Identification of a hydatidiform mole in twin pregnancy following assisted reproduction

PURPOSE

The aim of this study was to identify a co-existing hydatidiform mole (HM) in twin pregnancy from the abnormal mixed-genomic products of conception (POC) after assisted reproduction by histopathological review, evaluation of p57^kip2 immunostaining and short tandem repeat genotyping.

METHODS

Thirty-seven patients were collected with suspicion for HM by pathological morphology. They had two embryos individually transferred to their uterus after in vitro fertilization and presented two gestational sacs with undeveloped embryos or one sac with an abnormal area by ultrasonography.

RESULTS

Thirty patients were diagnosed as singleton pregnancy, including twenty-two non-molar gestations, six trisomy gestations, one homozygous complete mole and one heterozygous partial mole. Although six patients had ultrasonic imaging of two gestational sacs, the embryonic components in the vacant sac might fade away after transferring. Other seven patients were considered as twin pregnancy by the allelic genotype from two individual conceptions. For the patients with uniform p57^kip2 positivity, excessive paternal alleles indicated the potential partial HM in the twin pregnancy. For the patients demonstrated divergent and/or discordant p57^kip2 immunostaining, twin pregnancy with co-existing complete HM or mosaic conception were confirmed by genotyping of different villi population respectively. These patients were monitored by serum β-HCG, while one twin pregnancy with complete mole suffered invasive mole and received chemotherapy.

CONCLUSIONS

A strategy composed of selective clinicopathological screening, immunohistochemical interpretation and accurate genotyping is recommended for diagnostically challenging mixed-genomic POC of potential twin pregnancy with HM, especially to differentiate a non-molar mosaic conception from a partial mole.

Identification of human remains using Rapid DNA analysis

Rapid identification of human remains following mass casualty events is essential to bring closure to family members and friends of the victims. Unfortunately, disaster victim identification, missing persons identification, and forensic casework analysis are often complicated by sample degradation due to exposure to harsh environmental conditions. Following a mass disaster, forensic laboratories may be overwhelmed by the number of dissociated portions that require identification and reassociation or compromised by the event itself. The interval between the disaster and receipt of victim samples at a laboratory is critical in that sample quality deteriorates as the postmortem interval increases. When bodies decompose due to delay in collection, transport, and sample processing, DNA becomes progressively fragmented, adversely impacting identification. We have previously developed a fully automated, field-forward Rapid DNA identification system that produces STR profiles (also referred to as DNA IDs or DNA fingerprints) from buccal and crime scene samples. The system performs all sample processing and data interpretation in less than 2 h. Here, we present results on Rapid DNA identification performed on several tissue types (including buccal, muscle, liver, brain, tooth, and bone) from exposed human bodies placed above ground or stored in a morgue/cooler, two scenarios commonly encountered following mass disasters. We demonstrate that for exposed remains, buccal swabs are the sample of choice for up to 11 days exposure and bone and tooth samples generated excellent DNA IDs for the 1-year duration of the study. For refrigerated remains, all sample types generated excellent DNA IDs for the 3-month testing period.

An unbalanced tri-allelic pattern at the D10S1248 locus: Characteristics, genetic basis and transmission

To address issues related to unbalanced tri-allelic patterns, an example at the D10S1248 locus characterized by the sum of heights of alleles 13 and 15 approximately equal to allele 14 was intensively investigated. The coexistence of these three alleles was confirmed by profiling the rs2246512-D10S1248 marker using fluorescently labelled primers and allelic sequencing. Multi-tissue genotyping revealed that this pattern had chimeric characteristics, and pedigree analysis found that allele 13 or allele 14 were inherited to offspring independently of the other two alleles. These evidences suggest that the pattern should stem from a somatic mutation in early embryonic development and that peak height ratio is not an accurate indicator of mutation time point and direction. The rs2246538-D10S1248-rs2246512 marker was subsequently used to determine the mutation from allele 15 to allele 13. Notably, allele 13 with the lowest peak height was misidentified as a stutter peak when genotyped using next generation sequencing.

Slippage mutation rates in 15 autosomal short tandem repeat loci for forensic purposes in a Southeastern Brazilian population

Well-defined estimates of mutation rates in highly polymorphic tetranucleotide STR loci are a prerequisite for human identification in genetics laboratory routines useful for civil and criminal investigations. Studying 15 autosomal STR loci of forensic interest (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPOX, and vWA), we detected 193 slippage mutations (189 one-step and four two-step mutations) in 148 875 parent-child allelic transfers from 5171 paternity cases with true biological relationship (15 096 individuals; 4754 trios and 417 duos; 9925 meiosis) from the state of São Paulo, a very representative population of Brazil. The overall mutation rate was 1.3 × 10^-3 and the highest rates were observed at loci vWA (2.8 × 10^-3 ), FGA and D18S51 (2.7 × 10^-3 for both), while loci TH01 and TPOX did not present any mutations. The mean slippage mutation rate of paternal origin (1.8 × 10^-3 ) was six times higher than that observed for maternal origin (0.3 × 10^-3 ).

Characteristics of a novel cell line ZJU-0430 established from human gallbladder carcinoma

Background

Gallbladder cancer is the most common malignant neoplasm of the biliary tract, responsible for 80–95% of cases. Appropriate models are required for investigating the molecular pathogenesis of gallbladder cancer.

Methods

In this study, we aimed to establish a gallbladder cancer cell line from primary tumour. Single cell RNA sequencing, Light and electron microscopy, DNA content analysis, cytogenetic analysis, short tandem repeat (STR) DNA fingerprint analysis, immunophenotypic characterization, and xeno-transplantation were utilized to characterize the novel ZJU-0430 cell line in vitro and in vivo.

Results

The cell line showed multiple cell shapes and characteristic epithelial morphologies under the microscope, but no too much heterogeneity by scRNA-Seq, with a population doubling time (PDT) of 19.81 h, which was shorter than that for GBC-SD cells. An immunophenotypic analysis revealed that ZJU-0430 cells were positive for CD24, CD44, CD29 and CD133 expression, and partially positive for CD184, and CD326 expression, and negative for CD34, CD90, CD117, and CD338 expression, similar to the primary cancer cells. A pathological analysis confirmed the origination of cell line from gallbladder tumour. ZJU-0430 cells had higher migration, invasion and proliferation properties than GBC-SD cells in vitro, and showed in vivo tumorigenicity in nude mouse xenograft settings.

Conclusions

The results confirm the potential utility of ZJU-0430 cell line as a representative model of gallbladder cancer and suggest that it could be used in the in vitro and in vivo studies of gallbladder cancer pathogenesis and to develop new therapeutics.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0911-1) contains supplementary material, which is available to authorized users.

Short tandem repeats and methylation in the promoter region affect expression of cystathionine beta-synthase gene in the laying hen

Homocysteine can be converted to cysteine via the transsulfuration pathway where cystathionine beta-synthase (CBS) is a rate-limiting enzyme. Homocysteine is thought to play a role in bone remodelling and strength. Previous results indicated that some of the difference in bone strength of end-of-lay hens may be associated with CBS expression level. To investigate if differences in the promoter region of the CBS gene might be responsible for observed differences in gene expression between CBS alleles post mortem- and in-vitro expression studies have been undertaken. Transfection of the DF-1 avian cell line with a series of deletion fragments of the 5' promoter, or constructs containing three CBS allele sequences, with a luciferase reporter revealed that a core region of -155 to +131 bp in the CBS promoter was essential for mRNA expression. We found that a variable number of short tandem repeats (7 nucleotide motif and 6 nucleotide repeats) in the core region of the promoter affecting the transcriptional activity and a strong effect for gene expression. However, methylation of the 6 nucleotide repeats varied between allelic variants and these maybe responsible for differences in promoter activity. Our findings indicated variable short tandem repeats and the differentially methylated sites in the promoter region may be responsible for CBS expression differences in the bone of laying hens.

Disease-only alleles at the extreme ends of the human ZMYM3 exceptionally long 5' UTR short tandem repeat in bipolar disorder: A pilot study

OBJECTIVE

The X-linked ZMYM3 gene (also known as ZNF261) contains the longest STR, (GA)32, identified in a human protein-coding gene 5'UTR (ENST00000373998.5: ZMYM3-207). This STR reaches maximum length in human, and is located in a complex string of four consecutive GA-STRs with a human-specific formula across the complex. A previous study in Iranian male schizophrenia (SCZ) patients revealed co-occurrence of the extreme short and long alleles of the STR with SCZ. Here we studied the allelic distribution of this STR in bipolar disorder (BD) type I. The interval encompassing the human ZMYM3 STR complex was PCR-amplified and sequenced in 546 male subjects, consisting of 157 BD patients and 389 controls.

