Validation and casework application of a Y chromosome specific STR multiplex

A series of validation experiments was performed for a Y chromosome specific STR multiplex system following the suggestions made by the Technical Working Group DNA Analysis Methods (TWGDAM). The multiplex PCR products were detected on Perkin-Elmer 373 and 377 automated sequencers using two labeling colors. No problems regarding the stability, robustness and sensitivity of the Y STR multiplex were observed. Mixture studies revealed a cut off rate similar to autosomal STRs for mixtures of male DNAs and no interference of any female admixture. The comparison of the Y STR results to the autosomal typing results for 56 nonprobative semen stains and swabs, showed a slightly higher success rate in detecting the semen donor’s alleles for the Y STR multiplex. Two examples are shown to illustrate the usefulness of Y STR typing for DNA mixtures. In one case the Y STR results confirmed an isolated exclusion; in the other case, the interpretation of a mixture was clarified since the Y STR results proved the presence of DNA from at least two semen donors. Y STR typing is a valuable addition to the forensic DNA testing panel.     

A rare mutation in the primer binding region of the Amelogenin X homologue gene

Use of Amelogenin locus typing as a gender marker incorporated in STR multiplexes is common practice in forensic genetics analysis. Among 5534 Polish male individuals tested using the SGMPlus kit, one was found to lack the amelogenin X-specific homologue (0.02%). The same result was obtained with other commercial kits which also amplify the amelogenin locus, namely ProfilerPlus and PowerPlex16. When alternative amelogenin primers external to but encompassing the initial amplicon were applied, an X homologue product was seen. Sequencing of the X homologue amelogenin allele revealed C to G mutation located at the most 3′ base of the commonly used amelogenin reverse primer. To our knowledge, this mutation and failure to amplify the X homologue of the amelogenin gene has not been reported for the European population.     

Integration of the AmpFlSTR Identifiler PCR Amplification Kit with SRY-specific primers for gender identification

Dropout of the amelogenin Y-specific allele due to an interstitial deletion of the Yp involving the amelogenin Y locus (AMELY) can cause misidentification of sex genotype with potentially serious consequences in personal identification processes and criminal investigations. Inclusion of additional sex-defining markers in forensic DNA typing kits is therefore advisable. In this study, the co-amplification of the sex-determining region Y (SRY) gene and 16 STR loci included in the AmpFlSTR Identifiler PCR Amplification Kit was evaluated. Combination of SRY and Identifiler primers did not compromise the amplification outcome and generated a 90 bp male-specific SRY fragment, showing a reproducible peak height ratio in comparison with the AMELY peak. The SRY peak was detectable in presence of amounts of template DNA as low as 125 pg, and in mixed samples with a male/female DNA ratio of 1:100.     

“YFlag” – A Single‐base Extension Primer Based Method for Gender Determination

Assigning the gender of a DNA contributor in forensic analysis is typically achieved using the amelogenin test. Occasionally, this test produces false‐positive results due to deletions occurring on the Y chromosome. Here, a four‐marker “YFlag” method is presented to infer gender using single‐base extension primers to flag the presence (or absence) of Y‐chromosome DNA within a sample to supplement forensic STR profiling. This method offers built‐in redundancy, with a single marker being sufficient to detect the presence of male DNA. In a study using 30 male and 30 female individuals, detection of male DNA was achieved with c. 0.03 ng of male DNA. All four markers were present in male/female mixture samples despite the presence of excessive female DNA. In summary, the YFlag system offers a method that is reproducible, specific, and sensitive, making it suitable for forensic use to detect male DNA.     

联合应用常染色体STR和X-STR标记鉴定单亲疑难案例

目的通过对常染色体和X染色体遗传标记的检测,探讨单亲疑难案例的鉴定策略。方法提取3个单亲鉴定案例的6份血样,采用Goldeneye 20A试剂盒和AGCU21＋1试剂盒检测常染色体上39个STR基因座,采用自主研制的16重X-STR扩增系统检测X染色体上16个STR基因座。结果用Goldeneye 20A试剂盒检测后发现每个单亲案例均有一个基因座不符合遗传规律,当常染色体STR基因座增加到39个时,案例1累计出现3个矛盾基因座;案例2和案例3均没有出现新的矛盾基因座。X染色体STR分型结果显示案例1有8个矛盾基因座,案例2和案例3无矛盾基因座,与常染色体分型结论相符。结论对于出现单基因座不符合遗传规律的母女、母子、父女单亲案例鉴定,不仅可以增加新的常染色体STR检测,也可以增加X染色体STR的检测,这样在相互验证的同时也能获得更加可靠的鉴定意见。     

