Genetic distribution of 39 STR loci in 1027 unrelated Han individuals from Northern China

Developmental Validation of the Novel Five-Dye-Labeled Multiplex Autosomal STR Panel and Its Forensic Efficiency Evaluation

Short tandem repeats (STRs) are the most frequently used genetic markers in forensic genetics due to their high genetic diversities and abundant distributions in the human genome. Currently, the combined DNA index system is commonly incorporated into various commercial kits for forensic research. Some novel STRs that are different from the combined DNA index system were not only used to assess complex paternity cases but also could provide more genetic information and higher forensic efficiency in combination with those commonly used STRs. In this study, we validated forensic performance of a novel multiplex amplification STR panel to evaluate its sensitivity, species specificity, forensic application values, and so on. Obtained results revealed that the kit showed high sensitivity, and the complete allelic profile could be observed at 0.125 ng DNA sample. In addition, the kit possessed high species specificity, good tolerance to common inhibitors, and accurate genotyping ability. More importantly, STRs out of the kit displayed high discrimination power and probability of exclusion. To sum up, the novel kit presented in this study can be viewed as a promising tool for forensic human identification and complex paternity analysis.

Genetic and structural characterization of 20 autosomal STR loci from the Henan Han population of central China

AIM

This study was designed to investigate the genetic polymorphisms and forensic parameters of the 20 autosomal short tandem repeat (STR) loci included in the PowerPlex® 21 System (Promega, USA) in the Henan Han population with a view to expand the genetic information available for this population in human genome databases.

SUBJECTS AND METHODS

We evaluated the genetic polymorphisms from 20 autosomal STR loci using DNA typing based on 2995 individuals from the Henan Han population in central China and then used this information to investigate the genetic relationships between this population and the other 10 Han populations across China. These comparisons included genetic distance, phylogenetic trees, and principal component analysis (PCA).

RESULTS

We identified a total of 290 alleles and 1343 genotypes within the Henan Han population, with none of these loci deviating from their Hardy-Weinberg equilibrium (HWE). The population comparisons revealed that geographically close populations demonstrated closer genetic relationships. Thus, the Henan Han population was shown to be close to both the Beijing Han and Tianjin Han populations, creating a single cluster. In addition, these 20 STR loci exhibited a high degree of genetic polymorphisms, making them suitable for individual identification and parentage testing.

CONCLUSIONS

The results of this study will enrich the forensic databases of Chinese Han populations and serve as a resource for further studies in these populations.

The Polymorphism Analyses of Short Tandem Repeats as a Basis for Understanding the Genetic Characteristics of the Guanzhong Han Population

The short tandem repeat (STR) loci are polymorphic markers in the combined DNA index system (CODIS) and non-CODIS STR loci. Due to the highly polymorphic characteristic of STR loci, they are popular and widely used in forensic DNA typing laboratories. In this study, 22 STR loci (1 CODIS, 21 non-CODIS STR loci) and an Amelogenin locus were genotyped and analyzed in 590 unrelated individuals of the Guanzhong Han population. None of the 22 STR loci deviated from the Hardy-Weinberg equilibrium, and all the loci were in the linkage equilibrium state. We observed 247 alleles, and the corresponding allelic frequencies ranged from 0.0008 to 0.3695 in the Guanzhong Han population. The combined power of discrimination and the cumulative exclusion probability was 0.999 999 999 999 999 999 999 999 999 346 36 and 0.999 999 999 709 74, respectively. The results including Nei's D _A genetic distance, multidimensional scaling analysis, and principal component analysis showed that the Guanzhong Han population has closer genetic affinities with Northern Han, Chengdu Han, and Xinjiang Hui groups from China based on allelic frequencies of 15 overlapped STR loci from Guanzhong Han and 13 reference groups. The present results indicated that Microreader™ 23sp ID kit included highly polymorphic loci, and it could be well used for individual identification, paternity testing, and population genetics in the Guanzhong Han population.

Comprehensive analyses for genetic diversities of 19 autosomal STRs in Chinese Kazak group and its phylogenetic relationships with other continental populations

