Fetal male lineage determination by analysis of Y-chromosome STR haplotype in maternal plasma

The aim of this study is to determine the fetus Y-STR haplotype in maternal plasma during pregnancy and estimate, non-invasively, if the alleged father and fetus belong to the same male lineage. The study enrolled couples with singleton pregnancies and known paternity. All participants signed informed consent and the local ethics committee approved the study. Peripheral blood was collected in EDTA tubes (mother) and in FTA paper (father). Maternal plasma DNA was extracted by using NucliSens EasyMAG. Fetal gender was determined by qPCR targeting DYS-14 in maternal plasma and it was also confirmed after the delivery. From all included volunteers, the first consecutive 20 mothers bearing male fetuses and 10 mothers bearing female fetuses were selected for the Y-STR analysis. The median gestational age was 12 weeks (range 12–36). All DNA samples were subjected to PCR amplification by PowerPlex Y23, ampFLSTR Yfiler, and two in-house multiplexes, which together accounts for 27 different Y-STR. The PCR products were detected with 3500 Genetic Analyzer and they were analyzed using GeneMapper-IDX. Fetuses’ haplotypes (Yfiler format) were compared to other 5328 Brazilian haplotypes available on Y-chromosome haplotypes reference database (YHRD). As a result, between 22 and 27 loci were successfully amplified from maternal plasma in all 20 cases of male fetuses. None of the women bearing female fetuses had a falsely amplified Y-STR haplotype. The haplotype detected in maternal plasma completely matched the alleged father haplotype in 16 out of the 20 cases. Four cases showed single mismatches and they did not configure exclusions; 1 case showed a mutation in the DYS 458 locus due to the loss of one repeat unit and 3 cases showed one DYS 385I/II locus dropout. All mismatches were confirmed after the delivery. Seventeen fetuses’ haplotypes were not found in YHRD and one of them had a mutation, which corresponded to the paternity probability of 99.9812% and 95.7028%, respectively. Three fetuses’ haplotypes occurred twice in YHRD, which corresponded to paternity probability of 99.9437%. In conclusion, high discriminatory fetal Y-STR haplotype could be determined from maternal plasma during pregnancy starting at 12 weeks of gestation. All male fetuses could be attributed to the alleged father male lineage early in pregnancy. The high probability of paternity associated with each case suggests that the relationship is not random and this strategy can be use as an alternative for male fetal kinship analysis.     

Investigation of paternity with alleged father deceased or missing: Analysis of success at the end of the report

In this work we present a retrospective study of 858 cases of paternity investigation performed in Rio Grande do Sul, Southern Brazil, from 2007 to 2012, where the alleged father was deceased or missing. These cases represent 3.3% (858/26187) of paternity tests performed in that period. Considering the analysis of 17 DNA short tandem repeat loci, we present here the proportion of cases with conclusive results according to the number of relatives of the unavailable alleged father investigated and their kinship. The results show 81.0% (695/858) of cases with conclusive results and their characteristics.     

Comparative evaluation of alternative batteries of genetic markers to complement autosomal STRs in kinship investigations: autosomal indels vs. X-chromosome STRs

Kinship investigations such as paternity are currently solved using sets of (commercially available) highly polymorphic autosomal short tandem repeats (STRs), which lead to powerful likelihood ratios (LR). Still, some difficult cases arise whenever the kinship is much more remote or if the alternative hypotheses are not correctly formulated due to the lack of information (for e.g. there is an unknown relationship between the alleged and the true fathers). In these situations, beyond the routinely used marker set, laboratories usually enlarge the number and/or the type of markers analysed. Among these, autosomal indels and X-chromosome STRs have gained popularity. The aim of this study was to compare the results obtained after complementing an initial set of autosomal STRs with indels or with X-chromosome-specific STRs in simulated paternity cases where the alleged father is a close relative of the real one. Results show that in paternity cases where a low number of incompatibilities are observed, the best strategy is to increase the number of autosomal STRs under analysis. Nevertheless, if these are not available, our study globally shows that in father–daughter duos, a set of 12 X-STRs is more advantageous than 38 highly diverse autosomal biallelic markers. Additionally, the usefulness of X-STRs was also evaluated in cases where only a close relative of the alleged parent (father or mother) is available for testing. For those situations where these markers have the power to exclude, strong LR values are obtained. In the remaining cases, LRs are usually weak and sometimes the results are more likely under the wrong kinship hypothesis.     

