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Several mutations in the cystic fibrosis (CF) gene have been reported. Ten, including the most prevalent mutation in Caucasians, delta F508, are located in exon 10 of the gene, in addition to five sequence polymorphisms. We have previously presented a strategy based on denaturing gradient gel analysis for the rapid detection of any nucleotide variation in all the exons and their immediate flanking regions. We now report the application of this method to the simultaneous detection of all mutations and polymorphisms located in exon 10, together with the use of exon 10 polymorphisms, especially the most frequent one (M470V), as intragenic markers for prenatal diagnosis of cystic fibrosis in families with at least one affected child and unknown disease-causing mutations.

We describe a scanning procedure for the detection of beta-globin gene mutations and the prenatal diagnosis of beta-thalassemias. The method is based on the combined use of PCR and denaturing gradient gel electrophoresis (DGGE) of six amplified fragments encompassing the whole beta-globin coding region and splice junctions, as well as the promoter and 3' untranslated regions. The whole beta-globin gene can be rapidly scanned for the presence of deleterious mutations. The proposed diagnostic strategy provides a major improvement over current approaches to beta-globin gene analysis in both research and clinical laboratories, especially those which analyse DNA samples from individuals belonging to various ethnic or population groups. The use of this procedure has enabled us to detect six novel sequence changes in the beta-globin gene, including two deleterious mutations and four polymorphisms.

Genomic DNA from 170 unrelated hemophilia A patients was examined for gene defects in the coding region of the Factor VIII gene. Exons 18, 22-24 and 26 contain a CGA codon for arginine within the recognition sequence for the restriction enzyme Taq I. These five sites were amplified by the polymerase chain reaction and tested for abnormal Taq I restriction patterns. In five cases, the enzyme Taq I failed to digest the amplified fragments. Direct sequencing of the amplified products demonstrated a C to T transition in the coding strand of exons 18, 22 and 24 in three severe hemophilia A patients resulting in TGA termination codons. Two patients showed G to A transition in exons 24 and 26 reflecting a C to T transition in the non-coding strand substituting a glutamine for an arginine. Three deletions involving exon 26 and one exons 23-26 were found in severe hemophiliac patients. In contrast, exons 23 and 24 failed to amplify in one patient with a moderate form of the disease suggesting an in-frame splicing of exons 22 and 25. Exon 8 and the 3' end of exon 14 were analyzed by denaturing gradient gel electrophoresis (DGGE). Two patients with a moderate form of the disease demonstrated an abnormal electrophoretic pattern in exon 8 and sequencing demonstrated missense mutations at codon 372 for arginine within a thrombin activation site. One missense mutation was a C to T transition substituting cysteine for arginine and the other was an infrequent G to C transversion at an adjacent nucleotide changing the same arginine to proline.(ABSTRACT TRUNCATED AT 250 WORDS)

Thirty-three Tunisian patients, homozygous for Hb S, were examined. Haplotyping using nine restriction sites in the beta-globin gene cluster revealed that the most common type is the Benin type [---- + - + - +] which occurs at a frequency of 0.94% (31 cases); only one patient was homozygous for an atypical haplotype which shows some differences with the Benin haplotype at sites 1, 5, 6, and 8 [+ ---- + + + +]; the two remaining patients were assumed to be double heterozygotes for the Benin and atypical haplotypes. The presence of the atypical haplotype suggested a double origin of the beta S gene in Tunisia. Moreover, a heterogeneity in the Hb F production was observed, ranging between 2 to 16%, whereas the G gamma-globin expression was remarkably homogeneous in our patients with a normal amount approaching 40%. These results suggested the presence of a combination of several control factors.

We have determined the frequency of the cystic fibrosis (CF) delta F508 mutation in a large sample of CF patients originating from different areas of France, including the greater Paris, Brittany, Alsace, Lorraine and Rhône-Alpes regions. A total of 422 CF chromosomes were studied, and the defect was found to account for 75% of the mutant alleles. In the course of the survey, a rare nucleotide sequence polymorphism leading to an isoleucine to valine substitution at position 506 of the CF transmembrane conductance regulator protein has been characterized in an unaffected individual. Our data enable the evaluation of the probabilities that a chromosome negative for the delta F508 mutation carriers another CF defect.

