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Sequence-Specific Primer Polymerase Chain Reaction Genotyping of the Human TLR9 Promoter Polymorphism rs187084
Guilherme Castellani1, Fernanda Pelisson Massi2, Aléia Harumi Uchibaba Yamanaka2
1Laboratory of Medical Investigation in Dermatology and Immunodeficiencies (LIM-56), Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo (HCFMUSP), University of São Paulo, São Paulo, Brazil.
Current Protocols
|May 19, 2026
Summary
A new PCR-SSP method accurately genotypes the TLR9 rs187084 polymorphism. This accessible technique is ideal for large genetic studies on immune response and disease susceptibility.
Area of Science:
- Immunogenetics
- Molecular Biology
Background:
- Toll-like receptor 9 (TLR9) promoter single nucleotide polymorphisms (SNPs) impact immune signaling and disease susceptibility.
- The rs187084 (-1486T>C) variant is linked to altered TLR9 expression and various diseases.
- Existing genotyping methods like Sanger sequencing and TaqMan assays are costly or require specialized equipment.
Purpose of the Study:
- To describe a validated and optimized Polymerase Chain Reaction-Sequence Specific Primer (PCR-SSP) protocol for genotyping the human TLR9 promoter polymorphism rs187084.
- To provide a robust, accessible, and cost-effective alternative for large-scale genetic association studies.
Main Methods:
- Development and optimization of a PCR-SSP assay using conventional thermocyclers and agarose gel electrophoresis.
- Allele discrimination via reverse primers with differing 3' terminal nucleotides.
- Co-amplification of a human growth hormone (HGH) fragment as an internal control.
Main Results:
- The PCR-SSP protocol demonstrated specificity, sensitivity, and reproducibility.
- Successful genotyping of the TLR9 rs187084 polymorphism was achieved without specialized instrumentation or probe-based chemistries.
- Optimization of reaction conditions (MgCl2 concentration, primer ratios, annealing temperature) ensured assay performance.
Conclusions:
- The described PCR-SSP method is a robust and accessible tool for genotyping TLR9 rs187084.
- This protocol is suitable for population-based analyses and genetic association studies investigating TLR9's role in disease.
- It offers a cost-effective alternative to existing genotyping techniques for large cohorts.
