Development of a multiplex panel with 31 multi-allelic InDels for forensic DNA typing.

Insertion/Deletion (InDel) polymorphic genetic markers are abundant in human genomes. Diallelic InDel markers have been widely studied for forensic purposes, yet the low polymorphic information content limits their application and current InDel panels remain to be improved. In this study, multi-allelic InDels located out of low complexity sequence regions were selected in the datasets from East Asian populations, and a multiplex amplification system containing 31 multi-allelic InDel markers and the Amelogenin marker (FA-HID32plex) was constructed and optimized. The preliminary study on sensitivity, species specificity, inhibitor tolerance, mixture resolution, and the detection of degraded samples demonstrates that the FA-HID32plex is highly sensitive, specific, and robust for traces and degraded samples. The combined power of discrimination (CPD) of 31 multi-allelic InDel markers was 0.999 999 999 999 999 999 85, and the cumulative probability of exclusion (CPE) was 0.999 920 in a Chinese Han population, which indicates a high discrimination power. Altogether, the FA-HID32plex panel could provide reliable supplements or stand-alone information in individual identification and paternity testing, especially for challenging samples.

Evaluation of one-step RT-PCR multiplex assay for body fluid identification.

The discrimination of body fluid stains provides crucial evidence during the investigation of criminal cases. Previous studies have demonstrated the practical value of mRNA profiling in body fluid identification. Conventional strategy of mRNA profiling entails reverse transcription and PCR amplification in two separate procedures with different buffer systems. In this study, we subjected the one-step multiplex reverse transcription PCR strategy to mRNA profiling with the inclusion of the same 18 tissue-specific biomarkers in the F18plex system targeting peripheral blood, menstrual blood, vaginal secretion, saliva, semen, and urine. The Qiagen OneStep RT-PCR kit and Titanium One-Step RT-PCR kit were applied to multiplex construction, while reproducible profiling results were obtained with both kits. Compared to the F18plex system, similar expression profiles of biomarkers were obtained in targeted tissues, while expected cross-reaction was observed in non-targeted body fluids. However, CYP2B7P1 and SPINK5 were detected in menstrual blood samples, which was not observed using the F18plex system. Full-profiling results were obtained in all samples using 0.1 ng peripheral blood and semen RNA, and 1 ng menstrual blood, vaginal secretion, saliva, and urine RNA. In conclusion, the application of one-step mRNA profiling strategy could be a reliable and economical method for the simplified, specific, and simultaneous analysis of tissue-specific biomarkers for the discrimination of body fluid origin.

Genetic analysis of tri-allelic patterns at the CODIS STR loci.

In the routine of autosomal STR genotyping for forensic aims, tri-allelic patterns could be occasionally observed at a single locus in phenotypically normal individuals. Two predominant types of tri-allelic variants have been nominated. Uneven intensities of three alleles are normally considered as the Type 1 pattern, and balanced height of three alleles are considered as the Type 2 pattern. In this study, the prevalence of tri-allelic patterns at the CODIS STR loci was investigated in global populations based on previous reports. The frequencies of the Type 1 and Type 2 pattern manifest a correlation with the germline mutation rates at the CODIS STR loci. The irregular high frequencies of the Type 2 pattern at TPOX with low germline mutation rates could attribute to the stable inheritance of genomic rearrangement from ancestral origin. Furthermore, results from genetic pattern analysis show that only a single allele from STRs with the Type 1 pattern could be transmitted from parents to offsprings, while a single allele and a combination of two alleles from STRs with the Type 2 pattern present an equal opportunity of transmission from parents to offsprings. Altogether, these results provide a genetic portrait of STRs with tri-allelic patterns, which will help the genetic interpretation of tri-allelic patterns in forensic practice.

Genetic analysis of type 2 tri-allelic pattern at TPOX locus in the Chinese Han population.

Tri-allelic patterns can occasionally be observed during the profiling of short tandem repeats (STRs) in routine forensic practice. In previous studies, the Type 2 tri-allelic pattern at TPOX has been widely studied in African and Brazilian populations. In this study, we investigated the incidence, rearrangement, and inheritance of the Type 2 tri-allelic pattern at the TPOX locus in a Chinese Han population. The frequency of the Type 2 pattern at TPOX was approximately 0.0189%, and the major extra allele was allele 11 in the Chinese Han population. Two major allelic combinations, 8/11 and 11/12, were observed, which are different from the configuration of that in both African and Brazilian populations. Tight linkage between alleles 11 and 12 was observed in the majority of the Type 2 pattern at TPOX in the Chinese Han population, while the location of the extra copy on chromosome 2 was validated, which shows an identical ancestral origin. The excess allelic combination 8/11 implies a homogeneous origin and tight linkage relationship. However, the rearrangement in the Type 2 pattern with the 8/11 allelic combination remained unknown. Altogether, these results show the configuration of the Type 2 tri-allelic pattern at the TPOX locus in the Chinese Han population, which will assist in the understanding of the Type 2 tri-allelic pattern at the TPOX locus in the global population.

