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Biomedical subjects

Duangporn Jamsai

Publications and source records attributed to Duangporn Jamsai.

9 recordsLinked to original sources
PubMed2006

A humanized BAC transgenic/knockout mouse model for HbE/beta-thalassemia.

Hemoglobin E (HbE) is caused by a G-->A mutation at codon 26 of the beta-globin gene, which substitutes Glu-->Lys. This mutation gives rise to functional but unstable hemoglobin and activates a cryptic splice site causing mild anemia. HbE reaches a carrier frequency of 60-80% in some Southeast Asian populations. HbE causes serious disease when co-inherited with a beta-thalassemia mutation. In this study, we report the creation and evaluation of humanized transgenic mice containing the beta(E) mutation in the context of the human beta-globin locus. Developmental expression of the human beta(E) locus transgene partially complements the hematological abnormalities in heterozygous knockout mice ((mu)beta(th-3/+)) and rescues the embryonic lethality of homozygous knockout mice ((mu)beta(th-3/th-3)). The phenotype of rescued mice was dependent on the transgene copy number. This mouse model displays hematological abnormalities similar to HbE/beta-thalassemia patients and represent an ideal in vivo model system for pathophysiological studies and evaluation of novel therapies.

Animals↗
PubMed2006

Humanized beta-thalassemia mouse model containing the common IVSI-110 splicing mutation.

Splicing mutations are common causes of beta-thalassemia. Some splicing mutations permit normal splicing as well as aberrant splicing, which can give a reduced level of normal beta-globin synthesis causing mild disease (thalassemia intermedia). For other mutations, normal splicing is reduced to low levels, and patients are transfusion-dependent when homozygous for the disease. The development of therapies for beta-thalassemia will require suitable mouse models for preclinical studies. In this study, we report the generation of a humanized mouse model carrying the common IVSI-110 splicing mutation on a BAC including the human beta-globin ((hu)beta-globin) locus. We examined heterozygous murine beta-globin knock-out mice ((mu)beta(th-3/+)) carrying either the IVSI-110 or the normal (hu)beta-globin locus. Our results show a 90% decrease in (hu)beta-globin chain synthesis in the IVSI-110 mouse model compared with the mouse model carrying the normal (hu)beta-globin locus. This notable difference is attributed to aberrant splicing. The humanized IVSI-110 mouse model accurately recapitulates the splicing defect found in comparable beta-thalassemia patients. This mouse model is available as a platform for testing strategies for the restoration of normal splicing.

Alternative Splicing↗
PubMed2006

Molecular mechanism of high hemoglobin F production in Southeast Asian-type hereditary persistence of fetal hemoglobin.

Hereditary persistence of fetal hemoglobin (HPFH) is associated with a high level of hemoglobin F (HbF) synthesis in adult heterozygotes. In this study, 2 of 6 unrelated HPFH Thai families were found to be Southeast Asian-type HPFH (SEA-HPFH) by analyses of the hematologic data and Southern blot hybridization with polymerase chain reaction-amplified DNA probes. DNA mapping with a probe for a delta-globin fragment showed a 27-kb deletion of DNA that included the beta-globin gene and the 3' deoxyribonuclease I hypersensitive site 1 (3'HS1) sequence downstream. Deletion of the insulator, 3'HS1, and the juxta-position of the HPFH-3 core enhancer downstream to the 3' breakpoint have been postulated to be the cause of high HbF production in these individuals. To test this hypothesis, we transfected K562 cells with 4 different bacterial artificial chromosome constructs containing the enhanced green fluorescent protein (EGFP) gene at the position of the Agamma-globin gene (pEBAC/148beta:EGFP). Flow cytometry was used to compare EGFP expression from the pEBAC/148beta:EGFP construct with the HPFH-3 core enhancer immediately 5' to the SEA-HPFH breakpoint (pEnH), from the pEBAC/148beta:EGFP construct with 8 kb of the breakpoint sequence and the HPFH-3 core enhancer (pSEA-HPFH), and from the construct with 3'HS1 followed by the pSEA-HPFH sequence (pSEA-HPFH_3pHS1). The results show that high HbF production in SEA-HPFH occurs from a deletion of the 3'HS1 sequence and the juxtaposition of the HPFH-3 enhancer downstream to the delta-globin gene.

Adolescent↗
PubMed2005

Transgene copy number-dependent rescue of murine beta-globin knockout mice carrying a 183 kb human beta-globin BAC genomic fragment.