Efficiency Analysis of EX16 +10Y Kit on Detection of the Uygur Population in Xinjiang ProvinceCSCD

Objective: To analyse the efficiency of EX16+10Y kit on the forensic detection of the Uygur in Xinjiang province. Methods: The blood samples were extracted from 4 620 male individuals of Uygur in Xinjiang province, and amplified by EX16+10Y kit. The typing of amplification products was performed by 3130xl genetic analyzer. Results: The genotyping graphs of 15 autosomal STR loci and 10 Y -chromosomal STR loci from 4 620 male individuals of Uygur in Xinjiang province were acquired completely. The genotype distribution of 15 autosomal STR loci was consistent with Hardy-Weinberg equilibrium. The heterozygosity, polymorphism information content and discrimination power of STR loci were 0.637-0.838, 0.580-0.860 and 0.811-0.978, respectively. There were 766 haplotypes in 10 Y -chromosomal STR loci. Conclusion: The test results of EX16+10Y kit is accurate and trustworthy, which can simultaneously be used for the individual identification and the screening of paternal pedigree in practical work. © 2018 by the Editorial Department of Journal of Forensic Medicine.     

Rapid amplification of commercial STR typing kits

Forensic DNA typing is currently conducted in approximately 8–10 h. The process includes DNA extraction, quantitation, multiplex PCR amplification, and fragment length detection. Today's commercial multiplex short tandem repeat (STR) typing kits are not optimized for rapid PCR thermal cycling. Current protocols require approximately 3 h for amplifying a multiplex containing 15 STR loci plus amelogenin. With the continuing development of miniaturization technologies such as microfluidic and micro-capillary devices, there is a desire to reduce the overall time required to type DNA samples. Such miniature devices could be used for initial screening at a crime scene, at a border, and at airports. There is also the benefit of reducing the required PCR amplification time for labs typing single-source reference samples. Surveys of fast processing polymerases working in combination with rapid cycling protocols have resulted in the development of a ‘rapid’ PCR amplification protocol. Results are obtained in less than 36 min run on a standard peltier-based thermal cycler employing a heating rate of 4 °C/s. Capillary electrophoresis characterization of the PCR products indicates good peak balance between loci, strong signal intensity and minor adenylation artifacts. Genotyping results are concordant with standard amplification conditions utilizing a standard 3 h (non-rapid) thermal cycling procedure. The rapid assay conditions are robust enough to routinely amplify 0.5 ng of template DNA (with 28 cycles).     

New autosomal STR loci

Additional STR loci can be beneficial for a number of human identity, forensic casework, and DNA database applications. The marker selection and characterization process applied at NIST in developing these new loci and assays are described along with concordance testing results from non-overlapping PCR primers. A 23plex for simultaneous amplification of 22 autosomal STR loci and an amelogenin sex-typing assay is also demonstrated.     

11个Y—STR基因座遗传多态性研究

目的 调查11个Y染色体STR基因座的遗传多态性。方法 利用PCR扩增和聚丙烯酰胺凝胶电泳技术对广州地区汉族群体无关男性血样进行11个Y—STR基因座的分型。结果 11个Y—STR基因座在广州地区汉族群体分别发现3～5个等位基因,GD值最低为0.3037(DYS434),最高为0.8455(DYS390)。结论 11个Y—STR基因座在广州地区汉族群体均具有较高的遗传多态性,可应用于法科学个体识别和亲子鉴定。     

Quality control of PCR primers used in multiplex STR amplification reactions

Reliable amplification of short tandem repeat (STR) DNA markers with the polymerase chain reaction (PCR) is dependent on high quality PCR primers. The particular primer combinations and concentrations are especially important with multiplex amplification reactions where multiple STR loci are simultaneously copied. Commercially available kits are now widely used for STR amplification and subsequent DNA typing. We present here the use of high performance liquid chromatography (HPLC) and time-of-flight mass spectrometry (TOF-MS) methods for characterization of commercially available STR kits.     

Erroneous gender identification by the amelogenin sex test

Human gender identification, based on the amelogenin gene, has important applications in forensic casework, prenatal diagnosis, DNA databasing, and blood sample storage. However, we report on the first known case, in the Israeli population, of an amelogenin sex test failure on a phenotypically normal male. He was typed as a female by both the AmpFlSTR SGM plus and GenePrint kits. Subsequent, karyotyping of the soldier's blood sample showed no abnormalities. These results suggest that the determination of sex, based on the amelogenin test, should be interpreted cautiously.     

