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C J Larsen

Publications and source records attributed to C J Larsen.

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

Dual localization of the human gene encoding hnRNP I/PTB protein to chromosomes 19p13.3 and 14q23.

A cDNA probe representative of the human hnRNP I/PTB gene was used to perform fluorescence in situ hybridization (FISH) on metaphases of human chromosomes. A new localization was found on band 19p13.3 in addition to the previously reported localization to band 14q23. Identical results were obtained when FISH analysis was repeated with probes covering different parts of the hnRNP I cDNA clone. This supported the notion that most, if not all, of the sequences of the different parts of this clone are present on both chromosomes. Moreover, Southern blot analysis of DNAs from interspecies somatic hybrids containing chromosomes 19 and 14 revealed that the whole hnRNP I cDNA probe generated very similar patterns in each hybrid DNA. These data suggest that two closely related copies of the hnRNP I gene exist in the human genome.

Blotting, Southern↗
PubMed1996

Presence of three recurrent chromosomal reaarrangements, t(2;3)(p12;q37), del(8)(q24), and t(14;18), in an acute lymphoblastic leukemia.

A complex chromosomal abnormality associating three recurrent rearrangements, t(2;3)((p12;q37), del (8)(q24) and t(14;18)(q32;q21), was detected in a patient with acute lymphoblastic leukemia of the Burkitt type. Southern blot studies showed rearrangements of the MYC, BCL2, and JH genes, thus confirming the cytogenetic data. However, no rearrangement of the LAZ3/BCL6 gene, normally localized on band 3q27, could be detected. The simultaneous presence of three recurrent rearrangements specific for lymphoid malignancies addresses the question of their timing in the malignant process and the prognostic significance of the association of such anomalies.

Adult↗
PubMed1995

A new type of p16INK4/MTS1 gene transcript expressed in B-cell malignancies.

Chromosome band 9p21-22 is frequently altered by nonrandom abnormalities, mainly deletions, in hemopoietic malignancies of the lymphoid lineage. We have analysed a translocation t(9;14)(p21-p22;q11) in a B-cell type acute lymphoblastic leukemia. Location of the 14q11 breakpoint within the TCR-alpha/delta locus allowed the isolation of a fusion transcript composed of a 3' segment containing part of the constant region of the TCR-alpha gene and a 5' segment from chromosome 9, designated 0.18. This 0.18 segment was also part of cDNAs isolated from two tumoral B-cell lines (RPMI-8226, Raji). In both cases, 0.18 was juxtaposed 5' to a sequence corresponding to exons 2 and 3 of the p16INK4/MTS1 gene which is located on band 9p21-22. Unexpectedly, none of the two ATG codons found in 0.18 was in phase with that of the exons 2 and 3 of p16INK4/MTS1. Furthermore, in vitro translation product of a RPMI-8226 cDNA clone generated a product that was not immunoprecipitated by antibodies specific of the C-terminal end of the p16INK4/MTS1 protein. Evidence for similar transcripts in non tumoral lymphoid B cells (unstimulated peripheral blood lymphocytes (PBL) and lymphoblastoid cell lines) were obtained by using amplimers representative of the 0.18 segment and the p16INK4/MTS1 exon 2. Altogether, these data are consistent with the existence of a new type of p16INK4/MTS1 transcript whose significance is discussed.

Base Sequence↗
PubMed1994

The BCMA gene, preferentially expressed during B lymphoid maturation, is bidirectionally transcribed.

In a previous study of a t(4;16)(q26;p13) translocation, found in a human malignant T-cell lymphoma the BCMA gene, located on chromosome band 16p13.1, has been characterized. In this study we show that the BCMA gene is organized into three exons and its major initiation transcription site is located 69 nucleotides downstream of a TATA box. RNase protection assays demonstrated that the BCMA gene is preferentially expressed in mature B cells, suggesting a role for this gene in the B-cell developmental process. A cDNA complementary to the BCMA cDNA was cloned and sequenced and its presence was assessed by RNase protection assay and anchor-PCR amplification. This antisense-BCMA RNA is transcribed from the same locus as BCMA, and exhibits mRNA characteristic features, e.g. polyadenylation and splicing. It also contains an ORF encoding a putative 115 aa polypeptide, presenting no homology with already known sequences. RNase protection assays demonstrated the simultaneous expression of natural sense and antisense-BCMA transcripts in the majority of human B-cell lines tested.