C-terminus of heat shock protein 60 can activate macrophages by lectin-like oxidized low-density lipoprotein receptor 1.

Immune responses against antigens generally require an efficient activation of antigen-presenting cells (APCs). Currently, the targeting of vaccine antigens to APCs has emerged as a promising strategy for boosting vaccine immunogenicity. Here, we reported that the C-terminus of heat shock protein 60 (HSP60C) can activate mouse peritoneal macrophages to secret a series of cytokines, and phosphorylation of p38 mitogen-activated protein kinase (MAPK) and NF-κB p65 was involved in the pathway. We showed that the activation effect of HSP60C on macrophages was independent of toll-like receptor (TLR) 4 and the TLR-associated myeloide differentiation factor 88 (MyD88). Knockdown of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) reduced the activation of HSP60C-induced macrophage p38 MAPK, NF-κB p65 and cytokine secretion to some extent. Finally, we found that HSP60C up-regulated the expression of LOX-1 on macrophages and ovalbumin (OVA) model antigen fused with HSP60C markedly enhanced OVA-specific IgG responses. Thus, our results unravel a novel LOX-1-dependent pathway by which HSP60C can effectively activate macrophages and APCs targeting based on LOX-1 interaction is a promising approach to improve vaccines.

Characterization of the extra copy of TPOX locus with tri-allelic pattern.

BACKGROUND: An STR locus with tri-allelic pattern is occasionally observed in routine forensic casework. The extra copy of TPOX locus with tri-allelic pattern in populations has been assumed to be inserted into an X chromosome, which took place forth before the Bantu expansion in Africa. Nonetheless, the exact location of the duplication and the form of rearrangement in the human genome has not been clarified yet. RESULTS: In this study, we investigated the extra copy of type 2 tri-allelic pattern at TPOX in various populations. While allele 10 is the major third allele in Africa, allele 11 appears more frequent in America and overwhelming in Chinese and Korean populations, which might attribute to the population substructures. Results from the investigation of family cases showed that the transmission of the extra allele had a similar genetic pattern of autosomal genes. Furthermore, a whole-genome sequencing followed by bioinformatics analysis revealed that the intact form of chromosomal duplication and rearrangement occurred ~ 407 kb away from the authentic TPOX locus on chromosome 2 in two cases. The breakpoints of the insertion were further validated in most other tri-allelic subjects, which can imply the identical origin from the ancestral extra copy. Nevertheless, de novo chromosomal duplication and rearrangement at thyroid peroxidase gene occur in populations. CONCLUSIONS: Instead of the extra allele 10 in African populations, the main third allele at TPOX with tri-allelic pattern is allele 11 in Chinese and Korean populations. The insertion of the extra copy into chromosome 2 occurs in most subjects with tri-allelic pattern at TPOX and demonstrates the transmission of the third allele from parents to offspring. The breakpoints of the ancestral extra copy are defined, which shows evidence of its inheritance from African populations. In addition, the simple validation method would help improve tri-allelic pattern calling, distinguish de novo chromosomal rearrangements, and also count the frequencies among different geographic regions. Therefore, the statistical interpretation of tri-allelic pattern at TPOX could be enhanced during forensic practice.

Characterization of tissue-specific biomarkers with the expression of circRNAs in forensically relevant body fluids.

