Minimal residual disease detection in Tunisian B-acute lymphoblastic leukemia based on immunoglobulin gene rearrangements.

IGH gene rearrangement and IGK-Kde gene deletion can be used as molecular markers for the assessment of B lineage acute lymphoblastic leukemia (B-ALL). Minimal residual disease detected based on those markers is currently the most reliable prognosis factor in B-ALL. The aim of this study was to use clonal IGH/IGK-Kde gene rearrangements to confirm B-ALL diagnosis and to evaluate the treatment outcome of Tunisian leukemic patients by monitoring the minimal residual disease (MRD) after induction chemotherapy. Seventeen consecutive newly diagnosed B-ALL patients were investigated by multiplex PCR assay and real time quantitative PCR according to BIOMED 2 conditions. The vast majority of clonal VH-JH rearrangements included VH3 gene. For IGK deletion, clonal VK1f/6-Kde recombinations were mainly identified. These rearrangements were quantified to follow-up seven B-ALL after induction using patient-specific ASO. Four patients had an undetectable level of MRD with a sensitivity of up to 10-5. This molecular approach allowed identification of prognosis risk group and adequate therapeutic decision. The IGK-Kde and IGH gene rearrangements might be used for diagnosis and MRD monitoring of B-ALL, introduced for the first time in Tunisian laboratories.

Familial hematological malignancies: ASXL1 gene investigation.

PURPOSE: Familial aggregation among patients with several hematological malignancies has been revealed. This emphasizes the importance of genetic factors. Only few genes predisposing to familial hematological malignancies have been reported until now due to the low occurrence. We have described in previous study PRF1 and CEBPA variants that might contribute to the background of genetic factors, which encourage us to extend our investigations to other cooperating genes. The aim of this study is to determine whether germline additional sex combs-like 1 (ASXL1) gene mutations may be involved? METHODS/PATIENTS: In this study, we investigated the candidate gene ASXL1 by direct sequencing in 88 unrelated Tunisian and French families with aggregated hematological malignancies. RESULTS: We report a new p.Arg402Gln germline missense substitution in two related Tunisian patients which has not been previously described. We identified here this variant for the first time in non-Hodgkin lymphoma. The p.Arg402Gln variant was not found in 200 control chromosomes. In silico analysis has predicted potential deleterious effect on ASXL1 protein. CONCLUSIONS: From an extended candidate genes analyzed in the field of familial hematological malignancies, ASXL1 might be involved. This variant should be considered since a potential damaging effect was predicted by in silico analysis, with a view to develop functional assay in order to investigate the biological assessment.

Minimal residual disease detection in Tunisian B-acute lymphoblastic leukemia based on immunoglobulin gene rearrangements

IGH gene rearrangement and IGK-Kde gene deletion can be used as molecular markers for the assessment of B lineage acute lymphoblastic leukemia (B-ALL). Minimal residual disease detected based on those markers is currently the most reliable prognosis factor in B-ALL. The aim of this study was to use clonal IGH/IGK-Kde gene rearrangements to confirm B-ALL diagnosis and to evaluate the treatment outcome of Tunisian leukemic patients by monitoring the minimal residual disease (MRD) after induction chemotherapy. Seventeen consecutive newly diagnosed B-ALL patients were investigated by multiplex PCR assay and real time quantitative PCR according to BIOMED 2 conditions. The vast majority of clonal VH-JH rearrangements included VH3 gene. For IGK deletion, clonal VK1f/6-Kde recombinations were mainly identified. These rearrangements were quantified to follow-up seven B-ALL after induction using patient-specific ASO. Four patients had an undetectable level of MRD with a sensitivity of up to 10-5. This molecular approach allowed identification of prognosis risk group and adequate therapeutic decision. The IGK-Kde and IGH gene rearrangements might be used for diagnosis and MRD monitoring of B-ALL, introduced for the first time in Tunisian laboratories.

Molecular study of CEBPA in familial hematological malignancies.