Short tandem repeats (STRs) play an essential role in forensic genetics due to their high degree of polymorphisms, wide distributions and easy detection method. In this study, allelic frequencies and forensic statistical parameters of the 19 autosomal STR loci in a Kazak ethnic group were calculated, and its genetic relationships with reference populations were assessed in order to understand population structure better and enrich population genetic data for forensic practice in Chinese Kazak ethnic group. There were 226 identified alleles with the corresponding allelic frequencies ranging from 0.0008 to 0.5295 in the 628 unrelated healthy Kazak individuals in Xinjiang Uygur Autonomous Region. All autosomal STRs were conformed to the Hardy-Weinberg equilibrium after Bonferroni’s correction. The cumulative power of discrimination and the combined probability of exclusion of all the 19 autosomal STRs were 0.999 999 999 999 999 999 999 997 162 and 0.999 999 994 484, respectively. Furthermore, the D_A distances and Fixation index values of pairwise populations, principal component analysis, multidimensional scaling analysis, phylogenetic tree analysis and structure analysis were conducted to probe the genetic relationships between the Kazak group and other reference populations. The population genetic results showed that these 19 autosomal STR loci were characterised by high genetic diversities in the Kazak group. Furthermore, the studied Kazak group had close genetic relationships with the Uyghur group and the Uzbek group. The present results may facilitate understanding the genetic background of the Chinese Xinjiang Kazak group.

Development of an NGS panel containing 42 autosomal STR loci and the evaluation focusing on secondary kinship analysis

High-throughput next-generation sequencing (NGS) is a feasible technique to detect considerably more markers and simultaneously obtain length and sequence information in a single reaction. In this study, we developed an NGS panel including 42 commonly used autosomal short tandem repeats (STRs) and amelogenin on the Illumina MiSeq FGx™. Sequencing accuracy was validated by the consistency of 2800M Control DNA detected using the ForenSeq™ DNA Signature Prep Kit and Sanger sequencing. Nomenclature incompatibility was found between NGS-STR and CE-STR typing at 9 loci (D3S3045, D6S477, D7S3048, D9S925, D14S608, D17S1290, D18S535, D21S1270, GATA198B05), despite the correct sequence. The difference was caused by the two different methods of identifying motif sequence and a one-to-one correspondence can be found. We evaluated the panel by investigating consistency, sequencing sensitivity and the effectiveness of the 2nd-degree relationship identification. Herein, we present sequencing results from 58 unrelated individuals of the Hebei Han population. The total discrimination power (TDP) and cumulative probability of exclusion for trio paternity testing (CPE_trio) of the 42 NGS-STR panels reached 1-2.84 × 10^-57 and 1-9.87 × 10^-21, respectively. By family simulation and likelihood ratio (LR) calculation, this panel was shown to have effectiveness for the 2nd-degree kinship identification similar to the ForenSeq™ DNA Signature Prep Kit and certain advantages compared with it due to the relatively small number of loci. As expected, it provides new data for the development of NGS-STR typing technology.

Forensic characteristics and population genetics of Chinese Kazakh ethnic minority with an efficient STR panel

On the purpose of enhancing the forensic efficiency of CODIS STR loci, new STR loci have been gradually discovered and developed into some commercial multiplex systems. Recently, 22 STR loci including 18 non-CODIS STR loci and four CODIS STR loci were investigated in 501 unrelated healthy individuals of Kazakh ethnic group. Seven to 20 alleles at the different loci were identified and altogether 276 alleles for 22 selected loci were detected with the corresponding allelic frequencies ranging from 0.0010 to 0.3623. No significant deviation was observed from the Hardy-Weinberg equilibrium test for any of the 22 STRs. The value of cumulative power of discrimination in Kazakh group was 1-1.00E^-28. Analyses of population differentiations and genetic distances between Kazakh and other Chinese groups presented that the Kazakh group with the Uygur group. These 22 STR loci evenly distributed on 22 different autosomal chromosomes were characterized by high genetic diversities and therefore could be utilized in the forensic cases to further increase the discrimination performance.

Genetic polymorphisms and mutation rates of 16 X-STRs in a Han Chinese population of Beijing and application examples in second-degree kinship cases

As a supplementary tool in forensic cases, X chromosomal short tandem repeats (X-STRs) might bridge large pedigree gaps and bring inspiration to forensic practices for the special mode of inheritance. To standardize the application of X-STRs, the DNA Commission of the International Society for Forensic Genetics (ISFG) presented recommendations concentrating on biostatistical evaluations. Following this guideline, in this study, 1247 (655 females and 592 males) unrelated individuals and 770 families originating from a Han Chinese population of Beijing were investigated with 16 X-STRs. The combined PDF and PDM were 0.999999999999994 and 0.999999997, respectively. The combined MECKrüger, MECKishida, MECDesmarais, and MECDesmarais duo were 0.999972736708864, 0.999999975670766, 0.999999975720931, and 0.999993489709197, respectively. In addition, a population comparison demonstrated that genetic heterogeneity widely exists between the Han population of Beijing and other populations, especially southern Han Chinese, European, and West African populations. Additionally, the overall mutation rates of the paternal and maternal germlines of the 16 X-STRs were 0.0021 and 0.0003, respectively. Among them, HPRTB showed the highest paternal mutation rate of 0.0094. Finally, based on these forensic parameters, the likelihood ratios of four second-degree kinship cases were evaluated. Comparing with autosomal STR, X-STR showed significant advantages for hypothesis exclusion. Our study indicated that the 16 X-STR loci are highly polymorphic in the Han population of Beijing and could be a satisfactory complimentary tool for forensic applications.