The cystic fibrosis (CF) gene was recently identified as a gene spanning 250 kilobases (kbp) and coding for a 1480 amino acid protein, cystic fibrosis transmembrane conductance regulator (CFTR). Approximately 70% of CF mutations involve a three-base-pair deletion in CFTR exon 10, resulting in the loss of a phenylalanine at position 508 in the gene product (delta F508). In order to screen for other molecular defects, we have used a strategy based on denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified gene segments. This method, which permits rapid detection of any sequence change in a given DNA stretch, was used successfully to analyse 61 non-delta F508 CF chromosomes from French CF patients. A study of CFTR exons 10, 11, 14a, 15 and 20 detected three mutations located in exons 14a, 15 and 20, along with several nucleotide sequence polymorphisms. These nucleotide changes were identified by direct sequencing of PCR fragments displaying altered electrophoretic behaviour, together with some of the polymorphisms and mutations previously characterized by others. The strategy presented here constitutes a valuable tool for the development of carrier testing for individuals or couples with a family history of cystic fibrosis, and will contribute to deciphering the functionally important regions of the CFTR gene.

The polymerase chain reaction (PCR) allows the detection of minimal amounts of nucleic sequences and has been successfully used to test for the chronic myeloid leukemia-specific bcr/abl transcripts. We studied blood samples from 17 patients who had undergone allogeneic bone marrow transplantation for CML, using a modified polymerase chain reaction-based assay for the detection of leukemic mRNA. This nested PCR technique was found to be highly sensitive, detecting the chimeric bcr/abl transcript in 16 of 17 patients including several long-term survivors. Cytogenetic techniques failed to detect Ph mitoses. The clinical significance of the persisting bcr/abl transcript for long periods following BMT is poorly understood and remains to be elucidated by further studies.

We have determined the spectrum of mutations producing beta-thalassemia (beta-thal) in Tunisia by direct DNA analysis using hybridization with allele-specific oligonucleotide probes and restriction endonuclease assay. In all, 34 unrelated beta-thal patients originating from different parts of the country were available for study. The beta-globin gene cluster of each was subjected to haplotype analysis, and on the basis of this analysis, we tested each patient's DNA for one or more mutations previously shown to be linked to that haplotype. We identified four previously unreported haplotypes and found that this population differs from others in Mediterranean areas in the frequency of the beta-thal haplotypes, the unexpected observation being the high frequency of haplotype IX. Six different point mutations were found, accounting for 62% of beta-thal genes in this Tunisian population. The molecular defects known to be the most frequent in Mediterraneans (nonsense codon 39, IVS1 nt 110, IVS1 nt 6) only make up 37% of the mutant genes. One as yet undescribed mutation (IVS1 nt 2 T----G) was identified by molecular cloning and sequencing. Our results should help the implementation of a prenatal diagnosis program for beta-thal in Tunisia.

We report the study by restriction mapping of alpha genes in a case of Hb H disease in Tunisia. The genotype is: -alpha/-alpha which by itself is not usually responsible for the HbH phenotype. We postulate that the two remaining alpha genes are dysfunctional, this is under study.

In order to perform prenatal diagnosis of beta-thalassemia by DNA analysis in Tunisia, we investigated molecular defects and their frequencies. We have determined which haplotypes are associated with beta zero or beta +-thalassemia phenotypes. Six of the haplotypes described by Orkin were observed among 15 patients homozygous for beta zero (11) or beta +-thalassemia (4). We also investigated the molecular defects. The frameshift mutation in codon 6, characterized by Mst II seems more frequent than the beta 39 non sense mutation indicating that Tunisian patients differ from other Mediterranean patients from Algeria or Italy. Results concerning beta +-thalassemia are too preliminary to draw any conclusion. The study is currently being enlarged with other molecular probes and restriction enzymes.