RESULTS

We found three alleles at the extreme short (17-repeat) and long (38- and 43-repeat) ends of the allele distribution curve in the BD cases (4.4% of the BD alleles) that were not detected in the controls (Mid p < 0.0001). These alleles overlapped with the extreme disease-only alleles detected previously in the SCZ patients. Domain reconstruction of the GA-STR complex revealed significant structural alteration as a result of various sequence repeats and nucleotide compositions at the inter and intraspecies levels.

CONCLUSION

The ZMYM3 "exceptionally long" 5' UTR STR findings may alter our perspective of disease pathogenesis in psychiatric disorders, and set an example in which the low frequency alleles at the extreme short and long ends of the human STRs are, at least in part, a result of natural selection against these alleles and their unambiguous link to major human disorders.

Complete Paternal Uniparental Disomy of Chromosome 2 in an Asian Female Identified by Short Tandem Repeats and Whole Genome Sequencing

Uniparental disomy (UPD) is a rare type of chromosomal aberration that has sometimes been detected in paternity testing. We examined a 3-person family (father, mother, daughter) first by using short tandem repeat markers, which revealed 4 markers, TPOX, D2S1338, D2S1772, and D2S441, on chromosome 2 that were not transmitted in a Mendelian style. We then performed whole genome sequencing (WGS) to determine the range of the UPD. Chromosome 2 in the daughter showed a complete paternal UPD. To the best of our knowledge, this is the 4th case of complete paternal UPD of chromosome 2 with no clinical phenotype. Our study suggests that WGS, when performed to enhance the accuracy and reliability of parentage testing, can provide a powerful method to detect an UPD.

Forensic characteristics and phylogenetic structure of Eastern Chinese Han populations residing along the Yangtze Basin revealed by 19 autosomal STR loci

In present study, forensic parameters based on the population data of nineteen autosomal short tandem repeats (STRs) loci were estimated in Chinese Han populations from three riverfront areas of Yangtze Basin in Eastern China. The combined power of discrimination (CPD) were 0.9999999999999999999999883, 0.9999999999999999999999846 and 0.9999999999999999999999863, respectively. The combined power of exclusion (CPE) were 0.999999992248957, 0.999999989800400 and 0.999999989799819, respectively. Furthermore, the genetic relationships among our studied populations and 32 previously investigated populations residing in other areas of China were also analyzed based on pairwise genetic distances (F_ST). The multidimensional scaling (MDS) plot and phylogenetic tree indicated that our studied populations were majorly clustered with the Han populations along the Yangtze Basin and populations to the north of it. In summary, our results supported that the 19 autosomal STR loci, which were polymorphic and informative in forensic identification, could also be applied in population genetics studies.

A comparative study for the isolation of exogenous trace DNA from fingernails

Often fingernails from a victim or suspect involved in a physical assault, such as murder or sexual assault, are submitted to crime laboratories for DNA testing of foreign/exogenous biological material; however, very few studies have been conducted comparing the effectiveness of different sampling methods on the removal of foreign/exogenous DNA while minimizing the fingernail endogenous DNA. In this study three different sampling methods (swabbing, PBS soak, and PrepFiler® lysis buffer soak) were compared in order to identify one that minimizes the amount of endogenous DNA removed and maximizes the amount of foreign/exogenous male DNA removed. The samples were processed using the Tecan HIDEVO150 robot in order to reduce analyst time and the DNA mixtures were interpreted using the probabilistic genotyping software STRmix™. For each sampling method the quantity of male DNA, the mixture proportions, the number of foreign/exogenous male alleles detected, the amount of DNA degradation, and the discrimination power via the likelihood ratio obtained for the foreign/exogenous male DNA donor were determined and compared. The PrepFiler® lysis buffer soak and swabbing sampling methods appear to be equally effective at removing foreign/exogenous DNA from fingernails; however, the lysis buffer soak sampling method extracts more female endogenous DNA from the fingernail and the female DNA is degraded. Marginally higher likelihood ratios were obtained for the swab samples versus the PrepFiler® lysis buffer soak samples; therefore, it was determined that the swabbing sampling method was the best sampling method for the recovery of foreign exogenous DNA from fingernails while minimizing the amount of endogenous DNA removed.

Massively parallel sequencing techniques for forensics: A review

DNA sequencing, starting with Sanger's chain termination method in 1977 and evolving into the next generation sequencing (NGS) techniques of today that employ massively parallel sequencing (MPS), has become essential in application areas such as biotechnology, virology, and medical diagnostics. Reflected by the growing number of articles published over the last 2-3 years, these techniques have also gained attention in the forensic field. This review contains a brief description of first, second, and third generation sequencing techniques, and focuses on the recent developments in human DNA analysis applicable in the forensic field. Relevance to the forensic analysis is that besides generation of standard STR-profiles, DNA repeats can also be sequenced to look for polymorphisms. Furthermore, additional SNPs can be sequenced to acquire information on ancestry, paternity or phenotype. The current MPS systems are also very helpful in cases where only a limited amount of DNA or highly degraded DNA has been secured from a crime scene. If enough autosomal DNA is not present, mitochondrial DNA can be sequenced for maternal lineage analysis. These developments clearly demonstrate that the use of NGS will grow into an indispensable tool for forensic science.

Link between short tandem repeats and translation initiation site selection

BACKGROUND

Despite their vast biological implication, the relevance of short tandem repeats (STRs)/microsatellites to the protein-coding gene translation initiation sites (TISs) remains largely unknown.

METHODS

We performed an Ensembl-based comparative genomics study of all annotated orthologous TIS-flanking sequences in human and 46 other species across vertebrates, on the genomic DNA and cDNA platforms (755,956 TISs), aimed at identifying human-specific STRs in this interval. The collected data were used to examine the hypothesis of a link between STRs and TISs. BLAST was used to compare the initial five amino acids (excluding the initial methionine), codons of which were flanked by STRs in human, with the initial five amino acids of all annotated proteins for the orthologous genes in other vertebrates (total of 5,314,979 pair-wise TIS comparisons on the genomic DNA and cDNA platforms) in order to compare the number of events in which human-specific and non-specific STRs occurred with homologous and non-homologous TISs (i.e., ≥ 50% and < 50% similarity of the five amino acids).

RESULTS

We detected differential distribution of the human-specific STRs in comparison to the overall distribution of STRs on the genomic DNA and cDNA platforms (Mann Whitney U test p = 1.4 × 10-11 and p < 7.9 × 10-11, respectively). We also found excess occurrence of non-homologous TISs with human-specific STRs and excess occurrence of homologous TISs with non-specific STRs on both platforms (p < 0.00001).

CONCLUSION

We propose a link between STRs and TIS selection, based on the differential co-occurrence rate of human-specific STRs with non-homologous TISs and non-specific STRs with homologous TISs.

13-loci STR multiplex system for Brazilian seized samples of marijuana: individualization and origin differentiation

It is known that Cannabis in Brazil could either originate from Paraguay or be cultivated in Brazil. While consumer markets in the North and Northeast regions are maintained by national production, the rest of the country is supplied with Cannabis from Paraguay. However, the Brazilian Federal Police (BFP) has exponentially increased the seizure number of Cannabis seeds sent by mail. For this reason, the aim of the study was to assess the 13-loci short tandem repeat (STR) multiplex system proposed by Houston et al. (2015) to evaluate the power of such markers in individualization and origin differentiation of Cannabis sativa samples seized in Brazil by the BFP. To do so, 72 Cannabis samples seized in Brazil by BFP were analyzed. The principal coordinate analysis (PCoA) and probability identity (PI) analysis were computed. Additionally, the Cannabis samples' genotypes were subjected to comparison by Kruskal-Wallis H, followed by a multiple discriminant analysis (MDA). All samples analyzed revealed a distinct genetic profile. PCoA clearly discriminated the seizure sets based on their geographic origin. A combination of seven loci was enough to differentiate samples' genotypes, and the PI for a random sample is approximately one in 50 billion. The Cannabis samples were 100% correct as classified by Kruskal-Wallis H, followed by an MDA. The results of this study demonstrate that the 13-loci STR multiplex system successfully achieved the aim of sample individualization and origin differentiation and suggest that it could be a useful tool to help BFP intelligence in tracing back-trade routes.