Ultrafast STR Separations on Short‐Channel Microfluidic Systems for Forensic Screening and Genotyping

There are situations in which it is important to quickly and positively identify an individual. Examples include suspects detained in the neighborhood of a bombing or terrorist incident, individuals detained attempting to enter or leave the country, and victims of mass disasters. Systems utilized for these purposes must be fast, portable, and easy to maintain. DNA typing methods provide the best biometric information yielding identity, kinship, and geographical origin, but they are not portable and rapid. This study details the development of a portable short‐channel microfluidic device based on a modified Agilent 2100 bioanalyzer for applications in forensic genomics. The system utilizes a denaturing polymer matrix with dual‐channel laser‐induced fluorescence and is capable of producing a genotype in 80 sec. The device was tested for precision and resolution using an allelic ladder created from 6 short tandem repeat (STR) loci and a sex marker (amelogenin). The results demonstrated a precision of 0.09–0.21 bp over the entire size range and resolution values from 2.5 to 4.1 bp. Overall, the results demonstrate the chip provides a portable, rapid, and precise method for screening amplified short tandem repeats and human identification screening.     

Uses of the NIST 26plex STR assay for human identity testing

Ongoing work at the U.S. National Institute of Standards and Technology has focused on the characterization of 26 autosomal STR loci for human identity testing. These 26 loci are in addition to the existing 13 U.S. core loci and those found in PowerPlex16 and Identifiler commercial STR typing kits. The amplification of the 26 loci has been optimized for degraded extracts in unique miniplex panels and also for reference samples as a single reaction 26plex assay. A study has been performed comparing genotypes obtained with the 26plex primers to those with miniplex panels for allele drop out and concordance. The forensic utility of the 26plex assay was evaluated for situations where additional loci are beneficial. The utility of this large multiplex was also tested in a case involving DNA extracted from degraded bone samples. The 26plex can serve as a low-cost assay (compared to commercially available kits) useful for both sorting comingled remains and providing additional markers for increased statistical support for samples that require “non-trio” family references for human identification.     

Effectiveness of Coupled Application of AmpFℓSTR Yfiler Kit and Reduced Size Y‐chromosomal Short Tandem Repeat Analysis for Archeological Human Bones

The AmpF?STR Yfiler PCR Amplification (Yfiler) kit continues to be improved for a better analytical efficiency in cases of highly degraded DNA. The authors endeavored to determine whether coupling of the Yfiler kit with supplemental multiplex amplification of some Y‐STR loci is a more efficient analytical mode for poorly preserved human femurs (n = 15) discovered at Korean archeological sites. To reveal locus profiles not easily obtained by Yfiler analysis, custom‐designed primers were adopted for the DYS390, DYS391, DYS392, DYS438, DYS439, and DYS635 loci. The success rate for 16 Y‐STR locus profiles obtained from the 15 femurs was improved from 18.33% (in the use of Yfiler kit only) to 49.17% (the coupled use of Yfiler and custom‐designed primers). In this study, the authors established that the custom‐designed primers offer a markedly improved success rate for obtainment of Y‐STR profiles from degraded aDNA not easily identified by sole use of the Yfiler assay.     

A study on the effects of degradation and template concentration on the amplification efficiency of the STR Miniplex primer sets

In forensic DNA analysis, the samples recovered from the crime scene are often highly degraded leading to poor PCR amplification of the larger sized STR loci. To avoid this problem, we have developed STR markers with redesigned primer sequences called "Miniplexes" to produce smaller amplicons. To assess the effectiveness of these kits, we have tested these primer sets with enzymatically degraded DNA and compared the amplifications to a commercial kit. We also conducted sensitivity and peak balance studies of three Miniplex sets. Lastly, we report a case study on two human skeletal remain samples collected from different environmental conditions. In both types of degraded DNA, the Miniplex primer sets were capable of producing more complete profiles when compared to the larger sized amplicons from the commercial kit. Correct genotypes were obtained at template concentrations as low as 31 pg/25 microL. Overall, our data confirm that our redesigned primers can increase the probability of obtaining a usable profile in situations where standard kits fail.     

