Application of Medical Statistical and Machine Learning Methods in the Age Estimation of Living Individuals.

In the study of age estimation in living individuals, a lot of data needs to be analyzed by mathematical statistics, and reasonable medical statistical methods play an important role in data design and analysis. The selection of accurate and appropriate statistical methods is one of the key factors affecting the quality of research results. This paper reviews the principles and applicable principles of the commonly used medical statistical methods such as descriptive statistics, difference analysis, consistency test and multivariate statistical analysis, as well as machine learning methods such as shallow learning and deep learning in the age estimation research of living individuals, and summarizes the relevance and application prospects between medical statistical methods and machine learning methods. This paper aims to provide technical guidance for the age estimation research of living individuals to obtain more scientific and accurate results.

Establishment and Application of a 42-plex Microhaplotype Assay in Forensic Genetics.

OBJECTIVES: To establish and forensically verify a 42 microhaplotypes (mircohaps, MHs) multiplex assay system based on next-generation sequencing (NGS), and to explore the application value of this system in the practice of forensic genetics. METHODS: A total of 42 highly polymorphic MHs were selected from previous studies, and sequenced by the MiSeq FGxTM platform to verify the repeata-bility, sensitivity, specificity, stability, and mixture analysis ability of the detection system. Through population genetic investigation of 102 unrelated Chinese Han individuals in Liyang City, Jiangsu Province, China, the application value of this system in forensic genetics was evaluated. RESULTS: The sequencing repeatability of the 42-plex MHs assay was 100% and the sensitivity was as low as 0.062 5 ng. The system had the ability to withstand the interference of indigo (≤2 500 ng/µL), humic acid (≤9 ng/µL), hemoglobin(≤20 µmol), and urea (≤200 ng/µL) and to detect mixtures of 2 people (1∶19), 3 people (1∶1∶9) and 4 people (1∶1∶1∶9). Based on 102 individual data, the combined power of discrimination and the combined power of exclusion were 1-3.45×10-30 and 1-3.77×10-11, respectively, and the average effect value of alleles was 2.899. CONCLUSIONS: The 42-plex MHs assay was successfully established in this study and this system has high repeatability and sensitivity, good anti-jamming ability and mixture analysis ability. The 42 MHs are highly polymorphism and have good application value in individual identification and paternity testing.

Cross-Platform Application of DNA Methylation Age Estimation Model in Eastern Chinese Han Population.

OBJECTIVES: To evaluate the forensic application value of an age estimation model based on DNA methylation in eastern Chinese Han population, and to provide a theoretical basis for exploring age estimation models suitable for different detection platforms. METHODS: According to the 6 age-related methylation sites in the published blood DNA methylation age estimation models of Chinese Han population, the DNA methylation level of 48 samples was detected by pyrosequencing and next-generation sequencing (NGS). After submitting DNA methylation levels to the age estimation model, the DNA methylation ages were predicted and compared with their real ages. RESULTS: The 6 DNA methylation sites in both detection techniques were age-related, with an R2 of 0.85 and a median absolute deviation (MAD) of 4.81 years when using pyrosequencing；with an R2 of 0.84 and MAD of 4.41 years when using NGS. CONCLUSIONS: The blood DNA methylation age estimation model can be used under pyrosequencing and multi-purpose regional methylation enrichment sequencing technology based on NGS and it can accurately estimate the age.

Application of SNaPshot Technology in Semen-Specific cSNP Genetic Marker.

OBJECTIVES: To explore the feasibility of genetic marker detection of semen-specific coding region single nucleotide polymorphism (cSNP) based on SNaPshot technology in semen stains and mixed body fluid identification. METHODS: Genomic DNA (gDNA) and total RNA were extracted from 16 semen stains and 11 mixtures composed of semen and venous blood, and the total RNA was reverse transcribed into complementary DNA (cDNA). The cSNP genetic markers were screened on the validated semen-specific mRNA coding genes. The cSNP multiplex detection system based on SNaPshot technology was established, and samples were genotyped by capillary electrophoresis (CE). RESULTS: A multiplex detection system containing 5 semen-specific cSNPs was successfully established. In 16 semen samples, except the cSNP located in the TGM4 gene showed allele loss in cDNA detection results, the gDNA and cDNA typing results of other cSNPs were highly consistent. When detecting semen-venous blood mixtures, the results of cSNP typing detected were consistent with the genotype of semen donor and were not interfered by the genotype of venous blood donor. CONCLUSIONS: The method of semen-specific cSNPs detection by SNaPshot technology method can be applied to the genotyping of semen (stains) and provide information for determining the origin of semen in mixed body fluids (stains).