Ratios and distances of pull-up peaks observed in GlobalFiler kit data

Short tandem repeat (STR) analysis is widely used for forensic examinations with a capillary electrophoresis instrument such as the 3500xL Genetic Analyzer. This instrument adapts multi-locus STR kits to examine up to 27 loci using a 6-fluorescent dye system and corrects the spectral overlap between each dye. However, inaccurate spectral correction can cause pull-up peaks. Here, we examined the pull-up peaks observed in GlobalFiler kit data in terms of their peak height ratios and distances from their parent allele peaks when using the 3500xL and the 3130xl Genetic Analyzers. With the 3500xL, 546 pull-up peaks were observed, and their pull-up ratios averaged 1.03 ± 0.32% (range 0.260-2.80%). Of the 546 pull-up peaks, 534 peaks (97.8%) were within ±1 bp from their parent allele peaks. Overall, the pull-up peaks toward adjacent shorter wavelength channels (e.g., from yellow to green) tended to be observed in the left side (shorter bp) of the corresponding parent allele peaks, and the opposite side tendency was observed for those pull-up peaks toward adjacent longer wavelength channels. These tendencies were also observed in the GlobalFiler data generated with the 3130xl and in the data obtained by injecting a J6 matrix standard with LIZ 500 or 600 v2 size standard into the 3500xL and 3130xl. Inspection of raw data revealed that the shift of pull-up peaks from their parent allele peaks was derived from sigmoid, pull-down, or slightly shifted pull-up shapes. Based on the obtained data, we propose a standard for assessment of questionable pull-up peaks.

Match probabilities for Y-chromosomal profiles: A paradigm shift

Calculating match probabilities for genetic profiles under the hypothesis that a person of interest (henceforth the 'suspect') is not the donor of a particular forensic trace is challenging because the reference population is usually not clear-defined in such cases. Hence, the concept of 'suspect population' was introduced to allow for the fact that possible alternative trace donors often resemble the suspect in terms of their geographic, ethnic and social affiliation. In fact, they may even be genetically related to the suspect. Although the possibility of relatedness affects the size of the match probability in general, this is not a practically relevant issue for autosomal profiles owing to the stochastic independence of the markers included. The situation is, however, different for Y-chromosomal short tandem repeat (STR) profiles. Here, almost all profile matches are likely to be identical by descent, and profile identity may be common even among distantly related males. The degree of relatedness between suspect and alternative trace donors is thus a critical aspect of the evaluation of Y-chromosomal STR profile matches. All methods hitherto proposed to derive match probabilities for such cases, including our own, were anti-conservative in that they equated the suspect population to a database population (of virtually unrelated individuals). The nature of the true suspect population, however, is usually unknown and hard, if not impossible, to determine so that calculation of proper match probabilities remains a difficult task. Therefore, since lower Y-chromosomal match probabilities would result from higher mutation rates, even for close relatives, future research should rather focus upon the characterization of novel and more mutable Y-chromosomal STRs.

Paternity testing using massively parallel sequencing and the PowerSeq™ AUTO/Y system for short tandem repeat sequencing

Massively parallel sequencing (MPS) is gaining attention as a new technology for routine forensic casework, including paternity testing. Recently released MPS multiplex panels provide many more loci compared to CE methods, plus provide sequence-based alleles that together improve the statistical power of the genetic testing. Here, an MPS system (PowerSeq™ AUTO/Y) was applied for STR sequencing in the study of first-degree STR sequence allele inheritance from families in Southern Brazil. In 29 trios (mother-child-father) analyzed, the paternity index values generally increased when data from sequence-based analysis were used in comparison to length-based data. Further, allele inconsistencies (e.g., single repeat mutation events) between child and parents could be resolved with MPS by assessing the core repeat and flanking region sequences. Lastly, the sequence information allowed for identification of isoalleles (alleles of the same size, but different sequence) to determine specific paternal and maternal inheritances. The results from this study showed advantages of implementing sequence-based analysis, MPS, in paternity testing with improved statistical calculations and a greater resolution for the trios/families tested.

Genetic characteristics of Y-chromosome short tandem repeat haplotypes from cigarette butt samples presumed to be smoked by North Korean men

Korea has been divided into South Korea and North Korea for over 70 years. DNA profiles of the North Korean population have never been reported in the Y-chromosome STR Haplotype Reference Database (YHRD; https://yhrd.org ). To investigate genetic features of Y-chromosome STR haplotypes of the North Korean population for the first time. Genomic DNA was isolated from 838 cigarette butts assumed to have been smoked by North Korean men and amplified with PowerPlex Y23 (PPY23) kit. Statistical parameters were calculated using Nei's formula and analysis of molecular variance (AMOVA). Multidimensional scaling (MDS) plot was constructed by the AMOVA tool and neighbor-joining (NJ) tree was constructed by MEGA 6.06. A total of 121 haplotypes were analyzed for PPY23 loci from a sample population. Haplotype diversity and discrimination capacity were 0.9992 and 0.9837, respectively. Genetic diversities ranged from 0.2981 to 0.9716. For the 16 Y-filer loci and eight minimal loci, respectively 90.9 and 82.6% of the matched haplotypes were estimated to belong to haplogroup O, representing the Southeast and East Asian type. The MDS plot and NJ tree indicated that the samples are most closely related to South Korean. In addition, p-value in the pairwise comparison to the South Korean was slightly above statistical significance (p = 0.0534). The Y-STR haplotypes of the samples were unique and highly genetically polymorphic. Despite the separation between North and South Korea for 70 years, they can still be considered a single genetic population, based on Y-STR haplotypes.

Sequence-based US population data for the SE33 locus

A set of 1036 U.S. Population Samples were sequenced using the Illumina ForenSeq DNA Signature Prep Kit. This sample set has been highly characterized using a variety of marker systems for human identification. The FASTQ files obtained from a ForenSeq DNA Signature Prep Kit experiment include several STR loci that are not reported in the associated software. These include SE33, DXS8377, DXS10148, DYS456, and DYS461. The sequence variation within the autosomal STR marker SE33 was evaluated using a customized bioinformatic approach to identify and characterize the locus in the 1036 data set. The analysis identified 53 unique alleles by length and 264 by sequence. An additional 10 alleles were detected when selected extended flanking regions were examined to resolve discordances. Allele frequencies and SE33 sequence motif patterns are reported for the 1036 data set. The comparison of numerical allele calls derived from sequence data to the allele calls obtained from commercial capillary electrophoresis-based STR typing kits resulted in 100% concordance, after manual data review and confirmation sequencing of three flanking region deletions. The analysis of this data set involved significant manual sequence curation and information support from length-based genotypes to ensure high confidence in the sequence-based allele calls. The challenges of interpreting the sequence data for SE33 consisted of high sequence noise, allele-size dependent variance in coverage, and heterozygote imbalance. As allele length increased, sequence depth of coverage and quality decreased at the terminal end. Accordingly, heterozygous genotype imbalance increased in proportion to increased distance between alleles.

Genetic diversities and phylogenetic analysis of 18 autosomal STR loci in the Uyghur population living in Ili, Northwest China

Ili is located in northernmost Xinjiang, China. The Uyghur population only accounts for 15.90% of the total population in the nation. There is currently no large population data-based data set in Ili Uyghur. In this study, we investigated the genetic diversities of 18 autosomal short tandem repeat (STR) loci in 1129 Uyghur individuals living in Ili. The values of combined power of discrimination (CPD) and combined probability of exclusion (CPE) were 0.99999999999999999999990244 and 0.99999995645, respectively. Furthermore, we explored the genetic relationships between the Ili Uyghur population and 32 previously published populations. The results indicated that the Ili Uyghur population was more closely related to the Xinjiang Kazakh population. In addition, It was worth noting that significant differences were observed between Ili the Uyghur population and the Uyghur1 and Uyghur2 populations at the shared 15 loci, with significant differences at 7 and 11 loci after Bonferroni adjustment (p = 0.05/495 ≈ 0.00010).

