Developmental validation of the STRSeqTyper122 kit for massively parallel sequencing of forensic STRs.

Massively parallel sequencing allows for integrated genotyping of different types of forensic markers, which reduces DNA consumption, simplifies experimental processes, and provides additional sequence-based genetic information. The STRseqTyper122 kit genotypes 63 autosomal STRs, 16 X-STRs, 42 Y-STRs, and the Amelogenin locus. Amplicon sizes of 117 loci were below 300 bp. In this study, MiSeq FGx sequencing metrics for STRseqTyper122 were presented. The genotyping accuracy of this kit was examined by comparing to certified genotypes of NIST standard reference materials and results from five capillary electrophoresis-based kits. The sensitivity of STRseqTyper122 reached 125 pg, and > 80% of the loci were correctly called with 62.5 pg and 31.25 pg input genomic DNA. Repeatability, species specificity, and tolerance for DNA degradation and PCR inhibitors of this kit were also evaluated. STRseqTyper122 demonstrated reliable performance with routine case-work samples and provided a powerful tool for forensic applications.

Developmental validation of a high-resolution panel genotyping 639 Y-chromosome SNP and InDel markers and its evolutionary features in Chinese populations.

Uniparental-inherited haploid genetic marker of Y-chromosome single nucleotide polymorphisms (Y-SNP) have the power to provide a deep understanding of the human evolutionary past, forensic pedigree, and bio-geographical ancestry information. Several international cross-continental or regional Y-panels instead of Y-whole sequencing have recently been developed to promote Y-tools in forensic practice. However, panels based on next-generation sequencing (NGS) explicitly developed for Chinese populations are insufficient to represent the Chinese Y-chromosome genetic diversity and complex population structures, especially for Chinese-predominant haplogroup O. We developed and validated a 639-plex panel including 633 Y-SNPs and 6 Y-Insertion/deletions, which covered 573 Y haplogroups on the Y-DNA haplogroup tree. In this panel, subgroups from haplogroup O accounted for 64.4% of total inferable haplogroups. We reported the sequencing metrics of 354 libraries sequenced with this panel, with the average sequencing depth among 226 individuals being 3,741×. We illuminated the high level of concordance, accuracy, reproducibility, and specificity of the 639-plex panel and found that 610 loci were genotyped with as little as 0.03 ng of genomic DNA in the sensitivity test. 94.05% of the 639 loci were detectable in male-female mixed DNA samples with a mix ratio of 1:500. Nearly all of the loci were genotyped correctly when no more than 25 ng/µL tannic acid, 20 ng/µL humic acid, or 37.5 µM hematin was added to the amplification mixture. More than 80% of genotypes were obtained from degraded DNA samples with a degradation index of 11.76. Individuals from the same pedigree shared identical genotypes in 11 male pedigrees. Finally, we presented the complex evolutionary history of 183 northern Chinese Hans and six other Chinese populations, and found multiple founding lineages that contributed to the northern Han Chinese gene pool. The 639-plex panel proved an efficient tool for Chinese paternal studies and forensic applications.

Application of Duplex Droplet Digital PCR Detection of miR-888 and miR-891a in Semen Identification.

OBJECTIVES: To establish a system for simultaneous detection of miR-888 and miR-891a by droplet digital PCR (ddPCR), and to evaluate its application value in semen identification. METHODS: The hydrolysis probes with different fluorescence modified reporter groups were designed to realize the detection of miR-888 and miR-891a by duplex ddPCR. A total of 75 samples of 5 body fluids (including peripheral blood, menstrual blood, semen, saliva and vaginal secretion) were detected. The difference analysis was conducted by Mann-Whitney U test. The semen differentiation ability of miR-888 and miR-891a was evaluated by ROC curve analysis and the optimal cut-off value was obtained. RESULTS: There was no significant difference between the dual-plex assay and the single assay in this system. The detection sensitivity was up to 0.1 ng total RNA, and the intra- and inter-batch coefficients of variation were less than 15%. The expression levels of miR-888 and miR-891a detected by duplex ddPCR in semen were both higher than those in other body fluids. ROC curve analysis showed that the AUC of miR-888 was 0.976, the optimal cut-off value was 2.250 copies/µL, and the discrimination accuracy was 97.33%; the AUC of miR-891a was 1.000, the optimal cut-off value was 1.100 copies/µL, and the discrimination accuracy was 100%. CONCLUSIONS: In this study, a method for detection of miR-888 and miR-891a by duplex ddPCR was successfully established. The system has good stability and repeatability and can be used for semen identification. Both miR-888 and miR-891a have high ability to identify semen, and the discrimination accuracy of miR-891a is higher.