Forensic molecular genetic diversity analysis of Chinese Hui ethnic group based on a novel STR panel

In present study, the genetic polymorphisms of 22 autosomal short tandem repeat (STR) loci were analyzed in 496 unrelated Chinese Xinjiang Hui individuals. These autosomal STR loci were multiplex amplified and genotyped based on a novel STR panel. There were 246 observed alleles with the allele frequencies ranging from 0.0010 to 0.3609. All polymorphic information content values were higher than 0.7. The combined power of discrimination and the combined probability of exclusion were 0.999999999999999999999999999426766 and 0.999999999860491, respectively. Based on analysis of molecular variance method, genetic differentiation analysis between the Xinjiang Hui and other reported groups were conducted at these 22 loci. The results indicated that there were no significant differences in statistics between Hui group and Northern Han group (including Han groups from Hebei, Henan, Shaanxi provinces), and significant deviations with Southern Han group (including those from Guangdong, Guangxi provinces) at 7 loci, and Uygur group at 10 loci. To sum up, these 22 autosomal STR loci were high genetic polymorphic in Xinjiang Hui group.

A 472-SNP panel for pairwise kinship testing of second-degree relatives

Kinship testing based on genetic markers, as forensic short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs), has valuable practical applications. Paternity and first-degree relationship can be accurately identified by current commonly-used forensic STRs and reported SNP markers. However, second-degree and more distant relationships remain challenging. Although ∼10⁵-10⁶ SNPs can be used to estimate relatedness of higher degrees, genome-wide genotyping and analysis may be impractical for forensic use. With rapid growth of human genome data sets, it is worthwhile to explore additional markers, especially SNPs, for kinship analysis. Here, we reported an autosomal SNP panel consisted of 342 SNP selected from >84 million SNPs and 131 SNPs from previous systems. We genotyped these SNPs in 136 Chinese individuals by multiplex amplicon Massively Parallel Sequencing, and performed pairwise gender-independent kinship testing. The specificity and sensitivity of these SNPs to distinguish second-degree relatives and the unrelated was 99.9% and 100%, respectively, compared with 53.7% and 99.9% of 19 commonly-used forensic STRs. Moreover, the specificity increased to 100% by the combined use of these STRs and SNPs. The 472-SNP panel could also greatly facilitate the discrimination among different relationships. We estimated that the power of ∼6.45 SNPs were equivalent to one forensic STR in the scenario of 2nd-degree relative pedigree. Altogether, we proposed a panel of 472 SNP markers for kinship analysis, which could be important supplementary of current forensic STRs to solve the problem of second-degree relative testing.

Phylogenic analysis and forensic genetic characterization of Chinese Uyghur group via autosomal multi STR markers

We investigated the allelic frequencies and forensic descriptive parameters of 23 autosomal short tandem repeat loci in a randomly selected sample of 1218 unrelated healthy Uyghur individuals residing in the Xinjiang Uyghur Autonomous Region, northwest China. A total of 281 alleles at these loci were identified and their corresponding allelic frequencies ranged from 0.0004 to 0.5390. The combined match probability and combined probability of exclusion of all loci were 5.192 × 10⁻²⁹ and 0.9999999996594, respectively. The results of population genetic study manifested that Uyghur had close relationships with those contiguous populations, such as Xibe and Hui groups. In a word, these autosomal short tandem repeat loci were highly informative in Uyghur group and the multiplex PCR system could be used as a valuable tool for forensic caseworks and population genetic analysis.

Development of a rapid 21-plex autosomal STR typing system for forensic applications

DNA-STR genotyping technology has been widely used in forensic investigations. Even with such success, there is a great need to reduce the analysis time. In this study, we established a new rapid 21-plex STR typing system, including 13 CODIS loci, Penta D, Penta E, D12S391, D2S1338, D6S1043, D19S433, D2S441 and Amelogenin loci. This system could shorten the amplification time to a minimum of 90 min and does not require DNA extraction from the samples. Validation of the typing system complied with the Scientific Working Group on DNA Analysis Methods (SWGDAM) and the Chinese National Standard (GA/T815-2009) guidelines. The results demonstrated that this 21-plex STR typing system was a valuable tool for rapid criminal investigation.