Autosomal and Y-STR analysis of degraded DNA from the 120-year-old skeletal remains of Ezekiel Harper

The 120-year-old skeletal remains of Confederate Civil War soldier Captain Ezekiel “Zeke” Harper were exhumed by court order in January 2011 for DNA analysis. The goal of the DNA testing was to support or refute whether Captain Harper had fathered a son (Earl J. Maxwell) with his Native American maid prior to his murder in 1892. Bones with adequate structural integrity (left tibia, right tibia, right femur, mandible, four teeth) were retrieved from the burial site and sent to the Institute of Applied Genetics in Fort Worth, Texas for analysis. Given the age and condition of the remains, three different extraction methods were used to maximize the probability of DNA recovery. The majority of the DNA isolates from over fifty separate bone sections yielded partial autosomal STR genotypes and partial Y-STR haplotypes. After comparing the partial results for concordance, consensus profiles were generated for comparison to reference samples from alleged family members. Considering the genetic recombination that occurs in autosomal DNA over the generations within a family, Y-STR analysis was determined to be the most appropriate and informative approach for determining potential kinship. Two of Earl J. Maxwell's grandsons submitted buccal samples for comparison. The Y-STR haplotypes obtained from both of these reference samples were identical to each other and to the alleles in Ezekiel Harper's consensus profile at all 17 loci examined. This Y-STR haplotype was not found in either of two major Y-STR population databases (U.S. Y-STR database and YHRD). The fact that the Y-STR haplotype obtained from Ezekiel's skeletal remains and Earl's grandsons is not found in either population database demonstrates its rarity and further supports a paternal lineage relationship among them. Results of the genetic analyses are consistent with the hypothesis that Earl J. Maxwell is the son of Ezekiel Harper.     

X-chromosome data for 12 STRs: Towards an Argentinian database of forensic haplotype frequencies

The analysis of X-chromosome STRs is useful in certain kinship cases for which autosomal markers provide insufficient statistical power. Particularly, powerful results are achieved in paternity cases with a daughter, when the alleged father is not accessible for analysis, contrarily to his unquestioned mother or daughter. However, representative haplotype frequencies for this type of markers are not available for some populations, as is the case of Argentina, which prevents the quantification of the proof in routine forensic analyses. In this work we present haplotype frequencies for the 12 X-chromosome STRs included in the Investigator Argus X-12 kit, as well as segregation data, obtained from the analysis of the genetic profiles of 457 father-daughter duos, which gave us information on 914 (unrelated) haplotypes from residents of all Argentinian provinces.     

Paternity evaluation in cases lacking a mother and nondetectable alleles

In parentage testing the formulae for computing paternity index and exclusion probability generally ignores the presence of nondetectable alleles at the loci tested. In contrast, it is now known that even when paternity testing is done with hypervariable DNA markers, nondetectable alleles should not be ignored. This work presents simple formulae needed with this consideration, to analyze paternity evaluation from DNA markers in cases where the mother of the disputed child is unavailable for testing. It is shown that even a modest frequency of nondetectable alleles (e.g., 2–5% per locus) may have a substantial impact on the paternity index when the child and/or the alleged father exhibits a single-banded DNA profile at a locus. Use of such formulae can generate a high probability of exclusion and a high paternity index when multiple independently segregating hypervariable DNA markers are used.     

Non-invasive prenatal paternity testing from maternal blood

Prenatal paternity analysis can be performed only after invasive sampling of chorionic villi or amnionic fluid. Aiming to enable noninvasive paternity testing, we attempted to amplify fetal alleles from maternal plasma. Cell-free DNA was isolated from plasma of 20 pregnant women and amplified with ampFLSTR Identifiler and ampFLSTR Yfiler kits. Unfortunately, autosomal fetal alleles were heavily suppressed by maternal DNA, and the only locus that was reliably amplified with AmpFLSTR Identifiler kit was amelogenin, which revealed only fetal gender. Much better success was obtained with AmpFLSTR Yfiler kit, which, in the case of male fetuses, successfully amplified between six and 16 fetal loci. All amplified fetal alleles matched the alleles of their putative fathers, confirming the tested paternity. To the best of our knowledge, this is a first report of noninvasive prenatal paternity testing. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Paternity exclusion power: Comparative behaviour of autosomal and X-chromosomal markers in standard and deficient cases with inbreeding