Massively parallel sequencing of STRs using a 29-plex panel reveals stutter sequence characteristics.

Massively parallel sequencing of forensic STRs simultaneously provides length-based genotypes and core repeat sequences as well as flanking sequence variations. Here, we report primer sequences and concentrations of a next-generation sequencing (NGS)-based in-house panel covering 28 autosomal STR loci (CSF1PO, D1GATA113, D1S1627, D1S1656, D1S1677, D2S441, D2S1776, D3S3053, D5S818, D6S474, D6S1017, D6S1043, D8S1179, D9S2157, D10S1435, D11S4463, D13S317, D14S1434, D16S539, D18S51, D18S853, D20S482, D20S1082, D22S1045, FGA, TH01, TPOX, and vWA) and the sex determinant locus Amelogenin. Preliminary evaluation experiments showed that the panel yielded intralocus- and interlocus-balanced sequencing data with a sensitivity as low as 62.5 pg input DNA. A total of 203 individuals from Yunnan Bai population were sequenced with this panel. Comparative forensic genetic analyses showed that sequence-based matching probability of this 29-plex panel reached 2.37 × 10-29 , which was 23 times lower than the length-based data. Compound stutter sequences of eight STRs were compared with parental alleles. For seven loci, repeat motif insertions or deletions occurred in the longest uninterrupted repeat sequences (LUS). However, LUS and non-LUS stutters co-existed in the locus D6S474 with different sequencing depth ratios. These results supplemented our current knowledge of forensic STR stutters, and provided a sound basis for DNA mixture deconvolution.

The ancestry inference of Chinese populations using 74-plex SNPs system.

A panel of ancestry informative SNPs (AISNPs) can be used to analyze the genetic components of a population and infer the ancestral origin of a DNA sample. Previously, we have selected a 74-AISNPs panel and used it to infer the ancestry of unknown individuals in the following ten geographical regions: Sub-Saharan Africa, North Africa, Europe, Pacific, Americas, Southwest Asia, South Asia, North Asia, East Asia and Southeast Asia. We have also established a 74-plex SNPs assay based on SEQUENOM system. In the present study, we genotyped 1371 individuals from 14 populations of China using this multiplex assay, and validated its ability to infer the ancestry in Chinese populations. Firstly, based on the reference database of 3628 individuals from 57 world populations, Structure and Heatmap were employed to evaluate the population differentiation capacity. The training data include 1654 individuals from 14 Chinese populations and 3 populations from 1K Genome, which are not included in the reference database. Then the likelihood ratio and ancestry components were analyzed for individual ancestry assignment using the 74-plex SNPs. The minimum amount of DNA required for a full genotype of the 74 SNPs is 1.5 ng, which is applicable for forensic analysis. The results demonstrate that this system can be used in differentiating the population from ten geographical regions. The ancestry inference accuracy for EUR/SAFR/AME population is 95.4%, 71.0% for East Asia and 66.4% for Southeast Asia respectively. The ancestry inference inclusive rate for EUR/SAFR/AME population is 1.06%, 17.9% for East Asia and 33.3% for Southeast Asia respectively. The results suggest that this method can be used in forensic investigations of criminal cases.

[The effect of EDARV370A on facial and ear morphologies in Uyghur population].

The ectodysplasinA receptor gene (EDAR) plays an important role in the development of ectoderm. The derived G allele of its key missense variant EDARV370A is prevalent in East Asians and Americans, but rare in Africans and Europeans. This leads to distinct ectodermal-derived phenotypes between different continental groups, such as the straighter and thicker hair, more eccrine sweat glands, feminine smaller breasts, shovel incisors characteristic of East Asians. At present, we know little about the association between EDARV370A and facial and ear morphology characteristics. To better understand the effect of EDARV370A on craniofacial phenotypes, we systematically examined the association between EDARV370A and 136 facial quantitative phenotypes, one chin ordinal phenotype and six ear ordinal phenotypes in 715 Uyghurs. The quantitative phenotypes were derived by applying our automated landmark annotation method to facial 3D photos and the ordinal phenotypes were manually graded from facial 2D photos. The analysis identified significant association (P<0.05 after multiple testing correction) between EDARV370A and eight facial phenotypes, one chin phenotype and three ear morphology phenotypes. Our study thus elucidated the pleotropic effect of EDARV370A on craniofacial phenotypes in a European-Asian admixed Uyghur population.