Genome-scale portrait and evolutionary significance of human-specific core promoter tri- and tetranucleotide short tandem repeats

BACKGROUND

While there is an ongoing trend to identify single nucleotide substitutions (SNSs) that are linked to inter/intra-species differences and disease phenotypes, short tandem repeats (STRs)/microsatellites may be of equal (if not more) importance in the above processes. Genes that contain STRs in their promoters have higher expression divergence compared to genes with fixed or no STRs in the gene promoters. In line with the above, recent reports indicate a role of repetitive sequences in the rise of young transcription start sites (TSSs) in human evolution.

RESULTS

Following a comparative genomics study of all human protein-coding genes annotated in the GeneCards database, here we provide a genome-scale portrait of human-specific short- and medium-size (≥ 3-repeats) tri- and tetranucleotide STRs and STR motifs in the critical core promoter region between - 120 and + 1 to the TSS and evidence of skewing of this compartment in reference to the STRs that are not human-specific (Levene's test p < 0.001). Twenty-five percent and 26% enrichment of human-specific transcripts was detected in the tri and tetra human-specific compartments (mid-p < 0.00002 and mid-p < 0.002, respectively).

CONCLUSION

Our findings provide the first evidence of genome-scale skewing of STRs at a specific region of the human genome and a link between a number of these STRs and TSS selection/transcript specificity. The STRs and genes listed here may have a role in the evolution and development of characteristics and phenotypes that are unique to the human species.

Non-invasive prenatal paternity testing using cell-free fetal DNA from maternal plasma: DNA isolation and genetic marker studies

Invasive prenatal paternity tests can result in miscarriage and congenital malformations; therefore, a non-invasive method of testing is preferable. However, little progress could be made in this field until the introduction of cell-free fetal DNA (cffDNA) in 2009. In this review, two aspects regarding the history and development of non-invasive prenatal paternity testing (NIPAT) are summarized: (1) extraction and enrichment of cffDNA and (2) genetic marker-based studies. Although column-based kits are used widely for NIPAT, some researchers have suggested that an automated method, such as magnetic extraction, generally has a higher cffDNA yield than that of manual column-based extraction; therefore, its popularity might increase in the near future. In addition, size- and methylation-based enrichment methods are expected to perform better than formaldehyde-based methods. On the other hand, single nucleotide polymorphism-based techniques have contributed to NIPAT, whereas the application of short tandem repeat testing has so far been restricted to pregnant women bearing male fetuses only. Additional methods and techniques are expected to be innovated to facilitate the forensic practice of NIPAT.

Genetic variation of 17 X-chromosome STR loci in Tunisian population of Nabeul

In the present study, the genetic variations of 17 X-STR markers (DXS8378, DXS9898, DXS7133, GATA31E08, GATA172D05, DXS6801, DXS7423, DXS6809, DXS6799, DXS7132, DXS9902, DXS6800, DXS6789, DXS10075, DXS10079, DXS6807, and DXS6803) were analyzed in 139 unrelated individuals in Nabeul, aiming to perform an X-STR database for anthropological and forensic purposes. Our results indicate that DXS6809 was the most polymorphic locus, whereas DXS6807 was the least informative marker. In addition, the obtained values for the statistical parameters of forensic interest, i.e., the power of discrimination in males (PD_M) and females (PD_F), as well as the mean exclusion chance in duos (MEC_D) and trios (MEC_T) have demonstrated that this panel of 17 X-STRs is highly informative and useful for forensic application and anthropological research. Additionally, pairwise genetic distances based on F_ST were calculated between Nabeul population and other populations extracted from the literature. Genetic distances were represented in a non-metric MDS plot and clustering of populations according to their geographic locations and their historical relationship was detected.

Improving the efficacy of the standard DNA differential extraction method for sexual assault evidence

The efficacy of a DNA differential extraction procedure relies on reducing the amount of non-sperm female DNA carryover into the sperm fraction, while providing a sufficient recovery of male DNA from the sperm cell component. A standard approach to this extraction is to use a mild initial lysis step to digest the female (epithelial cell) component in the mixture, followed by a series of centrifugation and wash steps to further purify the resulting sperm-pellet fraction. This sperm fraction is then digested in the presence of a chemical reducing agent in preparation for DNA extraction. This method has been employed with relatively few changes since its introduction in the mid-1980s, despite numerous attempts to develop new or improved procedures. In this report, we demonstrate that it is possible to improve the efficacy of the standard differential extraction by applying simple modifications that can reduce the amount of female DNA carryover into the sperm fraction, with no adverse effects on the recovery of male DNA. In one modification, the addition of a second mild lysis step at the beginning of the differential extraction procedure improved the average male-to-female DNA ratio in the sperm fraction by 3- to 6-fold. In another modification, a "tube transfer" step was added to move the re-suspended sperm pellet to a new tube for the second mild lysis and subsequent wash steps. With this modification, the average male-to-female DNA ratio in the sperm fraction was improved by 4- to 90-fold, relative to results obtained for the non-modified differential extraction method. These modifications may be accomplished using tools and reagents that are already present in most forensic DNA laboratories, so that implementation should be relatively low-cost and practical.

Skewing of the genetic architecture at the ZMYM3 human-specific 5' UTR short tandem repeat in schizophrenia

Differential expansion of a number of human short tandem repeats (STRs) at the critical core promoter and 5' untranslated region (UTR) support the hypothesis that at least some of these STRs may provide a selective advantage in human evolution. Following a genome-wide screen of all human protein-coding gene 5' UTRs based on the Ensembl database ( http://www.ensembl.org ), we previously reported that the longest STR in this interval is a (GA)₃₂, which belongs to the X-linked zinc finger MYM-type containing 3 (ZMYM3) gene. In the present study, we analyzed the evolutionary implication of this region across evolution and examined the allele and genotype distribution of the "exceptionally long" STR by direct sequencing of 486 Iranian unrelated male subjects consisting of 196 cases of schizophrenia (SCZ) and 290 controls. We found that the ZMYM3 transcript containing the STR is human-specific (ENST00000373998.5). A significant allele variance difference was observed between the cases and controls (Levene's test for equality of variances F = 4.00, p < 0.03). In addition, six alleles were observed in the SCZ patients that were not detected in the control group ("disease-only" alleles) (mid p exact < 0.0003). Those alleles were at the extreme short and long ends of the allele distribution curve and composed 4% of the genotypes in the SCZ group. In conclusion, we found skewing of the genetic architecture at the ZMYM3 STR in SCZ. Further, we found a bell-shaped distribution of alleles and selection against alleles at the extreme ends of this STR. The ZMYM3 STR sets a prototype, the evolutionary course of which determines the range of alleles in a particular species. Extreme "disease-only" alleles and genotypes may change our perspective of adaptive evolution and complex disorders. The ZMYM3 gene "exceptionally long" STR should be sequenced in SCZ and other human-specific phenotypes/characteristics.

Population genetic analysis of the Globalfiler STR loci in 3032 individuals from the Altay Han population of Xinjiang in northwest China

The genetic polymorphisms of 21 autosomal short tandem repeat (STR) loci included in the GlobalFiler™ PCR Amplification Kit were evaluated in 3032 unrelated individuals Altay Han of Xinjiang, northwest China. All of the loci reached the Hardy-Weinberg equilibrium. These loci were examined to determine allele frequencies and forensic statistical parameters. SE33 showed the greatest power of discrimination in Altay Han population, whereas TPOX showed the lowest. The combined discrimination power and probability of excluding paternity of the 21 autosomal STR loci were 0.999999999999999999999999889838 and 0.999999996664704, respectively. Both pairwise genetic distance and phylogenetic methods indicated that the Altay Han had the closest genetic relationship with the Han origin and Hui populations. The present results revealed that the GlobalFiler system had a high level of polymorphism in Altay Han population and hence could be a powerful tool for forensic application and population genetic study.

