Examination of method to detect silent allele on D19S433 locus

Abstract

　In the Japanese population, D19S433 silent allele is rarely detected in cases of testing with commercial STR kits. The silent allele causes inconsistency of STR typing results between kits and false negative parentage despite the true biological parentage. The cause of this problematical mismatch is reported that the mutation is a base change (G>A) 32 nucleotides downstream from the 3′ end of the AAGG repeats (G32A), so reverse primer in STR kits fail to anneal to the binding site, consequently no STR peak or extremely low peak is detected. In this study, volunteers originated from 4 silent-allelic pedigrees are examined whether the silent allele was judged by AmpFlSTR Identifiler Plus PCR amplification kit, PowerPlex Fusion system, and GlobalFiler PCR amplification kit, furthermore they carry G32A mutation or not by direct sequencing, SNaPshot genotyping, and TaqMan genotyping. In conclusion, it has been identified that all silent-allelic peaks are caused by G32A mutation and followed by Mendelian genetics. Actually, some factors influence the formation of silent allele, such as primer binding fidelity, improvement of other PCR reagents, and PCR cycle conditions. When the suspected silent-allelic peak appears, additional tests with multiple STR kits which containing alternative primer will be recommended.