Optimization and validation of analysis method based on 27-plex SNP panel for ancestry inference.

Anthropology generally divides the individuals into the East Asian Mongolia race, European Caucasian race and African Nigro race. The 27-plex single nucleotide polymorphism (SNP) panel for ancestry information has been established to differentiate samples from East Asian, European, African and admixture populations of East Asian and European origin by genotyping and ancestry inference. To infer ancestry for unknown individuals, we established an optimized analysis pipeline based on the likelihood ratio, ancestry component and individual ancestry assignment. Four samples from East Asian, European, African and admixture populations of East Asian and European origin were tested using the optimized analysis pipeline. Cross validation within basic referential database and validation of 1 010 test samples were both used to evaluate the inference process. The results showed that accuracy of the method was higher than 99% in East Asia, Europe, Africa and admixture populations. The inference method can characterize the ancestry information of DNA donors, and has important practical application values in the field of human molecular and forensic genetics.

Screening of highly discriminative microhaplotype markers for individual identification and mixture deconvolution in East Asian populations.

Microhaplotypes are forensic genetic markers that combine single nucleotide polymorphisms in close proximity to one another. Highly discriminative microhaplotype markers could be superior to short tandem repeats (STRs) in DNA mixture deconvolution investigations because they are not interfered by stutters. In this study, the effective number of alleles (Ae) and discrimination power values of microhaplotypes and STRs were compared. It was found that current microhaplotypes are not as discriminative as commonly used forensic STRs. Effective screening of highly discriminative microhaplotype markers were consequently conducted for East Asian populations. To satisfy different forensic application needs, four sets of microhaplotypes with Ae values ≥ 4 were screened for under different conditions that included marker length and physical distances between markers. While the four sets contained 703, 301, 337, and 190 microhaplotypes, their average Ae values reached 5.38, 6.30, 7.39, and 5.61, respectively. The microhaplotype group containing 301 markers (maximum length of 200 bp and separated by ≥ 5 million bases) was further investigated. The results showed that none of the 301 loci were exactly the same as those previously reported, while seven loci partially overlapped with known markers. While Ae values of 45 loci were ≥ 8, the Ae value of the mh17WL-008 locus reached a maximum of 93.57. Further analysis showed that the newly identified microhaplotype markers were also highly polymorphic in African, American, European, and South Asian populations.

Evaluation of the MHSeqTyper47 kit for forensically challenging DNA samples.

Microhaplotypes have been highly regarded for forensic mixture DNA deconvolution because they do not experience interference from stutters in the same way as short tandem repeat markers, and they tend to be more polymorphic than single nucleotide polymorphism markers. However, forensic microhaplotype kits have not been reported. The MHSeqTyper47 kit genotypes 47 microhaplotype loci. In this study, MiSeq FGx sequencing metrics for MHSeqTyper47 were presented, and the genotyping accuracy of this kit was examined. The sensitivity of MHSeqTyper47 reached 62.5 pg, and full genotyping results were obtained from degraded DNA samples with degradation indexes ≤ 3.00. Full genotypes were obtained in the presence of 100 ng/µL tannin, 50 µM heme, 25 ng/µL humic acid, and 1.25 µg/µL indigo dye. In DNA mixture studies, a minimum of 31 loci of the minor contributor were correctly genotyped at 1:99 or 99:1 mixing ratios, with the cumulative random matching probability of these loci reaching 4.54 × 10-25. Mixing ratios could be reliably predicted from two-donor DNA mixtures based on the loci with four called alleles. Taken together, these data showed that the MHSeqTyper47 kit was effective for forensically challenging DNA analysis.

Sequence polymorphisms of forensic Y-STRs revealed by a 68-plex in-house massively parallel sequencing panel.

