Haplotype-Based Analysis of MDR1/ABCB1 Gene Polymorphisms in a Turkish Population

The three functional single-nucleotide polymorphisms (SNPs) of the MDR1 gene, C1236T, G2677T/A, and C3435T, exhibit an interpopulation difference. In this study, we analyzed the haplotype frequencies of these three SNPs in 107 unrelated healthy Turkish subjects and compared them with those of other reported populations. We found that C1236T, G2677T/A, and C3435T SNPs are expected to be structured in 10 different haplotypes, with 4 prominent haplotypes T-T-T (33.7%), C-G-C (25.0%), T-G-C (10.9%), and C-T-T (8.7%). There was a statistically significant linkage disequilibrium between all C1236T, G2677T/A, and C3435T SNPs (p<0.0001); however, our results indicated that only loci 2677 and 3435 show relatively strong linkage disequilibrium (Lewontin's coefficient [D'] = 0.74, Pearson's correlation [r(2)] = 0.47). The haplotype frequency distribution of our study group was found to be significantly different from that in Han Chinese, Uygur Chinese, Kazakh Chinese, Indian, Malay, Japanese, Caucasian, and Ashkenazi Jewish populations (p<0.0001). The results of this study may contribute to population-specific haplotype data on the MDR1 gene and may serve as a basis for studies on response to P-glycoprotein substrate drugs as well as for future association studies of certain diseases in Turkish population.