Messenger RNA (mRNA) markers have been extensively investigated for the identification of forensically relevant body fluids and tissues based on their expression profiles among cell types. As products of the backsplicing of pre-mRNAs, circular RNAs (circRNAs) share exonic sequences with their linear counterparts. The inclusion of circRNAs in mRNA profiling is shown to facilitate the detection of biomarkers in the identification of body fluids. In this study, we identified the expression of circRNAs of 14 out of 45 biomarkers from five body fluid types using outward-facing primer sets and revealed the ratio of circular to total transcripts of biomarkers by RNase R treatment. Furthermore, our results of qPCR analysis show that the inclusion of circRNAs in the detection of biomarkers, including HBA and ALAS2 for blood; MMP7 and MMP10 for menstrual blood; HTN3 for saliva; SPINK5, SERPINB3, ESR1, and CYP2B7P1 for vaginal secretions; TGM4, KLK3, and PRM2 for semen; and SLC22A6 and MIOX for urine, does not impair the specificity of these biomarkers. Additionally, a high copy number of targets from linear transcripts could be employed to increase the detection sensitivity of TGM4 and KLK3 with a low expression level of circRNAs in urine samples. Altogether, these results will help with the development of robust multiplex assays for body fluid identification.

Identification and assessment of a subset of Y-SNPs with recurrent mutation for forensic purpose.

Y chromosome has an important role in the forensic practice due to its unique paternal inheritance pattern. Y-chromosomal single nucleotide polymorphisms (Y-SNPs) could provide supplementary information while the application of Y-chromosomal STR (Y-STR) haplotypes encounter their limitations. Y-SNPs with recurrent mutation can be seen in different Y-chromosomal haplogroups, which might help discriminate different paternal pedigrees. In this study, a host of candidate Y-SNPs with recurrent mutation were obtained based on population data from 1000 Genome Project. Further, 8 Y-SNPs from a small part of candidates were confirmed to be polymorphic in 2 or more Y-chromosomal haplogroups (sub-haplogroups) in the Chinese Han population. With a haplotype diversity value of 0.9367, the investigated subset of Y-SNPs with recurrent mutation shows a high discrimination power. Therefore, Y-SNPs with recurrent mutation should function as useful markers to provide information in the forensic applications.

Identification and Characterization of Nine Novel X-Chromosomal Short Tandem Repeats on Xp21.1, Xq21.31, and Xq23 Regions.

The application of X-chromosomal short tandem repeats (X-STRs) has been recognized as a powerful tool in complex kinship testing. To support further development of X-STR analysis in forensic use, we identified nine novel X-STRs, which could be clustered into three linkage groups on Xp21.1, Xq21.31, and Xq23. A multiplex PCR system was built based on the electrophoresis. A total of 198 unrelated Shanghai Han samples along with 168 samples from 43 families was collected to investigate the genetic polymorphism and forensic parameters of the nine loci. Allele numbers ranged from 5 to 12, and amplicon sizes ranged from 146 to 477 bp. The multiplex showed high values for the combined power of discrimination (0.99997977 in males and 0.99999999 in females) and combined mean exclusion chances (0.99997918 and 0.99997821 in trios, 0.99984939 in duos, and 0.99984200 in deficiency cases). The linkage between all pairs of loci was estimated via Kosambi mapping function and linkage disequilibrium test, and further investigated through the family study. The data from 43 families strongly demonstrated an independent transmission between LGs and a tight linkage among loci within the same LG. All these results support that the newly described X-STRs and the multiplex system are highly promising for further forensic use.

Assessing Autosomal InDel Loci With Multiple Insertions or Deletions of Random DNA Sequences in Human Genome.

Multiple mutational events of insertion/deletion occurring at or around InDel sites could form multi-allelic InDels and multi-InDels (abbreviated as MM-InDels), while InDels with random DNA sequences could imply a unique mutation event at these loci. In this study, preliminary investigation of MM-InDels with random sequences was conducted using high-throughput phased data from the 1000 Genomes Project. A total of 3,599 multi-allelic InDels and 6,375 multi-InDels were filtered with multiple alleles. A vast majority of the obtained MM-InDels (85.59%) presented 3 alleles, which implies that only one secondary insertion or deletion mutation event occurred at these loci. The more frequent presence of two adjacent InDel loci was observed within 20 bp. MM-InDels with random sequences presented an uneven distribution across the genome and showed a correlation with InDels, SNPs, recombination rate, and GC content. The average allelic frequencies and prevalence of multi-allelic InDels and multi-InDels presented similar distribution patterns in different populations. Altogether, MM-InDels with random sequences can provide useful information for population resolution.

Calculation of the Paternity Index for STR with tri-allelic patterns in paternity testing.

