Polymorphisms rs7041 (c.1296T>G) and rs4588 (c.1307C>A) and Distribution of Gc Variants in a Population of Hemodialysis Patients in Abidjan

Abstract

Background: Vitamin D deficiency is associated with chronic kidney disease (CKD). Renal failure patients are routinely supplemented with vitamin D to compensate for this deficiency. The response to vitamin D supplementation can vary according to variants in the Gc (Vitamin D-binding protein) gene. The combination of two single-nucleotide polymorphisms (SNPs), rs7041 (c.1296T>G) and rs4588 (c.1307C>A), in the Gc gene forms three variants, namely Gc1f (c.1296 T, c.1307C), Gc1s (c.1296G, c.1307C), Gc2 (c.1296T, c.1307A), which result in six vitamin D-binding protein (DBP) phenotypes. Significant variations in variant frequency are reported in different populations. Objectif: The aim of our study was to determine the distribution of Gc genotypes and variants in a population of haemodialysis patients. Methods and Results: Genomic DNA from forty-eight blacks Africans adults with CKD were extracted from whole blood samples. The DNA region spanning the two SNPs of interest was amplified by PCR. The amplified DNA was subjected to the action of restriction enzymes, StyI and HaeIII in two different reactions. Genotyping was performed by analysis of the length of restriction fragments by 2.5% agarose gel electrophoresis. The mean age of the study population was 42±12 years, with a sex ratio of 1.6. The C/C genotype of rs4588 (c.1307C>A) was the most frequent, followed by the T/T genotype (90.6%) of rs7041 (c.1296T>G). Three DBP phenotypes, Gc1f-1f (c.1296T, c.1307C/p.432Asp, p.436Thr): 89.6 %, Gc1s-1s (c.1296 G, c.1307C/p.432Glu, p.436Thr): 8.3 %, and Gc1f/Gc1s: 2,1% were identified. Conclusion: Finally, the Gc1f variant was the most frequent. Our results suggest the need for vitamin D testing to establish the correlation between the observed Gc genotypes/variants and vitamin D status in the study population.