Ozlem Bulbul

52 additional reference population samples for the 55 AISNP panel

Ancestry inference for a person using a panel of SNPs depends on the variation of frequencies of those SNPs around the world and the amount of reference data available for calculation/comparison. The Kidd Lab panel of 55 AISNPs has been incorporated in commercial kits by both Life Technologies and Illumina for massively parallel sequencing. Therefore, a larger set of reference populations will be useful for researchers using those kits. We have added reference population allele frequencies for 52 population samples to the 73 previously entered so that there are now allele frequencies publicly available in ALFRED and FROG-kb for a total of 125 population samples.

A panel of 74 AISNPs: Improved ancestry inference within Eastern Asia

Many ancestry informative SNP (AISNP) panels have been published. Ancestry resolution in them varies from three to eight continental clusters of populations depending on the panel used. However, none of these panels differentiates well among East Asian populations. To meet this need, we have developed a 74 AISNP panel after analyzing a much larger number of SNPs for Fst and allele frequency differences between two geographically close population groups within East Asia. The 74 AISNP panel can now distinguish at least 10 biogeographic groups of populations globally: Sub-Saharan Africa, North Africa, Europe, Southwest Asia, South Asia, North Asia, East Asia, Southeast Asia, Pacific and Americas. Compared with our previous 55-AISNP panel, Southeast Asia and North Asia are two newly assignable clusters. For individual ancestry assignment, the likelihood ratio and ancestry components were analyzed on a different set of 500 test individuals from 11 populations. All individuals from five of the test populations - Yoruba (YRI), European (CEU), Han Chinese in Henan (CHNH), Rondonian Surui (SUR) and Ticuna (TIC) - were assigned to their appropriate geographical regions unambiguously. For the other test populations, most of the individuals were assigned to their self-identified geographical regions with a certain degree of overlap with adjacent populations. These alternative ancestry components for each individual thus help give a clearer picture of the possible group origins of the individual. We have demonstrated that the new AISNP panel can achieve a deeper resolution of global ancestry.

Evaluating a subset of ancestry informative SNPs for discriminating among Southwest Asian and circum-Mediterranean populations

Many different published sets of single nucleotide polymorphisms (SNPs) and/or insertion-deletion polymorphisms (InDels) can serve as ancestry informative markers (AIMs) to distinguish among continental regions of the world. For a focus on Southwest Asian ancestry we chose to start with the Kidd Lab panel of 55 ancestry-informative SNPs (AISNPs) because it already provided good global reference data (FROG-kb: frog.med.yale.edu) in a set of 73 population samples distinguishing at least 8 biogeographic clusters of populations. This panel serves as a good first tier ancestry panel. We are now interested in identifying region-specific second tier panels for more refined distinction among populations within each of the global regions. We have begun studying the global region centered on Southwest Asia and the region encompassing the Mediterranean Sea. We have incorporated 10 populations from North Africa, Turkey and Iran and included 31 of the original 73 populations and eleven 1000 Genomes Phase3 populations for a total of 3129 individuals from 52 populations, all typed for the 55 AISNPs. We have then identified the subset of the 55 AISNPs that are most informative for this region of the world using Heatmap, Fst, and Informativeness analyses to eliminate those SNPs essentially redundant or providing no information among populations in this region, reducing the number of SNPs to 32. STRUCTURE and PCA analyses show the remaining 32 SNPs identify the North African cluster and appropriately include the Turkish and Iranian samples with the Southwest Asian cluster. These markers provide the basis for building an improved, optimized panel of AISNPs that provides additional information on differences among populations in this part of the world. The data have also allowed an examination of the accuracy of the ancestry inference based on 32 SNPs for the newly studied populations from this region. The likelihood ratio approach to ancestry inference embodied in FROG-kb provides highly significant population assignments within one order of magnitude for each individual in the Turkish, Iranian, and Tunisian populations.

