Analysis of beta-thalassemia mutations and beta-locus control region hypersensitive sites 2, 3 and 4 in southern Thailand.

beta-Thalassemia mutations in 221 chromosomes of unrelated southern Thai patients were analyzed. Using dot blot hybridization of PCR amplified DNA with 15 allele specific oligonucleotide probes for beta-thalassemia mutations 196/221 (89%) of the alleles were characterized. Ten mutations were identified, of which six [codon 41/42 (TTCTTT-TT), IVS1 nt5(G-C), codon 19 (AAC-AGC), codon 17 (AAG-TAG), IVS1 nt1(G-T), -28 TATA (A-G)], accounted for 85%. Among the 25 uncharacterized alleles, 15 were analyzed by automated fluorescent DNA sequencing of the whole beta-globin gene with normal results in 7 alleles. Four mutations, previously described were detected in 8 alleles. They were a G-A at IVS1 nt1 in one heterozygote, a G-T at IVS1 nt1 in one heterozygote, codon 15 (TGG-TAG) in two heterozygotes and poly A(AATAAA-AATAGA) in two homozygotes. The polyadenylation mutations, previously demonstrated in the Malaysian population have been first detected in Thailand. It is remarkable that the IVS1 nt1 (G-A) mutation, previously reported in the Mediterranean population has been found only in the south of Thailand. This mutation was probably imported from Portugal. In former times the Portuguese had settled in Phuket in southern Thailand. In order to find a causative mutation in the rest of 7 true unknowns we performed direct DNA sequencing of the core fragments of the beta-Locus Control Region Hypersensitive Sites (LCR HS) 2,3 and 4 in these 7 samples. DNA sequencing of HS2 and HS3 fragments showed normal results. The heterozygote A/G was present in the palindromic sequence of the LCR HS4 (TGGGGACCCCA) in 6 beta-thalassemia samples. The same heterozygote A/G was found in 5/12 normal subjects. The allele frequency of A (0.79) is obviously higher than that of G (0.21). This could be due to the stability of the palindromic structure. When an A is in the middle of the palindromic sequence, the hairpin structure is formed. In contrast the hairpin structure disappears when a G is in the middle of the palindromic sequence. This structure is not further symmetric and may not be so stable as the hairpin structure. beta-Thalassemia mutations in southern Thailand are very heterogeneous and their distribution is different from other parts of the country.

Molecular basis of beta-thalassemia in Thai Muslim patients in the the south of Thailand.

Among a sample of 29 unrelated Thai Muslim children, a total of 37 beta thalassemia genes was identified and 33 out of 37 mutations (89%) were characterized giving 6 different mutations. Four mutations [IVS-1 nt 5 (G-C), codon 19 (A-G), codons 41/42 (-CTTT) and IVS-1 nt 1 (G-T)] account for 86%. IVS-1 nt 5 (G-C) is the most common mutation found in Thai Muslim patients. Thai Muslim patients share the four most common mutations with Malays.

Clinical, hematological and molecular features in Thais with beta-Malay/beta-thalassemia and beta-Malay/HbE.

A total of 50 patients and relatives were studied comprising 12 cases of compound heterozygosity of beta-Malay and beta + thalassemia, 10 cases of compound heterozygosity of beta-Malay and beta degree thalassemia, 10 cases of beta-Malay and HbE and 18 cases of beta-Malay heterozygosity. Patients with beta-Malay and HbE had very mild clinical symptoms or were asymptomatic of thalassemia disease in the absence of blood transfusion. Homozygosity of beta-Malay produce mild clinical symptoms of thalassemic disease with normal facial characteristics and were not transfusion dependent. Patients with beta-Malay and IVS 1 nt 5 (G-C) had severe clinical symptoms, and were transfusion dependent. Patients with beta-Malay and beta degree thalassemia had severe clinical symptoms, delayed weight and height in relation to age, were transfusion dependent and had classical features of thalassemic diseases.

The spectrum of beta-thalassemia mutations in southern Thailand.

Beta-thalassemia mutations in 282 alleles of 253 unrelated individuals originating from various provinces in the south of Thailand were characterized by dot blot hybridization, specific PCR-amplification and direct DNA sequencing. It was possible to characterize the mutations in 274 (97.2%) of alleles studied. Twelve different point mutations and two different large deletions of the beta-globin gene were identified. Seven common mutations, namely 4 bp deletion at codons 41/42. IVS1 position 5 (G-C), codon 19 (AAC-AGC), codon 17 (AAG-TAG), IVS1 position 1 (G-T), position -28 (A-G) and 3.5 kb deletion, accounted for about 91.5%. The mutations at mRNA cap site + 1 (A-C) and IVS1 position 1 (G-A), previously undescribed in Thailand, were found in 1 and 2 individuals, respectively. A novel mutation of 105 bp deletion at the 5' end of beta-globin gene was detected in a family originating from this area. The knowledge from this study should be useful for planning of genetic counseling and prenatal diagnosis programs for patients with beta-thalassemia in the south of Thailand.

Molecular heterogeneity of beta-thalassemia in Thailand.

beta-Globin genes in 294 chromosomes of beta-thalassemia homozygotes and patients of beta-thalassemia/HbE in the northeast, the middle and the south of Thailand were analyzed by the PCR related techniques: dot blot hybridization, direct restriction assay, direct cloning and direct sequencing of the amplified DNA fragments. Twelve different mutations were detected at various frequencies. They are an A-G at-28, codon 19 (AAC-AGC), a G-T at IVS-1 nt1,a G-C at IVS-1 nt5, a C-T at IVS-2 nt654, a G addition in codons 8/9, a C deletion in codon 41, a 4 bp deletion in codons 41/42, an A addition in codons 71/72, an AAG-TAG in codon 17, a CAG-TAG in codon 26, a TAC-TAA in codon 35 and a 8 bp deletion in codons 123-125. We also developed allele specific-polymerase chain reaction to facilitate non-radioactive detection of the mutation. Origins and spread of mutations are speculated based on the results of determination of haplotypes and frameworks that are linked to the thalassemia alleles.

Antibody responses in human gnathostomiasis.

Sera from 4 patients with parasitologically confirmed gnathostomiasis and from 18 healthy individuals were studied by SDS-PAGE and Western blot analysis using radioiodinated protein A to detect antibody responses against crude aqueous somatic extract of advanced third stage larvae of Gnathostoma spinigerum (L3G). It was found that the L3G extract was highly complex, comprising of more than 40 polypeptides among which more than 20 components were antigenic in human. The relative M.W. of the proteins ranged from 13 kd to 150 kd with the major antigenic bands at 150, 135, 120, 94, 84, 82, 72, 55, 54, 49, 43, 38, 35, 32 and 28 kd. All 4 sera from gnathostomiasis patients gave almost an identical pattern of reactivities against the L3G antigens whereas sera from the normal individuals gave much lower reactivities against the L3G antigen of M.W. 38 kd and, in certain individuals, those of 49 and 43 kd. The present findings suggest that the serum antibody response against the parasite is specific and may be useful in a specific or a confirmed immunodiagnosis of human gnathostomiasis.