Search PubMed⌕ Search

Biomedical subjects

T H Huisman

Publications and source records attributed to T H Huisman.

At least 55 records · Page 3Linked to original sources
PubMed1996

The importance of the 3' untranslated region for the expression of the alpha-globin genes.

With a reverse transcription-polymerase chain reaction procedure, we have determined the relative quantities of alpha 2- and alpha 1-mRNA in several patients with heterozygosities for alpha 2- or alpha 1-globin gene mutations, in subjects with two forms of alpha-thalassemia-2 (-3.7 kb; -4.2 kb), and in two children with an alpha-globin gene triplication. Mutations in either one of the two genes do not affect the mRNA production, and the alpha 2- to alpha 1-mRNA ratios in our heterozygotes are the same (approximately 2.7) as in normal persons with four alpha-globin genes, while the alpha/alpha X ratios of approximately 1.7 for alpha 2 variants and of approximately 6.2 for alpha 1 variants agree with the theoretic values. The deletion of 3.7 kb (leading to the formation of the alpha 2 alpha 1 hybrid gene) and of 4.2 kb (resulting in the presence of only the alpha 1 gene) causes the alpha 2/alpha 1 ratio to decrease to approximately 1.7, indicating that both are expressed as an alpha 1 gene. Data obtained for an Hb G-Philadelphia heterozygote (alpha alpha/-alpha G) show that the alpha 2 alpha 1 hybrid gene produces approximately 30% less mRNA than an alpha 1-globin gene on a normal chromosome, which may be caused by loss of some sequences 3' to the alpha 2 gene. The same may be the case for the alpha 1-globin gene on the chromosome with the 4.2 kb alpha-thal-2 deletion. These results suggest an important role for sequences located 3' to the terminating codon in regulating transcription. Support for this hypothesis was obtained from data for the two children with an alpha-globin gene triplication; the high alpha 2/alpha 1-mRNA ratio can be explained by assuming that the alpha 1 alpha 2 hybrid gene of the alpha 2(alpha 1 alpha 2)alpha 1 triplication expresses as an alpha 2 gene.

Gene Deletion↗
PubMed1996

The relative levels of different types of beta-mRNA and beta-globin in BFU-E derived colonies from patients with beta chain variants; further evidence for somatic mosaicism in the Hb Costa Rica carrier [beta 77(EF1)His-->Arg].

We have identified and quantitated the different types of mRNA in single BFU-E derived colonies from Hb S and Hb Atlanta [beta 75 (E19)Leu-->Pro] heterozygotes and observed that the normal and mutated mRNAs were present in equal quantities. Similar studies for the different protein products gave less accurate data because high performance liquid chromatography methods were not sensitive enough for the analysis of a single colony, and as many as five colonies needed to be combined. The level of Hb S (approximately 40%) was the same as in red cell lysates of the Hb S heterozygote, while that of the unstable beta-Atlanta chain was lower than expected from the values observed in red cells. Similar studies for a carrier of the stable Hb Costa Rica [beta 77(EF1) His-->Arg] which was reported to be the result of a somatic cell mutation (1) gave quite different data. Dot-blot analysis with 32P-labeled probes and allele specific amplification methodology identified numerous colonies with beta A-mRNA only, while 12-15% of the colonies contained both beta A- and beta-Costa Rica-mRNA. This limited distribution of the beta-Costa Rica-mRNA was confirmed by hemoglobin analysis with anion exchange high performance liquid chromatography. These results are considered to provide additional and convincing evidence for a somatic mosaicism for the CAC-->CGC mutation at codon 77 of the beta gene which occurred during the development of the embryo and results in the presence of only some 6-8% of the abnormal Hb Costa Rica in the circulating red cells.

Erythroid Precursor Cells↗
PubMed1996

Hb Costa Rica or alpha 2 beta 2 77(EF1)His --> Arg: the first example of a somatic cell mutation in a globin gene.