Evaluation of reliability on STR typing at leukemic patients used for forensic purposes

Over the past decades, main advances in the field of molecular biology, coupled with benefits in genomic technologies, have led to detailed molecular investigations in the genetic diversity generated by researchers. Short tandem repeat (STR) loci are polymorphic loci found throughout all eukaryotic genome. DNA profiling identification, parental testing and kinship analysis by analysis of STR loci have been widely used in forensic sciences since 1993. Malignant tissues may sometimes be the source of biological material for forensic analysis, including identification of individuals or paternity testing. There are a number of studies on microsatellite instability in different types of tumors by comparing the STR profiles of malignant and healthy tissues on the same individuals. Defects in DNA repair pathways (non-repair or mis-repair) and metabolism lead to an accumulation of microsatellite alterations in genomic DNA of various cancer types that result genomic instabilities on forensic analyses. Common forms of genomic instability are loss of heterozygosity (LOH) and microsatellite instability (MSI). In this study, the applicability of autosomal STR markers, which are routinely used in forensic analysis, were investigated in order to detect genotypes in blood samples collected from leukemic patients to estimate the reliability of the results when malignant tissues are used as a source of forensic individual identification. Specimens were collected from 90 acute and 10 chronic leukemia volunteers with oral swabs as well as their paired peripheral blood samples from the Oncology Centre of the Department of Hematology at Istanbul University, during the years 2010–2011. Specimens were tested and compared with 16 somatic STR loci (CSFIPO, THO1, TPOX, vWA, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11 and FGA) widely used in forensic identification and kinship. Only two STR instabilities were encountered among 100 specimens. An MSI in the FGA loci and a LOH in the D2S1338 loci were determined in two individuals separately. Our results demonstrate that the use of the biological samples from leukemia patients in forensic identification and kinship testing is questionable, especially if known microsatellite instability is available. Genetic instabilities may alter the STR polymorphism, leading to potential errors on forensic identification of individuals. Therefore, typing of autosomal STRs from leukemia patients should be performed with both healthy and malignant tissue samples of individual as references.

Ancestry inference of 96 population samples using microhaplotypes

Microhaplotypes have become a new type of forensic marker with a great ability to identify and deconvolute mixtures because massively parallel sequencing (MPS) allows the alleles (haplotypes) of the multi-SNP loci to be determined directly for an individual. As originally defined, a microhaplotype locus is a short segment of DNA with two or more SNPs defining three or more haplotypes. The length is short enough, less than about 300 bp, that the read length of current MPS technology can produce a phase-known sequence of each chromosome of an individual. As part of the discovery phase of our studies, data on 130 microhaplotype loci with estimates of haplotype frequency data on 83 populations have been published. To provide a better picture of global allele frequency variation, we have now tested 13 more populations for 65 of the microhaplotype loci from among those with higher levels of inter-population gene frequency variation, including 8 loci not previously published. These loci provide clear distinctions among 6 biogeographic regions and provide some information distinguishing up to 10 clusters of populations.

Estimation of the Y-chromosomal short tandem repeat (Y-STR) mutation rates in Turkey

Abstract Background: The Non-recombining region of the Y-chromosome (NRY) is transferred from father to son in an unchanged form without recombination in meiosis. Since Short tandem repeats on Y-chromosome (Y-STRs) in this region do not have any recombination, these regions are identical in all male individuals who are related to the father except for mutations. Therefore, these regions gain importance in identification for the forensic sciences or determination of paternity. In determination of paternity, if mismatches are observed between father and child, population-specific mutation rates should be used to determine whether it is a mutation or a true exclusion. Therefore in this study, we aim to determine the mutation rates of 17 Y-STR loci in Turkey. Material and methods: 17 Y-STR loci were typed by using AmpFlSTR® Yfiler™ Kit in 90 volunteer father-son pairs. Mutation rates were calculated and compared with other populations. Results: The mutations were found between three father-son pairs at DYS439 and DYS458 loci. In addition, a duplication in DYS389 II loci* 30, 31 was observed. The average mutation rate was determined as 1.96×10−3 for Turkish population. Conclusion: This investigation will contribute to minimize the possibility of false exclusion of the father-son and kinship relations.

