β-Globin gene cluster haplotypes of Hb D-Los Angeles in Mazandaran Province, Iran.

Several types of hemoglobin D (Hb D) are distinguishable by DNA analysis, and the aim of this study was to identify the types of Hb D variant and β-globin gene haplotypes linked to Hb D in Mazandaran Province, northern Iran. Fifty five individuals were identified as Hb D carriers, and PCR-RFLP analysis revealed that all 55 had the Hb D-Los Angeles type. To identify haplotypes associated with the β(D) allele, family linkage analysis, using the PCR-RFLP method for seven polymorphisms in the β-globin gene cluster, was carried out on families of 23 of these 55 individuals. We observed three different haplotypes in association with Hb D-Los Angeles. In most cases (91.4%) β(D) alleles were linked to haplotype I [+ - - - - + +]. Haplotype II [- + + - + + +] and an atypical haplotype [- + + - - + -] were each in association with the β(D) allele in only one case (4.3%). This is the first report worldwide of the [- + + - - + -] haplotype in association with Hb D-Los Angeles. We conclude that more than 90% of the evaluated Hb D-Los Angeles alleles in Mazandaran have the same origin, and the two rare haplotypes may represent different genetic origins and/or other molecular events, such as gene conversion or recombination, in the region.