Pyrosequencing assay for genotyping of the Transcobalamin II 776C>G polymorphism

The 776C>G polymorphism of the Transcobalamin II gene is located in a GC-rich region and TaqMan real-time polymerase chain reaction (PCR) does not yield satisfactory genotyping results. We therefore hypothesized that a method based on DNA sequencing would be needed for this single nucleotide polymorphism (SNP) analysis; Pyrosequencing technology was tested for this purpose. A Pyrosequencing protocol was developed, optimized and applied to a sample of 389 Swedish senior citizens. The three genotypes CC, CG, and GG consistently yielded typical programs that were readily distinguishable from each other. The prevalence of the mutated allele in the studied Swedish population was q=0.445. It is concluded that the TC II 776C>G polymorphism can be reliably genotyped by Pyrosequencing technology.