DETECTION OF DELETION α(+)-THALASSEMIA MUTATION [-α (3.7), -α (4.2)] BY QUANTITATIVE PCR ASSAY.

In Thailand, Hb H (α0(-thal/α(+)-thal) disease is highly prevalent. We designed 3 primer sets (A, B and C) to detect -α (3.7) and -α (4.2) deletion types of α(+)-thal by quantitative (q)PCR. The A and C primer sets were used to amplify DNA sequences at the 3' terminal regions of HBA2 and HBA1 gene, respectively, and the B primer set was used to amplify an upstream DNA sequence at the 5' flanking region of HBA1 gene. The relative quantities of the PCR products (based on threshold cycle (CT) values) of the 3 primer sets were calculated according to the equation R = 2-ΔΔCT, and these values were used to distinguish between -α (3.7) and -α (4.2) deletion mutations. The type of α(+)-thal mutations was determined by calculating the difference between R (C-A) and R (C-B), yielding a value either of 0.5 or 1.0, which indicates the copy number of the target DNA compared with normal diploid control. Measured values that are close to 0.5 indicate there is a single allele of the target DNA. This method was applied to 250 DNA samples recruited for this study, and the R (C-A) and R (C-B) value determined for 185 cases of non α-thal was 1.03 ± 0.04 and 0.95 ± 0.08, respectively, for 41 cases of -α (3.7) α-thal trait 0.49 ± 0.04 and 0.45 ± 0.04, respectively, and for 2 cases of -α (4.2) α(+)-thal trait 0.5 ± 0.1 and 1.01 ± 0.06, respectively. The allele frequency of -α (3.7) and -α (4.2) mutation was 0.092 and 0.004, respectively. These results were in con- cordance with those obtained by conventional gap-PCR. The method described here is simple, accurate and feasible for screening of α(+)-thal carriers and should provide valuable information for genetic counselling of patients at risk of having a child with Hb H disease.

Hypotensive and vasorelaxant effects of sericin-derived oligopeptides in rats.

Sericin-derived oligopeptides obtained from silk cocoons were investigated for the in vivo hypotensive effect and investigated for the underlying mechanism involved in vasodilation in isolated rat thoracic aorta. In normotensive anesthetized rats, oligopeptides induced an immediate and transient hypotensive activity. In rat aortic rings, oligopeptides induced a concentration-dependent vasorelaxation in vessels precontracted with both KCl and phenylephrine (PE) with endothelium-intact or endothelium-denuded rings. In endothelium-intact rings, pretreatment with N ω -Nitro-L-arginine methyl ester hydrochloride (L-NAME, 100 µM), an inhibitor of the NO synthase (NOS) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1 µM), a selective inhibitor of the guanylyl cyclase enzyme, significantly reduced the relaxant effect of oligopeptides. However, indomethacin, an inhibitor of the cyclooxygenase, had no effect on oligopeptides-induced relaxation. In addition, pretreatment with tetraethylammonium (TEA, 5 mM) reduced the maximal relaxant effect induced by oligopeptides. By contrast, relaxation was not affected by 4-aminopyridine (4-AP, 1 mM), glibenclamide (10 µM), or barium chloride (BaCl2, 1 mM). In depolarization Ca(2+)-free solution, oligopeptides inhibited calcium chloride- (CaCl2-) induced contraction in endothelium-denuded rings in a concentration-dependent manner. Nevertheless, oligopeptides attenuated transient contractions in Ca(2+)-free medium containing EGTA (1 mM) induced by 1 µM PE, but they were not affected by 20 mM caffeine. It is obvious that potent vasodilation effect of oligopeptides is mediated through both the endothelium and the vascular smooth muscle.

Detection of Hb H disease genotypes common in northern Thailand by quantitative real-time polymerase chain reaction and high resolution melting analyses.

