97.4%, sensitivity: 0.968, specificity: 0.991). By developing both a new cartilage age model and a tissue differentiation model, our study significantly expands the use of the VISAGE Enhanced Tool while increasing the amount of DNA methylation-based information obtained from a single sample and a single forensic laboratory analysis. Both models have been placed in the open-access Snipper forensic classification website.

Development and evaluations of the ancestry informative markers of the VISAGE Enhanced Tool for Appearance and Ancestry

The VISAGE Enhanced Tool for Appearance and Ancestry (ET) has been designed to combine markers for the prediction of bio-geographical ancestry plus a range of externally visible characteristics into a single massively parallel sequencing (MPS) assay. We describe the development of the ancestry panel markers used in ET, and the enhanced analyses they provide compared to previous MPS-based forensic ancestry assays. As well as established autosomal single nucleotide polymorphisms (SNPs) that differentiate sub-Saharan African, European, East Asian, South Asian, Native American, and Oceanian populations, ET includes autosomal SNPs able to efficiently differentiate populations from Middle East regions. The ability of the ET autosomal ancestry SNPs to distinguish Middle East populations from other continentally defined population groups is such that characteristic patterns for this region can be discerned in genetic cluster analysis using STRUCTURE. Joint cluster membership estimates showing individual co-ancestry that signals North African or East African origins were detected, or cluster patterns were seen that indicate origins from central and Eastern regions of the Middle East. In addition to an augmented panel of autosomal SNPs, ET includes panels of 85 Y-SNPs, 16 X-SNPs and 21 autosomal Microhaplotypes. The Y- and X-SNPs provide a distinct method for obtaining extra detail about co-ancestry patterns identified in males with admixed backgrounds. This study used the 1000 Genomes admixed African and admixed American sample sets to fully explore these enhancements to the analysis of individual co-ancestry. Samples from urban and rural Brazil with contrasting distributions of African, European, and Native American co-ancestry were also studied to gauge the efficiency of combining Y- and X-SNP data for this purpose. The small panel of Microhaplotypes incorporated in ET were selected because they showed the highest levels of haplotype diversity amongst the seven population groups we sought to differentiate. Microhaplotype data was not formally combined with single-site SNP genotypes to analyse ancestry. However, the haplotype sequence reads obtained with ET from these loci creates an effective system for de-convoluting two-contributor mixed DNA. We made simple mixture experiments to demonstrate that when the contributors have different ancestries and the mixture ratios are imbalanced (i.e., not 1:1 mixtures) the ET Microhaplotype panel is an informative system to infer ancestry when this differs between the contributors.

Development and inter-laboratory validation of the VISAGE enhanced tool for age estimation from semen using quantitative DNA methylation analysis

The analysis of DNA methylation has become an established method for chronological age estimation. This has triggered interest in the forensic community to develop new methods for age estimation from biological crime scene material. Various assays are available for age estimation from somatic tissues, the majority from blood. Age prediction from semen requires different DNA methylation markers and the only assays currently developed for forensic analysis are based on SNaPshot or pyrosequencing. Here, we describe a new assay using massively parallel sequencing to analyse 13 candidate CpG sites targeted in two multiplex PCRs. The assay has been validated by five consortium laboratories of the VISible Attributes through GEnomics (VISAGE) project within a collaborative exercise and was tested for reproducible quantification of DNA methylation levels and sensitivity with DNA methylation controls. Furthermore, DNA extracts and stains on Whatman FTA cards from two semen samples were used to evaluate concordance and mimic casework samples. Overall, the assay yielded high read depths (> 1000 reads) at all 13 marker positions. The methylation values obtained indicated robust quantification with an average standard deviation of 2.8% at the expected methylation level of 50% across the 13 markers and a good performance with 50 ng DNA input into bisulfite conversion. The absolute difference of quantifications from one participating laboratory to the mean quantifications of concordance and semen stains of remaining laboratories was approximately 1%. These results demonstrated the assay to be robust and suitable for age estimation from semen in forensic investigations. In addition to the 13-marker assay, a more streamlined protocol combining only five age markers in one multiplex PCR was developed. Preliminary results showed no substantial differences in DNA methylation quantification between the two assays, indicating its applicability with the VISAGE age model for semen developed with data from the complete 13-marker tool.