Genetic analysis of Southern Brazil subjects using the PowerSeq™ AUTO/Y system for short tandem repeat sequencing

With the advent of Next-Generation Sequencing technology, sequencing of short tandem repeats (STRs) allows for a more detailed analysis when compared to size-based fragment methods (capillary electrophoresis-CE). The implementation of high-throughput sequencing can help uncover deeper genetic diversities of different populations. Subjects from the South region of Brazil present a particular and more homogeneous ancestry background when compared to other regions of the country. Both autosomal and Y- STRs have been analyzed in these individuals; however, all analyses published to date encompass data from CE-based fragment analysis. In this study, a genetic analysis of 59 individuals from Southern Brazil was performed on STR sequences. Forensically relevant STRs were PCR-enriched using a prototype of the PowerSeq™ AUTO/Y system (Promega Corp.). Next-generation sequencing was performed on an Illumina MiSeq instrument. The raw data (FASTQ files) were processed using a custom designed sequence processing tool, Altius. Isoalleles, which are sequence-based allelic variants that do not differ in length, were observed in nine autosomal and in six Y- STRs from the core global forensic marker set. The number of distinctive alleles based on sequence was higher when compared to those based on length, 37.3% higher in autosomal STRs and 13.8% higher in Y-STRs. The most polymorphic autosomal locus was D12S391, which presented 38 different sequence-based alleles. Among the loci in the Y chromosome, DYS389II presented the highest number of isoalleles. In comparison to CE analysis, Observed and Expected Heterozygosity, Polymorphic Information Content (PIC) and Genetic Diversity also presented higher values when the alleles were analyzed based on their sequence. For autosomal loci, Polymorphic Information Content (PIC) was 2.6% higher for sequence-based data. Diversity was 9.3% and 6.5% higher for autosomal and Y markers, respectively. In the analysis of the repeat structures for the STR loci, a new allele variant was found for allele 18 in the vWA locus. The STR flanking regions were also further investigated and sixteen variations were observed at nine autosomal STR loci and one Y-STR locus. The results obtained in this study demonstrate the importance of genetic analysis based on sequencing and highlight the diversity of the South Brazilian population when characterized by STR sequencing.

Forensic features and phylogenetic analyses of Sichuan Han population via 23 autosomal STR loci included in the Huaxia Platinum System

Short tandem repeats (STRs) are DNA regions with a variable number of repeated units (2-6 bp) and attractive to genetic application like forensic, population genetics, and anthropological studies. The Huaxia Platinum System allows the multiplex amplification of 23 autosomal STR loci and two gender determination loci. In the present study, genetic polymorphisms of these 23 autosomal STR loci were first obtained from 309 Sichuan Han individuals, southwest China. No evidence of deviation from the Hardy-Weinberg equilibrium (HWE) was identified. The combined match probability (CMP), combined power of discrimination (CPD), and combined power of exclusion (CPE) are 1.087 × 10^-27, 0.999999999999999999999999999, and 0.9999999996 in the Sichuan Han Chinese population, respectively. The inter-population differentiation, PCA, MDS, and phylogenetic analysis revealed that Sichuan Han had a closer genetic relationship with neighboring Han Chinese populations. Our findings indicated that the 23 autosomal STR loci are polymorphic and informative in studied southwestern Chinese Han population and can be utilized as a powerful tool for forensic applications. In addition, population comparisons demonstrated that the genetic similarities widely existed among Han Chinese populations distributed in different administrative divisions, and genetic differences had existed between minorities (most prominently for Uyghur and Kazakh) and Han groups.

Study of autosomal STR loci with IBS method in full sibling identification

OBJECTIVE

We investigated the application of 51 autosomal short tandem repeat (STR) loci with the identity by state (IBS) method and a discriminant function algorithm in full-sib identification.

METHODS

A total of 342 pairs of full sibs (FSs) and 3900 pairs of unrelated individuals (UIs) were genotyped for 51 STR loci. Groups were formed in accordance with discrimination power (DP) values and the number of loci, and IBS scores of FSs and UIs were analyzed and compared. The discriminant functions of FS-UI were determined by using the Fisher discriminant with SPSS software.

RESULTS

All IBS in FSs and UIs groups showed normal distributions and there were significant differences between FS-UI. Receiver operating characteristic curves revealed that the detection efficiency of full-sib identification was affected by both the locus polymorphism and the number of loci detected. Comparing the rate of false positive and false negative of discriminant function between groups, a higher average DP value and larger number of loci detected were associated with a lower rate of miscarriage of justice and were more helpful for full-sib identification.

CONCLUSION

STRs with higher DP values should be selected when additional autosomal markers are required for FS identification. Discriminant analysis with the IBS method is highly applicable for the FS-UI test.

Identification of a common single nucleotide polymorphism at the primer binding site of D2S1360 that causes heterozygote peak imbalance when using the Investigator HDplex Kit

Phenomena known as null alleles and peak imbalance can occur because of mutations in the primer binding sites used for DNA typing. In these cases, an accurate statistical evaluation of DNA typing is difficult. The estimated likelihood ratio is incorrectly calculated because of the null allele and allele dropout caused by mutation-induced peak imbalance. Although a number of studies have attempted to uncover examples of these phenomena, few reports are available on the human identification kit manufactured by Qiagen. In this study, 196 Japanese individuals who were heterozygous at D2S1360 were genotyped using an Investigator HDplex Kit with optimal amounts of DNA. A peak imbalance was frequently observed at the D2S1360 locus. We performed a sequencing analysis of the area surrounding the D2S1360 repeat motif to identify the cause for peak imbalance. A point mutation (G>A transition) 136 nucleotides upstream from the D2S1360 repeat motif was discovered in a number of samples. The allele frequency of the mutation was 0.0566 in the Japanese population. Therefore, human identification or kinship testing using the Investigator HDplex Kit requires caution because of the higher frequency of single nucleotide polymorphisms at the primer binding site of D2S1360 locus in the Japanese population.

Genetic polymorphisms for 19 autosomal STR loci of Chongqing Han ethnicity and phylogenetic structure exploration among 28 Chinese populations

The allele frequencies and forensic statistical parameters of 19 autosomal short tandem repeat (STR) loci (D8S1179, D21S11, D7S820, CSF1P0, D3S1358, THOl, D13S317, D16S539, D2S1338, D19S433, vWA, TPOX, D18S51, D5S818, FGA, D6S1043, Penta D, Penta E, and D12S391) included in the Goldeneye™ DNA ID system 20A kit were obtained in 671 Chinese Han individuals residing in Chongqing, Southwest China. All 19 STR loci were identified in agreement with the Hardy-Weinberg equilibrium. A total of 238 alleles were observed with corresponding allele frequencies that varied from 0.0007 to 0.5119. The combined power of discrimination and the combined probability of exclusion for 19 STR loci in the Chongqing Han population were 0.99999999999999999999998954 and 0.99999998387, respectively. The findings indicated that the 19 autosomal STR loci were highly polymorphic in the Chongqing Han population and can be used as a powerful tool in personal identification and parentage testing. Our genetic study enriched the Chinese local forensic reference database. Population comparisons and phylogenetic analyses revealed that genetic heterogeneity widely existed among the Chongqing Han, Xinjiang Uyghur, and Kazakh populations as well as demonstrated that genetic similarity was tightly associated with those of close geographic origin or of the same ethnic origin.

STRait Razor v2s: Advancing sequence-based STR allele reporting and beyond to other marker systems

STRait Razor has provided the forensic community a free-to-use, open-source tool for short tandem repeat (STR) analysis of massively parallel sequencing (MPS) data. STRait Razor v2s (SRv2s) allows users to capture physically phased haplotypes within the full amplicon of both commercial (ForenSeq) and "early access" panels (PowerSeq, Mixture ID). STRait Razor v2s may be run in batch mode to facilitate population-level analysis and is supported by all Unix distributions (including MAC OS). Data are reported in tables in string (haplotype), length-based (e.g., vWA allele 14), and International Society of Forensic Genetics (ISFG)-recommended (vWA [CE 14]-GRCh38-chr12:5983950-5984049 (TAGA)₁₀ (CAGA)₃ TAGA) formats. STRait Razor v2s currently contains a database of ∼2500 unique sequences. This database is used by SRv2s to match strings to the appropriate allele in ISFG-recommended format. In addition to STRs, SRv2s has configuration files necessary to capture and report haplotypes from all marker types included in these multiplexes (e.g., SNPs, InDels, and microhaplotypes). To facilitate mixture interpretation, data may be displayed from all markers in a format similar to that of electropherograms displayed by traditional forensic software. The download package for SRv2s may be found at https://www.unthsc.edu/graduate-school-of-biomedical-sciences/molecular-and-medical-genetics/laboratory-faculty-and-staff/strait-razor.

