Developmental validation of a novel six-dye typing system with 47 A-InDels and 2 Y-InDels.

In this study, a multiplex amplification system including 47 autosomal InDels, 2 Y-chromosome InDels, and the sex-determining marker (Amelogenin) was developed with six fluorescent dyes labeling. These InDels were selected from the previous study based on a series of criteria (0.3 < MAF < 0.5, HET > 0.4, etc). The system was designated the AGCU InDel 50 kit and was validated in a series of studies, including a degradation study; tests for sensitivity, species specificity, reproducibility, stability, applicability to case samples, balance of peak height, and PCR conditions; and a population study. The results showed that AGCU InDel 50 kit was quite sensitive, specific, stable in several PCR conditions or exposure to PCR inhibitors, especially against degradation. 74 case samples and 50 paternity cases with STR mutation events were tested using PowerPlex 21 System, AGCU InDel 50 kit, and Investigator DIPplex kit, and the results showed that the ratio of loci detected with the developed kit were close to Investigator DIPplex kit, but considerably higher than PowerPlex 21 System for case samples containing low amounts of degraded DNA. As for 50 paternity cases, no mutation was observed in any InDels locus, and the CPIs based on 47 autosomal InDels contained in the AGCU InDel 50 kit were all higher than those based on 30 InDels contained in Investigator® DIPplex kit, except 3 cases. In the population study, 203 unrelated individuals from the Guangdong Han population were detected using the AGCU InDel 50 kit, and the values of combined power of discrimination and combined power of exclusion were 0.999 999 999 999 999 and 0.9997, respectively. Thus, AGCU InDel 50 kit is suitable for individual identification and as a supplemental tool for paternity testing. It is reproducible, accurate and robust for forensic applications and human genetic studies.