Age Estimation Based on DNA Methylation and Its Application Prospects in Forensic Medicine / 法医学杂志

With the improvement of DNA methylation detection techniques, studies on age-related methylation sites have found more age-specific ones across tissues, which improves the sensitivity and accuracy of age estimation. In addition, the establishment of various statistical models also provides a new direction for the age estimation of tissues from different sources. This review summarizes the related studies of age estimation based on DNA methylation from the aspects of detection technology, age-related cytosine phosphate guanine site and model selection in recent years.

Effects of Peripheral Blood Different Pretreatment Methods and Preservation Time on RNA Quality / 法医学杂志

OBJECTIVES@#To evaluate the effects of different pretreatment methods and preservation time on RNA quality of peripheral blood samples, and to optimize the preservation method of peripheral blood samples.@*METHODS@#Eight pretreatment methods were used to preprocess the peripheral blood from 3 healthy unrelated individuals and the treated samples were stored at -80 ℃. Total RNA of samples was extracted using Quick-RNATM Miniprep Plus kit. DNA/RNA ShieldTM was added to peripheral blood and total RNA was extracted after preservation at -80 ℃ for 0, 5, 10, 15, 30 and 60 days, respectively. The concentration, purity and integrity of RNA were determined. Statistical analyses were performed by SPSS 22.0 software to compare the differences in RNA yield, purity and integrity among the eight pretreatment methods.@*RESULTS@#In terms of purity, leukocyte pretreated with RNAlaterTM and directly cryopreservation peripheral blood showed the worst purity. The other six methods showed better purity. In terms of yield, blood cells with DNA/RNA ShieldTM came out with the highest yield, followed by peripheral blood with DNA/RNA ShieldTM. In terms of integrity, peripheral blood preserved in PAXgene Blood RNA tube method had the best integrity. Except for peripheral blood pretreated with DNA/RNA ShieldTM and blood cells pretreated with DNA/RNA shieldTM, the other five methods had statistical differences when compared to the method by keeping peripheral blood in PAXgene Blood RNA tube. The purity of RNA stored at six-time gradients ranged from 1.815 to 1.952. With the increase of storage time, RNA yield decreased from 4.516 ng to 1.039 ng, and RNA integrity decreased from 8.533 to 7.150.@*CONCLUSIONS@#According to the results of total RNA's yield, purity and integrity, peripheral blood pretreated with DNA/RNA ShieldTM was the best pretreatment method. After the pretreatment, samples can be preserved for up to 60 days in low temperature.

Progress on Copy Number Variation and Its Application in Forensic Medicine / 法医学杂志

Recently, researches on copy number variation （CNV） have extended to every field, such as etiological exploration and precise treatment of complex diseases, as well as genetic breeding and evolution. The unique genetic characteristics of CNV have made people gradually believe that it could be used as a biological genetic marker to solve related problems. With the development of detection technology, application of CNV in forensic medicine will increase gradually. In this paper, the concept and development of CNV, as well as its application in forensic medicine are summarized, to provide new ideas for the practical application of CNV in the future.

Evaluating the Efficiency of REPLI-g® Single Cell Kit for Trace DNA Amplification / 法医学杂志

Objective To evaluate the efficiency of REPLI-g® Single Cell Kit for sample DNA amplification, and explore its application value in forensic trace DNA amplification. Methods Three DNA extraction kits were selected to extract DNA from peripheral blood of 10 unrelated individuals. The DNA yield and purity of the three DNA extraction kits were compared. According to the results of comparison, one DNA sample was selected to concentrate and dilute, then used as the initial sample of whole genome amplification （WGA）. REPLI-g® Single Cell Kit was used to amplify the initial sample at the whole genome level. The amplification yield and amplification times were calculated, and the distribution of DNA fragments was detected by agarose gel electrophoresis. Goldeneye® DNA ID System 20A Kit was used to perform the STR typing of the initial sample and DNA samples amplified at the whole genome level to evaluate the performance of REPLI-g® Single Cell Kit in trace DNA amplication in terms of purity and yield as well as the success rate of STR typing. Results After comparison, one DNA sample was selected from QIAsymphony® DNA Investigator® Kit extracts to concentrate and dilute as the initial sample of WGA. After amplifying the whole genome of a series of initial samples by REPLI-g® Single Cell Kit, the lowest average of amplification yield reached 8.77×103 ng, while the average of the corresponding amplification times reached 1.40×106. DNA fragments were large and concentrated. The STR typing success rate of WGA samples became lower with the decrease of initial samples used, but when the amount of samples was lower than 0.5 ng, the STR typing success rate of samples after DNA WGA was higher than that of samples without DNA WGA. Conclusion REPLI-g® Single Cell Kit can increase the yield of template DNA. Especially for trace DNA, the STR typing success rate can be improved to a certain extent.

Research Progress on InDel Genetic Marker in Forensic Science / 法医学杂志

Genetic markers in forensic DNA typing experienced the variable number of tandem repeats （VNTR） sequences and the short tandem repeats （STR） sequences. With the emerge of sequencing technology, the third generation of genetic markers were found out, which usually have two alleles including single nucleotide polymorphism （SNP） and insertion/deletion （InDel）, also known as biallelic genetic markers. Because of the insertions or deletions of DNA fragments, InDel genetic marker reveals DNA fragment length polymorphism and widely distributes across the whole genome. InDel genetic marker is numerous and has the characteristics of STR and SNP genetic markers, which has been applied in the fields of genetics and anthropology. This review focuses on the research progress of InDel genetic marker in forensic science, aiming to review and summarize the main research findings in recent years and provide clues for future researches.