Familial aggregation in patients with several haematological malignancies has been described, but the genetic basis for this familial clustering is not known. Few genes predisposing to familial haematological malignancies have been identified, among which RUNX1 and CEBPA have been described as predisposing genes to acute myeloid leukemia (AML). Recent studies on RUNX1 suggest that germline mutations in this gene predispose to a larger panel of familial haematological malignancies than AML. In order to strengthen this hypothesis, we have screened CEBPA for germline mutations in several families presenting aggregation of hematological malignancies (including chronic or acute, lymphoid or myeloid leukemias, Hodgkin's or non Hodgkin's lymphomas, and myeloproliferative or myelodysplastic syndromes) with or without solid tumours. Although no deleterious mutations were found, we report two novel and rare variants of uncertain significance. In addition, we confirm that the in frame insertion c.1175_1180dup (p.P194_H195dup) is a germline polymorphism.

Bovine serum brevin. Purification by hydrophobic chromatography and properties.

Brevin, an actin-severing protein present in serum from numerous mammals, has been purified to homogeneity from bovine serum, using hydrophobic chromatography as the last purification step. The physicochemical parameters of brevin have been established and some of them studied in the absence and presence of Ca2+. Brevin exhibits an apparent Stokes radius, Rs, of 3.4 nm, an intrinsic sedimentation coefficient S degrees 20, W, of 4.8 S and 4.4 S in the absence and presence of Ca2+ respectively, indicative of calcium-induced conformational change. The native molecular mass of brevin was found to be 68 kDa and the hydrodynamic data suggest that the protein is an asymmetric molecule. Sedimentation equilibrium studies demonstrated that Ca2+ affects the shape (asymmetry) of brevin without altering its molecular mass. Limited tryptic and chymotryptic digestion of brevin distinguishes the Ca2+-induced conformation from the EGTA one. No change in the electrophoretic migration of brevin was seen upon Ca2+ addition. Several isoforms were detected by two-dimensional gel electrophoresis. Brevin increases the rate of nucleation of actin but decreases the rate of elongation of the filaments and the steady-state viscosity of F-actin in substoichiometric amounts, as measured by viscometric assays under high shear conditions. Electron microscopic examination documents these effects. Brevin produces shorter actin filaments and binds to the 'barbed' end of filaments to which monomers add preferentially during elongation, as demonstrated by indirect immunogold staining of antibodies against brevin. Filament elongation occurs only at the slowly growing end. An enzyme-linked immunosorbent assay was developed and used to detect and quantify brevin and related proteins in extracts of different bovine cells and tissues. Liver and smooth muscles were found to contain the highest amounts of the severing protein.

Detection of antigen receptor gene rearrangements in lymphoproliferative malignancies by fluorescent polymerase chain reaction.

Monoclonal rearrangements of antigen receptor genes in lymphoproliferative diseases are characterized by the specific sequence and the length of their junctional region, which can be used as markers of the proliferating clone. PCR techniques have greatly simplified routine detection of monoclonal rearrangements. But on the one hand, identification of the sequences requires sequencing methods and on the other hand, sizing of rearrangements by conventional analysis of PCR products on agarose or nondenaturing polyacrylamide gels may be uncertain. We have developed an approach based on amplification of rearranged IGH, TCRG and TCRD locus by fluorescent PCR associated to a computerized analysis of generated PCR products allowing their objective sizing. We tested this method on DNA samples from patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia, whose pattern of IGH and TCRG rearrangements had been previously identified by Southern blot techniques. TCRG-PCR assay allowed detection of 100% of rearranged samples. No false-negative results were found but a high rate (60%) of Southern-negative and PCR-positive samples were identified. TCRD PCR-assay detected VD1-JD1 or VD2-D2/3 rearrangements in both acute lymphoblastic leukemia and chronic lymphocytic leukemia samples. IGH PCR assay permitted detection of all known rearranged samples. The sensitivity of these three different PCR assays (1% leukemic cells) was equivalent to that of other published PCR protocols. These results show the validity and reliability of the fluorescent PCR method for routine detection of IGH, TCRG and TCRD rearrangements. Sizing of PCR products by computerized analysis was also validated. It provides additional information on rearrangement patterns in lymphoproliferative diseases, as clonal rearrangements can be recognized by their size. This can be of great interest in various circumstances, particularly for detection and follow-up of oligoclonality.