Amino Acid Sequence↗
PubMed1994

Distinct MLL gene rearrangements associated with successive acute monocytic and lymphoblastic leukemias in the same patient.

A patient with acute monocytic leukemia (AMoL) and t(6;11)(q27;q23) developed acute lymphoblastic leukemia (ALL) and t(4;11)(q21;23), 10 months after complete remission of the AMoL. The MLL gene, normally located at band 11q23, appeared differently rearranged in the cells of these two leukemias, showing a different origin for the two malignant clones. The responsibility of etoposide, used in treatment of the AML, in the occurrence of the ALL is probable in this patient.

Adult↗
PubMed1994

[The BCL2 gene, prototype of a gene family that controls programmed cell death (apoptosis)].

The BCL2 gene is the most representative member of a family of genes that control cell homeostatic processes in the course of the developmental and adult life. Some members of the BCL2 family (bcl-2 alpha, bcl-xL) inhibit apoptosis, whereas some other (Bax, Bclxs) induce it. The biological activity of these proteins is dictated by: 1) their capacity to be integrated in specific membranes of the cytoplasm; 2) their ability to homo- or hetero-dimerize, due to the presence of two highly conserved domains which are a signature of this gene family. The bcl-2 protein exhibits two main biochemical properties: it acts in an antioxidant metabolic pathway aimed at eliminating oxygene free radicals that induce lesions in DNA, lipids and proteins; it modulates intracellular Ca++ fluxes. BCL2 (and presumably its congeners) interplay with other genes involved in the tight control of cell proliferation and programmed cell death (c-myc, p53). A more comprehensive view of BCL2 functions should benefit to cancer chemotherapy by improving rational approach of the antitumor drug mechanisms.

Animals↗
PubMed1994

Alterations of the putative tumor suppressor gene p16/MTS1 in human hematological malignancies.

The chromosome band 9p21-22 is frequently rearranged or deleted in a variety of tumors including hematological malignancies. This supports the notion of a tumor suppressor gene in this chromosome region. Indeed, the p16/MTS1 gene encoding a cyclin-dependent kinase (CDK) inhibitor has been shown to be frequently deleted and/or inactivated by nonsense mutations in a number of tumors. We have examined 98 DNA samples from blood, bone marrow cells and lymph node biopsies of patients with leukemia (ALL and AML) or lymphoma (follicular lymphoma and T-cell lymphoma), using Southern blot hybridization and a p16/MTS1-specific probe. Molecular abnormalities, mainly homozygous deletions, were found principally in ALL (8 out of 22 patients), much less frequently in AML (2/32) and lymphoma (2/32). While these data argue in favor of a large involvement of p16/MTS1 in ALL, AML and lymphomas appear to be less frequently implicated.

Adult↗
PubMed1994

GATA-and SP1-binding sites are required for the full activity of the tissue-specific promoter of the tal-1 gene.

The tal-1 gene, which is frequently activated in human T cell acute leukemias (T-ALLs), codes for a protein of the basic helix-loop-helix family (b-HLH) and potentially a transcription factor. In human and murine hematopoiesis tal-1 is expressed during the differentiation of the erythroid, megakaryocytic and mastocytic cell lineages. The expression of tal-1 appears to be comodulated with that of the transcription factor GATA-1 gene, suggesting that the GATA-1 protein may regulate the tal-1 gene activity in these hematopoietic lineages. To get further insights into the molecular mechanisms that control tal-1 expression, we have isolated 5' sequences of the murine gene and compared them to their human counterparts. The 5' flanking sequences from the two genes show several regions of high homology. The alignment of both sequences enabled us to predict that similarly, to the human, the mouse gene contains two alternative first exons (Ia and Ib). Remarkably, in both species, the proximal region of the tissue-specific exon Ia (i.e. gene segment -122 to +1) contains two GATA-motifs (at -65 and -33) and one SP-1 consensus binding site (-59). Mobility shift assays demonstrate that GATA proteins are able to interact with both GATA-motifs in a sequence specific fashion, but with different efficiencies. Moreover transfection studies show that the GATA-1 protein directly mediates tal-1 transcription by interacting with the -122/+1 fragment, defined as a minimal promoter in erythroid cells. Mutagenesis of the promoter establishes that the -33 GATA-binding site present in this fragment is critical for tal-1 expression in erythroid cells, but by itself does not lead to full promoter activity. Indeed, further mutations show that the second -65 GATA-binding site and the binding motif for SP1 (-59) significantly contribute to the overall activity of the proximal tal-1 promoter. Altogether, our data provide evidence that GATA-1 cooperates with the transcription factor SP1 to mediate the erythroid-specific expression of the tal-1 gene.