We used quantitative real-time polymerase chain reaction (qPCR) and high resolution melting (HRM) analyses for the detection of the common α-thalassemia (α-thal) genotypes in 40 northern Thai Hb H (ß4) patients. The α(0)-thal [- -(SEA) (Southeast Asian) deletion] was detected by a multiplex gap real-time PCR. To determine the α(+)-thal, three primer pairs were designed. The A-primer pair was used to amplify the 3' terminal DNA sequences of the HBA2 gene, and the B-primer pair amplified the 5' flanking region of the HBA1 gene. The C-primer pair amplified the 3' terminal DNA sequences of the HBA1 gene and was used as an internal control. The -α(4.2) (leftward) and -α(3.7) (rightward) deletions were determined by monitoring the absence of PCR product(s). The Hb H patients who had a negative PCR result for the A-primer pair but positive for the B- and C-primer pairs carried the -α(4.2) deletion, while the -α(3.7) deletion carriers were negative for the A- and B-primer pairs. In the case of Hb H with Hb Constant Spring (Hb CS, α142, Term→Gln; HBA2: c.427T>C), all primer pairs were positive, HRM analysis of the PCR product of the A-primer pair was introduced to analyze the Hb CS gene. It can distinguish clearly between normal and Hb CS genotypes. The applied methods for the determination of the α(0)- and α(+)-thal genotypes revealed the results to be as accurate as conventional gap-PCR and the direct DNA sequencing methods but resulted in a much simpler and faster procedure.

Detection of beta-thalassemia mutations using a multiplex amplification refractory mutation system assay.

We developed two sets of a multiplex amplification refractory mutation system (M-ARMS) assay to identify specific beta-thalassemia (beta-thal) mutations that are common in Thailand. The first one was for the detection of mutants with codon 17 (A>T), IV S-I-1 (G >T)), codons 41/42 (-TCT T) and codons 71/72 (+A), while the second one was for the -87 (C>A), -28 (A>G) and IVS-II-654 (C>T). Application of the proposed assay to 282 persons with beta-thal trait revealed a positive result in 276 cases (97.8%). There were 258 cases (91.5%) positive for the set 1 M-ARMS assay and 18 cases (6.4%) were positive for set 2. Six cases (2.2%) were negative for both sets 1 and 2, and were further characterized by DNA sequencing. The mutations detected by the set 1 M-ARMS assay were 113 cases (40.1%) of codons 41/42, 95 (33.7%) of codon 17, 41 (14.5%) of IVS-I-1 and nine cases (3.2%) of codons 71/72, while by set 2 there were 12 cases (4.2%) of -28, four cases(1.4%) of -87 and two cases (0.7%) of IVS-II-654. Mutations undetectable by M-ARMS assay were two cases of codons 27/28 (+C), one case of codon 35 (C>A), one of codon 43 (G>T), one of -31 (A>G) and one of IVS-I-5 (C>G). The M-ARMS assay proved to be a valuable tool for the analysis of beta-thal mutations. The method is robust, accurate, simple, speedy and cost-effective. The application of this assay will facilitate genetic counseling and prenatal diagnosis for severe thalassemia in high-risk pregnancies.

Homogeneity of beta(0)-thalassemia codon 17 (A-->T) alleles in Northern Thailand using a direct DNA sequencing method.

The aim of this study was to characterize beta-globin gene micro-haplotype polymorphisms (frameworks) associated with a beta-thalassemia mutations common in Northern Thailand using a direct DNA sequencing method. A total of 11 beta-thalassemia major patients homozygous for the codon 17 (A-->T) mutation admitted to Chiang Mai University Hospital were examined. All 22 alleles were found to contain the Asian framework 3A. The homogeneity of the framework associated with the codon 17 (A-->T) mutation indicates a relatively recent origin of the codon 17 (A-->T) mutation. Similar studies in other East Asian populations may provide information concerning the origin and the migrational spread of this beta-thalassemia mutation.

Spontaneous mutation of the hemoglobin Leiden (beta 6 or 7 Glu-->0) in a Thai girl.

We report a case of 12-year old Thai girl suffering from mild non-transfusion-dependent thalassemia intermedia. She is the single child in her family. On examination she looked pale; there was no hepatosplenomegaly. The Hb concentration was 9 g/dL. Hb typing and molecular mutation study revealed compound heterozygosity for HbE and Hb Leiden (alpha2beta26/7-Glu, codon 6/7-GAG). The proportion of HbE was 47% whereas that of Hb Leiden was 39%. The patient had no HbA. Hb typing of her father and mother revealed HbE trait, and no Hb Leiden was demonstrated. As the paternity test confirmed the parenthood, we assume that Hb Leiden has arisen by spontaneous mutation. A study of the beta< or= -globin gene framework by molecular cloning and subsequent DNA sequencing of the beta-globin gene in the members of the family indicated that the Hb Leiden mutation occurred on a maternal inherited chromosome. The deletion of codon 6 or 7 (-GAG) of the beta-globin gene in the patient may be due to an unequal crossing over during the mother's oogenesis.