Sequence polymorphisms of Y chromosome short tandem repeat (Y-STR) markers can be unveiled using next generation sequencing (NGS). Compared to capillary electrophoresis, NGS has the advantage of distinguishing between some alleles of the same length. Here, a 68-plex in-house panel covering 67 Y-STR loci and the sex determinant Amelogenin locus, was developed. The accuracy of this panel was 100% concordant with three standard reference samples. The sensitive was as low as 250 pg. A total of 466 length-based alleles, 806 sequence-based alleles, and 149 haplotypes were observed across 149 Chinese Han individuals. The total haplotype diversity and discrimination capacity was 1.0000 in detected samples. The DYS710 locus possessed the highest diversity by sequence among these Y-STRs, with 109 sequence-based alleles observed. Micro-variant alleles with the same length were observed in 39 Y-STR loci, with their sequence variations mainly attributable to repeat pattern variations. While the number of sequence-based alleles identified for DYS447, DYS449, DYS710, DYS720 and DYF387S1a/b was approximately three times that of their length-based alleles, flanking sequence variations were observed in 18 alleles. In addition, 201 sequence-based alleles in 42 loci were newly discovered. This significantly expanded the knowledge of human Y-STR sequence polymorphisms. Collectively, the 68-plex panel provided reliable Y-STR results as well as higher resolution for paternal lineage analysis.

New cell separation technique for the isolation and analysis of cells from biological mixtures in forensic caseworks.

AIM: To isolate mucosal cells of the perpetrator in a sexual assault case from a complex mixture of his mucosal cells and the victim's skin by micromanipulation prior to genomic analysis. METHODS: To capture and analyze mucosal cells we used the micromanipulation with on-chip low volume polymerase chain reaction (LV-PCR). Consensus DNA profiles were generated from 5 replicate experiments. RESULTS AND CONCLUSIONS: We validated the use of micromanipulation with on-chip LV-PCR for genomic analysis of complex biological mixtures in a fatal rape case. The perpetrator's mucosal cells were captured from nipple swabs of the victim, and a single-source DNA profile was generated from cell mixtures. These data suggest that micromanipulation with on-chip LV-PCR is an effective forensic tool for the analysis of specific cells from complex samples.

Allelic diversity and forensic estimations of the Beijing Hans: Comparative data on sequence-based and length-based STRs.

Short tandem repeat (STR) profiling is routinely used in forensic genetics. At present, STR analysis is mainly performed by capillary electrophoresis (CE). However, due to limitations associated with the CE method, STR genotyping has been limited to length polymorphisms only. Because next generation sequencing (NGS) is capable of providing full resolution STR data at the sequence variation level, the individual identification capability of forensic STR loci could be significantly improved. Here we present sequence-based STR data for the Beijing Han population in which 291 individuals were screened for 23 commonly used forensic STRs using the SeqTypeR24 CASE kit on an Ion PGM platform. In total, 234 length-based alleles and 356 sequence-based alleles, which included 22 novel core repeat sequences, were observed. The sequence-based matching probability and power of discrimination were superior to the length-based numbers for 16 loci bearing micro-variant alleles. Combined matching probability reached 8.2 × 10-29 for 23 STR loci at the sequence level. This was two orders of magnitude higher than the parameters at length level and provides a data base for sequence-based STR casework applications.

A 124-plex Microhaplotype Panel Based on Next-generation Sequencing Developed for Forensic Applications.

Microhaplotypes are an emerging type of forensic genetic marker that are expected to support multiple forensic applications. Here, we developed a 124-plex panel for microhaplotype genotyping based on next-generation sequencing (NGS). The panel yielded intralocus and interlocus balanced sequencing data with a high percentage of effective reads. A full genotype was determined with as little as 0.1 ng of input DNA. Parallel mixture experiments and in-depth comparative analyses were performed with capillary-electrophoresis-based short tandem repeat (STR) and NGS-based microhaplotype genotyping, and demonstrated that microhaplotypes are far superior to STRs for mixture deconvolution. DNA from Han Chinese individuals (n = 256) was sequenced with the 124-plex panel. In total, 514 alleles were observed, and the forensic genetic parameters were calculated. A comparison of the forensic parameters for the 20 microhaplotypes with the top Ae values in the 124-plex panel and 20 commonly used forensic STRs showed that these microhaplotypes were as effective as STRs in identifying individuals. A linkage disequilibrium analysis showed that 106 of the 124 microhaplotypes were independently hereditary, and the combined match probability for these 106 microhaplotypes was 5.23 × 10-66. We conclude that this 124-plex microhaplotype panel is a powerful tool for forensic applications.

