CISH promoter polymorphism effects on T cell cytokine receptor signaling and type 1 diabetes susceptibility

BACKGROUND Impaired regulatory T cell immunity plays a central role in the development of type 1 diabetes (T1D). Interleukin-2 receptor (IL-2R) signaling is essential for regulatory T cells (TREG), and cytokine-inducible SH2-containing protein (CIS) regulates IL-2R signaling as a feedback inhibitor. Previous studies identified association of CISH promoter region single nucleotide polymorphisms (SNPs) with susceptibility to infectious diseases. METHODS Here we analyzed allele frequencies of three CISH SNPs (i.e., rs809451, rs414171, rs2239751) in a study of T1D patients (n = 260, onset age < 5 years, duration > 10 years). Minor allele frequencies were compared to a control cohort of the 1000 Genomes Project. Assigned haplotypes were determined for effects on T1D manifestation and severity. Finally, the CISH haplotype influence on cytokine signaling and function was explored in T cells from healthy donors. RESULTS We detected similar minor allele frequencies between T1D patients and the control cohort. T1D onset age, residual serum C-peptide level, and insulin requirement were comparable between different haplotypes. Only minor differences between the haplotypes were found for in vitro cytokine (i.e., IL-2, IL-7)-induced CIS mRNA expression. STAT5 phosphorylation was induced by IL-2 or IL-7, but no differences were found between the haplotypes. TREG purified from healthy donors with the two most common haplotypes showed similar capacity to inhibit heterologous effector T cells. CONCLUSIONS This study provides no evidence for an association of CISH promoter SNPs with susceptibility to T1D or severity of disease. In contrast to previous studies, no influence of different haplotypes on CIS mRNA expression or T cell-mediated functions was found.