Genetics background of β-thalassemia (3.5 kb deletion) in Southern Thailand: Haplotype analysis using novel reverse dot blot hybridization

β-thalassemia (β-thal) (3.5 kb deletion or NC_000011.10:g.5224302-5227791del3490bp) is a common mutation in southern Thailand. This study aimed to determine genetic diversity in subjects with β-thal (3.5 kb deletion) alleles and to ascertain the origin of this mutation using haplotype and phylogenetic analysis. The study was carried out on members of the southern Thai population, including 45 normal individuals, 116 heterozygous β-thal (3.5 kb deletion) and one homozygous β-thal (3.5 kb deletion). The 5'-haplotype in β-globin gene cluster was examined using newly developed reverse dot blot hybridization (RDB) and compared with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results showed 100% concordance between the haplotype patterns of these two methods. From a total of 324 chromosomes, nine haplotypes were segregated. Haplotype H2 (+ - - - -) was the predominant haplotype observed in all 118 β-thal (3.5 kb deletion) chromosomes, which revealed a single origin. The phylogenetic tree demonstrated that β-thal (3.5 kb deletion) has an older genetic defect in this region. Moreover, the developed RDB is simple, less time-consuming, inexpensive, and does not restriction enzyme digestion.