Increased forensic efficiency of DNA fingerprints through simultaneous resolution of length and nucleotide...

Short tandem repeat (STR) typing is the most powerful method for determining the origin of a sample for a number of molecular disciplines such as medical genetics, population genetics, tumor analysis, transplantation medicine, or forensic crime scene analysis. STR alleles are routinely differentiated based upon their fragment size by electrophoresis under denaturing conditions, which does not take nucleotide variability into consideration. This simplification leads to loss of biological information as the nature of the individual sequence motifs that build an STR is not described. An alternative detection platform would be mass spectrometry, which captures the underlying sequence variation by comparing the molecular masses of DNA fragments. Here, we demonstrate that the combination of ion-pair reversed-phase high-performance liquid chromatography and electrospray ionization quadrupole time-of-flight mass spectrometry (ICEMS) is able to simultaneously detect length and nucleotide variability in STRs. Overall, 21 forensically relevant STRs that are also used in other scientific fields were screened in an Austrian population sample for the occurrence of nucleotide variability within or close to the repeat region. A total of 11 of the investigated loci (SE33, D2S1338, vWA, D21S11, D3S1358, D16S539, D8S1179, D7S820, D13S317, D5S818, and D2S441) brought additional allele (sequence) variants. Forensic efficiency, as determined by typical statistical parameters, was significantly increased by 20 to 30%. The beauty of ICEMS-STR-analysis is the fact that it represents one of the few technological advancements that allows direct comparison of newly generated data with existing data such as stored in DNA databases, which have a retarding effect on new developments.