FlexPlex27-highly multiplexed rapid DNA identification for law enforcement, kinship, and military applications

Rapid DNA identification is the use of a rugged, field-deployable system to generate short tandem repeat (STR) profiles in law enforcement, military, immigration, and homeland security applications. A performance verification study was conducted on the ANDE Rapid DNA identification system using FlexPlex27, a highly multiplexed, 27 locus assay that generates data for the expanded CODIS core loci and all additional STR loci required for international databasing. The assay contains 23 autosomal loci (D1S1656, D2S1338, D2S441, D3S1358, D5S81, D6S1043, D7S820, D8S1179, D10S1248, D12S391, D13S317, D16S539, D18S51, D19S433, D21S11, D22S1045, FGA, CSF1PO, Penta E, TH01, vWA, TPOX, and SE33), three Y-chromosomal loci (DYS391, DYS576, and DYS570), and Amelogenin. Study results demonstrate that the instrument is reliable, reproducible, accurate, robust, and ready for a large scale, comprehensive developmental validation by NDIS-participating laboratories. The additional loci in the FlexPlex assay allow for improved STR profile sharing globally, increase the power of discrimination for identification matches, and improve the effectiveness of kinship analyses.

Practical informativeness of short tandem repeat loci for chimerism analysis in hematopoietic stem cell transplantation

OBJECTIVE

Short tandem repeat (STR) loci are most frequently used for chimerism analysis after hematopoietic stem cell transplantation (HSCT). The aim of this study was to evaluate the practical informativeness of STR chimerism by integrating theoretical and analytical points.

METHODS

Theoretical and practical informativess of 16 STR loci were evaluated from 1249 pairs of recipients and donors who were prepared for HSCT.

RESULTS

Theoretical informativeness was influenced by genetic diversity including allele frequency and heterozygosity, and was higher in the unrelated HSCT group (90.5±5.3%) compared to the related HSCT group (66.2±4.4%). Practical informativeness was lower than theoretical (6.1±1.7%) because several STR loci were excluded due to stutter peaks and less reliable results, especially in type II-2 donor-recipient match pattern with no recipient-specific allele. We simulated an efficient STR combination for reliable chimerism analysis. Eight informative STR loci were required to analyze chimerism with at least one practically informative locus in the related HSCT group (D18S51, FGA, D2S1338, D13S317, D8S1179, D21S11, D16S539 and D7S820) while only three loci were needed in the unrelated group (D2S1338, FGA and D18S51). A minimum set of 2, 4 or 7 STR loci were required to provide at least 1, 3 or 5 practically informative loci in 95% of the unrelated HSCT group while 3, 8 or 12 loci were required in the related HSCT group.

CONCLUSION

We deducted the practical informativeness of STR chimerism, identified the major influencing factors on the practical informativeness of each STR locus, and successfully simulated the efficient STR combination for reliable chimerism analysis.

STR-realigner: a realignment method for short tandem repeat regions

Background

In the estimation of repeat numbers in a short tandem repeat (STR) region from high-throughput sequencing data, two types of strategies are mainly taken: a strategy based on counting repeat patterns included in sequence reads spanning the region and a strategy based on estimating the difference between the actual insert size and the insert size inferred from paired-end reads. The quality of sequence alignment is crucial, especially in the former approaches although usual alignment methods have difficulty in STR regions due to insertions and deletions caused by the variations of repeat numbers.

Results

We proposed a new dynamic programming based realignment method named STR-realigner that considers repeat patterns in STR regions as prior knowledge. By allowing the size change of repeat patterns with low penalty in STR regions, accurate realignment is expected. For the performance evaluation, publicly available STR variant calling tools were applied to three types of aligned reads: synthetically generated sequencing reads aligned with BWA-MEM, those realigned with STR-realigner, those realigned with ReviSTER, and those realigned with GATK IndelRealigner. From the comparison of root mean squared errors between estimated and true STR region size, the results for the dataset realigned with STR-realigner are better than those for other cases. For real data analysis, we used a real sequencing dataset from Illumina HiSeq 2000 for a parent-offspring trio. RepeatSeq and lobSTR were applied to the sequence reads for these individuals aligned with BWA-MEM, those realigned with STR-realigner, ReviSTER, and GATK IndelRealigner. STR-realigner shows the best performance in terms of consistency of the size of estimated STR regions in Mendelian inheritance. Root mean squared error values were also calculated from the comparison of these estimated results with STR region sizes obtained from high coverage PacBio sequencing data, and the results from the realigned sequencing data with STR-realigner showed the least (the best) root mean squared error value.

Conclusions

The effectiveness of the proposed realignment method for STR regions was verified from the comparison with an existing method on both simulation datasets and real whole genome sequencing dataset.

Combined effects of multiple linked loci on pairwise sibling tests

The advanced multiplex STR system, PowerPlex Fusion, includes four linked locus pairs. The conventional Identifiler system has one pair of linked loci. Therefore, sibling tests conducted using the advanced system might be more affected by linkage than those conducted using the conventional system. This study simulated single and combined effects of the four linked locus pairs on pairwise sibling tests. Simulated genotypes of 100,000 pairs of full siblings and nonrelatives were constructed according to allele frequencies of the Japanese population. The single linkage effect was evaluated for simulated genotype data by calculating both the likelihood ratio accounting for the linkage between two loci and the likelihood ratio ignoring the linkage. The combined effect was obtained by multiplication of the respective single effects. Furthermore, we investigated the possibility that ignoring the linkage affects subject classification by introducing a scale of the likelihood ratio into sibling tests. The single effect in the Identifiler analysis was 0.645-1.746 times if the linkage was ignored. Overestimations and underestimations were predictable from the identical-by-state status at two linked loci. The combined effect in the PowerPlex Fusion analysis was 0.217-7.390 times. Ignoring the linkage rarely caused a false conclusive or inconclusive result, even from PowerPlex Fusion analysis. Application of the advanced system improved sibling tests considerably. The additional examined loci were more beneficial than the adverse effect of the linkage derived from the four linked locus pairs.

Next-generation sequencing analysis of off-ladder alleles due to migration shift caused by sequence variation at D12S391 locus

In short tandem repeat (STR) analysis, length polymorphisms are detected by capillary electrophoresis (CE). At most STR loci, mobility shift due to sequence variation in the repeat region was thought not to affect the typing results. In our recent population studies of 1501 Japanese individuals, off-ladder calls were observed at the D12S391 locus using PowerPlex Fusion in nine samples for allele 22, one sample for allele 25, and one sample for allele 26. However, these samples were typed as ordinary alleles within the bins using GlobalFiler. In this study, next-generation sequencing analysis using MiSeq was performed for the D12S391 locus from the 11 off-ladder samples and 33 other samples, as well as the allelic ladders of PowerPlex Fusion and GlobalFiler. All off-ladder allele 22 in the nine samples had [AGAT]11[AGAC]11 as a repeat structure, while the corresponding allele was [AGAT]15[AGAC]6[AGAT] for the PowerPlex Fusion ladder, and [AGAT]13[AGAC]9 for the GlobalFiler ladder. Overall, as the number of [AGAT] in the repeat structure decreased at the D12S391 locus, the peak migrated more slowly using PowerPlex Fusion, the reverse strand of which was labeled, and it migrated more rapidly using GlobalFiler, the forward strand of which was labeled. The allelic ladders of both STR kits were reamplified with our small amplicon D12S391 primers and their mobility was also examined. In conclusion, off-ladder observations of allele 22 at the D12S391 locus using PowerPlex Fusion were mainly attributed to a relatively large difference of the repeat structure between its allelic ladder and off-ladder allele 22.

Short tandem repeat number estimation from paired-end reads for multiple individuals by considering coalescent tree

BACKGROUND

Two types of approaches are mainly considered for the repeat number estimation in short tandem repeat (STR) regions from high-throughput sequencing data: approaches directly counting repeat patterns included in sequence reads spanning the region and approaches based on detecting the difference between the insert size inferred from aligned paired-end reads and the actual insert size. Although the accuracy of repeat numbers estimated with the former approaches is high, the size of target STR regions is limited to the length of sequence reads. On the other hand, the latter approaches can handle STR regions longer than the length of sequence reads. However, repeat numbers estimated with the latter approaches is less accurate than those with the former approaches.

