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Tap gene associations in UK caucasoids
R P Donn1, E J Davies, W Thomson
1ARC Epidemiology Research Unit, University of Manchester, UK.
Summary
This study determined transporter gene allele frequencies in a UK population, finding TAP1A and TAP2A as most common. It also identified a new TAP2 allele and explored associations with rheumatoid arthritis.
Area of Science:
- Immunogenetics
- Molecular Biology
- Population Genetics
Background:
- The TAP1 and TAP2 genes encode subunits of the transporter associated with antigen processing (TAP) complex.
- TAP is crucial for the presentation of endogenous antigens to T cells, playing a role in immune surveillance and autoimmune diseases.
Purpose of the Study:
- To determine the allele frequencies of TAP1 and TAP2 genes in a healthy UK Caucasoid population.
- To identify novel TAP alleles and investigate potential linkage disequilibrium with HLA genes, particularly in the context of rheumatoid arthritis.
Main Methods:
- Amplification Refractory Mutation System-Polymerase Chain Reaction (ARMS-PCR) was used to genotype TAP1 and TAP2 alleles.
- Population-based frequency analysis and family studies were conducted.
Main Results:
- TAP1A was the most frequent TAP1 allele (76%). TAP2A (75%), TAP2B (43%), TAP2C (11%), TAP2D (8%), and TAP2E (6%) were the most common TAP2 alleles.
- A novel TAP2 allele, TAP2H, was identified. Ambiguities in TAP2 genotyping were resolved using family studies, confirming TAP2A/2D combinations.
- No significant linkage disequilibrium was found between TAP1 and TAP2, or between TAP genes and HLA-DP. TAP2B showed association with DR1, and TAP2D with DR4. In RA families, TAP2D was linked to DRB1*0401.
Conclusions:
- The study provides comprehensive allele frequency data for TAP1 and TAP2 in a UK population.
- Identified associations between specific TAP2 alleles and HLA-DR types suggest a role in susceptibility to diseases like rheumatoid arthritis.