Mitogenome evidence shows two radiation events and dispersals of matrilineal ancestry from northern coastal China to the Americas and Japan.

Although it is widely recognized that the ancestors of Native Americans (NAs) primarily came from Siberia, the link between mitochondrial DNA (mtDNA) lineage D4h3a (typical of NAs) and D4h3b (found so far only in East China and Thailand) raises the possibility that the ancestral sources for early NAs were more variegated than hypothesized. Here, we analyze 216 contemporary (including 106 newly sequenced) D4h mitogenomes and 39 previously reported ancient D4h data. The results reveal two radiation events of D4h in northern coastal China, one during the Last Glacial Maximum and the other within the last deglaciation, which facilitated the dispersals of D4h sub-branches to different areas including the Americas and the Japanese archipelago. The coastal distributions of the NA (D4h3a) and Japanese lineages (D4h1a and D4h2), in combination with the Paleolithic archaeological similarities among Northern China, the Americas, and Japan, lend support to the coastal dispersal scenario of early NAs.

Age Estimation Based on DNA Methylation and Its Application Prospects in Forensic Medicine.

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.

Traceability of Geographic Origin Using Human Skin and Oral Microbiota.

OBJECTIVES: To explore the possibility of using human skin and oral microorganisms to estimate the geographic origin of an individual through the sequencing analysis of bacterial 16S rRNA gene. METHODS: Microbial DNA was extracted from the palm and oral microorganisms of the Han population in Shanghai and Chifeng, Inner Mongolia, and the composition and diversity of the microbiota were analyzed by full-length 16S rRNA gene sequencing. Then, differential species were screened and a geographic location prediction model was constructed. RESULTS: The compositions of palm and oral microorganisms between Shanghai and Chifeng samples were both different. The abundance and uniformity of palm side skin microorganisms were higher in Chifeng samples than in Shanghai samples, while there was no significant difference in oral microorganisms. Permutational multivariate analysis of variance (PERMANOVA) confirmed that the ß-diversity between the samples from the two places were statistically significant, and the coefficients of determination (R2) for skin and oral samples were 0.129 and 0.102, respectively. Through principal co-ordinates analysis (PCoA), the samples from the two places could be preliminarily distinguished. The predictive model had the accuracies of 0.90 and 0.83 for the geographic origin using the skin and oral samples, respectively. CONCLUSIONS: There are differences in the compositions of palm and oral microbiota between Han populations in Shanghai and Chifeng. The prediction model constructed by the random forest algorithm can trace the unknown individuals from the above two places.

Genetic Polymorphism of 16 X-STR Loci in Xinjiang Uygur Population.

OBJECTIVES: To study the genetic polymorphism and population genetic parameters of 16 X-STR loci in Xinjiang Uygur population. METHODS: The Goldeneye® DNA identification system 17X was used to amplify 16 X-STR loci in 502 unrelated individuals (251 females and 251 males). The amplified products were detected by 3130xl genetic analyzer. Allele frequencies and population genetic parameters were analyzed statistically. The genetic distances between Uygur and other 8 populations were calculated. Multidimensional scaling and phylogenetic tree were constructed based on genetic distance. RESULTS: In the 16 X-STR loci, a total of 67 alleles were detected in 502 Xinjiang Uygur unrelated individuals. The allele frequencies ranged from 0.001 3 to 0.572 4. PIC ranged from 0.568 8 to 0.855 3. The cumulative discrimination power in females and males were 0.999 999 999 999 999 and 0.999 999 999 743 071, respectively. The cumulative mean paternity exclusion chance in trios and in duos were 0.999 999 997 791 859 and 0.999 998 989 000 730, respectively. The genetic distance between Uygur population and Kazakh population was closer, and the genetic distance between Uygur and Han population was farther. CONCLUSIONS: The 16 X-STR loci are highly polymorphic and suitable for identification in Uygur population, which can provide a powerful supplement for the study of individual identification, paternity identification and population genetics.

Efficiency Analysis of Uncle-Nephew Relationship Identification by Increasing STR Markers and Adding Reference Samples.

