Prenatal diagnosis of α- and ß-thalassemias in southern Thailand.

We report our work on prenatal diagnosis of α-thalassemia, ß-thalassemia and other hemoglobinopathies in southern Thailand. DNA-based diagnosis was offered to 1906 pregnancies at risk for thalassemia using a combination method of multiplex-PCR and reverse dot blot analysis to detect seven α-globin and 47 ß-globin mutations. The most commonly detected mutation of α0-thalassemia was a South-East Asian deletion (98%), followed by a Thai deletion (2%). Twenty-eight ß-globin mutations were identified. Fourteen common mutations, including cod 19 A-G (18.6%), cod 41/42 -TCTT (14.4%), IVS1#5 G-C (13.2%), 3.5 kb deletion (9.2%), cod 17 A-T (7.7%), -28 A-G (7.3%), IVSI#1 G-T (7.1%), 12.5 kb deletion (δß)0 (5.7%), HPFH6 (4.2%), IVS2#654 C-T (2.7%), 45 kb deletion (1.9%), Asian Indian-inversion-deletion Gγ(Aγδß)0 (1.6%), cod 41 -C (1.5%) and cod 71/72 +A (1.3%) were detected, accounting for 96.5% of all mutations detected. The most common hemoglobin variant was Hb E, accounting for 97.86%. Prenatal diagnosis of 1906 couples at risk showed 22.0% normal, 51.2% carrier and 26.8% affected. The present study provides important information for diagnosis and control of severe thalassemia diseases.

Molecular characterization of Hb H disease in southern Thailand.

Genotypes of 260 individuals with hemoglobin H (Hb H) disease originating from various provinces in southern Thailand were characterized by multiplex PCR (M-PCR) and reverse dot blot hybridization (RDB). M-PCR was used to amplify target fragments and then hybridized with allele-specific oligonucleotide (ASO) probes which were bound on a nylon membrane. A total of eight α-thalassemia (α-thal) mutations, which produced eight Hb H disease genotypes (α0-thal/α+-thal), were detected. The most common form of α0-thal was -SEA with a frequency of 99.23%. The other form (0.77%) of α0-thal mutation was a THAI deletion (-THAI). The deletional α+-thal mutations comprised 3.7 kb (-α3.7) and 4.2 kb (-α4.2) deletions which were found in 172 (66.15%) and 5 (1.92%) alleles, respectively. The incidence of non-deletional α+-thal in decreasing order was Hb Constant Spring (Hb CS, αCS) 28.85%, Hb Quong Sze (Hb QS, αQS) 1.54%, and Hb Paksé (Hb PS, αPS) 0.77%. The genotype characterization of Hb H disease and the development of the RDB technic for detection of α-thal mutations presented in this study enable the prenatal diagnosis of Hb Bart's hydrops fetalis syndrome.

MiR-155 enhances phagocytic activity of ß-thalassemia/HbE monocytes via targeting of BACH1.

Abnormal red blood cell (RBC) clearance in ß-thalassemia is triggered by activated monocytes. Recent reports indicate that miRNA (miR-) plays a role in monocyte activation. To study phagocytic function, we co-cultured monocytes of normal, non-splenectomized and splenectomized ß-thalassemia/HbE individuals with RBCs obtained from normal, non-splenectomized and splenectomized ß-thalassemia/HbE individuals. The phagocytic activity of ß-thalassemia/HbE monocytes co-cultured with ß-thalassemia/HbE RBCs was significantly higher than that of normal monocytes co-cultured with normal RBCs. Upregulation of monocyte miR-155 was observed in ß-thalassemia/HbE patients. Increased miR-155 was associated with reductions in BTB and CNC Homology1 (BACH1) target gene expression and increased phagocytic activity of ß-thalassemia/HbE monocytes. Taken together, these findings suggested that increased miR-155 expression in activated monocytes leads to enhanced phagocytic activity via BACH-1 regulation in ß-thalassemia/HbE. This provides novel insights into the phagocytic clearance of abnormal RBCs in ß-thalassemia/HbE.

Molecular basis and hematological features of hemoglobin variants in Southern Thailand.

Hemoglobinopathy (abnormal hemoglobin or hemoglobin variant) is an inherited disorder that results in the abnormal structure of globin chains of the hemoglobin (Hb) molecule. Many abnormal Hbs have been characterized worldwide, including more than 20 variants in Thailand. The Bio-Rad Variant II HPLC system is used for investigating hemoglobin variants at Songklanagarind Hospital. This system has been shown to be a sensitive, specific, and reproducible method, but some hemoglobin variants such as Hb Tak and Hb D-Punjab cannot, as yet, be clearly separated by this method. The aim of this study was to investigate the prevalence of hemoglobinopathy in southern Thailand using DNA sequencing and study the severity of each hemoglobin variant. A total of 58 hemoglobin variant samples were obtained from blood samples undergoing routine hemoglobin typing at Songklanagarind Hospital. Genomic DNAs were extracted from the samples, and the globin genes were analyzed by using PCR-direct sequencing. The molecular analysis revealed eight hemoglobin variants: 28 Hb C, 12 Hb D-Punjab, 7 Hb Tak, 4 Hb G-Makassar, 2 Hb Lepore-Hollandia, 2 Hb Q-Thailand, 2 Hb O-Indonesia, and 1 Hb Hope. The distribution of hemoglobin variants in southern Thailand is associated with geographic and/or ethnic backgrounds. This study may help hematologists understand better the prevalence of hemoglobin variants and their hematological features in this region.