Development of a 9-locus X-STR multiplex PCR system for genetic analysis of three ethnic populations in China.

X-chromosome short tandem repeats (X-STR) analysis has been confirmed to be effective for kinship testing such as in deficiency paternity cases. The aim of this study was to develop a new multiplex polymerase chain reaction (PCR) system that can simultaneously amplify 9 X-STR loci (GATA172D05, DXS10159, DXS6797, HPRTB, DXS10079, DXS6789, DXS9895, DXS10146 and GATA31E08) in the same PCR reaction, and to obtain the database of the 9 X-STR loci in three ethnic populations in China. The genetic data of 815 (404 females and 411 males) unrelated Han Chinese from Hubei province, and Yi and Zhuang Chinese from Yunnan province were analyzed by using this multiplex system. The results showed that a total of 93 alleles for all these loci were found, and 7 to 20 alleles for each locus were observed. All of the analyzed loci were in agreement with Hardy-Weinberg equilibrium after Bonferroni correction in the three studied populations. The polymorphism information content (PIC) and power of discrimination (PD) in females were 0.6566-0.8531 and 0.8639-0.9684, respectively. Pairwise comparisons of allele frequency distribution showed significant differences in the most of these loci between different populations. The results indicate that this multiplex system is very useful for forensic analysis of different ethnic populations in China.

Age-related DNA methylation changes for forensic age-prediction.

There is no available method of age-prediction for biological samples. The accumulating evidences indicate that DNA methylation patterns change with age. Aging resembles a developmentally regulated process that is tightly controlled by specific epigenetic modifications and age-associated methylation changes exist in human genome. In this study, three age-related methylation fragments were isolated and identified in blood of 40 donors. Age-related methylation changes with each fragment was validated and replicated in a general population sample of 65 donors over a wide age range (11-72 years). Methylation of these fragments is linearly correlated with age over a range of six decades (r = 0.80-0.88). Using average methylation of CpG sites of three fragments, a regression model that explained 95 % of the variance in age was built and is able to predict an individual's age with great accuracy (R (2 )= 0.93). The predicted value is highly correlated with the observed age in the sample (r = 0.96) and has great accuracy of average 4 years difference between predicted age and true age. This study implicates that DNA methylation can be an available biological marker of age-prediction. Further measurement of relevant markers in the genome could be a tool in routine screening to predict age of forensic biological samples.

Isolation and identification of age-related DNA methylation markers for forensic age-prediction.

Age-prediction is an important part of forensic science. There is no available method of individual age-prediction for general forensic biological samples at crime scenes. Accumulating evidence indicates that aging resembles a developmentally regulated process tightly controlled by specific age-associated methylation exists in human genome. This study isolated and identified eight gene fragments in which the degree of cytosine methylation is significantly correlated with age in blood of 40 donors. Furthermore, we validated two CpG sites of each gene fragment and replicated our results in a general population sample of 40 males and 25 females with a wide age-range (11-72 years). The methylation of these fragments is linear with age over a range of six decades (Fragment P1 (r=-0.64), P2 (r=-0.58), P3 (r=-0.79), R1 (r=0.82), R2 (r=0.63), R3 (r=0.59), R4 (r=0.63) and R5 (r=0.62)). Using average methylation of two CpG sites from each fragment, we built a regression model that explained 95% of the variance in age and is able to predict the age of an individual with great accuracy (R(2)=0.918). The predicted values are highly correlated with the observed age in the sample (r=0.91). This study implicates that DNA methylation will be an available biological marker of age-prediction. Furthermore, measurement of relevant sites in the genome could be a tool in routine forensic screening to predict age of biological samples.

[Genetic polymorphism of 23 Y chromosome biallelic markers in Wuhan Han population].

To search polymorphic Y chromosome biallelic markers in Chinese Han population, and obtain their population genetic data. Genotyping of 23 biallelic markers on human Y chromosome (M7, M9, M50, M88, M89, M95, M111, M117, M119, M121, M122, M134, M159, M164, M175, M214, LINE1, MSY2, RPS4Y711, SRY465, IMS-JST164520, IMS-JST021354 and IMS-JST003305) were carried out in a sample of 160 unrelated Chinese male individuals living in Wuhan using fragment length discrepant allele specific PCR (FLDAS-PCR) and PAGE technique. In all 23 biallelic markers, genetic polymorphism were identified for 20 loci in Wuhan Han population except for M50, M159 and M164, and the ranges of gene diversity (GD) were 0.0126-0.4855. A total of 35 different haplogroups (Hg1-35) were observed and the haplogroup diversity (HD) was 0.9471. The haplogroups formed by 20 biallelic markers are highly polymorphic, and can be used in forensic science and population evolution studies.

[A study of genetic polymorphism of the STR loci D20S85 and D6S477 in Han population living in Wuhan].

OBJECTIVE: The genetic polymorphism of two STR loci, D20S85 and D6S477, were studied in 280 unrelated Chinese individuals in Wuhan. METHODS: The PCR amplified products were analyzed by PAGE and silver staining. RESULTS: 10 and 9 alleles were observed in these two STR loci, and the discriminating power (DP) were 0.9085 and 0.9127 respectively. No deviations from Hardy-Weinberg equilibrium were found. The two STR loci had been successfully applied to individual identification and paternity testing. CONCLUSION: The results demonstrated that the two loci were useful for forensic identification.