RESULTS

We proposed a new statistical model named coalescentSTR that estimates repeat numbers from paired-end read distances for multiple individuals simultaneously by connecting the read generative model for each individual with their genealogy. In the model, the genealogy is represented by handling coalescent trees as hidden variables, and the summation of the hidden variables is taken on coalescent trees sampled based on phased genotypes located around a target STR region with Markov chain Monte Carlo. In the sampled coalescent trees, repeat number information from insert size data is propagated, and more accurate estimation of repeat numbers is expected for STR regions longer than the length of sequence reads. For finding the repeat numbers maximizing the likelihood of the model on the estimation of repeat numbers, we proposed a state-of-the-art belief propagation algorithm on sampled coalescent trees.

CONCLUSIONS

We verified the effectiveness of the proposed approach from the comparison with existing methods by using simulation datasets and real whole genome and whole exome data for HapMap individuals analyzed in the 1000 Genomes Project.

Developmental validation of the DNAscan™ Rapid DNA Analysis™ instrument and expert system for reference sample processing

Since the implementation of forensic DNA typing in labs more than 20 years ago, the analysis procedures and data interpretation have always been conducted in a laboratory by highly trained and qualified scientific personnel. Rapid DNA technology has the potential to expand testing capabilities within forensic laboratories and to allow forensic STR analysis to be performed outside the physical boundaries of the traditional laboratory. The developmental validation of the DNAscan/ANDE Rapid DNA Analysis System was completed using a BioChipSet™ Cassette consumable designed for high DNA content samples, such as single source buccal swabs. A total of eight laboratories participated in the testing which totaled over 2300 swabs, and included nearly 1400 unique individuals. The goal of this extensive study was to obtain, document, analyze, and assess DNAscan and its internal Expert System to reliably genotype reference samples in a manner compliant with the FBI's Quality Assurance Standards (QAS) and the NDIS Operational Procedures. The DNAscan System provided high quality, concordant results for reference buccal swabs, including automated data analysis with an integrated Expert System. Seven external laboratories and NetBio, the developer of the technology, participated in the validation testing demonstrating the reproducibility and reliability of the system and its successful use in a variety of settings by numerous operators. The DNAscan System demonstrated limited cross reactivity with other species, was resilient in the presence of numerous inhibitors, and provided reproducible results for both buccal and purified DNA samples with sensitivity at a level appropriate for buccal swabs. The precision and resolution of the system met industry standards for detection of micro-variants and displayed single base resolution. PCR-based studies provided confidence that the system was robust and that the amplification reaction had been optimized to provide high quality results. The DNAscan integrated Expert System was examined as part of the Developmental Validation and successfully interpreted the over 2000 samples tested with over 99.998% concordant alleles. The system appropriately flagged samples for human review and failed both mixed samples and samples with insufficient genetic information. These results demonstrated the integrated Expert System makes correct allele calls without human intervention.

Investigation of single nucleotide polymorphism loci susceptible to degradation by ultraviolet light

DNA in biological fluids is often degraded by environmental factors. Given that single nucleotide polymorphism (SNP) analyses require shorter amplicons than short tandem repeat (STR) analyses do, their use in human identification using degraded samples has recently attracted attention. Although various SNP loci are used to analyze degraded samples, it is unclear which ones are more appropriate. To characterize and identify SNP loci that are susceptible or resistant to degradation, we artificially degraded DNA, obtained from buccal swabs from 11 volunteers, by exposure to ultraviolet (UV) light for different durations (254 nm for 5, 15, 30, 60, or 120 min) and analyzed the resulting SNP loci. DNA degradation was assessed using gel electrophoresis, STR, and SNP profiling. DNA fragmentation occurred within 5 min of UV irradiation, and successful STR and SNP profiling decreased with increasing duration. However, 73% of SNP loci were still detected correctly in DNA samples irradiated for 120 min, a dose that rendered STR loci undetectable. The unsuccessful SNP typing and the base call failure of nucleotides neighboring the SNPs were traced to rs1031825, and we found that this SNP was susceptible to UV light. When comparing the detection efficiencies of STR and SNP loci, SNP typing was more successful than STR typing, making it effective when using degraded DNA. However, it is important to use rs1031825 with caution when interpreting SNP analyses of degraded DNA.

A novel MSX1 intronic mutation associated with autosomal dominant non-syndromic oligodontia in a large Chinese family pedigree

BACKGROUND

Tooth agenesis is a common developmental dental anomaly. The aim of the study was to identify the causal genetic mutation in a four-generation Chinese family affected with non-syndromic autosomal dominant tooth agenesis.

METHODS

Genome-wide scanning was performed using the Illumina Linkage-12 array. Genotyping of short tandem repeat markers was used to finely map the causative locus. Haplotype analysis and Sanger sequencing was performed to precisely locate the position and nature of the gene defect.

RESULTS

Clinical examination of the available 23 family members showed variable tooth agenesis in 10 subjects, ranging from oligodontia to mild hypodontia. Genome-wide scanning and haplotype analyses identified the 4p16.1-p16.3 region with a maximum multi-point LOD score of 3.50, which overlapped with the MSX1 gene. A single heterozygous point mutation IVS1-5 G>A in the MSX1 gene was exclusively detected in the 10 family members affected with tooth agenesis. Sequencing of MSX1 cDNA revealed that the intronic mutation did not affect the normal splicing pattern of the pre-mRNA. However, real-time qPCR analysis of lymphocyte RNA showed that the level of MSX1 mRNA was significantly decreased in individuals heterozygous for the mutation.

CONCLUSIONS

We identified and characterized a novel intronic mutation in the MSX1 gene in a large Chinese pedigree, adding to the small repertoire of MSX1 mutations associated with autosomal dominant tooth agenesis. We hypothesize that the variable degree of tooth agenesis observed in each affected individual may be due to sub-optimal levels of MSX1 expression during critical stages tooth development.

Genetic mapping of 15 human X chromosomal forensic short tandem repeat (STR) loci by means of multi-core parallelization

Typing of X chromosomal short tandem repeat (X STR) markers has become a standard element of human forensic genetic analysis. Joint consideration of many X STR markers at a time increases their discriminatory power but, owing to physical linkage, requires inter-marker recombination rates to be accurately known. We estimated the recombination rates between 15 well established X STR markers using genotype data from 158 families (1041 individuals) and following a previously proposed likelihood-based approach that allows for single-step mutations. To meet the computational requirements of this family-based type of analysis, we modified a previous implementation so as to allow multi-core parallelization on a high-performance computing system. While we obtained recombination rate estimates larger than zero for all but one pair of adjacent markers within the four previously proposed linkage groups, none of the three X STR pairs defining the junctions of these groups yielded a recombination rate estimate of 0.50. Corroborating previous studies, our results therefore argue against a simple model of independent X chromosomal linkage groups. Moreover, the refined recombination fraction estimates obtained in our study will facilitate the appropriate joint consideration of all 15 investigated markers in forensic analysis.

Comparative performance of AmpFLSTR® Identifiler® Plus PCR amplification kit and QIAGEN® Investigator® IDplex Plus kit

Many forensic STR kits are currently available in the market. The AmpFLSTR® Identifiler® Plus kit, which targets 15 STRs, is commonly used worldwide. The Thai forensic DNA community is built around it in terms of instrument, databases, and interpretation. QIAGEN's IDplex Plus kit targets the same loci, but the PCR cycling time is shorter by about 90min. A direct comparison that assesses forensic parameters and applicability to casework between the two kits has never been carried out. In this study, we performed a direct comparison between the two kits using serial dilutions of two control DNA samples and 60 randomly selected casework samples, including samples taken from improvised explosive devices and terrorist raids. We statistically compared the performance of the two kits in terms of peak height, number of allele detected (allelic drop-out), intra-locus balance, inter-locus balance, inhibitor tolerance, stutter ratio, concordance, and allelic drop-in. The results demonstrate that both kits are statistically similar in performance. IDplex Plus gave higher peak heights in sensitivity test and tolerated inhibitors better, but had slightly worse inter-locus balances and stutter ratios. However, these differences were not practically significant, as seen by the resulting profiles of the casework samples (p=0.601). The performance on low-template samples also was not different. In conclusion, laboratories looking to replace the aging Identifiler® Plus might consider the IDplex Plus as a faster, more robust alternative that fits right into their existing structure without further investment in instrument and DNA database. Having more kits available worldwide by different companies could help bring the technology to different forensic laboratories and the justice system as a whole.

