Molecular characterization of D-Korean persons: development of a diagnostic strategy

BACKGROUND: D- frequencies show wide racial differences: in particular, in Korean persons it is approximately 1/100th of that in Caucasians (0.15% vs. 15%). The molecular mechanisms of D- may be unique to races, and thus specific molecular diagnostic approaches are necessary for individual races. Such marked racial differences have been attributed to the founder effect. It was hypothesized that D- frequencies may be affected by genomic variations of Rhesus boxes, which are instruments of unequal crossing-over. STUDY DESIGN AND METHODS: First, the molecular basis of D- in Korean donors was characterized. A total of 264 D- persons were analyzed by performing RHD exon polymerase chain reaction (PCR), Rhesus box hybrid PCR-Psfl, RHD sequencing, and a novel RHD-CE-D hybrid PCR. Second, with sequencing analysis, Rhesus boxes in Korean and Caucasian persons were compared. RESULTS: Of 264 D- Korean individuals, 74 percent completely lacked RHD, 9 percent had RHD-CE-D hybrid, and 17 percent had point mutations. Three genetic causes, RHD deletion, RHD-CE(2-9)-D-2, and 1227G > A, explained 99.4 percent of D- alleles in Korean persons. Three novel mutations were also found. The identity region of 10 Rhesus boxes in Korean persons was in complete concordance with that in Caucasian persons. CONCLUSION: In this study, a molecular diagnostic strategy was established and the genetic causes of almost all D- Korean persons was able to be diagnosed with a simple decision tree. The study provides a good example of the molecular diagnosis of D- persons, especially in low-frequency areas. Our hypothesis that D-frequencies are affected by genomic variations in Rhesus boxes was excluded. Rather, racial differences may be influenced by the founder effect.