OBJECTIVES: To estimate the system efficiency of uncle-nephew relationship identification by increasing STR markers and adding reference samples based on the test results of simulated data and real samples, so as to provide references for selecting the appropriate number of STRs and reference samples for uncle-nephew relationship identification. METHODS: Five common models of uncle-nephew relationship identification were constructed by adding different reference samples. In each model, the likelihood ratio (LR) for 10 000 pairs of uncle-nephew relationships and 10 000 pairs of unrelated individuals were simulated by detecting 19, 39 or 55 STRs, and the system efficiency at different thresholds was simulated. The samples of the Han population in Zhejiang were collected, and 55 autosomal STRs were obtained by using SiFaSTRTM 23plex kit, Goldeneye® DNA ID 22NC kit and AGCU 21+1 PCR amplification kit. When 19, 39 and 55 STRs were detected, the LR of each model and system efficiency under different thresholds were calculated and compared with the simulation results. RESULTS: Under the same detection system, the calculated results of simulated data and corresponding true samples were basically consistent. In the same model, there was a positive correlation between the system efficiency of uncle-nephew relationship identification and the number of STRs detected. Moreover, the system efficiency of introducing relatives was higher than identifying only two individuals. The order of preference for the introduction of relatives was the full sibling (or mother) of the uncle and the full sibling (or mother) of the nephew. CONCLUSIONS: The system efficiency of uncle-nephew relationship identification could be improved by increasing the number of STRs and introducing known relatives, which would provide the basis for selecting the most appropriate detection system and reference individuals in actual cases.

Establishment of Multiplex Amplification System of STR Loci in Felis Catus and Its Forensic Application.

OBJECTIVES: To construct a Felis catus STR loci multiplex amplification system and to evaluate its application value by testing the technical performance. METHODS: The published Felis catus STR loci data were reviewed and analyzed to select the STR loci and sex identification loci that could be used for Felis catus individual identification and genetic identification. The fluorescent labeling primers were designed to construct the multiplex amplification system. The system was validated for sensitivity, accuracy, balance, stability, species specificity, tissue identity and mixture analysis, and investigated the genetic polymorphisms in 145 unrelated Felis catus samples. RESULTS: Sixteen Felis catus autosomal STR loci and one sex determining region of Y (SRY) were successfully selected, and constructed a multiplex amplification system containing the above loci. The complete profile of all alleles could still be obtained when the amount of DNA template was as low as 0.25 ng. There was no specific amplification peak in other common animal samples. Population genetic surveys showed that total discrimination power (TDP) of the 16 STR loci was 1-3.57×10-20, the cumulative probability of exclusion (CPE) was 1-6.35×10-5 and the cumulative probability of matching was 3.61×10-20. CONCLUSIONS: The Felis catus STR multiplex amplification system constructed in this study is highly sensitive, species-specific, and accurate in typing results, which can provide an effective solution for Felis catus species identification, individual identification and kinship identification in the field of forensic science.

Application Progress of Massively Parallel Sequencing Technology in STR Genetic Marker Detection.

In recent years, more and more forensic genetics laboratories have begun to apply massively parallel sequencing (MPS) technology, that is, next-generation sequencing (NGS) technology, to detect common forensic genetic markers, including short tandem repeat (STR), single nucleotide polymorphism (SNP), the control region or whole genome of mitochondrial DNA (mtDNA), as well as messenger RNA (mRNA), etc., for forensic practice, such as individual identification, kinship analysis, ancestry inference and body fluid identification. As the most widely used genetic marker in forensic genetics, STR is currently mainly detected by capillary electrophoresis (CE) platform. Compared with CE platform, MPS technology has the advantages of simultaneous detection of a large number of genetic markers, massively parallel detection of samples, the polymorphism of sequence detected by NGS makes STR have the advantages of higher resolution and system efficiency. However, MPS technology is expensive, there is no uniform standard so far, and there are problems such as how to integrate MPS-STR data with the existing CE-STR database. This review summarizes the current status of the application of MPS technology in the detection of STR genetic markers in forensic genetics, puts forward the main problems that need to be solved urgently, and prospects the application prospect of this technology in forensic genetics.

Application of SifaInDel 45plex System in the Han and Mongolian Populations.

