ABSTRACT
Hemoglobin (Hb) Korle-Bu (beta73; Asp-Asn) is the most frequent of the rare beta-chain variants in the population of West Africa whereas Hb E (beta26; Glu-Lys) is common among the Southeast Asian population. We report a hitherto undescribed condition in which these two beta-chain variants co-segregate. The proband was a 19-year-old Thai pregnant woman in her second trimester of pregnancy who visited our thalassemia screening unit. Cellulose acetate electrophoresis and high-performance liquid chromatography (HPLC) analysis of Hb detected one abnormal Hb in addition to the Hb E. Analysis of DNA sequences revealed a GAT-AAT mutation at codon 73 in trans to a GAG-AAG mutation at codon 26 of the beta-globin gene. Polymerase chain reaction (PCR) analysis of the alpha-globin gene cluster of the patient detected a 3.7-kb deletional alpha-thalassemia 2. Family study identified that her mother had the same genotype and her father was a simple Hb E carrier. The hematological data of these unusual cases of hemoglobinopathy are presented and compared with a simple heterozygote for Hb Korle-Bu found in another unrelated Thai family. beta-Globin gene haplotype linked to the Thai beta(Korle-Bu) and a simple DNA assay based on allele-specific PCR for rapid diagnosis of Hb Korle-Bu are also described.
Subject(s)
Gene Deletion , Hemoglobin E/genetics , Hemoglobins, Abnormal/genetics , Heterozygote , alpha-Thalassemia/genetics , Adolescent , Adult , Aged , Asparagine , Aspartic Acid , Base Sequence/genetics , Chromosome Segregation , Female , Glutamic Acid , Humans , Lysine , Male , Middle Aged , Pregnancy , ThailandABSTRACT
OBJECTIVE: To establish a rapid PCR method for simultaneous detection of beta-thalassemia and alpha-thalassemia 1 genes for diagnosis of complex alphabeta-thalassemia syndrome. DESIGN AND METHODS: Using multiplex allele specific PCR approach, we evaluated a simultaneous detection of the SEA type alpha-thalassemia 1 and the common Southeast Asian beta-thalassemia and hemoglobin E genes. The system was tested on known cases of double heterozygote for alpha- and beta-thalassemias and in a prenatal diagnosis of complex alphabeta-thalassemia syndrome. RESULTS: Co-inheritance of alpha-thalassemia 1 (SEA type) with each of the common beta-thalassemia genes in Southeast Asian and with hemoglobin E could be identified in a single PCR reaction. A successful application of this simultaneous detection system in prenatal diagnosis of a complex thalassemia syndrome caused by an EFBart's disease was demonstrated in a Thai family. CONCLUSION: We have shown that correct diagnosis of double heterozygosity for alpha-thalassemia 1 and beta-thalassemia or hemoglobin E could be obtained using a simultaneous multiplex PCR. These rapid PCR assays would facilitate characterization and prenatal diagnosis of complex thalassemia syndromes in the regions where both alpha- and beta-thalassemias and hemoglobin E are common.
Subject(s)
Hemoglobin E/analysis , Polymerase Chain Reaction , Prenatal Diagnosis , alpha-Thalassemia/genetics , beta-Thalassemia/genetics , Chorionic Villi Sampling , Electrophoresis, Agar Gel , Female , Fetal Diseases/diagnosis , Globins/genetics , Heterozygote , Humans , Male , Mutation , Paternity , Pedigree , Pregnancy , Pregnancy Trimester, Second/genetics , Reference Values , alpha-Thalassemia/diagnosis , beta-Thalassemia/diagnosisABSTRACT
We describe hematologic and DNA characterization of 12 hemoglobin C heterozygotes and three compound heterozygotes for hemoglobin C and hemoglobin E found in Thailand. Amplification and DNA analysis of genomic DNA by the polymerase chain reaction procedure permitted the identification of the beta(C) mutation at codon 6 of beta-globin gene (beta 6; GAG-AAG). beta-Globin gene haplotype analysis demonstrated that all beta(C) globin genes detected in these Thai individuals were associated with the haplotype (+ - - - - - +), indicating a non-African origin of this abnormal hemoglobin in Thailand. On routine hemoglobin typing, hemoglobin C is usually mistakenly identified as hemoglobin E because of theirs similar mobilities on cellulose acetate electrophoresis. The simple DNA assay for hemoglobin C based on an allele-specific polymerase chain reaction for accurate diagnosis of hemoglobin C was therefore developed.
