High-throughput SNP genotyping with the Masscode system

QIAGEN Genomics, Inc, has developed the Masscode tagging system for DNA labeling and detection. In this application, the Masscode system is described as applied to high-throughput single-nucleotide polymorphism (SNP) genotyping. The labeling system is based on a small-moleculal-weight tag that is covalently attached through a photocleavable linker to a DNA oligonucleotide. The tagged oligonucleotide is used as a primer in an allele-specific PCR SNP discrimination assay. The allele-spscific amplicons are differentiated through their Masscode tag assignments. After a photolysis step to cleave the tags from the amplicon, the samples are introduced into a single quadrupole mass spectrometry detection system for analysis. Genotyping determinations are based on the relative proportions of the paired allele tags. The system has a lower limit of detection in the femtomolar range (10(-15) M). At present, 30 different Masscode tags may be used simultaneously in a multiplex fashion to routinely provide more than 40,000 SNP genotyping measurements daily. Further developments will allow for the simultaneous detection of several hundred tags.