OBJECTIVES: To investigate the genetic polymorphism of InDel loci in SifalnDel 45plex system in the Han population in Jiangsu Province and the Mongolian population in Inner Mongolia, and to evaluate the effectiveness of the system in forensic medicine. METHODS: SifaInDel 45plex system was used for genotyping in blood samples of 398 unrelated individuals from the above two populations, and allele frequencies and population genetic parameters of the two populations were calculated respectively. Eight intercontinental populations in the gnomAD database were used as reference populations. The genetic distances between the two studied populations and eight reference populations were calculated based on the allele frequencies of 27 autosomal-InDels (A-InDels). The phylogenetic trees and multidimensional scaling (MDS) analysis diagrams were constructed accordingly. RESULTS: Among two studied populations, the 27 A-InDels and 16 X-InDels showed no linkage disequilibrium between each other and the allele frequency distributions were in Hardy-Weinberg equilibrium. The CDP of the 27 A-InDels in two studied populations were all higher than 0.999 999 999 9, and the CPEtrio were all less than 0.999 9. The CDP of the 16 X-InDels in Han in Jiangsu and Mongolian in Inner Mongolia female and male samples were 0.999 997 962, 0.999 998 389, and 0.999 818 940, 0.999 856 063, respectively. The CMECtrio were all less than 0.999 9. The results of population genetics showed that the Jiangsu Han nationality, Inner Mongolia Mongolian nationality and East Asian population clustered into one branch, showing closer genetic relationship. The other 7 intercontinental populations clustered into another group. And the above 3 populations displayed distant genetic relationships with the other 7 intercontinental populations. CONCLUSIONS: The InDels in the SifaInDel 45plex system have good genetic polymorphism in the two studied populations, which can be used for forensic individual identification or as an effective complement for paternity identification, and to distinguish different intercontinental populations.

Application and Prospect of RNA Profiling Analysis in Forensic Body Fluid Identification.

In forensic physical evidence identification, the accurate identification of the individual origin and their body fluid composition of the biological samples obtained from the crime scene play a critical role in determining the nature of a crime. In recent years, RNA profiling has become one of the fastest developing methods for body fluids identification. Due to the characteristics of tissue or body fluid specific expression, various types of RNA markers have been proven to be promising candidate markers for body fluids identification in previous studies. This review summarizes the research progress of RNA markers in body fluids identification, including the RNA markers that have been effectively verified in current research and their advantages and disadvantages. Meanwhile, this review prospects the application of RNA markers in forensic medicine.

Forensic Application of ForenSeqTM DNA Signature Prep Kit in Zhengjiang She Ethnic Group.

OBJECTIVES: To evaluate the ability of the ForenSeqTM DNA Signature Prep kit (ForenSeq kit) in analyzing the sequence information of STRs in Zhejiang She ethnic group and its forensic application efficacy. METHODS: A total of 50 Zhejiang She ethnic group samples were sequenced with the ForenSeq kit on the MiSeq FGx platform. The data was analyzed using ForenSeqTM universal analysis software to obtain the motif structure and flank regions of the 58 STRs, then compared with PCR-CE typing results to test the consistency. At last, the allele frequency and population genetic parameters were calculated. RESULTS: A total of 448 sequence polymorphic alleles were detected in 50 samples of Zhejiang She ethnic group. Compared with fragment length polymorphism detected by PCR-CE, 82 alleles were increased by MPS detection based on ForenSeq kit, and 7 SNPs variation were detected in the flanking regions of 6 loci. The 22 male individuals were genotyped, and total 19 haplotypes were detected in 24 Y chromosome STRs of these 22 males. The cumulative discrimination power of the 27 autosomal STRs was 1-8.87×10-30, the cumulative probability of exclusion of duo-testing was 0.999 999 962 640 657, the cumulative probability of exclusion of trios-testing was 0.999 999 999 999 633. CONCLUSIONS: Based on MPS typing technology, using the ForenSeq kit greatly improves the detection efficiency. In addition, the 58 STRs have good genetic polymorphisms in Zhejiang She ethnic group, which are suitable for individual identification and paternity identification in forensic application.

Effects of Peripheral Blood Different Pretreatment Methods and Preservation Time on RNA Quality.

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.

Effect of organic solvent on enzymatic degradation of cyclic PBS-based polymers by lipase N435.

Poly(butylene succinate-co-cyclohexane dimethanol succinate) (P(BS-co-CHDMS)) and poly(butylene succinate-co-butanediol cyclohexanedicarboxylic acid) (P(BS-co-BCHDA)) were catalytically degraded by Candida antarctica lipase Novozyme 435 (N435) in CHCl3 and THF. The results indicated that the degradation rate was P(BS-co-CHDMS) > P(BS-co-BCHDA) > poly(butylene succinate) (PBS). The degradation rate of copolyesters was higher in CHCl3 than in THF, the highest degradation rate of 67% being obtained for P(BS-co-CHDMS). Hence, the CHCl3 solvent is more suitable for the enzyme-catalytic degradation of copolyesters, since the lipase can easier recognize the butylene succinate (BS-), (butanediol cyclohexanedicarboxylic acid) (BCA-), and (cyclohexane dimethanol succinate-type) (CMS-type) ester bonds in this solvent. Moreover, it can recognize the CMS-type ester bonds with a higher specificity than the (butanediol cyclohexanedicarboxylic acid type) (BCA-type) ester bonds. Molecular simulation results indicated that the structure of the lipase was stable in CHCl3 and THF. However, CHCl3 proved to be more suitable for a stable activity of the enzyme. The active pocket contains acyl-binding hydrophilic residues which are recognized by the substrate. The increase in the content of saturated cycles can increase the hydrophobicity of the substrate and thus, the amount of substrate bond to enzyme active site is increased, which facilitates the enzymatic degradation of copolyesters.

