Quantities of adult, fetal and embryonic globin chains in the blood of eighteen- to twenty-week-old human fetuses

Impact of the detection of ζ-globin chains and hemoglobin Bart's using immunochromatographic strip tests for α0-thalassemia (--SEA) differential diagnosis

α⁰-Thalassemia is an inherited hematological disorder caused by the deletion of α-globin genes. The Southeast Asian deletion (--^SEA) is the most common type of α⁰-thalassemia observed in Southeast Asian countries. Regarding WHO health policy, an effective α⁰-thalassemia screening strategy is needed to control new severe α-thalassemia cases. In this study, a monoclonal antibody panel was used to develop immunochromatographic (IC) strip tests for detecting the Hb Bart’s and ζ-globin chain. Among 195 samples, all α⁰-thalassemia traits (78 α⁰-thalassemia (--^SEA) and 4 α⁰-thalassemia (--^THAI)) had low MCV or MCH values. The sensitivity, specificity, PPV and NPV of the IC strip tests for ζ-globin and Hb Bart’s for screening α⁰-thalassemia (--^SEA) within the low MCV or MCH samples were 100%, 65.2%, 90.7%, 100% and 96.2%, 47.8%, 86.6%, 78.6%, respectively. All 4 α⁰-thalassemia (--^THAI) traits were negative for ζ-globin chains but positive for Hb Bart’s using the IC strip tests. These results led to a α⁰-thalassemia screening being proposed in which blood samples are first evaluated by MCV, MCH and Hb typing. Samples with high MCV and MCH values are excluded for the presence of the α⁰-thalassemia gene. Samples with low MCV or MCH values are assayed using the developed IC strip tests, where only samples testing positive are further assayed for α⁰-thalassemia by PCR. Patients with Hb H, EA Bart’s or EF Bart’s diseases do not need to use this IC strip assay. Thus, in this study, a simple and cost effective α⁰-thalassemia point of care test was developed.

Association of Tissue-Specific DNA Methylation Alterations with α-Thalassemia Southeast Asian Deletion

In the wild-type allele, DNA methylation levels of 10 consecutive CpG sites adjacent to the upstream 5′-breakpoint of α-thalassemia Southeast Asian (SEA) deletion are not different between placenta and leukocytes. However, no previous study has reported the map of DNA methylation in the SEA allele. This report aims to show that the SEA mutation is associated with DNA methylation changes, resulting in differential methylation between placenta and leukocytes. Methylation-sensitive high-resolution analysis was used to compare DNA methylation among placenta, leukocytes, and unmethylated control DNA. The result indicates that the DNA methylation between placenta and leukocyte DNA is different and shows that the CpG status of both is not fully unmethylated. Mapping of individual CpG sites was performed by targeted bisulfite sequencing. The DNA methylation level of the 10 consecutive CpG sites was different between placenta and leukocyte DNA. When the 10th CpG of the mutation allele was considered as a hallmark for comparing DNA methylation level, it was totally different from the unmethylated 10th CpG of the wild-type allele. Finally, the distinct DNA methylation patterns between both DNA were extracted. In total, 24 patterns were found in leukocyte samples and 9 patterns were found in placenta samples. This report shows that the large deletion is associated with DNA methylation change. In further studies for clinical application, the distinct DNA methylation pattern might be a potential marker for detecting cell-free fetal DNA.

Development of a fluorescence immunochromatographic assay for the detection of zeta globin in the blood of (--(SEA)) α-thalassemia carriers

Southeast Asian deletion (--(SEA)) α-thalassemia is an inherited monogenic disorder of human hemoglobin, and embryonic globin ζ (hemoglobin ζ, zeta globin chain or Hb zeta chain) has been shown to be a marker that can be used for the identification of carriers of the (--(SEA)) α-thalassemia deletion. In this work, a fluorescence immunochromatographic assay (FL-ICA) was established to detect the zeta globin chain in the hemolysates of carriers of the (--(SEA)) α-thalassemia deletion. This assay can be completed within 10min using a simple UV detector and does not suffer from interference from the red background color of the hemolysate. A total of 314 blood samples were tested by FL-ICA and ELISA. The results of these assays were confirmed by PCR, the standard technique for genetic disease testing. The sensitivity and specificity of this novel FL-ICA were 100% and 98.0%, respectively; the corresponding values for the ELISA performed simultaneously were 100% and 99.2%, respectively. In conclusion, a new FL-ICA-a simple, fast, convenient, low-cost method-was developed that may be useful in both high-throughput screening and individual detection of the (--(SEA)) α-thalassemia deletion in carriers. Additionally, this qualitative FL-ICA may enlighten the development of a new systems for analysis of other target molecules using whole-blood samples.

Embryonic Hemoglobins Are Expressed in Definitive Cells

Human embryonic ζ and ɛ globin chains are synthesized in yolk sac–derived primitive erythroid cells, and decrease rapidly during definitive erythropoiesis. Examination of ζ and ɛ globin expression at the cellular level using dual-color immunofluorescence staining with specific monoclonal antibodies showed that embryonic globin proteins are present in definitive erythroid cells. More than half of fetal erythrocytes were positive for ζ and ∼5% for ɛ globin. Approximately one third of newborn red blood cells were ζ-positive and less than 1% ɛ-positive. Adult erythrocytes did not have embryonic globins. Erythroblasts that developed in liquid cultures also contained embryonic globin in amounts which declined with ontogenic age, and the proportion of positive cells in vitro was less than in the comparable erythrocytes that developed in vivo. Thus, embryonic globin chains are synthesized in definitive erythroid cells and decrease with ontogeny. Modulation of embryonic globin gene expression is not solely due to a switch from primitive to definitive erythropoiesis.

EDMA 2000 as a matrix for high-performance liquid chromatography of human haemoglobin chains

An ethylenedimethacrylate polymer-based matrix (EDMA 2000) is described that shortens the time for separation of haemoglobin (Hb) chains to 30 min, compared with the use of C4 large-pore Vydac columns, commonly used for reversed-phase HPLC of Hb variants. EDMA 2000 was successfully used for the isolation of an abnormal beta-chain of the unstable Hb recently characterized as Hb Nottingham.

The structure and function of normal and abnormal haemoglobins

This chapter reviews general aspects of the normal human haemoglobins which include those predominantly present in the embryo, the fetus and newborn baby, and in the normal adult. Special emphasis is given to factors which affect the levels of fetal haemoglobin in the adult because increased percentages of Hb F can be of great benefit to adults with certain haemoglobinopathies such as sickle cell anaemia and beta-thalassaemia. A review of the numerous Hb variants published since the discovery of Hb S in 1959 reveals a steady stream of newly detected abnormalities; most of these are the result of single-point mutations in the alpha-, beta-, gamma-, or delta-globin genes. Of the more than 600 variants listed in a repository, some 200 have clinical significance because of a decreased stability, a change in functional properties, among others. Methodology developed for the detection and quantitation of normal and abnormal Hb components has been greatly modified during the past 30 years; isoelectrofocusing and different fast developing micro chromatographic procedures are the methods of choice. Analyses of DNA isolated from the white cells has become most useful for the final characterization of the variants; this methodology consists of amplification of a desired segment of DNA and identification of a mutation with labelled oligonucleotide probes. Additional methods include sequence determination of this amplified DNA and identification of known mutations with an allele specific amplification procedure.