CTLA-4 (+49A/G) Polymorphism in Type 1 Diabetes Children of Sudanese Population

Background Type 1 diabetes mellitus (T1DM) is an organ-specific T cell-mediated autoimmune disease, characterized by destruction of pancreatic islets. Cytotoxic lymphocyte antigen-4 ( CTLA-4 ) is a negative regulator of T cell proliferation, thus conferring susceptibility to autoimmunity. Aims This study aimed to investigate the association of CTLA-4 +49A/G (rs231775) polymorphism with a risk of T1DM in Sudanese children. Methods This a case-control study included 100 children with T1DM, referred to the pediatric clinic at referral pediatric teaching hospital in Gezira State-Sudan. Hundred unrelated healthy controls were recruited from departments in the same hospital. Genomic deoxyribonucleic acid (DNA) was extracted from Ethylenediaminetetraacetic Acid (EDTA)-preserved blood using QIAamp DNA Blood Mini Kit (QIAamp Blood) (QIAGEN, Valencia, CA). The polymerase chain reaction PCR restriction fragment length polymorphism (PCR-RFLP) and sequencing were applied for the CTLA-4 (+49A/G) genotyping. The changes accompanied the polymorphism were evaluated using relevant bioinformatics tools. Results The genotype and allele frequencies of the CTLA-4 (+49A/G) polymorphism were significantly different between the patients and controls ( p =0.00013 and 0.0002, respectively). In particular, the frequency of the G allele, GG homozygous genotype, and AG heterozygous genotype were significantly increased in patients than in controls ([28% versus 7%, odds ratio (OR)=5.16, 95% confidence interval [CI]=2.77-9.65, p =0.00] [12% versus 2%, OR=6.68, CI=1.46-30.69, p =0.01] [32% versus 10%, OR=4.24, CI=1.95-9.21, p =0.00], respectively). The presence of the G allele (homozygous) showed an influence on the signal peptide polarity, hydrophobicity, and alpha -helix propensity of the CTLA-protein. Conclusion The results further support the association of CTLA-4 (+49A/G) polymorphism and the risk of T1DM in our study population.