Double heterozygotism Hb E-beta zero thalassemia was discovered in two children born to an Alaouite Syrian family. Clinical, biological and radiological findings were similar to those in Cooley disease. Splenectomy allowed reduction in the frequency of blood transfusions. Hb E disease is frequent in South East Asia and results in a mild hemolytic anemia in homozygous patients. Hb E disease is a thalassemia syndrome with decrease production of beta E RNA messenger, and imbalanced alpha/beta E chains. Association with the thalassemia gene increases the imbalanced of chain synthesis explaining the severity of the disease. These were the first cases of Hb E-thal in Syria.

Deficiency in coagulation factor IX, a plasma glycoprotein constituent of the clotting cascade, results in hemophilia B, an inherited recessive X-linked bleeding disorder. Some affected individuals, referred to as antigen positive or CRM+, express an inactive factor IX gene product at normal levels and are expected to have natural mutations altering domains of the molecule that are critical for its correct function. The serine protease catalytic domain of activated factor IX, encoded by exons VII and VIII of the gene, is a possible target for such mutations. We designed a strategy allowing rapid analysis of this region through enzymatic amplification of genomic DNA, analysis of the amplification products by denaturing gradient gel electrophoresis, and direct sequencing of the fragments displaying an altered melting behavior. This procedure permitted us to characterize two previously undescribed mutations. Factor IX Angers is a G-to-A substitution generating an Arg in place of a Gly at amino acid 396 of the mature factor IX protein. Factor IX Bordeaux is an A-to-T substitution introducing a nonsense codon in place of the normal codon for Lys at position 411. Moreover, the already described factor IX Vancouver defect was found in three apparently independent families. These results provide further insight into the molecular heterogeneity of hemophilia B. In addition, we demonstrate the usefulness of this rapid screening procedure, which has broad applications in human genetics and can be used as an alternative to RFLP analysis in carrier detection or prenatal diagnosis studies.

A murine model of sickle cell disease was tested by studying the polymerization of hybrid hemoglobin tetramers between alpha mouse and human beta S or beta S Antilles chains were prepared from Hb S Antilles, which was a new sickling hemoglobin inducing a sickle cell syndrome more severe than Hb S. The hybrid molecules did not polymerize in solution, indicating that the mouse alpha chains inhibited fiber formation. Consequently, a mouse model for sickle cell disease requires the transfer and expression of both alpha and beta S or beta S Antilles genes.

The development of molecular biology techniques has considerably increased our knowledge of the gene and its functioning. When applied to haemophilia, these techniques make it possible to identify the genes involved, to analyse their structure and to explain how their function is altered by mutations. This has resulted in the used of new methods of diagnosis, prevention and treatment.

We have delineated the molecular lesions causing beta-thalassemia in Spain, a country that has witnessed the passage of different Mediterranean populations over the centuries, in order to evaluate the extent of heterogeneity of these mutations and to make possible simplified prenatal diagnosis of the disorder in that country. The use of the polymerase chain-reaction (PCR) technique to preferentially amplify beta-globin DNA sequences that contain the most frequent beta-thalassemia mutations in Mediterraneans enabled us to rapidly analyze 58 beta-thalassemia alleles in a dot-blot format either by hybridization with allele-specific radiolabeled oligonucleotide probes or by direct sequence analysis of the amplification product. The Spanish population carries seven different beta-thalassemia mutations; the nonsense codon 39 is predominant (64%), whereas the IVS1 position 110 mutation, the most common cause of beta-thalassemia in the eastern part of the Mediterranean basin, is underrepresented (8.5%). The IVS1 mutation at position 6 accounts for 15% of the defects and leads to a more severe form of beta+-thalassemia than originally described in most of the patients we studied. In this study, we demonstrate further the usefulness of the dot-blot hybridization of PCR-amplified genomic DNA in both rapid population surveys and prenatal diagnosis of beta-thalassemia.