In paternity testing the informativeness of genetic markers is traditionally measured through the probability of finding, in randomly chosen individuals, inconsistencies with parent to child Mendelian rules of transmission. This statistic, called power of exclusion (PE), paternal exclusion chance or probability, can be defined for duos (mother not typed) or trios (random false fathers are matched against mother/child pairs) and performed both for autosomal and X-chromosomal markers (restricted to paternity testing involving daughters). PE is an a priori statistic, in the sense of not depending on the individual's genetic data of a case, being dependent however on the estimates of genetic markers allele (or haplotype) frequencies.We have studied the behaviour of this statistic in situations where the randomness assumption is not met, because either (a) the alleged – and false – father is related to the true one, or (b) there is a non-negligible level of background relatedness in the population.For the first case, we derived general (autosomal and X-chromosomal) PE formulas for duos and trios for any genealogy linking alleged father and child, highlighting that the PE of each marker only depends on a single kinship parameter associated with their pedigree. In this case we also estimate a lower bound for the number of extra markers needed to be analysed to achieve the same global power as for unrelated individuals. In the second situation, we demonstrate that for realistic values of the coancestry coefficient the decrease in PE due to population inbreeding is very moderate even when duos are analysed.In this work, beyond the aforementioned issues, we also discuss the suitability of assuming the pedigree father–daughter for calculating the X-PE, since X-markers are not the tool of choice in laboratorial routine when the alleged father is available for testing. Indeed, X-markers are particularly useful in situations where the alleged father is not available for testing but experts are able to type the mother or a daughter of his. Such increase of power is due to the paternal genealogies: half- and full-sisters, and grandmother–granddaughter, having a non-null X-PE even when only duos are analysed in contrast to what happens for autosomes. Algebraic expressions for these cases are also presented.     

Analysis of aborted fetal material using autosomal STR markers in forensic cases of sexual assault

Sexual violence represents a widespread social problem associated with serious lifelong consequences. In many cases, an outcome of sexual violence is the victim's unwanted pregnancy, usually ended in an abortion. The objective of this paper is to report five rape cases, including rapes of a minor and young woman, two incest cases and a case of human trafficking for sexual exploitation, where every case resulted in the victim's pregnancy. In each case, pregnancy was terminated in the first trimester or at the beginning of the second trimester in the relevant medical center or clinic. Fresh fetal blood or aborted tissue samples were delivered to our laboratory in order to perform paternity testing for the purpose of proving the crime. DNA extraction using Qiagen Dneasy™ Tissue Kit was optimized according to the sample type. Amplification of autosomal STR (Short Tandem Repeat) markers was performed using the PowerPlex®16 System. In two cases, mixtures of maternal and fetal DNA in the aborted fetal material were found. Using the LRmix Studio v.2.1.5 Software for interpreting DNA mixtures based on a probabilistic model, the likelihoods of maternal contribution and presence of fetal allelic variants inherited from the alleged father/suspect were calculated. Based on these results, we confirmed the presence of assumed fetal fractions (determined before software analysis) in the mixtures. In all cases, positive paternity proved the crime (probabilities of paternity >99.9999%). This cases report once again pointed out the importance of DNA analysis in the process of clarifying and solving forensic cases and demonstrated that the LRmix Studio v.2.1.5 Software can deal with complex cases such as sexual assaults.     

High autosomal STR allele sharing between full siblings

Multiplexes of polymorphic tetranucleotide Short Tandem Repeats (STRs) are regularly employed for forensic identification and kinship testing. If the DNA profiles of two samples match, there is a high probability that the samples have originated from the same individual. Match probabilities are calculated to evaluate the strength of DNA evidence. Relatives often share more alleles than unrelated individuals. High allele sharing among relatives can complicate source attribution of a DNA profile. In this paper, a case of high allele sharing of autosomal STR loci between two full siblings is reported and implications in source attribution are discussed.     

