Abstract
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 α-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.
Keywords
CTLA-4 - polymorphism - type 1 diabetes Mellitus - Sudanese
