Allele frequencies of two polymorphisms associated with the factor IX gene in Iranian population

Indirect genetic diagnosis using polymorphic DNA markers can be useful in large-scale screening programs, which is technically simpler, more rapid and amenable. The main objective of this study was to test the informativeness of two common intragenic markers ( TaqI and XmnI) in Iranian haemophilia B families to detect the carriers by using a strategy that would be accurate and informative, yet less expensive compared to direct mutation analysis. The efficacy of these sites has been examined in 50 unrelated Iranian haemophilia B families and 50 normal females. The method used was polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP), which is economical and the enzymes XmnI and TaqI are cheap enough to be accessible in most of laboratories in developing countries. Our results show that 25% of X-chromosomes had the restriction site for TaqI enzyme. The XmnI site was 21%. The heterozygosity rates for TaqI and XmnI polymorphisms were 37% and 38%, respectively. Using the two polymorphisms together, the informative rate reached 46%. Taking advantage of TaqI and XmnI polymorphisms, carrier detection was performed for seven females with unknown status in five haemophilia B families (including one large extended family) with positive history. Six of the girls were normal and one was haemophilia B carrier. Therefore, carrier detection might be possible for informative Iranian haemophilia B families in the familial cases. Additionally, similarities in term of heterozygosity rates for these two polymorphic sites were seen between some European and Iranian populations.