The calculation of the paternity index (PI) value of common bi-allelic genotypes at STR loci has been standardized in paternity cases. However, for tri-allelic patterns, a rare category of genotyping aberration in forensic practice, the statistical analysis in paternity testing remains disputed. The Type 1 tri-allelic pattern generally results from somatic mutation in the early stage of individual development. The Type 2 tri-allelic pattern is commonly generated by segmental duplication in the genome. In this study, practical and theoretical aspects of the evaluation of evidence concerning the Type 1 and Type 2 tri-allelic patterns in healthy individuals are discussed based on the likelihood ratio (LR) in different categories of kinship cases. The calculation of the PI value concerning tri-allelic genotypes is formulated according to the generation and genetic transmission of tri-allelic patterns. Meanwhile, a package tool named TriPI is developed to assist the calculation of the PI value in paternity testing concerning tri-allelic subjects, which could benefit the evaluation of the weight of evidence in the interpretation of tri-allelic pattern in forensic practice.

Concordance and characterization of massively parallel sequencing at 58 STRs in a Tibetan population.

BACKGROUND: Massively parallel sequencing (MPS) is a promising supplementary method for forensic casework in short tandem repeats (STRs) genotyping, owing to several advantageous features in comparison to traditional capillary electrophoresis (CE). However, the application of MPS in casework requires accessible datasets from the worldwide population to enrich the allele frequencies of sequence-based STR genotypes. METHODS: In this study, we report the characterization of sequence-based allele frequencies of 58 STRs from a Tibetan population comprising 120 unrelated individuals using the ForenSeq™ DNA Signature Prep Kit. A concordance study evaluating MPS and CE allele data was performed to ensure that MPS is compatible with current CE-based forensic databases. The diversity of observed alleles, allele frequencies, and forensic parameters per locus by length (LB), sequence without flanking region (RSB), and sequence with flanking region (FSB) were analyzed and compared. RESULTS: The concordance study demonstrated a concordance rate exceeding 99%. The combined random match probability (RMP) for the 26 A-STRs was 2.04 × 10-29 , 1.93 × 10-31 , and 9.56 × 10-33 for LB, RSB, and FSB, respectively. Similar trends were observed in other forensic parameters resulting from the increase in the number of unique alleles available. A total of 111 and 113 unique haplotypes in the Y-STR loci were observed when using length-based and sequence-based alleles, respectively. In addition, we identified 35 novel alleles at 25 loci and 25 polymorphisms in the flanking regions at 17 STRs. CONCLUSIONS: Our data suggest that MPS- and CE-derived alleles are compatible. MPS-based analysis of the STR data substantially increased the allele diversity and improved the forensic parameters, which clearly demonstrated the advantages of MPS in comparison to CE. With more pooled data and larger-scale validation, MPS could play a valuable role in forensic genetics and might be an additional tool for routine casework.

Characterizing Y-STRs in the Evaluation of Population Differentiation Using the Mean of Allele Frequency Difference between Populations.

Y-chromosomal short tandem repeats (Y-STRs) are widely used in human research for the evaluation of population substructure or population differentiation. Previous studies show that several haplotype sets can be used for the evaluation of population differentiation. However, little is known about whether each Y-STR in these sets performs well during this procedure. In this study, a total of 20,927 haplotypes of a Yfiler Plus set were collected from 41 global populations. Different configurations were observed in multidimensional scaling (MDS) plots based on pairwise genetic distances evaluated using a Yfiler set and a Yfiler Plus set, respectively. Subsequently, 23 single-copy Y-STRs were characterized in the evaluation of population differentiation using the mean of allele frequency difference (mAFD) between populations. Our results indicated that DYS392 had the largest mAFD value (0.3802) and YGATAH4 had the smallest value (0.1845). On the whole, larger pairwise genetic distances could be obtained using the set with the top fifteen markers from these 23 single-copy Y-STRs, and clear clustering or separation of populations could be observed in the MDS plot in comparison with those using the set with the minimum fifteen markers. In conclusion, the mAFD value is reliable to characterize Y-STRs for efficiency in the evaluation of population differentiation.

Development of a multiplex system for the identification of forensically relevant body fluids.