Assessment on Application of 24 Y-STR Loci in Forensic Science / 法医学杂志

OBJECTIVES@#To select a Y-STR marker system with strong haplotype identification ability, appropriate mutation rate and high compatibility and to assess its forensic application.@*METHODS@#The 24 Y-STR loci were tested by self-built fluorescent multiplex system, and the forensic assessment was conducted by 139 pairs of father-son samples collected in Jinan, Shandong province.@*RESULTS@#Totally 176 alleles were identified among the 24 Y-STR loci in the sample of 139 unrelated individuals labeled with father, and the gene diversity （GD） distributed between 0.083 7 （DYS645）-0.966 9 （DYS385a/b）. According to the 24 Y-STR loci, 139 different haplotypes were detected from 139 unrelated male individuals labeled with father in Han population of Shandong province and with no shared haplotype observed. The overall haplotype diversity （HD） was 1 and the discrimination capacity （DC） was 1. A total of 5 one-step mutations events were observed among the 24 Y-STR loci in 139 pairs of father-son. The average mutation rate was 0.001 5 [95% CI （0.000 5, 0.003 5）].@*CONCLUSIONS@#The system of 24 Y-STR loci shows a strong individual recognition ability and low mutation rate in the population in Jinan, Shandong province, and it has good application value in forensic science.

Establishment of 43-plex SNP Typing System and Its Forensic Application / 法医学杂志

Objective To evaluate the application of 43-plex SNP typing system in forensic science. Methods The typing of 43 SNP loci in 123 unrelated Han individuals from East China was detected by MALDI-TOF-MS. The application value of 43-plex SNP typing system was assessed according to the foren-sic parameters of population genetics. Results All the 43 SNP loci of 123 individuals showed no signifi-cant departure from Hardy-Weinberg equilibrium (P>0.05). Excepted rs1355366, rs2270529, rs10776839 and rs938283, there were 39 SNP loci had minor allele frequencies (MAF), which were greater than 0.25. Among the 25 loci MAFs, 24 ranged from 0.4 to 0.5, while 3 were close to 0.4. The DP, CDP, PIC, Ho, PEtrio and PEduo of the 43 SNP loci were 0.2901-0.6544, 1-9.8×10-11, 0.1708-0.5000, 0.1557-0.5935, 0.0854-0.2500 and 0.0146-0.1250, respectively. The CPEtrio and CPEduo were 0.999986 and 0.9924361, respectively. Conclusion The 43-plex SNP typing system in present study shows a high polymorphism, which can be an effective supplement and verification for traditional STR genetic markers. It also can be used with other commercial kits for the forensic paternity testing and individual identification.

Forensic Application of SiFaSTRTM 23plex DNA ID System in Han Population of Eastern China / 法医学杂志

Objective To investigate the genetic polymorphism of 21 autosomal STR loci and DY S391 locus of SiFaSTRTM 23plex DNA ID system in Han population of eastern China and to evaluate its ap-plication value in forensic science. Methods Typing test of 2000 unrelated individuals was performed using SiFaSTRTM 23plex DNA ID system. The population genetic parameters of STR loci were statistically analysed. A total of 3198 parentage confirmed cases were detected with that system and the mutation conditions were observed in 21 autosomal STR loci. Results All the 21 autosomal STR loci showed no significant departure from Hardy-Weinberg equilibrium (P>0.05). The Ho ranged from 0.6175 to 0.9270. The DP ranged from 0.7964 to 0.9869, as well as the PIC distributed from 0.5611 to 0.9123. The CDP was 0.999999999999999. The CPEduo was 0.999997431701961, while CPEtrio was 0.999999999654865. Five alleles were detected in DY S391 locus, with the allele frequency from 0.0040 to 0.7290, and GD was 0.4189. Except D13S317 and D10S1248, seventy-six mutation events were observed at the rest nineteen autosomal STR loci. Among them, seventy-five (98.68％) were one step mutation, and only one (1.32％) was three steps mutation. The mutation rate ranged from 0.2465×10-3 to 2.7114×10-3, and the averaged mutation rate was 0.8921×10-3 (95％ CI: 0.70×10-3-1.10×10-3). In 33 trio mutation cases, the proportion of the paternal mutation and the maternal mutation was 2.09:1. Conclusion The involved STRs are highly polymorphic in Eastern Han population with acceptable mutation rates by the SiFaSTRTM 23plex DNA ID system, which is suitable for paternity testing and individual identification.

Research Progress on Discrimination of Monozygotic Twins / 法医学杂志

Individual identification plays an import role in the practice of forensic medicine, and often provides crucial evidence for the analysis and detection of criminal cases.However, for individual identification in complex situations, such as monozygotic (MZ) twins assumed to be genetically identical, it is impossible to distinguish one from the other by using traditional forensic DNA typing system.Therefore, how to discriminate the MZ twins has become and will continue to be one of the difficult problems in forensic field.This paper summarized the genetic and epigenetic changes recently identified in MZ pairs, which might provide a new insight to forensic discrimination of MZ twins.