Development of a SNP panel for predicting biogeographical ancestry and phenotype using massively parallel sequencing

Inferring ancestry and physical characteristics of an unknown individual can contribute to the direction of the investigation and to clarify the event for unknown contributors, cold cases or identification of missing persons and disaster victims. The objective of this study is to develop a custom SNP panel on massively parallel sequencing devices for predicting the biogeographic ancestry and phenotype of an individual. We focused on a two‐tier approach to enhance ancestry. Our MPS panel contains two ancestry informative SNP (AISNPs) panels (i.e., Kidd 55 and SWA panel) to differentiate Southwest Asia from Europe and other continental regions. Then we integrated the set of phenotype informative SNPs into a set of AISNPs. The final set of 156 SNPs was evaluated on the following: sensitivity, genotype concordance, mixtures, ancestry assignment, and phenotype prediction. SNP rs6599400 had consistently poor performance and was removed from further analyses. The extreme mixture (1:10) was difficult to interpret for minor contributor. Ancestry assignment and phenotype predictions (for eye, hair and skin) were accurate for samples’ population origin. The results show that the developed panel provides high coverage data that can be used for inferring ancestry and predicting eye, hair, and skin color from the intermediate population regions.

Prediction of human eye colour using highly informative phenotype SNPs (PISNPs)

ABSTRACT One of the rapidly developing areas in human genetics and genomics is detection of candidate Single Nucleotide Polymorphism (SNPs) for human complex traits. These findings can be used in the field of forensics for predicting the externally visible characteristics (EVCs) of a given individual based on a sample of DNA alone. Eye colour is currently the most thoroughly investigated EVC for forensic genetic applications. In this study, eye colour prediction performance of two currently available major methods was assessed in a set of 100 individuals from Turkey by applying the two statistical approaches of multinomial logistic regression (MLR) and Bayes analysis using each statistical approach’s online portal (https://hirisplex.erasmusmc.nl/ and http://mathgene.usc.es/snipper/eyeclassifier.html) designed for SNP-based forensic prediction for this phenotype. On one hand, eye colour prediction results for IrisPlex SNPs have a high success rate for correctly predicting blue/brown phenotypes but not for green-hazel or intermediate dark phenotypes. On the other hand, Snipper analysis improved detection of intermediate phenotypes but increased the number of unclassified individuals given the prediction probability threshold applied. This study adds data that can be used as a reference for future eye colour prediction investigations in forensic cases.

Application of next generation sequencing in forensic science [Yeni nesil dizilemenin adli bilimlerde kullanýmý]

Next Generation Sequencing (NGS) Technology has been emerged and started to use in genetic research since the 2000s. Until today, various methods which are faster, high throughput and low cost have been developed. NGS Technologies have been gradually developed and the quality of sequencing has been reached the high level and forensic genetics labs have moved to this technology for recent years. NGS Technologies provide new opportunities for forensic genetics research. NGS Technologies enable to analysis of many forensic genetic markers (as STRs, SNPs, mRNA) in only one experiment. Besides, NGS technologies are applicable for different practices which are essential in forensic researches. Among these, create of a DNA database, ancestry and phenotype studies, monozygotic twin studies, identification of body fluids and species, forensic microbiology studies can be considered. This review has been written to focus on NGS technologies in forensic genetics applications and to be a reference study for next forensic researchers.

Heteropaternal Superfecundation: A Case Report in Turkey

Superfecundation is the fertilization of two or more ova from the same cycle by sperm from separate acts of sexual intercourse. Heteropaternal superfecundation occurs when two different males father fraternal twins. This article reports a case of paternity identification in twins. The results showed that each twin had come from a different father.