Genetic polymorphisms of twelve X-STRs of the investigator Argus X-12 kit and additional six X-STR centromere region loci in an Egyptian population sample

Recently, many researchers have focused on analysis of different X-chromosomal STRs as they bear the potential to efficiently complement the analysis of autosomal and Y-chromosomal STRs in solving special complex kinship deficiency cases. In the current study we examined a sample of 250 unrelated Egyptian males with the Investigator Argus X-12 kit (Qiagen GmbH, Hilden, Germany) which detects 12 X-STR markers distributed over the entire X-chromosome as four closely linked clusters. Microvariant off ladder alleles as well as null alleles have been detected in some loci. Furthermore, discordant results were observed between the Investigator Argus X-12 and the Mentype® Argus X-8 kits (Biotype AG, Dresden, Germany). New primers were designed for loci DXS10101, DXS10146 and DXS10148 to correct the allele drop outs observed in these loci with the Investigator Argus X-12 kit. Additionally, DNA sequence analysis revealed the polymorphisms responsible for the allele drop outs. Furthermore, six additional X-STRs (DXS10161, DXS10159, DXS10162, DXS10163, DXS10164 and DXS10165) located in the centromere region at Xp11.21-Xq11.1 were examined in a single multiplex reaction. Allele and haplotype frequencies as well as different forensic statistical parameters of the 18 X-STR loci tested indicated that they are highly informative in different forensic applications in the Egyptian population. However, some modifications still need to be performed on the Investigator Argus X-12 kit before its use in forensic casework is validated.