A Comparison of Forensic Age Prediction Models Using Data From Four DNA Methylation Technologies

Individual age estimation can be applied to criminal, legal, and anthropological investigations. DNA methylation has been established as the biomarker of choice for age prediction, since it was observed that specific CpG positions in the genome show systematic changes during an individual’s lifetime, with progressive increases or decreases in methylation levels. Subsequently, several forensic age prediction models have been reported, providing average age prediction error ranges of ±3–4 years, using a broad spectrum of technologies and underlying statistical analyses. DNA methylation assessment is not categorical but quantitative. Therefore, the detection platform used plays a pivotal role, since quantitative and semi-quantitative technologies could potentially result in differences in detected DNA methylation levels. In the present study, we analyzed as a shared sample pool, 84 blood-based DNA controls ranging from 18 to 99 years old using four different technologies: EpiTYPER^®, pyrosequencing, MiSeq, and SNaPshot^TM. The DNA methylation levels detected for CpG sites from ELOVL2, FHL2, and MIR29B2 with each system were compared. A restricted three CpG-site age prediction model was rebuilt for each system, as well as for a combination of technologies, based on previous training datasets, and age predictions were calculated accordingly for all the samples detected with the previous technologies. While the DNA methylation patterns and subsequent age predictions from EpiTYPER^®, pyrosequencing, and MiSeq systems are largely comparable for the CpG sites studied, SNaPshot^TM gives bigger differences reflected in higher predictive errors. However, these differences can be reduced by applying a z-score data transformation.

Development of a methylation marker set for forensic age estimation using analysis of public methylation data and the Agena Bioscience EpiTYPER system

Individual age estimation has the potential to provide key information that could enhance and extend DNA intelligence tools. Following predictive tests for externally visible characteristics developed in recent years, prediction of age could guide police investigations and improve the assessment of age-related phenotype expression patterns such as hair colour changes and early onset of male pattern baldness. DNA methylation at CpG positions has emerged as the most promising DNA tests to ascertain the individual age of the donor of a biological contact trace. Although different methodologies are available to detect DNA methylation, EpiTYPER technology (Agena Bioscience, formerly Sequenom) provides useful characteristics that can be applied as a discovery tool in localized regions of the genome. In our study, a total of twenty-two candidate genomic regions, selected from the assessment of publically available data from the Illumina HumanMethylation 450 BeadChip, had a total of 177 CpG sites with informative methylation patterns that were subsequently investigated in detail. From the methylation analyses made, a novel age prediction model based on a multivariate quantile regression analysis was built using the seven highest age-correlated loci of ELOVL2, ASPA, PDE4C, FHL2, CCDC102B, C1orf132 and chr16:85395429. The detected methylation levels in these loci provide a median absolute age prediction error of ±3.07years and a percentage of prediction error relative to the age of 6.3%. We report the predictive performance of the developed model using cross validation of a carefully age-graded training set of 725 European individuals and a test set of 52 monozygotic twin pairs. The multivariate quantile regression age predictor, using the CpG sites selected in this study, has been placed in the open-access Snipper forensic classification website.

MC1R gene variants and non-melanoma skin cancer: a pooled-analysis from the M-SKIP project

BACKGROUND

The melanocortin-1-receptor (MC1R) gene regulates human pigmentation and is highly polymorphic in populations of European origins. The aims of this study were to evaluate the association between MC1R variants and the risk of non-melanoma skin cancer (NMSC), and to investigate whether risk estimates differed by phenotypic characteristics.

METHODS

Data on 3527 NMSC cases and 9391 controls were gathered through the M-SKIP Project, an international pooled-analysis on MC1R, skin cancer and phenotypic characteristics. We calculated summary odds ratios (SOR) with random-effect models, and performed stratified analyses.

RESULTS

Subjects carrying at least one MC1R variant had an increased risk of NMSC overall, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC): SOR (95%CI) were 1.48 (1.24-1.76), 1.39 (1.15-1.69) and 1.61 (1.35-1.91), respectively. All of the investigated variants showed positive associations with NMSC, with consistent significant results obtained for V60L, D84E, V92M, R151C, R160W, R163Q and D294H: SOR (95%CI) ranged from 1.42 (1.19-1.70) for V60L to 2.66 (1.06-6.65) for D84E variant. In stratified analysis, there was no consistent pattern of association between MC1R and NMSC by skin type, but we consistently observed higher SORs for subjects without red hair.

