Abstract
BackgroundGenetic polymophisms of the Duffy antigen receptor for the chemokines (DARC) gene successfully protected against blood stage infection by Plasmodium vivax infection. The Fy (a-, b-) phenotype is predominant among African populations, particularly those originating from West Africa, and it is rare among non-African populations. The aim of this study was to analyse the frequency of four Duffy blood groups based on SNPs (T-33C, G125A, G298A and C5411T) in two local tribes of Sudanese Arabs, the Shagia and Manasir, which are both from the region of the Fourth Nile cataract in Sudan.MethodsAn analysis of polymorphisms was performed on 217 individuals (126 representatives of the Shagia tribe and 91 of the Manasir). Real-time PCR and TaqMan Genotyping Assays were used to study the prevalence of alleles and genotypes.ResultsThe analysis of allelic and genotype frequency in the T-33C polymorphisms demonstrated a significant dominance of the C allele and CC genotype (OR = 0.53 [0.32-0.88]; p = 0.02) in both tribes. The G125A polymorphism is associated with phenotype Fy(a-, b-) and was identified in 83% of Shagia and 77% of Manasir. With regard to G298A polymorphisms, the genotype frequencies were different between the tribes (p = 0,002) and no single AA homozygote was found. Based on four SNPs examined, 20 combinations of genotypes for the Shagia and Manasir tribes were determined. The genotype CC/AA/GG/CT occurred most often in Shagia tribe (45.9%) but was rare in the Manasir tribe (6.6%) (p < 0.001 Shagia versus Manasir). The FY*AES allele was identified in both analysed tribes. The presence of individuals with the FY*A/FY*A genotype was demonstrated only in the Shagia tribe.ConclusionThis is probably the first report showing genotypically Duffy-negative people who carry both FY*BES and FY*AES. The identification of the FY*AES allele in both tribes may be due to admixture of the non-African genetic background. Taken as a whole, allele and genotype frequencies between the Shagia and the Manasir were statistically different. However, the presence of individuals with the FY*A/FY*A genotype was demonstrated only in the Shagia tribe.
Highlights
Genetic polymophisms of the Duffy antigen receptor for the chemokines (DARC) gene successfully protected against blood stage infection by Plasmodium vivax infection
The G125A polymorphism is associated with phenotype Fy(a, b-) and was identified in 83% of Shagia and 77% of Manasir
The purpose of this study was to analyse the genetic structure of the Shagia and Manasir tribes using the variability of the single nucleotide polymorphisms in Duffy gene, such as two typical for African populations SNPs: T-33 C [5,29] and G125A [14,30], along with two other SNPs: G298A [31,32,33] and C5411T
Summary
Genetic polymophisms of the Duffy antigen receptor for the chemokines (DARC) gene successfully protected against blood stage infection by Plasmodium vivax infection. Duffy antigen is present in two major allelic forms, differing in an amino acid at position 42 in coding sequence (G125A) (i.e. glycine in FY*A and aspartic acid in FY*B) [5,6,7,8,9] and point mutation at position T-33°C (previously described as T-46°C) in GATA box responsible for the FY*AES (ES = erythrocyte silent) and the FY*BES alleles (common African allele) [3,10,11,12,13,14,15,16] These four alleles: FY*A, FY*B, FY*AES and FY*BES contribute to a total of ten genotypes: FY*A/FY*A, FY*A/FY*B, FY*A/FY*AES, FY*A/FY*BES, FY*B/FY*B, FY*B/FY*AES, FY*B/FY*BES, FY*AES/FY*AES, FY*AES/FY*BES, FY*BES/FY*BES [17,18]. The last three genotypes of those above-mentioned are responsible for the phenotype Fy(a-, b-) which is responsible for resistance to malaria This phenotype is predominant among African people, especially those originating in West Africa and it is rare among non-African populations [11]. A less common variation of the allele FY*X, associated with weak expression of Fyb antigen was identified [8,10,20]
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