AmpFℓSTR<sup>®</sup> Identifiler<sup>®</sup> Direct Kit による口腔内細胞からの効率的な STR 型検査法の検証

Abstract

Direct amplification of short tandem repeats (STR) locus from reference sample without DNA extraction, quantification and dilution processes is one of the solutions to achieve a large amount of DNA profiling quickly. Therefore, in this study, AmpFℓSTR Identifiler Direct Kit (IDD) was tested in the laboratory of the National Police Agency. Buccal cells from 88 volunteers self-collected by using the EasiCollect device were transferred on FTA cards. One disk (φ1.2 mm) is punched from each of the 88 FTA cards and automatically distributed to PCR plates by BSD 1000. The optimal PCR cycles were examined using the PCR plates. PCR plate setup, capillary electrophoresis (CE) plate setup and CE were performed by Biomek FXP, Biomek 3000 and 3130xl Genetic Analyzer, respectively. The threshfold of peak detection was set as 150 relative fluorescence units (RFU), and all other conditions of electrophoresis and analysis were used according to the manufacture's recommendations. Number of proper full profiles obtained from 88 samples were 68 (77.3%), 33 (37.6%), 14 (15.9%) and 3 (3.4%) for 25, 26, 27 and 28 cycles PCR, respectively. Therefore, 25 cycles PCR was optimal for our laboratory. The 68 proper full profiles obtained with 25 cycles PCR were used for validation study. Average of peak height and heterozygous peak height ratio of each STR locus were 1000-2000 RFU and 90% or more, respectively. Intra-color balance and inter-locus balance were almost the same as those in previous study with AmpFℓSTR Identifiler Kit (ID), AmpFℓSTR Identifiler Plus Kit (IDPlus) and IDD. When a threshold value of 150 RFU was applied with the “marker-specific stutter ratio”, proper STR typing was possible. Our study indicated that IDD with 25 cycles PCR was applicable to STR typing of single-source buccal cells transferred on FTA card in our laboratory.