Influence of ether linkage on the enzymatic degradation of PBS copolymers: Comparative study on poly (butylene succinate-co-diethylene glycol succinate) and poly (butylene succinate-co-butylene diglycolic acid).

The difference of enzymatic degradation behavior between Poly (butylene succinate-co-diethylene glycol succinate) (PBS-co-DEGS) and Poly (butylene succinate-co-butylene diglycolic acid) (PBS-co-BDGA) was studied in a Tetrahydrofuran (THF)/toluene mixed system by Novozym 435 (N435, immobilized Candida Antarctica lipase supported on acrylic resin) catalysis for 30 h. These two copolymers (modified with alcoholic acid by ether linkage) were synthesized by melt polycondensation and characterized by 1H NMR. The average molecular weight and thermal property before and after degradation were determined by gel permeation chromatography (GPC) and thermogravimetric analysis (TGA), respectively. Results revealed that end-chain degradation of DEG20 (20% content diethylene glycol of diols) and intramolecular random degradation of DGA20 (20% content diglycolic acid of diacids) both occurred at the same time from 0 h to 12 h. TGA curves show that after degradation by N435, the T-5% of both copolymers decreased from about 300 °C to below 210 °C. In degradation products (linear and cyclic oligomers, no monomer was appeared below 10 degree of polymerization. According to the molecular docking results, the free binding energy between PC lipase and substrate was in the order of BDGAB < DEGSDEG < BSDEG < BSB. Thus, the enzymatic degradability of PBS-co-DEGS is more effective than that of PBS-co-BDGA.

[Research Progress of circRNA and Its Significance in Forensic Science].

RNA has received more attention in the field of forensic medicine and the development of the new biological markers based on RNA shows great significance in the analysis of complex cases. circular RNA (circRNA) is a kind of non-coding RNA which is widely reported recently. Although the regulatory mechanisms of generation and expression are not fully clear, the existing research indicates that circRNA has important biological functions. CircRNA has a cell-type-specific expression with great stability and a high expression level, which makes it meaningful in forensic applications potentially. In this paper, the research progress, the generation and regulation of circRNA as well as its biological characteristics and functions are summarized, which will provide references for related studies and forensic applications.

Downregulation of RPL15 may predict poor survival and associate with tumor progression in pancreatic ductal adenocarcinoma.

Early diagnosis and treatment in pancreatic ductal adenocarcinoma (PDAC) is still a challenge worldwide. The poor survival of PDAC patients mainly due to early metastasis when first diagnosed and lack of prognostic biomarker. Ribosomal protein L15 (RPL15), an RNA-binding protein, is a component of ribosomal 60S subunit. It was reported that RPL15 is dysregulated in various type of cancers. However, little is known about the role of RPL15 in PDAC carcinogenesis and progression. Herein, we clarified RPL15 expression status may serve as an independent prognostic biomarker in three independent PDAC patient cohorts. We found that RPL15 was dramatically decreased in PDAC tissues and cell lines. The high expression of RPL15 was inversely correlated with TNM stage, histological differentiation, T classification and vascular invasion. Low expression of RPL15 was significantly associated with poor overall survival of PDAC patients. Furthermore, we demonstrated that the reduction of RPL15 may promote invasion ability of pancreatic cell by inducing EMT process. In conclusion, decreased RPL15 expression is associated with invasiveness of PDAC cells, and RPL15 expression status may serve as a reliable prognostic biomarker in PDAC patients.

Progress of DNA-based Methods for Species Identification.

Species identification of biological samples is widely used in such fields as forensic science and food industry. A variety of accurate and reliable methods have been developed in recent years. The current review shows common target genes and screening criteria suitable for species identification, and described various DNA-based molecular biology methods about species identification. Additionally, it discusses the future development of species identification combined with real-time PCR and sequencing technologies.