We have identified a minor hemoglobin component (approximately 5%) in the blood of a healthy Costa Rican female, but not in her mother and two brothers (father not studied), that has an His --> Arg replacement at position beta 77 (Hb Costa Rica). No other amino acid replacements were observed and no beta- or gamma-chain-like peptides were present. Hb Costa Rica has abnormal stability. Sequence analyses of numerous polymerase chain reaction (PCR)-amplified segments of DNA that contain exon 2 of the beta gene failed to identify a CAC --> CGC (His --> Arg) mutation. The same was the case when cDNA was sequenced, indicating that a beta-Costa Rica-mRNA could not be detected with this procedure. Gene mapping of genomic DNA with Bg/II, BamHI, and HindIII gave normal fragments only and with the same intensity as observed for the fragments of a normal control. The quantities of the beta chain variants Hb J-Iran and Hb Fukuyama with related mutations at beta 77 vary between 30% and 45% in heterozygotes, whereas that of Hb F-Kennestone with the same His --> Arg mutation but in the G gamma-globin gene, is a high 40%-45% (as percentage of total G gamma) in a heterozygous newborn. These different observations exclude a heterozygosity of the A --> G mutation at codon beta 77, as well as a deletion comparable to that of Hbs Lepore or Kenya, or a beta-globin gene duplication, and point to a nontraditional inheritance of Hb Costa Rica. Allele-specific amplification of cDNA with appropriate primers identified the presence of a low level of mutated mRNA in the reticulocytes of the patient, which was confirmed by dotblot analysis of the same material with 32P-labeled probes. Comparable amplification products were not observed in genomic DNA. The A --> G mutation apparently occurred in a somatic cell at a relatively early stage in the development of the hematopoietic cell system, and Hb Costa Rica accumulated through rapid cell divisions in patchy areas in the bone marrow (somatic mosaicism). An unequal distribution of Hb Costa Rica over the red cells supports this possibility.

Adult↗
PubMed1995

A second, elongated, alpha 2-globin mRNA is present in reticulocytes from normal persons and subjects with terminating codon or poly A mutations.

With an RT-PCR procedure we have identified a second, elongated, alpha 2-globin mRNA in reticulocytes of normal persons and of patients with alpha-thal, particularly those with mutations in the terminating codon (TAA-->CAA; Hb Constant Spring; TAA-->TAT, Hb Paksé) or in the poly A site (AATAAA-->AATAAG). This type of mRNA is elongated because a result a cryptic poly A site 1048 bp past the terminating codon is used. Even some 5% of the alpha 2-mRNA of normal persons is of the elongated type. Quantitative data suggest high levels of this mRNA in heterozygous and homozygous carriers of poly A mutations and low levels in patients with the terminating codon mutations. Hematological and Hb data suggest that translation of these elongated mRNAs is minimal. No elongated alpha 1-mRNA has been observed.

Base Sequence↗
PubMed1995

Reverse dot-blot detection of the African-American beta-thalassemia mutations.

DNA-based diagnosis of the beta thalassemias provides accuracy to newborn screening genetic counseling, and prenatal diagnosis. However, the use of polymerase chain reaction (PCR)-based methods is challenged by the great number of different-beta-thalassemia mutations that exist even within defined ethnic groups. In this regard, the reverse dot-blot method offers a means of screening for several mutations with a single hybridization reaction. We have applied the reverse dot-blot method to the detection of the beta-thalassemia mutations of African-Americans. We used two biotin-labeled primer pairs in a duplex reaction to amplify and label two beta-globin target DNA fragments that encompass all known African-American beta-thalassemia mutations. The PCR products were denatured and hybridized to polyT-tailed, membrane-fixed, allele-specific probe pairs for the hemoglobin (Hb) S, Hb C, and 14 beta-thalassemia mutations and their corresponding wild-type sequences. Seven common mutations plus Hb S and Hb C were included on one diagnostic strip, and seven less common beta-thalassemia mutations were included on another strip. Carefully controlled, high stringency hybridization allowed accurate distinction of these alleles. Reverse dot-blot diagnosis of the less common beta-thalassemia mutations precludes the need for alternative, more technically challenging methods. This method provides a rapid, accurate method for diagnosis of beta thalassemia among African-Americans and other ethnic groups in which beta thalassemia occurs.