3T3 Cells↗
PubMed1993

Molecular analysis of a variant 18;22 translocation in a case of lymphocytic lymphoma.

We previously reported a 5' rearrangement of the BCL2 locus in a t(18;22) variant translocation found in a lymphocytic lymphoma. Primary structure analysis of both rearranged chromosomes confirmed the localization of the breakpoint in the so-called vcr region (for variant cluster region) that encompasses Z-DNA stretches 5' of the BCL2 locus, and in between J lambda 1 and C lambda 1 segments on the IGL locus. A 1,027 nucleotide segment from chromosome 22 was repeated on both derivative chromosomes 18q+ and 22q-. This segment contained an octanucleotide that was also present in the normal chromosome 18 close to the breakpoint. As a consequence of the translocation, a normal-sized BCL2 transcript was overexpressed in tumor cells.

Base Sequence↗
PubMed1993

Breakpoint clusters of the PML gene in acute promyelocytic leukemia: primary structure of the reciprocal products of the PML-RARA gene in a patient with t(15;17).

DNA studies of the translocation t(15;17) in acute promyelocytic leukemia (APL) have shown that the retinoic acid receptor alpha (RARA) gene on chromosome 17 is juxtaposed to the promyelocytic leukemia (PML) gene on chromosome 15. The PML breakpoints have been mapped to 3 clusters: bcr1, bcr2, and bcr3. We have examined the PML breakpoint distribution in a series of 33 Chinese patients with APL. Twenty-two patients fell within bcr1, 2 within bcr2, and 9 within bcr3. The primary structure of the reciprocal chromosome translocation joints of one patient and that of their normal counterparts have been determined and compared to those of 2 previously reported cases. These studies revealed possible topoisomerase II cleavage sites close to the breakpoints and suggested implications of DNA attachment sites to nuclear matrix. We propose that these features are relevant to the process of illegitimate recombination generating the translocation.

Base Sequence↗
PubMed1993

t(11;18)(q21;q21) may delineate a spectrum of diffuse small B-cell lymphoma with extranodal involvement.

We describe a patient with stage IV non-Hodgkin's lymphoma (NHL) and a t(11;18)(q21;q21) translocation. He presented with a gastric small B-cell lymphocytic lymphoma, expressing IgAL immunoglobulins without expression of CD10, CD5, and CD23 antigens. The lymphoma was the final development of a 6-year history of a monoclonal IgAL increase complicated by severe renal failure due to membranoproliferative glomerulonephritis. The clinical, histological, immunologic, and cytogenetic features of this patient are very similar to those observed in the five other patients with t(11;18) reported to date. This translocation therefore seems to delineate a new subtype of diffuse small B-cell lymphoma with involvement of mucosal sites. Involvement of the BCL2 oncogene on 18q21 could not be detected using molecular techniques with 5' as well as 3' BCL2 probes, indicating that other, so far unknown, genes relevant to lymphoid differentiation could be located in 18q21 and 11q21.

Antigens, CD↗
PubMed1993

Production of human p53 specific monoclonal antibodies and their use in immunohistochemical studies of tumor cells.

We describe the production of 13 new monoclonal antibodies induced by the product of the human p53 tumor suppressor gene. All these monoclonal antibodies recognize human p53 irrespective of the detection technique: ELISA, immunoblot or immunoprecipitation. These antibodies can be divided into four groups according to such criteria as localization of the recognized epitopes and reactivity with p53 originating from other organisms. One monoclonal antibody was successfully used for immunohistochemistry detection of p53 accumulation in breast carcinoma. This novel panel of monoclonal antibodies represents a further tool for the study of the p53 protein.

Animals↗
PubMed1993

Localization of the chromosome 15 breakpoints and expression of multiple PML-RAR alpha transcripts in acute promyelocytic leukemia: a study of 28 Chinese patients.