Streamlining the decision-making process for international DNA kinship matching using Worldwide allele frequencies and tailored cutoff log10LR thresholds

The identification of human remains belonging to missing persons is one of the main challenges for forensic genetics. Although other means of identification can be applied to missing person investigations, DNA is often extremely valuable to further support or refute potential associations. When reference DNA samples cannot be collected from personal items belonging to a missing person, a direct DNA identification cannot be carried out. However, identifications can be made indirectly using DNA from the missing person’s relatives. The ranking of likelihood ratio (LR) values, which measure the fit of a missing person for any given pedigree, is often the first step in selecting candidates in a DNA database. Although implementing DNA kinship matching in a national environment is feasible, many challenges need to be resolved before applying this method to an international configuration. In this study, we present an innovative and intuitive method to perform international DNA kinship matching and facilitate the comparison of DNA profiles when the ancestry is unknown or unsure and/or when different marker sets are used. This straightforward method, which is based on calculations performed with the DNA matching software BONAPARTE, Worldwide allele frequencies and tailored cutoff log₁₀LR thresholds, allows for the classification of potential candidates according to the strength of the DNA evidence and the predicted proportion of adventitious matches. This is a powerful method for streamlining the decision-making process in missing person investigations and DVI processes, especially when there are low numbers of overlapping typed STRs. Intuitive interpretation tables and a decision tree will help strengthen international data comparison for the identification of reported missing individuals discovered outside their national borders.     

Mutations or exclusion: an unusual case in paternity testing

In an immigration case with the scope of family reunification, the DNA extracted from the saliva samples of the male child, the alleged mother and the putative father was typed with 22 autosomal short tandem repeat (STR) systems. In seven STR systems, the alleged mother could be excluded from maternity, and the case then had to be regarded as a deficiency case. Taking this fact into consideration, only two exclusions were found for the putative father, and the question arose whether there was an exclusion of the putative father or the existence of two mutations. Autosomal STR typing could not clarify the case, but the application of eight Y-chromosomal markers showed that the alleged father could be excluded from paternity.     

Paternity testing that involves a DNA mixture

Here we analyse a complex disputed paternity case, where the DNA of the putative father was extracted from his corpse that had been inhumed for over 20 years. This DNA was contaminated and appears to be a mixture of at least two individuals. Furthermore, the mother's DNA was not available. The DNA mixture was analysed so as to predict the most probable genotypes of each contributor. The major contributor's profile was then used to compute the likelihood ratio for paternity. We also show how to take into account a dropout allele and the possibility of mutation in paternity testing.     

Pseudo-exclusion from paternity due to maternal uniparental disomy 16

The investigation of a case of disputed paternity revealed indirect exclusion of the alleged father in the haptoglobin system and in the DNA single-locus system D16S309/Hinf I (MS205). The paternity index for the non-exclusion systems was > 10⁶. Since both exclusion systems (HP and MS205) are located on chromosome 16, we investigated 10 microsatellite loci covering this chromosome with 10–20 cM resolution. Analysis of the child’s chromosome showed only alleles of maternal origin and lack of inheritance of paternal alleles for five informative loci. The markers close to the centromere of chromosome 16 were heterozygous, whereas distal loci were either heterozygous or homozygous for maternal alleles. This is consistent with a maternal meiosis I nondisjunction of chromosome 16 leading to maternal uniparental heterodisomy. This case emphasizes that the opinion of non-paternity should be based on the absence of paternal alleles at genetic systems located on at least two different chromosomes. Received: 23 December 1997 / Received in revised form: 9 February 1998     

