AN MSEI RFLP IN THE 5' FLANKING REGION OF THE FACTOR-IX GENE - ITS USE FOR HEMOPHILIA-B CARRIER DETECTION IN CAUCASIAN AND THAI POPULATIONS

We have identified an MseI restriction fragment length polymorphism (R FLP) in the 5' flanking region of the factor IX gene. RFLPs in the fac tor IX locus are routinely used as linkage markers to track defective factor IX genes through affected pedigrees, allowing diagnosis of the haemophilia B carrier state in female members of the kindred. Currentl y, seven intragenic polymorphic loci have been characterized allowing carrier diagnosis in 89% of cases in the Caucasian population. Additio nal screening with the MseI RFLP reported in this publication increase s this figure to 94% of cases. In Asian populations only one of these RFLPs (HhaI) is present at any significant frequency. Hence, carrier d etection rates are much reduced in comparison to the corresponding fig ure of 89% in Caucasians. We report that this MseI RFLP is also presen t in the Thai population. Indeed, when used in combination with the Hh aI polymorphism, the MseI RFLP should significantly improve the carrie r detection rate in the Thai population from 11% to 40% of cases.