Currently, mRNA profiling is widely investigated for forensic body fluid identification, while it is still required to advance the approach for those casework samples of limited quantity or low quality. The inclusion of circular RNAs (circRNAs) can facilitate the detection of mRNA markers in forensic body fluid identification. In this study, a multiplex assay for forensic body fluid identification (F18plex assay) was developed by incorporating 14 tissue-specific mRNA markers with circRNAs expression, 2 mRNA markers with high abundance and 2 housekeeping markers for the discrimination of the most common forensic body fluids, including blood, menstrual blood, saliva, vaginal secretion, semen and urine. The markers employed in the F18plex assay show similar specificity to previous reports. Additionally, even if all linear transcripts were completely erased, the expected markers in target biofluids could still be identified, which should help the discrimination of those aged biological stains. Results from sensitivity testing and the detection of mixtures demonstrate good sensitivity of the multiplex assay. Generally, full biomarker profiles could be obtained with ≥1 µl of blood, saliva, or semen, and ≥1 ng of total RNAs from menstrual blood, vaginal secretion, or urine samples, respectively, using this multiplex assay under the established conditions. Collectively, the newly established multiplex assay can assist in determining the biological origin of forensic stains.

A 16-plex Y-SNP typing system based on allele-specific PCR for the genotyping of Chinese Y-chromosomal haplogroups.

Y-chromosomal SNP (Y-SNP), with its stable inheritance and low mutation, can provide Supplementary information in forensic investigation. While commonly used Y-chromosomal STR haplotypes show their limitations, typing of Y-SNP would become a powerful complement. In this study, a 16-plex Y-SNP typing system based on allele-specific PCR (AS-PCR) was developed to discriminate four dominant Y-chromosomal haplogroups (C-M130, D-CTS3946, N-M231, and O-M175) and 12 predominant sub-haplogroups of O-M175 (O1a-M119, O1a1a1a-CTS3265, O1b-M268, O1b1a2-Page59, O2-M122, O2a1-L127.1, O2a1b-F240, O2a1b1a1-CTS5820, O2a2-P201, O2a2b1a1-M177, O2a2b1a1a1a-Y17728, O2a2b1a2-F114). A series of experimental validation studies including sensitivity, species specificity, male-female mixture and inhibition were performed. The discrimination of the typing system was preliminarily proved with a haplogroup diversity of 0.9239. Altogether, the Y-SNP typing system based on AS-PCR should be capable of distinguishing China's dominant Y-chromosomal haplogroups in a rapid and reliable manner, thus can be employed as a useful complement in forensic casework.

Genetic analysis of 29 Y-STR loci in the Chinese Han population from Shanghai.

The analysis of Y chromosomal short tandem repeats (Y-STRs) provides important information that can be used to forensic investigation and population studies. In this study, typing of 29 Y-STRs included in the PowerPlex® Y23 system (PPY23) and Yfiler™ Plus system (Yfiler plus) was performed on 843 unrelated male samples from Han population in Shanghai. Besides null, duplicate, and intermediate alleles reported in previous studies, an allele of 10 at DYS643 with a 2-base deletion in the flanking region was initially observed. The gene diversity (GD) values of the 29 Y-STRs range from 0.4186 at DYS438 to 0.9653 at DYS385a/b. The haplotype diversity of two commonly used haplotype sets, PPY23 set and Yfiler plus set is 0.999980 and 0.999997, respectively. Pairwise genetic distances between Han population in Shanghai and other Han populations estimated using Yfiler plus set are slightly larger than that between other Han populations. Visualization of pairwise genetic distances between 17 worldwide populations using multidimensional scaling (MDS) demonstrates the distribution of populations according to their ethno-geographic patterns. Compared with Yfiler set, Yfiler plus set appears to have a relatively high population discrimination capacity for these tested populations. Altogether, these results can provide useful information of Y-STRs for forensic investigation and population studies.

Null alleles and sequence variations at primer binding sites of STR loci within multiplex typing systems.

Rare variants are widely observed in human genome and sequence variations at primer binding sites might impair the process of PCR amplification resulting in dropouts of alleles, named as null alleles. In this study, 5 cases from routine paternity testing using PowerPlex®21 System for STR genotyping were considered to harbor null alleles at TH01, FGA, D5S818, D8S1179, and D16S539, respectively. The dropout of alleles was confirmed by using alternative commercial kits AGCU Expressmarker 22 PCR amplification kit and AmpFℓSTR®. Identifiler® Plus Kit, and sequencing results revealed a single base variation at the primer binding site of each STR locus. Results from the collection of previous reports show that null alleles at D5S818 were frequently observed in population detected by two PowerPlex® typing systems and null alleles at D19S433 were mostly observed in Japanese population detected by two AmpFℓSTR™ typing systems. Furthermore, the most popular mutation type appeared the transition from C to T with G to A, which might have a potential relationship with DNA methylation. Altogether, these results can provide helpful information in forensic practice to the elimination of genotyping discrepancy and the development of primer sets.