Molecular and hematological characterization of Hb Tak and Hb Pyrgos in Thailand.

Two hemoglobin variants that migrate abnormally on gel electrophoresis were found in four unrelated Thai individuals. One variant that migrate faster than HbA but more slowly than Hb Bart's was detected in two heterozygotes. Another abnormal Hb migrating between HbA2 and HbF was found in one heterozygote and one compound heterozygote with HbE. In all cases, no microcytic anemia was observed. PCR amplification and direct DNA sequencing established that the first variant was caused by a missense mutation at codon 83 (GGC-GAC) that leads to Gly to Asp substitution previously described as the Hb Pyrgos in a Greek boy. The second variant was caused by an AC insertion at the termination codon that leads to synthesis of elongated beta-globin chain known as the Hb Tak. Beta globin gene haplotype analysis demonstrated that each variant was found on the same chromosome background in Thai individuals. The simple non-radioactive DNA assays based on allele specific polymerase chain reaction for the detection of these two Hb mutations in a routine laboratory are described.

Beta-globin gene haplotypes in some minor ethnic groups in Thailand.

In order to provide population genetic data of various ethnic groups in Thailand, we have determined the type of hemoglobin by electrophoresis and the beta-globin gene haplotypes by PCR followed by restriction digestion in five small ethnic groups namely hill tribes, PhuTai, Chong, Lao Song and Sakai inhabiting in the north, northeast, east, central and south of Thailand, respectively. In each group, in addition to HbA and HbA2, the HbE, the most common hemoglobinopathy in Southeast Asia was detected at 2.5%, 51.6%, 84.0%, 8.6% and 11.8%, respectively. Haplotype analysis demonstrated that in all groups the beta A-globin gene was associated with various haplotypes and beta-globin gene frameworks. However, beta E -globin gene was associated with haplotypes ((-)+(-)+ + +(-)) and ((+)-(-)-(-)+(-)) on the beta-globin gene framework 2 in all ethnic groups except in Chong people whose the beta E-globin gene was mostly linked to haplotype ((-)+(-)++(-)+) and beta-globin gene framework 3 which was commonly found among Cambodian. It appears therefore that the Chong population is more related to Cambodian than Thai.

Molecular and hematological characterization of HbE heterozygote with alpha-thalassemia determinant.

Hemoglobin E and alpha-thalassemia are prevalent in Thailand. The chance that an individual heterozygous for HbE also carries an alpha-thalassemia determinant is high. In this individual, the amount of HbE and other hematological parameters may be differed from that of usual observation. In this study, a total of 132 HbE heterozygotes were screened for alpha-thalassemia 1 gene deletion by the polymerase chain reaction. Out of 132 cases, 71 could be completely analyzed for hematologic parameters. Forty-three of 88 cases with HbE less than 25% as measured using microcolumn chromatography were positive for this gene deletion. In twenty of these 43 alpha-thalassemia 1 positive cases, the average values of Hb, Hct, MCV, MCH, MCHC, RDW and HbE were 10.6 g/ dl, 33.1%, 64.8 fl, 21.0 pg, 32.3 pg/dl, 18.6% and 17.4%, respectively. Eight of 9 alpha-thalassemia 1 negative cases were positive for alpha-thalassemia 2 gene deletion in Southern blot analysis. In this later group, hematological parameters were similar to that of the former. Co-inheritance of the Hb Constant Spring gene has no direct effect on the level of HbE. No alpha-thalassemia 1 gene was detected in the remaining 34 cases whose HbE were above 25%. The average amount of Hb, Hct, MCV, MCH, MCHC, RDW and HbE were 12.4 g/dl, 37.7%, 79.7 fl, 26.2 pg, 32.7 pg/dl, 25.8% and 28.5%, respectively. Therefore, screening for HbE level below 25% may be a convenient way of identifying parents of carrying alpha-thalassemia 1 determinant.