We report the generation and characterisation of the first transgenic mice exclusively expressing normal human beta-globin ((hu)beta-globin) from a 183 kb genomic fragment. Four independent lines were generated, each containing 2-6 copies of the (hu)beta-globin locus at a single integration site. Steady state levels of (hu)beta-globin protein were dependent on transgene copy number, but independent of the site of integration. Hemizygosity for the transgene on a heterozygous knockout background ((hu)beta(+/0), (mu)beta(th-3/+)) complemented fully the hematological abnormalities associated with the heterozygous knockout mutation in all four lines. Importantly, the rescue of the embryonic lethal phenotype that is characteristic of homozygosity for the knockout mutation was also demonstrated in two transgenic lines that were homozygous for two copies of the (hu)beta-globin locus, and in one transgenic line, which was hemizygous for six copies of the (hu)beta-globin locus. Our results illustrate the importance of transgene copy number determination and of the hemizygosity/homozygosity status in phenotypic complementation studies of transgenic mice containing large heterologous transgenes. Transgenic mouse colonies with 100% (hu)beta-globin production from the intact (hu)beta-globin locus have been established and will be invaluable in comparative and gene therapy studies with mouse models containing specific beta-thalassemia mutations in the (hu)beta-globin locus.

Animals↗
PubMed2005

A humanized mouse model for a common beta0-thalassemia mutation.

Accurate animal models that recapitulate the phenotype and genotype of patients with beta-thalassemia would enable the development of a range of possible therapeutic approaches. Here we report the generation of a mouse model carrying the codons 41-42 (-TTCT) beta-thalassemia mutation in the intact human beta-globin locus. This mutation accounts for approximately 40% of beta-thalassemia mutations in southern China and Thailand. We demonstrate a low level of production of gamma-globins from the mutant locus in day 18 embryos, as well as production of mutant human beta-globin mRNA. However, in contrast to transgenic mice carrying the normal human beta-globin locus, 4-bp deletion mice fail to show any phenotypic complementation of the knockout mutation of both murine beta-globin genes. Our studies suggest that this is a valuable model for gene correction in hemopoietic stem cells and for studying the effects of HbF inducers in vivo in a "humanized" thalassemic environment.

Animals↗
PubMed2003

Insertion of common mutations into the human beta-globin locus using GET Recombination and an EcoRI endonuclease counterselection cassette.

A large number of mutations have been described in the human beta-globin locus causing thalassemia or various hemoglobinopathies. However, only a very limited number of these mutations have been studied in animal model systems in the context of the human beta-globin locus. We report here the use of the GET Recombination system with an EcoRI/Kan(R) counterselection cassette to facilitate the introduction of the HbE (codon 26, GAG-->AAG mutation and the codon 41-42 (-TTCT) deletion, two mutations found in high frequency in South-East Asia, into the human beta-globin locus. The counterselection cassette was first inserted into the target sequence in the beta-globin gene, and then a PCR fragment carrying the required modification was used to replace it. Efficient counterselection depends upon the tight regulation of the highly toxic EcoRI endonuclease gene by expression of lacI(q). Induction by IPTG during counterselection efficiently eliminates non-recombinant bacterial clones. The technique can be performed on any known gene sequence using current BAC technology, allowing identification and comparative functional analysis of key regulatory elements, and the development of accurate animal models for human genetic disorders.

Beta-Globulins↗
PubMed2003

Targeted modification of a human beta-globin locus BAC clone using GET Recombination and an I-Scei counterselection cassette.

There is a need for better approaches to allow precise engineering of large genomic BAC DNA fragments, to facilitate the use of intact genomic loci for therapeutic and biotechnology applications. We report an efficient method to insert any modification in any genomic locus, using a human beta-globin locus BAC clone as a model system. The modifications can range from single base changes to large insertions or deletions and leave no operational sequences. A counterselection cassette, consisting of an inducible I-SceI gene, its recognition site, and an antibiotic resistance gene, is inserted into the targeted region using GET Recombination. A PCR fragment carrying the modification but no selectable marker replaces the counterselection cassette in a second round of GET Recombination. The unique I-SceI site in the counterselection cassette is cut by I-SceI endonuclease, strongly selecting against nonrecombinant clones and yielding up to 30% correct recombinants.

Base Sequence↗
PubMed2003

Insertion of modifications in the beta-globin locus using GET recombination with single-stranded oligonucleotides and denatured PCR fragments.

We describe the use of the GET recombination system with oligonucleotides or single-stranded polymerase chain reaction (PCR) fragments to insert modifications in the human beta-globin locus without counterselection. The method involves recombination between oligonucleotides or denatured PCR fragments and homologous sequences in the beta-globin gene in a clone of 205-kb bacterial artificial chromosome (BAC), based on the inducible expression of the recE, recT, and gam genes. In this method, oligonucleotides or denatured PCR fragments are electroporated directly into cells carrying both the globin BAC and the pGETrec plasmid, after induction of the GET recombination system. Recombinant BAC clones are identified by PCR, using allele-specific amplification for the mutated sequences. We have used this approach to insert a unique restriction site as well as a common thalassemia mutation (stop codon 39, C-->T) into the human beta-globin locus. We have observed the frequency of recombinant clones to be as high as 1 in 100-200 clones. Therefore, this approach provides a simple and efficient method for introducing point mutations and other fine modifications into BACs, and should greatly facilitate the use of BACs for functional studies and therapeutic applications.

Base Sequence↗