Use of Tag single polymorphisms (SNPs) to screen PTPN21 for association with Graves' disease

Objective The protein-tyrosine-phosphate nonreceptor 22 gene (PTPN22) has recently been identified as a susceptibility locus for a number of autoimmune diseases including Graves' disease (GD). PTPN21 is another member of the PTPN family and its gene PTPN21 maps to the first reported region of genetic linkage to GD, GD-1, on chromosome 14q31. The aim of this study was to determine whether PTPN21 is acting as a GD susceptibility locus in UK Caucasian subjects. Design A case control association study of seven Tag single nucleotide polymorphisms (SNPs) (rs1469602, rs8007288, rs1998670, rs11622270, rs2274736, rs2295136 and rs366476) selected to predict 51 un-genotyped polymorphisms present within PTPN21. Patients Unrelated Caucasian patients of UK origin with GD and ethnically and gender matched control subjects with no family history of autoimmune disease were recruited. In total, DNA was obtained from 768 GD patients and 768 control subjects. Results No association of any of the seven Tag SNPs was detected with GD. Preliminary evidence of association of rs2274736 was found with younger age of GD onset (0-30 years) (OR = 1. 48 [95% CI = 1.11-1.97]). No other correlations with clinical phenotype or previously established susceptibility loci were detected. Conclusions Using a Tag SNP approach we screened PTPN21 as a susceptibility locus for GD and found no evidence for association with disease. Preliminary evidence for association of rs2274736 with younger age of GD onset requires replication in similar sized data sets to exclude a false positive result. Methods such as the Tag SNP approach significantly reduce the amount of genotyping required when screening candidate loci, including those within regions of chromosomal linkage.