Improved pairwise kinship analysis using massively parallel sequencing

In the present study, 67 individuals from two families were analyzed to explore the efficacy of the ForenSeq^™ DNA Signature Prep Kit for pairwise kinship analysis. Six types of pairwise relationships including 81 parent-offspring, 60 full siblings, 48 grandparent-grandchildren, 147 uncle/aunt-nephew/nieces, 97 first cousins and 190 non-relatives were generated from these two families and the corresponding likelihood ratio (LR) was calculated using either sequence-based or length-based STR genotype data (i.e., LR_sequence and LR_length). In addition, 10,000 pairs of different relationships were simulated to estimate the system powers of the STRs and SNPs in this panel. The results showed that 54, 9 and 5 additional alleles were observed based on sequence for 27 autosomal STRs, 24 Y-STRs and 7 X-STRs, respectively, compared to those based on length information and 11 novel alleles were identified. Five mutations were found for 58 STRs in 81 parent-offspring but no mutations were observed for SNPs. For 27 autosomal STR loci, the LRs were increased from 9.20, 7.87, 2.01, 2.07, 0.42 for log₁₀LR_length to 11.52, 10.12, 2.61, 2.60, 0.52 for log₁₀LR_sequence for paternity index (PI), full siblings index (FSI), grandparent-grandchild index (GI), uncle/aunt-nephew/niece index (UNI) and first cousins index (FCI), respectively. PI values for 94 SNPs separated more than those of 27 STRs if two individuals were non parent-offspring relatives. For the simulation study, the effectiveness was 1 for the parent-offspring relationship at the thresholds of t₁ = − 4 and t₂ = 4 and was 0.9998 for full siblings (t₁ = − 2, t₂ = 2). With an error rate of 0.42%, 93.02% of second degree relatives could be identified at the thresholds of t₁ = − 1 and t₂ = 1. However, the effectiveness was only 0.4300 for first cousins with a relatively high error rate of 2.68% (t₁ = − 1, t₂ = 1). In conclusion, STR typing according to the sequence information is more polymorphic, which increases the discrimination power for kinship testing. Compared to these 27 STR markers, 94 SNP markers in this panel have advantages in paternity testing especially when mutated STRs are involved or when a relative is an alleged parent. This panel is powerful enough to resolve paternity and full sibling testing. Most of the second degree relationships could be identified with low error rate while more markers are still needed for first cousins testing.     

False paternity with one or two mismatches using commercial STR kits

This study presents a case of false paternity where one or two mismatches were found by using three commercial STR kits. The analysis with the Identifiler kit yielded two mismatches at the loci D2S1338 and vWA. These data did not, however, enable us to exclude the alleged father, as the total number of excluding loci was less than three. Further STR loci were therefore employed to resolve the case. The PowerPlex 16 system yielded only one mismatch at the vWA locus previously found with the Identifiler kit. GenePhile G-Plex, on the other hand yielded two inconsistencies at D3S1744 and D18S536 (out of 15 loci in total). Since the disputed child was a female and we were not able to exclude the possible involvement of a close male relative, we choose to use Genephile X-Plex kit to finally resolve the case. Out of 13 loci tested, we found a complete match of the child's profile with the mother and eight mismatches with the alleged father, clearly indicating that the alleged father is not the biological father. This case emphasizes the usefulness of either Y-chromosome or X-chromosome DNA data for interpreting borderline paternity cases.     

Predicting biogeographical ancestry in admixed individuals – values and limitations of using uniparental and autosomal markers

When microsatellite profiles generated from crime scene samples do not match a known person, or eye-witness information is unreliable, highly informative uniparental and autosomal markers can help unveil biogeographical ancestry. However, as genetic admixture is becoming increasingly common in cosmopolitan societies, concern arises with their accuracy and suitability when dealing with samples from admixed individuals. Here we assess the ability to detect biogeographical ancestry in 85 individuals from self-declared Asian and European admixed families using a set of uniparental (Y and mitochondrial DNA) and autosomal single nucleotide polymorphisms, specifically selected to distinguish between these two biogeographical ancestries. Haplogroups and autosomal genotypes were investigated using STRUCTURE to detect levels of admixture. All haplogroups were characteristic of self-declared populations of origin. Overall, the autosomal markers inferred biogeographical ancestry more accurately in admixed individuals, showing no significant differences between observed and expected contribution from each population studied according to level of admixture, although some outliers were observed. We suggest a panel of highly informative autosomal and uniparental markers should be employed to infer biogeographical ancestry of an individual to help detect admixed ancestries.     