The human T-cell receptor gamma variable pseudogene V10 is a distinctive marker of human speciation.

The V10 variable gene of the human T-cell receptor gamma locus (TCRG-V10), the only member of the subgroup III, has a structural defect which inhibits the splicing of the leader intron. We show that there is a single point mutation in the V10 leader donor splice site responsible for this situation and that this mutation is found in the different populations tested, indicating that V10 corresponds to a pseudogene in humans. We restored the splice site by mutagenesis and obtained correct splicing in vitro. Analysis of the V10 germline gene in different primates reveals functional splice sites in the closest human apes, the chimpanzee and the gorilla. The splice competence of TCRG-V10 in higher primates was addressed in peripheral blood lymphocytes from chimpanzee by specific cDNA amplification, and correct splicing of the TCRG-V10 leader intron was found as well as a majority of in frame rearrangements involving only the TCRG-J1 or J2 segments. These results suggest that V10(+)gamma /delta T cells may represent an important subset in the non-human higher primates, contrary to the situation observed in the human.

Polymorphism of the T-cell receptor gamma variable and constant region genes in a Chinese population.

The human T-cell receptor gamma gene region spans 160 kb genomic DNA. Restriction fragment length polymorphisms (RFLPs) have been previously documented for the constant region (TRGC) genes, the joining (TRGJ) segments and the variable (TRGV) genes. We have recently defined the alleles of the T-cell receptor gamma V, J and C genes and we have described seven haplotypes of the V gamma subgroup I genes characterized either by RFLPs or by deletion or insertion of V gamma genes. The number of V gamma I genes may vary from 7 to 10 per haploid genome, the 9-gene haplotype being the most frequent. Allelic fragments can unambiguously characterize the TRGC2 gene with duplication or triplication of the exon 2. These alleles and haplotypes have been analyzed in four different populations (French, Lebanese, Tunisian and Black African). In this paper, we compare these allele and haplotype frequencies with those found in a Chinese population and we describe new TRGV allelic restriction fragments found only in the Chinese samples. These results and the previous data demonstrate the flexibility of the human T cell receptor gamma locus and the importance of unequal crossing-overs in the evolution of that locus. Moreover, they underline the importance of studying these polymorphisms in population genetics.

First study of immunoglobulin and T cell receptor gene rearrangements in chronic and acute lymphoblastic leukemias from Tunisia.

We report the first characterization at the immunological and molecular level of 12 cases of chronic lymphocytic leukemia (CLL) and acute lymphoblastic leukemia (ALL) from Tunisia. Our results show biallelic IgH gene rearrangement in B-CLL (6/6). A high ratio of T-ALL (4/6) was observed in Tunisian ALL leukemias. One T-ALL expressed CD10 (common ALL) which has already been found in some other cases of T-ALL. We report the occurrence of T cell receptor (TCR) beta and/or gamma gene rearrangements in two precursor B-ALL patients who had normally rearranged Ig genes. In one precursor B-ALL case, multiple rearranged IgH and TCR gamma bands allowed the identification of three clones. Such an oligoclonal ALL is interesting since only rare biclonal TCR beta or gamma gene rearrangements have been described.

Isolation of T cell receptor gamma/delta chain constant genes from minke whale.

The polymerase chain reaction using oligonucleotides based on consensus sequences from other species allowed us to amplify minke whale (Balaenoptera acutorostrata) T cell receptor (TcR) gamma and delta constant genes. Two types of Cgamma clones were obtained which only differ by one mismatch. These minke whale Cgamma clones showed 83% nucleotide and 70% amino acid sequence similarity to the corresponding region of the human TRGC genes. The minke whale Cdelta sequences were all identical, and showed 86% nucleotide and 77.8% amino acid sequence similarity to the human TRDC gene. The whale Cgamma and Cdelta clones were used as probes for Southern blot analysis. The data confirmed that there is a unique Cdelta gene in minke whale. Two different Cgamma genes were detected, one of them also cross-hybridizing with a human Cgamma probe, suggesting that the Cgamma locus in minke whale consists of at least two different constant genes.