The development of reduced size STR amplicons as tools for analysis of degraded DNA

New multiplex PCR sets of commonly used short tandem repeat (STR) markers have been developed to produce PCR products that are reduced in size when compared to standard commercial STR kits. The reduction in size of these amplicons can facilitate the examination and analysis of degraded DNA evidence by improving amplification efficiency. This "miniSTR" approach will permit current forensic practitioners to use STR markers and instrumentation already present in their laboratories and to generate genotyping data that is directly comparable to reference samples and searchable through the FBI's Combined DNA Index System (CODIS) databases. This paper discusses the development of these new primer sets and presents some initial results in the analysis of degraded and aged DNA samples. A method for removal of problematic fluorescent dye artifacts is also described. Comparison studies in over 100 samples have verified that these miniSTR primers can provide fully concordant results to commercial STR kits and can provide improved signal from degraded DNA specimens. These miniplex sets should prove valuable in the analysis of samples where allele dropout and reduced sensitivity of larger STR alleles occurs.     

Y-chromosome STR system, Y-PLEX 12, for forensic casework: development and validation

The Y-PLEX 12 system, developed for use in human identification, enables simultaneous amplification of eleven polymorphic short tandem repeat (STR) loci, namely DYS392, DYS390, DYS385 a/b, DYS393, DYS389I, DYS391, DYS389II, DYS 19, DYS439 and DYS438, residing on the Y chromosome and Amelogenin. Amelogenin provides results for gender identification and serves as internal control for PCR. The validation studies were performed according to the DNA Advisory Board's (DAB) Quality Assurance Standards. The minimal sensitivity of the Y-PLEX 12 system was 0.1 ng of male DNA. The mean stutter values ranged between 3.76-15.72%. A full male profile was observed in mixture samples containing 0.5 ng of male DNA and up to 400 ng of female DNA. Amelogenin did not adversely affect the amplification of Y-STRs in mixture samples containing male and female DNA. The primers for the Y-STR loci present in Y-PLEX 12 are specific for human DNA and some higher primates. None of the primate samples tested provided a complete profile at all 11 Y-STR loci amplified with the Y-PLEX 12 system. Y-PLEX 12 is a sensitive, valid, reliable, and robust multiplex system for forensic analysis, and it can be used in human forensic and male lineage identification cases.     

Direct STR amplification from whole blood and blood- or saliva-spotted FTA without DNA purification

The DNA purification step has been thought to be essential for typing of STR DNA. However, this process is time-consuming, and there is a risk of unexpected cross-contamination during purification. We report a new method for direct short tandem repeat (STR) amplification using a newly developed direct PCR buffer, AnyDirect, which can amplify STR loci from whole blood and blood- or saliva-spotted FTA cards without DNA purification. The autosomal and Y chromosomal STR loci were analyzed for whole blood and blood or saliva spots of random individuals, followed by comparison of the results with those of corresponding purified DNA. The results from whole blood and blood spots showed perfect concordance with those from purified DNA without allele or locus drop-out. However, in the case of saliva spots, no amplification or locus drop-out was observed in some of the samples, which offers a topic for further study. Additionally, some commercial hot-start DNA polymerases other than AmpliTaq Gold DNA polymerase were also found to be compatible with this buffer system. Therefore, this direct PCR buffer was demonstrated to be useful for fast forensic DNA analysis or criminal DNA databases for which there is no need to store DNA samples.     

Phylogenetic evidence for multiple independent duplication events at the DYS19 locus

Duplication events at Y chromosome STR loci have been repeatedly described in human populations. DYS19 is probably the best known example and it exhibits duplicate state in individuals from all continents. Despite the large amount of available data, evolutionary relationship between DYS19 duplication-bearing chromosomes has not been so far investigated. We address the genealogical correlation among such chromosomes by analysing newly identified DYS19 duplicated Y chromosomes by SNP genotyping and microsatellite-based network analysis. SNP and network analysis show that DYS19 duplicated Y chromosomes associate with different Y chromosome lineages. These results indicate that DYS19 duplication occurred more than once during human evolution.     

Triallelic patterns in STR loci used for paternity analysis: evidence for a duplication in chromosome 2 containing the TPOX STR locus

We report triallelic patterns in several short tandem repeat (STR) loci revealed by routine paternity testing using the commercial AMPFlSTR Profiler and AMPFlSTR SGMplus kits. One case where the TPOX-locus (2p25.3) produced three peaks from the blood sample of a child was analysed further. Quantitative polymerase chain reaction (QPCR) and STR typing of the DNAs of the family trio revealed a large (>1.59 Mb) duplication flanking the TPOX-locus in chromosome 2 in both the mother and child. The implications of such genetic anomalies for paternity testing are discussed.