Analysis of Autosomal SNPs in Paraffin-embedded Tissue Samples: Two Cases

Despite the numerous STR loci available for analysis of cases submitted to forensic laboratories, namely with the use of commercial kits that amplify mini ? short tandem repeats (STRs), some cases remain “unsolved” i.e. fail to yield a STR DNA profiling result or result in likelihood ratio calculations that are not sufficiently high. Autosomal single nucleotide polymorphisms (SNPs) may constitute a potential advantage to solve some of these difficult cases, as has already been described by others. In this work we present two revisited cases of our routine work, where the type of samples available for analysis was histological blocks of paraffin-embedded tissue samples from a man (Case 1-“lymph node”) and from a woman (Case 2). The application of autosomal SNPs in the analysis of paraffin-embedded tissues constitutes one of the possible approaches that can be used in our laboratory in some “difficult” cases, and is part of a validation process of the described methodology. Following extraction the two sample DNAs had already been genotyped with the routine commercial STR or mini-STR kits, like AmpFLSTR® Identifiler®, MiniFilerTM and NGMTM PCR Amplification Kits and compared to their respective reference samples. These samples were then typed for the 52 loci included in the in the SNP for ID 52 plex using a SNaPshotTM assay previously described by Sanchez et al. in order to test and validate this multiplex in real casework [1]. The study showed that autosomal SNP can be used as additional markers to the profiling of difficult samples such as paraffin embedded tissue.