Investigating kinship of Neolithic post-LBK human remains from Krusza Zamkowa,Poland using ancient DNA

We applied an interdisciplinary approach to investigate kinship patterns and funerary practices during the middle Neolithic. Genetic studies, radiocarbon dating, and taphonomic analyses were used to examine two grave clusters from Krusza Zamkowa, Poland. To reconstruct kinship and determine biological sex, we extracted DNA from bones and teeth, analyzed mitochondrial genomes and nuclear SNPs using the HID-Ion AmpliSeq™ Identity panel generated on Illumina and Ion Torrent platforms, respectively. We further dated the material (AMS ¹⁴C) and to exclude aquatic radiocarbon reservoir effects, measures of carbon and nitrogen stable isotopes for diet reconstruction were used. We found distinct mitochondrial genomes belonging to haplogroups U5b2a1a, K1c and H3d in the first grave cluster, and excluded maternal kin patterns among the three analyzed individuals. In the second grave cluster one individual belonged to K1a4. However, we could not affiliate the second individual to a certain haplogroup due to the fragmented state of the mitochondrial genome. Although the individuals from the second grave cluster differ at position 6643, we believe that more data is needed to fully resolve this issue. We retrieved between 26 and 77 autosomal SNPs from three of the individuals. Based on kinship estimations, taking into account the allelic dropout distribution, we could not exclude first degree kin relation between the two individuals from the second grave cluster. We could, however, exclude a first degree kinship between these two individuals and an individual from the first grave cluster. Presumably, not only biological kinship, but also social relations played an important role in the funerary practice during this time period. We further conclude that the HID-Ion AmpliSeq™ Identity Panel may prove useful for first degree kin relation studies for samples with good DNA preservation, and that mitochondrial genome capture enrichment is a powerful tool for excluding direct maternal relationship in ancient individuals.     

Efficacy of extended kinship analyses utilizing commercial STR kit in establishing personal identification

Unprecedented fidelity and specificity have afforded DNA testing its long reigning status as the gold standard for establishing personal identification. While the method itself is flawless, forensic experts have undoubtedly stumbled across challenging cases in which no reference samples for an unknown person (UP) are available for comparison. In such cases, experts often must resort to an assortment of kinship analyses-primarily those involving alleged parents or children of a UP-to establish personal identification. The present study derives likelihood ratio (LR) distributions from an extensive series of kinship simulations and places actual data, obtained from 120 cases in which personal identification of a UP was established via kinship analyses, to a comprehensive comparison in order to evaluate the efficacy of kinship assessments in establishing personal identification. A commercially available AmpFlSTR Identifiler kit was used to obtain DNA profiles. UP DNAs were extracted and isolated from fingernail (n=87), cardiac blood (24), carpal bone (7) and tooth (2). Buccal cells were procured from alleged kin (AK) for subsequent kinship analyses. In 72 cases 1-3 alleged children were available for comparison; in 46 cases, one or both alleged parents were available; and in the final 2 cases (involving a pair of bodies discovered together in a dwelling), their alleged children were typed for comparison. For each case a LR was calculated based on the DNA typing results. Interestingly, we found that the median LR observed in the actual cases virtually mirrored those of the simulations. With exception to 2 cases in which a silent allele was observed at D19S433, biological relatives showed a LR greater than 100 and in these cases, kinship between the UP and AK were further supported by additional forms of evidence. We show here that in the vast majority of identification cases where direct reference samples are unavailable for a UP, kinship analyses referring to alleged parents/children and using 15 standard loci is more than capable of establishing the identification of a UP. However, discretion should be advised for silent alleles which-albeit rare-are known to occur at loci such as D19S433, along with other mutations which could render a deceivingly reduced LR.     

Evaluation of the paternity probability on an application of minisatellite variant repeat mapping using polymerase chain reaction (MVR-PCR) to paternity testing

Minisatellite variant repeat (MVR) mapping using polymerase chain reaction (PCR) was applied to a practical case of paternity testing to evaluate the paternity probability. In order to obtain single allele mapping by allele-specific MVR-PCR, three flanking polymorphic sites for each of the MS31A and MS32 loci were investigated and all three individuals were typed as heterozygous for at least one flanking polymorphic site at each locus. Allele-specific MVR-PCR was then performed using genomic DNA. It was confirmed that one allele in the child was identical to that from the mother and the other one in the child was identical to that from the alleged father. Mapped allele codes were also compared with those in the database by dot-matrix analysis, and no identical allele was found although some motifs were shared with Japanese alleles. The paternity index and the probability of paternity exclusion in the case at these two MVR loci were calculated using the presumed values of the allele frequencies. These studies seem to illustrate the practical value of MVR mapping of MS31A and MS32 loci in paternity testing.