Base Sequence↗
PubMed1995

Genetic heterogeneity of beta-thalassemia in southeast Sicily.

In this study we have defined the spectrum of the beta-thalassemia mutations, the beta-thalassemia haplotypes, and the genotype-to-phenotype correlations in a large number of patients with different beta-thalassemia conditions. Seventeen different beta-thalassemia mutations were detected which included one chromosome each with Hb Dhonburi and Hb Lepore. Five alleles, namely, codon 39 (C-->T), IVS-I-110 (G-->A), IVS-I-6 (T-->C), IVS-II-745 (C-->G), and IVS-I-1 (G-->A), account for 90% of all beta-thalassemia mutations in 846 thalassemic chromosomes studied. Haplotyping for a large number of subjects showed that the five common mutations are linked to a few haplotypes. The presence of milder mutations, mainly IVS-I-6 (T C), in about 19% of our patients explains some of the clinical variables. Among the 37 patients with thalassemia of intermediate severity, only 6 were homozygous or compound heterozygous for two severe alleles. The type of beta-thalassemia is the main factor responsible for differences in the phenotypic expression of the disease in patients with Hb S-beta-thalassemia; patients with Hb S-beta(+)-thalassemia are less severely affected than those with Hb S-beta(0)-thalassemia. The five most frequent mutations have comparable distributions all over Sicily.

Fetal Hemoglobin↗
PubMed1995

Isobutyramide therapy in patients with sickle cell anemia.

We have administered Isobutyramide as a suspension over a period of 3 months, from a starting dose of 50 mg/kg/day up to 150 mg/kg/day, to four adult sickle cell (SS) anemia patients. The maximum dose was maintained for 3 weeks. The blood counts remained stable and the Hb F levels decreased slightly. The G gamma levels increased at the end of the trial, suggesting activation of the G gamma gene at the highest dose of Isobutyramide. Three patients showed a stable rate of hemolysis, while in one patient, an increase of lactate dehydrogenase occurred. None of the patients experienced pain crisis or organ-specific crisis, but all four complained about mild epigastric burning and a bitter taste. After the first month of treatment one patient complained about intolerable epigastric discomfort which was relieved by Omeprazole. Another patient complained about increasing dyspepsia in the 12th week leading to the termination of the trial. Oral Isobutyramide administration does not qualify as an effective treatment of SS patients.

Adult↗
PubMed1995

Hb Lulu Island (alpha 2 beta 2 107[G9]Gly-->Asp)-beta zero- thalassemia (codon 15; TGG-->TAG), a form of thalassemia intermedia.

Hb Lulu Island [beta 107(G9)Gly-->Asp] was discovered in an East Indian female who carried a common beta zero-thalassemia allele, i.e., codon 15, TGG-->TAG (is a stop codon) in trans. Both abnormalities were detected through sequencing of the amplified beta-globin genes and were confirmed by hybridization with 32P-labeled probes. Hb Lulu Island is mildly unstable with a borderline decrease in oxygen affinity; its instability is less severe than that of Hb Burke or beta 107(G9)Gly-->Arg. The compound heterozygosity expresses as a thalassemia intermedia with moderate anemia, a variable need for blood transfusions, Heinz body formation, and a red cell morphology which is typical for such a condition. The level of HbA2 was greatly increased (6.5-7.0%) as was the delta chain level (12% of total non-alpha) probably because of the instability of Hb Lulu Island and the decreased ability of the beta x chain to form dimers with the normal alpha chain.

Adult↗
PubMed1995

alpha-Thalassaemia in the population of Cyprus.