CONCLUSIONS

Our pooled-analysis highlighted a role of MC1R variants in NMSC development and suggested an effect modification by red hair colour phenotype.

Forensic ancestry analysis with two capillary electrophoresis ancestry informative marker (AIM) panels: Results of a collaborative EDNAP exercise

There is increasing interest in forensic ancestry tests, which are part of a growing number of DNA analyses that can enhance routine profiling by obtaining additional genetic information about unidentified DNA donors. Nearly all ancestry tests use single nucleotide polymorphisms (SNPs), but these currently rely on SNaPshot single base extension chemistry that can fail to detect mixed DNA. Insertion-deletion polymorphism (Indel) tests have been developed using dye-labeled primers that allow direct capillary electrophoresis detection of PCR products (PCR-to-CE). PCR-to-CE maintains the direct relationship between input DNA and signal strength as each marker is detected with a single dye, so mixed DNA is more reliably detected. We report the results of a collaborative inter-laboratory exercise of 19 participants (15 from the EDNAP European DNA Profiling group) that assessed a 34-plex SNP test using SNaPshot and a 46-plex Indel test using PCR-to-CE. Laboratories were asked to type five samples with different ancestries and detect an additional mixed DNA sample. Statistical inference of ancestry was made by participants using the Snipper online Bayes analysis portal plus an optional PCA module that analyzes the genotype data alongside calculation of Bayes likelihood ratios. Exercise results indicated consistent genotyping performance from both tests, reaching a particularly high level of reliability for the Indel test. SNP genotyping gave 93.5% concordance (compared to the organizing laboratory's data) that rose to 97.3% excluding one laboratory with a large number of miscalled genotypes. Indel genotyping gave a higher concordance rate of 99.8% and a reduced no-call rate compared to SNP analysis. All participants detected the mixture from their Indel peak height data and successfully assigned the correct ancestry to the other samples using Snipper, with the exception of one laboratory with SNP miscalls that incorrectly assigned ancestry of two samples and did not obtain informative likelihood ratios for a third. Therefore, successful ancestry assignments were achieved by participants in 92 of 95 Snipper analyses. This exercise demonstrates that ancestry inference tests based on binary marker sets can be readily adopted by laboratories that already have well-established CE regimes in place. The Indel test proved to be easy to use and allowed all exercise participants to detect the DNA mixture as well as achieving complete and concordant profiles in nearly all cases. Lastly, two participants successfully ran parallel next-generation sequencing analyses (each using different systems) and achieved high levels of genotyping concordance using the exercise PCR primer mixes unmodified.

Association of polymorphic sites in the OCA2 gene with eye colour using the tree scanning method

A number of genes are considered to affect normal variation in human pigmentation. Recent studies have indicated that OCA2 is the crucial gene involved in the high variation of iris colour present among populations of European descent. In this study, eleven polymorphisms of the OCA2 gene were examined in search of their association with different pigment traits. The evolutionary tree scanning method indicated that the strongest phenotypic eye colour variation is associated with the branch defined by nonsynonymous change rs1800407, which refers to amino acid causing change Arg419Gln located in exon 13. Single SNP analysis indicated that allele 419Gln is associated with green/hazel iris colour (p < 0.001). According to tree scanning analysis, the proportion of eye colour variation explained by this nucleotide position is merely 4%. Thus, additional variation present in the OCA2 gene and perhaps some other pigment related genes must be taken into account in order to explain the high phenotypic variation in iris colour.

Phylogeography of two European newt species--discordance between mtDNA and morphology

