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We previously reported an association between the SH2D2A gene encoding TSAd and multiple sclerosis (MS). Here a total of 2128 Nordic MS patients and 2004 controls were genotyped for the SH2D2A promoter GA repeat polymorphism and rs926103 encoding a serine to asparagine substitution at amino acid position 52 in TSAd. The GA(16)-rs926103()A haplotype was associated with MS in Norwegians (OR 1.4, P=0.04). A similar trend was observed among Danes. In the independent Norwegian, Danish and Swedish sample sets the GA(16) allele showed a combined OR of 1.13, P=0.05. Thus, the present study shows that the SH2D2A gene may contribute to susceptibility to MS.

We systematically assessed 53 genes involved in T cell signaling, among which 72 SNPs in 32 genes were reported in databases as causing non-synonymous amino acid substitutions. Screening of 41 of these SNPs in DNA pools from 4000 Norwegian controls showed that only 12 SNPs (29%) were polymorphic. These were tested for association to MS in DNA pools from 364 Norwegian MS patients. To eliminate sources of variance introduced by DNA pooling, the SNPs in the best-ranked PLCG1 as well as the PTPN22 gene were thereafter genotyped in individual MS and control samples, however, without finding evidence for association to MS.

T-cell-specific adapter protein (TSAd) involved in the negative control of T-cell activation is encoded by the SH2D2A gene. Our recent studies indicate that homozygosity for short (ie GA(13) and GA(16)) alleles of the SH2D2A gene promoter is associated with development of multiple sclerosis. To study whether the same SH2D2A promoter polymorphism also contributes to the genetic susceptibility to develop juvenile rheumatoid arthritis (JRA), we examined 210 JRA patients and 558 healthy unrelated controls from Norway. The frequency of the short allele GA(13) was increased among the JRA patients compared to control (0.098 vs 0.05; P(n=8)=0.042). There was a significant increased frequency of HLA-DRB1(*)08-positive patients carrying two copies of 'short' alleles GA(13) and/or GA(16) compared to healthy controls (16% vs 6%; P(n=4)=0.016). Our data indicate that the 'short' alleles of the SH2D2A promoter could contribute to the genetic susceptibility to JRA.