We have determined the alpha-thalassaemia (alpha-thal) determinants in 78 patients with Hb H disease from Cyprus; 25 were Turkish Cypriots and 53 were Greek Cypriots. Four deletional and three non-deletional alpha-thal alleles were present; the -alpha(3.7 kb) alpha-thal-2 and the --MED-I alpha-thal-1 were most frequently seen; --MED-II and -(alpha)20.5 deletions occurred at considerably lower frequencies. About 15% of all chromosomes carried a non-deletional alpha-thal-2 allele; of these the 5 nucleotide (nt) deletion at the first intervening sequence (IVS-I) donor splice site was present in approximately 8% of all chromosomes. Two types of polyadenylation signal (poly A) mutations were observed. No striking frequency differences were seen between Greek and Turkish Cypriot patients. Combinations of the various types of alpha-thal resulted in eight different forms of Hb H disease. The phenotypes were comparable except for great variations in the level of Hb H which was highest (average approximately 22%) in the 12 patients with the alpha 5nt alpha/--MED-I combination. One patient with the same form of Hb H disease but with an additional beta-thal (IVS-I-110,G-->A) heterozygosity had a most severe microcytosis and hypochromia with < 1% Hb H. Variations in the level of Hb H might correlate with the severity of the disease, although this was not evident from the haematological data.

Alleles↗
PubMed1995

Identification of several alpha-globin gene variations in a small Laotian family.

The present study concerns the identification of four alpha-globin gene deficiencies, one alpha 1-globin gene mutation, and one beta-globin gene mutation in a Laotian couple and their newborn baby. The parents were Hb E heterozygotes and the baby was an Hb E homozygote. The father carried the 4.2-kb deletion on one chromosome and a TAA-->CAA mutation at the terminating codon of the alpha 2-gene (Hb Constant Spring or CS) on the other chromosome. Moreover, the remaining alpha 1-globin gene on the chromosome with the 4.2-kb deletion was mutated at codon 74 (GAC-->CAC; Asp-->His; Hb Q-Thailand). The mother had the 3.7-kb deletion on one chromosome and a TAA-->TAT mutation at the terminating codon of the alpha 2-globin gene (Hb Paksé) of the second chromosome. The baby was a compound heterozygote for the two termination codon mutations and, at birth, had a high level of Hb Bart's (16.6%) reflecting a mild form of Hb H disease.

Adult↗
PubMed1995

Sickle cell anemia identified in a multiple-transfused patient through analysis of mRNA with an RT-PCR-based technique.

We report the identification of an Hb S homozygosity in a 29-year-old multiple-transfused patient with severe kidney disease using a new reverse-transcription polymerase chain reaction (RT-PCR) technique with mRNA as starting template. The procedure requires considerably less time than sequencing of genomic DNA and is recommended for use in the diagnosis of Hb S and other hemoglobinopathies.

Adult↗
PubMed1995

[Structural variants in hemoglobin occurring in the Czech Republic].

The authors present a review of clinical and laboratory findings of seven in the Czech Republic hitherto diagnosed structural haemoglobin variants. Unstable variants are found most frequently: Hb-Köln, Hb-St. Louis, Hb-Nottingham, Hb-E and Hb-Hradec Králové. The variant Hb-Hradec Králové (Hb-HK) or alpha 2 beta 2 115 (G17) Ala-Asp was newly detected. The great instability of Hb-HK chains makes classical diagnosis of Hb-pathy impossible. It was possible to identify it only at a molecular genetic level. A manifestation of Hb-HK instability is also the thalassaemic feature of the disease and the formation of Heinz bodies from free chains. The only representative of haemoglobins with a high oxygen affinity identified in this country was newly detected. It was given the name Hb-Olomouc or alpha 2 beta 2 86 (F2) Ala-Asp. This haemoglobin variant leads to erythrocytosis in father and son and the same clinical manifestations were recently described also in Japan. The last structural variant of haemoglobin found in this country is Hb-M Milwaukee or alpha 2 beta 2 67 (E11) Val-Glu which in our patients is manifested rather by haemolysis with formation of Heinz bodies than classical cyanosis. The cause of instability of Hb-M in our patients is not known. Hb-S was not diagnosed so far in the Czech Republic.

Adolescent↗