Sequence-Specific Primer Polymerase Chain Reaction Genotyping of the Human TLR9 Promoter Polymorphism rs187084...

This article describes a validated and optimized sequence-specific primer polymerase chain reaction (PCR-SSP) protocol for genotyping the human TLR9 promoter polymorphism rs187084 (-1486T>C). Promoter single nucleotide polymorphisms (SNPs) may influence transcriptional regulation and immune signaling. The rs187084 variant has been associated with altered TLR9 expression and susceptibility to infectious, inflammatory, and neoplastic diseases. Although Sanger sequencing provides high analytical accuracy, it is labor-intensive and costly for large cohorts. TaqMan allelic discrimination assays require fluorescent probes and real-time PCR instrumentation, increasing cost per sample. High-resolution melting (HRM) analysis depends on specialized melting platforms and curve interpretation expertise. The PCR-SSP strategy described here provides a robust and accessible approach based on conventional thermocyclers and standard agarose gel electrophoresis, without the need for specialized instrumentation or probe-based chemistries. Allele discrimination is achieved using reverse primers differing at the 3' terminal nucleotide. A 430-bp human growth hormone (HGH) fragment is co-amplified as internal control. Optimization of MgCl₂ concentration, primer ratios, and annealing temperature ensured specificity, sensitivity, and reproducibility. This protocol is suitable for genetic association studies and population-based analyses of TLR9 rs187084. © 2026 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: PCR-SSP genotyping of TLR9 rs187084 Support Protocol: Genomic DNA extraction from whole blood by the salting-out method.