The newts Triturus vulgaris and Triturus montandoni are sister species that exhibit contrasting levels of intraspecific morphological variation. Triturus vulgaris has a broad Eurasiatic distribution encompassing both formerly glaciated and unglaciated areas and shows substantial morphological differentiation in the southern part of its range, while T. montandoni, confined to the Carpathians, is morphologically uniform. We analysed sequence variation of two mtDNA fragments of the total length of c. 1850 bp in 285 individuals of both species collected from 103 localities. Phylogenetic analysis of 200 unique haplotypes defined 12 major clades, their age estimated at c. 4.5-1.0 million years (Myr). Most of the older clades were found in the southern part of the range, and also in central Europe, mainly in Romania. The distribution of mtDNA clades points to the existence of several glacial refugia, located in the Caucasus region, Anatolia, the Balkan Peninsula, Italy, and more to the north in central Europe. The concordance between mtDNA based phylogeny and the distribution of T. vulgaris subspecies was weak. Triturus montandoni haplotypes did not form a monophyletic group. Instead they were found in six clades, in five of them mixed with T. vulgaris haplotypes, most likely as a result of past or ongoing hybridization and multiple introgression of mtDNA from T. vulgaris to T. montandoni. Patterns of sequence variation within clades suggested long-term demographic stability in the southern groups, moderate and relatively old demographic growth in the populations inhabiting central Europe, and high growth in some of the groups that colonized northern parts of Europe after the last glacial maximum.

Mitochondrial phylogeography of the moor frog, Rana arvalis

The moor frog Rana arvalis is a lowland species with a broad Eurasiatic distribution, from arctic tundra through forest to the steppe zone. Its present-day range suggests that glacial refugia of this frog were located outside southern European peninsulas. We studied the species-wide phylogeographical pattern using sequence variation in a 682 base pairs fragment of mtDNA cytochrome b gene; 223 individuals from 73 localities were analysed. Two main clades, A and B, differing by c. 3.6% sequence divergence were detected. The A clade is further subdivided into two subclades, AI and AII differing by 1.0%. All three lineages are present in the Carpathian Basin (CB), whereas the rest of the species range, including huge expanses of Eurasian lowlands, are inhabited solely by the AI lineage. We infer that AII and B lineages survived several glacial cycles in the CB but did not expand, at least in the present interglacial, to the north. The geographical distribution and genealogical relationships between haplotypes from the AI lineage indicate that this group had two glacial refugia, one located in the eastern part of the CB and the other probably in southern Russia. Populations from both refugia contributed to the colonization of the western part of the range, whereas the eastern part was colonized from the eastern refugium only. The effective population size as evidenced by theta(ML) is an order of magnitude higher in the AI lineage than in the AII and B lineages. Demographic expansion was detected in all three lineages.

STR data for AmpF/STR Profiler Plus loci in south Poland

Frequency data of short tandem repeats (STR) loci included in the AmpF/STR Profiler Plus kit were collected from a sample of 253 random, unrelated individuals born in the south Poland region. All loci met Hardy-Weinberg expectation.

Y-chromosomal polymorphic loci DYS19, DYS390, DYS393 in a population sample from northern Poland

Short tandem repeats (STR) are presently of particular use in the field of forensic science, evolution and anthropology. Y-chromosomal STR systems are widely used for population genetics, population history, and for male identification in forensic cases. Here we present an examination of DYS19, DYS390 and DYS393 allele frequencies in a northern Polish population sample. The calculated indices reflect the potential of these markers for application in forensic casework. Statistically significant differences were observed between most western European populations and the Polish cohort when comparing homogeneity of distribution of DYS19 and DYS390 alleles. For three analyzed loci in a sample of 176 males, 43 haplotypes were observed. The studies revealed some rare alleles and a new allele, allele 16, in the DYS393 system. Sequencing by capillary electrophoresis (PE ABI 310) showed the presence of 16 GATA repetitive elements, confirming results obtained after capillary electrophoresis of the DNA fragment. Additionally, sequencing revealed the presence of a novel transversion (A->C) in the analyzed sample.

Vaccinia virus-induced changes in cytokine-regulated acute phase plasma protein synthesis by hepatoma cells

Human hepatoma cell line, HepG2, has been infected with vaccinia virus and synthesis of plasma proteins was determined by electroimmunoassay and corresponding mRNA's measured by Northern blotting. The inhibitory effect of the virus was dose- and time-dependent. Electrophoretic mobility shift assay revealed a decrease in C/EBP binding activities in nuclear extracts isolated from the infected hepatoma cells. Supershift analysis of the C/EBP isoforms showed alpha and beta subunit involvement in DNA binding. The treatment of the cells with interleukin-1, interleukin-6, and dexamethasone at the initial stage of infection appears to delay the virally induced inhibition of host cell protein synthesis. Thus, possible "protective" role of the acute phase cytokines in viral infection is proposed.