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Helen L. Winton, Jeffrey L. Bidwell, W. J. Armitage; Genetic Variants Of Thrombospondin-1 In High Risk Corneal Transplantation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1144.
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To examine single nucleotide polymorphisms (SNPs) and haplotypes in the thrombospondin-1 (TSP-1) gene, that may influence TSP-1 levels. TSP-1 can bind to and activate latent transforming growth factor beta (TGF-β) and is involved in molecular pathways between ocular cells and immune effectors. Deficiency of TSP-1 compromises ocular immune privilege and may therefore accelerate corneal allograft rejection.
Genomic DNA was obtained from peripheral blood of corneal transplant recipients at increased risk of allograft rejection. The samples were allocated to 2 groups based on the rejection status of the recipients at 3 years: namely, GS (rejection-free graft survival), and GF (reversible or irreversible rejection, or graft failure with a presumed immunological cause). Three SNPs were identified for analysis using SNP tagger: SNP-1 (rs1478604) A>G in the 5' untranslated region, SNP-6 (rs2228261) C>T, and SNP-9 (rs2228262) A>G, both in the coding region, with a frequency >1%. Primer3 was used to select primers. PCR-induced heteroduplex generator (IHG) analysis detected SNPs, with subsequent visualisation by polyacrylamide gel electrophoresis. Results were analysed by PHASE software using maximum likelihood haplotype frequencies and Yates’ corrected Chi square (Χ2) with Bonferroni correction for multiple comparisons. Pairwise linkage disequilibrium (LD), using Lewontin’s D' coefficient and Χ2 p values, were determined with Arlequin version 2.00.
The A allele of SNP-1 showed a higher frequency in the GF group compared to the GS group both individually (54%:43%) and within an extended haplotype. Four frequent haplotypes (>1%) ACA, GCG, GTA and GCA were observed (SNP-1, -6, -9). Haplotype ACA was significantly increased in the GF group (71%) (OR 2.27, CI 1.65-3.13, *p= 0.0000002, *pc= 0.000001) compared with the GS group (64%). There was high LD between SNPs (D' 0.89-1.00, *p= <0.001).
There was an increased risk of corneal allograft rejection in recipients with the A allele in SNP-1 (rs1478604). In addition, the haplotype ACA may confer additional risk of graft rejection in patients carrying this genotype. Our results point to the importance of genetic variants in the TSP-1 gene with clinical outcome.
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