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Molecular characterization of hemoglobin C in Thailand
K Sanchaisuriya1, G Fucharoen, N Sae-ung
1Department of Clinical Microscopy, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand.
Insights
Hemoglobin C heterozygotes in Thailand were identified using DNA analysis, revealing a non-African origin. A new polymerase chain reaction assay accurately diagnoses hemoglobin C, distinguishing it from hemoglobin E.
Area of Science:
- Genetics
- Molecular Biology
- Hematology
Background:
- Hemoglobin C (HbC) is an abnormal hemoglobin variant.
- Distinguishing HbC from Hemoglobin E (HbE) can be challenging due to similar electrophoretic mobilities.
- Understanding the genetic origin of HbC in Thailand is important.
Purpose of the Study:
- To characterize hematologic and DNA profiles of individuals with hemoglobin C in Thailand.
- To identify the molecular basis and origin of beta(C) globin genes in the Thai population.
- To develop a reliable DNA-based diagnostic assay for hemoglobin C.
Main Methods:
- Genomic DNA extraction and polymerase chain reaction (PCR) amplification.
- DNA sequencing to identify the beta(C) mutation at codon 6 of the beta-globin gene.
- Beta-globin gene haplotype analysis.
- Development of an allele-specific PCR assay for hemoglobin C detection.
Main Results:
- Identified 12 heterozygotes and 3 compound heterozygotes for HbC in Thailand.
- Confirmed the beta(C) mutation (GAG-AAG) at codon 6 of the beta-globin gene.
- Haplotype analysis indicated a non-African origin of beta(C) globin genes in these individuals.
- Demonstrated that HbC is often misidentified as HbE on routine electrophoresis.
Conclusions:
- The beta(C) globin gene in Thai individuals likely originated from a non-African source.
- A novel, allele-specific PCR assay provides accurate and reliable diagnosis of hemoglobin C.
- This DNA-based method overcomes limitations of traditional electrophoretic methods for HbC identification.
Abstract:
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.