Evaluation of a Novel 32 X-STR Loci Multiplex System in the Forensic Application

The AGCU X Plus STR system is a newly developed multiplex PCR kit that detects 32 X-chromosomal STR loci simultaneously.These are DXS6807,DXS9895,linkage group 1(DXS10148,DXS10135,DXS8378),DXS9902,DXS6795,DXS6810,DXS10159,DXS10162,DXS10164,DXS7132,linkage group 2(DXS10079,DXS10074,DXS10075),DXS981,DXS6800,DXS6803,DXS6809,DXS6789,DXS7424,DXS101,DXS7133,GATA172D05,GATA165B12,linkage group 3(DXS10103,HPRTB,DXS10101),GATA31E08 and linkage group 4(DXS8377,DXS10134,DXS7423).A major advantage of this kit is that it takes into account linkage between loci,in addition to detecting more X-STR loci.In order to evaluate the forensic application of 32 X-STR fl uorescence amplifi cation system,PCR settings,sensitivity,species specifi city,stability,DNA mixtures,concordance,stutter,sizing precision,and population genetics investigation were evaluated according to the Scientific Working Group on DNA Analysis Methods(SWGDAM)developmental validation guidelines.The study showed that the genotyping results of each locus were signifi cantly accurate when the DNA template was at least 62.5 pg.Complete profi les were obtained for the 1∶1 and 1∶3 combinations.A total of 209 unrelated individuals from Southern Chinese Han community,consisting of 84 females and 125 males,were selected for population studies,and 285 allele profi les were detected from 32 X-STR loci.The polymorphism information content(PIC)ranged from 0.2721 in DXS6800,to 0.9105 in DXS10135,with an average of 0.6798.DXS10135(PIC=0.9105)was the most polymorphic locus,with discrimination power(DP)of 0.9164 and 0.9871 for the male and female.The cumulative PD_(F),PD_(M),MEC_(trio) and MEC_(duo) valu es were all greater than 0.999999999.There were 78 different DXS10103-HPRTB-DXS10101 haplotypes among the 125 males,and the haplotype diversity was 0.9810.There was no signifi cant difference in the cumulative PD_(F),PD_(M),MEC_(trio) and MEC_(duo) values whether considering linkage or not.In summary,the new X-STR multiplex typing system is effective and reliable,which can be useful in human genetic analysis and kinship testing as a potent complement to autosomal STR typing.

Developmental Validation of the EX16+22Y System

The EX 16+22Y system is a polymerase chain reaction(PCR)-based amplification kit that enables typing of 15 autosomal short tandem repeat(STR)loci(i.e„D3S1358,D13S317,D7S820,D16S539,TPOX,TH01,D2S133&CSF1PO,D19S433,vWA,D18S51,D21S11,D8S1179,D5S81&and FGA)and 22 widely used Y chromosome STR(Y-STR)loci(DYS391,DYS527a/b,DYS635,DYS458,DYS456,DYS385a/b,DYS43&DYS44&DYS437,DYS19,DYS576,DYS533,DYS393,DYS389I/n,DYS439,DYS392,Y_GATA_H4,DYS390,and DYS481)which contains 20 core Y-STR recommended by the Ministry of Public Security and amelogenin.This multiplex system was designed for the simultaneous analysis of amelogenin-Y allele mutation,single-source searches,kinship(including familial searching),mixture profiles,international data sharing,and other forensic applications.In this study,the multiplex system was validated for sensitivity of detection,species specificity,DNA mixtures,stability,sizing precision,stutter,reproducibility,and PCR-based conditions according to the Scientific Working Group on DNA Analysis Methods developmental validation guidelines and Chinese criteria for the human fluorescent STR multiplex PCR reagent.The results show that the EX16+22Y system is a robust and reliable amplification kit which can be used for human identification testing.