Linkage Study Revealed Complex Haplotypes in a Multifamily due to Different Mutations in CAPN3 Gene in an Iranian Ethnic Group

Calpainopathy is an autosomal recessive form of limb girdle muscular dystrophies which is caused by mutation in CAPN3 gene. In the present study, co-segregation of this disorder was analyzed with four short tandem repeat markers linked to the CAPN3 gene. Three apparently unrelated Iranian families with same ethnicity were investigated. Haplotype analysis and sequencing of the CAPN3 gene were performed. DNA sample from one of the patients was simultaneously sent for next-generation sequencing. DNA sequencing identified two mutations. It was seen as a homozygous c.2105C>T in exon 19 in one family, a homozygous novel mutation c.380G>A in exon 3 in another family, and a compound heterozygote form of these two mutations in the third family. Next-generation sequencing also confirmed our results. It was expected that, due to the rare nature of limb girdle muscular dystrophies, affected individuals from the same ethnic group share similar mutations. Haplotype analysis showed two different homozygote patterns in two families, yet a compound heterozygote pattern in the third family as seen in the mutation analysis. This study shows that haplotype analysis would help in determining presence of different founders.

Typing Candida Species Using Microsatellite Length Polymorphism and Multilocus Sequence Typing

To gain more insight into the epidemiological relationships between isolates of Candida spp. obtained from various origins, several molecular typing techniques have been developed. Two methods have emerged in the 2000s as soon as enough knowledge of the Candida spp. genomes was available to choose adequate loci and primers, namely microsatellite length polymorphism (MLP) and multilocus sequence typing (MLST). To contrast with previous PCR-based methods, specific amplifications with stringent conditions easily reproducible are the basis of MLP and MLST. MLST relies on Sanger sequencing to detect single-nucleotide polymorphisms within housekeeping genes. MLP needs a first in silico step to select tandemly repeated stretches of two to five nucleotides. One of the two primers used to amplify a microsatellite locus is labeled and fragment sizing is automatically performed using high-resolution electrophoresis platforms. MLST provides results easily comparable between laboratories and active MLST schemes are publicly available for the main Candida species. For comparative studies, MLP needs standards to compensate for the electrophoretic variations depending on the platforms used. Both methods can help us gain insight into the genetic relatedness of fungal isolates, both with advantages and drawbacks, and the choice of one method rather than the other depends on the task in question.

Genome-wide identification of human- and primate-specific core promoter short tandem repeats

Recent reports of a link between human- and primate-specific genetic factors and human/primate-specific characteristics and diseases necessitate genome-wide identification of those factors. We have previously reported core promoter short tandem repeats (STRs) of extreme length (≥6-repeats) that have expanded exceptionally in primates vs. non-primates, and may have a function in adaptive evolution. In the study reported here, we extended our study to the human STRs of ≥3-repeats in the category of penta and hexaucleotide STRs, across the entire human protein coding gene core promoters, and analyzed their status in several superorders and orders of vertebrates, using the Ensembl database. The ConSite software was used to identify the transcription factor (TF) sets binding to those STRs. STR specificity was observed at different levels of human and non-human primate (NHP) evolution. 73% of the pentanucleotide STRs and 68% of the hexanucleotide STRs were found to be specific to human and NHPs. AP-2alpha, Sp1, and MZF were the predominantly selected TFs (90%) binding to the human-specific STRs. Furthermore, the number of TF sets binding to a given STR was found to be a selection factor for that STR. Our findings indicate that selected STRs, the cognate binding TFs, and the number of TF set binding to those STRs function as switch codes at different levels of human and NHP evolution and speciation.

Detection of a novel X-chromosomal short tandem repeat marker in Xq28 in four ethnic groups

DNA testing of X-chromosomal short tandem repeat (X-STR) polymorphisms has been the focus of attention in several studies, mainly due to its applicability in the investigation of complex kinship cases. Studies of X-STR in analyses of DNA sequences, population studies and DNA testing applications have been reported. We performed detection and population genetic study of a novel tetranucleotide X-STR locus in the present study. We identified a unique X-STR locus consisting of two tetranucleotides in Xq28. Although the STR is a simple tetranucleotide, its polymorphism was comparatively high [polymorphism information content (PIC)=0.7140] in Japanese subjects. In addition, the STR varied in structure among ethnic groups. We conclude that this locus will be useful for forensic DNA testing and anthropological studies.

Population data of 17 short tandem repeat loci in 2923 individuals from the Han population of Nantong in East China

Nantong is located in mid-eastern China, and the Han population in Nantong may be greatly affected by population admixture between northern and southern Han Chinese populations. In this study, we analyzed 17 autosomal short tandem repeat (STR) loci on 2923 unrelated individuals collected from the Han population of Nantong. No significant deviation from Hardy-Weinberg equilibrium was observed at all STR loci, and the expected heterozygosity ranged from 0.6184 to 0.9187. The combined match probability (CMP) was 3.87 × 10(-21), and the combined power of discrimination (CPD) was 99.999999999999999999613 %. No significant difference of allele frequencies was observed between Nantong and other Han populations at all STR loci, as well as Dai, Mongolian, and Tibetan. Significant differences were only observed between Nantong Han and Uyghur at TH01, as well as Nantong Han and Dong at CSF1PO and FGA. Nantong Han showed significant differences between She, Bouyei, and Miao at multiple STR loci.

Population genetic analysis of the GlobalFiler STR loci in 748 individuals from the Kazakh population of Xinjiang in northwest China

The six-dye GlobalFiler™ Express PCR amplification kit incorporates 21 commonly used autosomal short tandem repeat (STR) loci and three gender determination loci. In this study, we analyzed the GlobalFiler STR loci on 748 unrelated individuals from a Chinese Kazakh population of Xinjiang, China. No significant deviations from Hardy-Weinberg equilibrium and linkage disequilibrium were observed within and between 21 autosomal STR loci. SE33 showed the greatest power of discrimination in Kazakh population. The combined power of discrimination of Kazakh was 99.999999999999999999999996797 %. No significant differences of allele frequencies were observed between Kazakh and Uyghur at all 15 tested STR loci, as well as Mongolian. Significant differences were only observed between Kazakh and the other Chinese populations at TH01. Multiple STR loci showed significant differences between Kazakh and Arab, as well as South Portuguese. The multidimensional scaling plot (MDS) plot and neighbor-joining tree also showed Kazakh is genetically close to Uyghur.

Maternal T-Cell Engraftment Interferes With Human Leukocyte Antigen Typing in Severe Combined Immunodeficiency

OBJECTIVES

To report the laboratory investigation of a case of severe combined immunodeficiency (SCID) with maternal T-cell engraftment, focusing on the interference of human leukocyte antigen (HLA) typing by blood chimerism.

METHODS

HLA typing was performed with three different methods, including sequence-specific primer (SSP), sequence-specific oligonucleotide, and Sanger sequencing on peripheral blood leukocytes and buccal cells, from a 3-month-old boy and peripheral blood leukocytes from his parents. Short tandem repeat (STR) testing was performed in parallel.

RESULTS

HLA typing of the patient's peripheral blood leukocytes using the SSP method demonstrated three different alleles for each of the HLA-B and HLA-C loci, with both maternal alleles present at each locus. Typing results from the patient's buccal cells showed a normal pattern of inheritance for paternal and maternal haplotypes. STR enrichment testing of the patient's CD3+ T lymphocytes and CD15+ myeloid cells confirmed maternal T-cell engraftment, while the myeloid cell profile matched the patient's buccal cells.

CONCLUSIONS

Maternal T-cell engraftment may interfere with HLA typing in patients with SCID. Selection of the appropriate typing methods and specimens is critical for accurate HLA typing and immunologic assessment before allogeneic hematopoietic stem cell transplantation.

A silent allele in the locus D5S818 contained within the PowerPlex®21 PCR Amplification Kit

Three paternity tests cases were found with a single locus mismatch at the locus D5S818 with PowerPlex®21 PCR Amplification Kit (Promega). Forward and reverse primers were redesigned to type the samples again and to evaluate if there were alleles dropped out. The results showed the existence of a silent allele 12 in all the three families, due to a point mutation that changed cytosine to adenine at 90 nucleotides upstream from the 5' end of the AGAT repeat sequences in all the six individuals. A single locus mismatch due to a silent allele may occur in any locus using any kit. Therefore, we recommend using multiple kits to confirm the results in paternity testing cases with mismatches, especially when there is a single locus mismatch with homozygote involved.