Heterozygosis deficit of polymorphic markers linked to the β-globin gene cluster region in the Iranian population

OBJECTIVES Iran is considered as one of the high-prevalence areas for β-thalassemia with a rate of about 10% carrier frequency. Molecular diagnosis of the disease is performed both by direct sequencing and indirectly by the use of polymorphic markers present in the beta globin gene cluster. However, to date there is no reliable information on the application of the markers in the Iranian population. Here we report the results of an extended molecular analysis of five RFLP markers, XmnI, HindIIIA, HindIIIG, RsaI and HinfI, located within the β-globin gene cluster region in four subpopulations of Iran. MATERIALS AND METHODS A total of 552 blood samples taken from the Iranian subpopulations including Isfahan, Chaharmahal-O-Bakhtiari, Khuzestan and Hormozgan were genotyped using PCR-RFLP and sequencing. The allele frequency, the expected and observed heterozygosity, and Shannon's information index (I) of these markers were calculated. RESULTS Distribution of the allele frequencies for XmnI, HindIIIA, HindIIIG, RsaI and HinfI polymorphic markers did not differ significantly among the subpopulations examined. Overall observed heterozygosity ranged from 0.1706 for HindIIIA to 0.4484 for RsaI. The Shannon index was <1 for all the polymorphic markers in the populations studied. The data indicated that heterozygosity of these markers was low in the Iranian population. CONCLUSION The results suggested that genotyping of these markers is not informative enough once used as single markers for prenatal diagnosis and carrier detection of β-thalassemia in the Iranian population. However, haplotyping of these markers may provide more useful data in linkage analysis and prenatal diagnosis as well as carrier detections for β-thalassemia in Iranians.