Translocation (15;17)(q22;q12-q21) is a chromosome aberration specifically found in acute promyelocytic leukemia (APL), that generates a chimeric gene between the promyelocytic leukemia (PML) gene on chromosome 15 and the retinoic acid receptor alpha (RARA) gene, on chromosome 17. In the course of molecular investigations of a series of 28 Chinese patients with APL, we have simultaneously used Southern blot and reverse transcriptase polymerase chain reaction (RT-PCR) analysis to characterize the PML gene breakpoints on chromosome 15 and identify PML-RARA fusion transcripts. Our results confirmed the existence of the three recently described bcr1, bcr2, and bcr3 breakpoint cluster regions. In addition, structural data provided by PML-RARA transcripts allowed us to more accurately locate the 3' borders of clusters bcr1 and bcr3. Moreover, our data suggest a preferential localization of the breakpoints within bcr1 and bcr3. The primary structure of a 1.4 kb DNA segment flanking the 5' part of the PML gene and that of the bcr3 cluster (2.1 kb) were also established.

Base Sequence↗
PubMed1993

BCL2 gene activation and protein expression in follicular lymphoma: a report on 64 cases.

Rearrangements of the BCL2 gene and expression of bcl-2 protein were analyzed in a series of 64 cases of follicular lymphomas in order to establish a relationship between the rearrangements and the protein overexpression. Of the 64 cases, 41 showed BCL2 rearrangement involving one of the three breakpoint clusters: 30 in mbr, eight in mcr, and three in vcr. A double rearrangement mbr+vcr was detected in two cases. Twenty cases with bcl-2 protein expression in tumor cells exhibited no apparent rearrangement, suggesting the possible existence of other mechanisms activating the gene. Interestingly, expression of the LMP1 protein, the Epstein-Barr virus (EBV) encoded gene, whose capacity to induce BCL2 has been recently demonstrated, was only found in 2/41 cases in which BCL2 was rearranged. These data suggest that EBV infection is not an important mechanism in the activation of BCL2 in follicular lymphoma.

Antigens, Viral↗
PubMed1993

BCL2 complex rearrangement in follicular lymphoma: translocation mbr/JH and deletion in the vcr region of the same BCL2 allele.

Two rearrangements affecting the same allele of the BCL2 gene were characterized by molecular analysis of an untreated follicular lymphoma. The first rearrangement interested the major breakpoint region (mbr) on chromosome 18 and a JH segment on chromosome 14. The other one was located at the 5' end of the BCL2 gene, in the so called variant cluster region (vcr), and consisted of a series of deletions that removed part of a DNA region where initiation of transcription normally occurs. Interestingly, both rearrangements involved the same BCL2 allele. The simultaneous presence of mbr (or mcr) translocations and of minor rearrangements in vcr has been previously suggested by restriction map analysis in a significant number of follicular lymphomas. The significance of these abnormalities on the oncogenic process is discussed.

Alleles↗
PubMed1993

Some recent aspects of the molecular biology of human lymphoma.

Some recent aspects of the molecular biology of chromosome abnormalities that activate the BCL2 gene in B cell malignancies (follicular lymphoma, chronic lymphocytic leukemia) are discussed. We also report data showing that the Epstein-Barr virus (EBV) LMP-1 protein which can induce the expression of BCL2, is found infrequently in follicular lymphomas which exhibit no apparent BCL2 gene rearrangement.

Antigens, Viral↗
PubMed1992

A third tal-1 promoter is specifically used in human T cell leukemias.

A common feature of T cell acute lymphoblastic leukemias (T-ALLs) is the presence of structural alteration of the 5' part of the tal-1 locus, localized on chromosomal band 1p32. These alterations consist of either a t(1;14)(p32;q11) chromosomal translocation (3% of T-ALLs) or tald submicroscopic deletion (12-25% additional T-ALLs). We have characterized a case of T-ALL with t(1;14)(p32;q11) in which, unlike the majority of t(1;14), the recombination with the T cell receptor delta elements affected the 3' side of the tal-1 locus. In this case, tal-1 transcription is initiated from a promoter located within the fourth exon similarly to the DU 528 cell line. In a T-ALL bearing a t(1;14) affecting the 5' part of tal-1, two types of tal-1 transcripts were observed, namely those probably initiated from the D delta region juxtaposed to tal-1 by the translocation, and those from the exon 4 promoter. It is interesting that this exon 4 promotion was also found in leukemic T cell lines and T-ALL samples without apparent tal-1 genomic alteration. In contrast, no transcript initiated from the exon 4 promoter was found in T-ALL with tald1 or tald2 deletion. In these cells, tal-1 is expressed via SIL-tal-1 fused transcripts. Finally, this exon 4 initiation was detected neither in normal bone marrow, nor in malignant cells from the erythroid/megakaryocytic lineages. Taken as a whole, these data suggest that the exon 4 promoter is specifically active in T cell lineage.

Base Sequence↗