Massively Parallel Sequencing of Forensic STRs Using the Ion Chef™ and the Ion S5™ XL Systems.

Next-generation sequencing (NGS) has been used to genotype forensic short tandem repeat (STR) markers for individual identification and kinship analysis. STR data from several NGS platforms have been published, but forensic application trials using the Ion S5™ XL system have not been reported. In this work, we report sensitivity, reproducibility, mixture, simulated degradation, and casework sample data on the Ion Chef™ and S5™ XL systems using an early access 25-plex panel. Sensitivity experiments showed that over 97% of the alleles were detectable with down to 62 pg input of genomic DNA. In mixture studies, alleles from minor contributors were correctly assigned at 1:9 and 9:1 ratios. NGS successfully gave 12 full genotype results from 13 challenging casework samples, compared with five full results using the CE platform. In conclusion, the Ion Chef™ and the Ion S5™ XL systems provided an alternative and promising approach for forensic STR genotyping.

Mucosal cell isolation and analysis from cellular mixtures of three contributors.

In forensic genetic analyses, mixtures of various biological materials are common samples. Micromanipulation, which is performed based on differences in cellular morphology, is an effective method for the isolation of cells from mixtures. In this study, mucosal cell was isolated from somatic cellular mixtures (blood and saliva) based on micromanipulation and a low volume-PCR (LV-PCR) platform. One hundred and twenty-six parallel LV-PCR processes were performed using an Identifiler(®) kit, with 107 reactions yielding single-source DNA profiles. Among them, 54 full profiles (50%) and 37 partial profiles (13-15 loci) were obtained. Based on the above method, we obtained a single-source DNA profile from a cigarette butt contaminated by two victims' blood in a murder case. The generated genotype was used to query a DNA database, and a perfect match was found.

[Study of DNA identification in burned bones].

OBJECTIVE: For the purpose of solving a problems of DNA testing of burned bones. METHODS: We present a novel strategy to obtain DNA from burned bones based on the use of cetyltrimethylammonium bromide (CTAB) lysis buffer and isoamyl alcohol-chlorophorm extraction with subsequent DNA purification using the DNA IQ System. RESULTS: The methods were found to be effective in removing the PCR inhibitors from the burned bone. Then the extracted DNA was successfully genotyped by using the florescence labeling STR multiplex method. CONCLUSION: The results of this research will assist forensic scientists in the identification of DNA from victims whose bodies underwent significant trauma or burning, precluding the utilization of traditional forensic DNA identification techniques.

DNA profiling of spermatozoa by laser capture microdissection and low volume-PCR.

Genetic profiling of sperm from complex biological mixtures such as sexual assault casework samples requires isolation of a pure sperm population and the ability to analyze low abundant samples. Current standard procedure for sperm isolation includes preferential lysis of epithelial contaminants followed by collection of intact sperm by centrifugation. While effective for samples where sperm are abundant, this method is less effective when samples contain few spermatozoa. Laser capture microdissection (LCM) is a proven method for the isolation of cells biological mixtures, even when found in low abundance. Here, we demonstrate the efficacy of LCM coupled with on-chip low volume PCR (LV-PCR) for the isolation and genotyping of low abundance sperm samples. Our results indicate that this method can obtain complete profiles (13-16 loci) from as few as 15 sperm cells with 80% reproducibility, whereas at least 40 sperm cells are required to profile 13-16 loci by standard 'in-tube' PCR. Further, LCM and LV-PCR of a sexual assault casework sample generated a DNA genotype that was consistent with that of the suspect. This method was unable, however, to analyze a casework sample from a gang rape case in which two or more sperm contributors were in a mixed population. The results indicate that LCM and LV-PCR is sensitive and effective for genotyping sperm from sperm/epithelial cell mixtures when epithelial lysis may be insufficient due to low abundance of sperm; LCM and LV-PCR, however, failed in a casework sample when spermatozoa from multiple donors was present, indicating that further study is necessitated.