Biomedical subjects
Publications and source records attributed to C M Croce.
Somatic cell hybridization experiments between tumorigenic and nontumorigenic cells indicate that the differentiated state of the cells carrying the activated oncogene is important in the regulation of their expression.
The human germ-line position of c-erb-A, the cellular counterpart of v-erb-A, has been determined by in situ molecular hybridization of a 3H-labeled c-onc gene probe to meiotic pachytene chromosomes. Both v-erb-A and v-erb-B are the v-onc genes that are associated with induction of sarcoma and erythroblastosis in chicken by the avian erythroblastosis virus, a rapidly transforming RNA tumor virus. The position of c-erb-A, determined here to be at 17q21.33-q22, is in the same region of chromosome 17 in which a nonrandom break occurs in the generation of t(15;17), a translocation commonly seen in acute promyelocytic leukemia.
With a constant region probe (c-lambda) from the immunoglobulin light chain gene cluster, we performed in situ hybridization to bone marrow chromosome preparations from a patient with a Ph-positive form of acute lymphocytic leukemia. Results in this patient indicate that the immunoglobulin chain genes were involved in the 9;22 chromosome rearrangement.
Mouse-human hybrid cells preferentially segregating mouse chromosomes contain predominantly human histone mRNAs and synthesize human histone proteins. In contrast, hybrids segregating human chromosomes contain both human and murine histone mRNAs, yet synthesize only mouse histone proteins. These results suggest transcriptional control of histone gene expression in hybrids segregating mouse chromosomes and post-transcriptional regulation in hybrids segregating human chromosomes.
Explore the source record for details and available documents.
By using alpha-spectrin cDNA clones of murine and human origin and somatic cell hybrids segregating either mouse or human chromosomes, the gene for alpha-spectrin has been mapped to chromosome 1 in both species. This assignment of the mouse alpha-spectrin gene to mouse chromosome 1 by DNA hybridization strengthens the previous identification of the alpha-spectrin locus in mouse with the sph locus, which previously was mapped by linkage analysis to mouse chromosome 1, distal to the Pep-3 locus. By in situ hybridization to human metaphase chromosomes, the human alpha-spectrin gene has been localized to 1q22-1q25; interestingly, the locus for a non-Rh-linked form of elliptocytosis has been provisionally mapped to band 1q2 by family linkage studies.
Although it is known that the c-myc oncogene is rearranged in a head-to-head fashion with the immunoglobulin heavy chain locus in mouse plasmacytomas, it has not been clear whether the c-myc oncogene is translocated to the heavy chain locus on mouse chromosome 12 or whether the heavy chain locus is translocated to the c-myc locus on mouse chromosome 15. To determine which of these two possibilities is correct, we hybridized Chinese hamster fibroblasts with J558 mouse plasmacytoma cells that carry a reciprocal chromosome translocation between chromosomes 12 and 15, and we examined the segregating hybrids for the presence of the normal and rearranged mouse c-myc genes, for the presence of different regions of the mouse heavy chain locus, and for the presence of genes located on mouse chromosomes 12 and 15. The results of this analysis indicate that, as in human Burkitt lymphomas with the 8;14 chromosome translocation, the c-myc gene is translocated to the heavy chain locus in mouse plasmacytomas. Thus the orientation of the heavy chain locus on mouse chromosome 12 and of the c-myc gene on mouse chromosome 15 is the same as the orientation of the homologous loci in man.
Urokinase is one of the two plasminogen activators that catalyze the conversion of inactive plasminogen to plasmin. By combining somatic cell genetics, in situ hybridization, and Southern hybridization, we localized the human urokinase gene on the distal third of the long arm (q24-qter) of chromosome 10.
Complementary DNA clones representing the 3' half, the 5' half, and the entire coding region of the human terminal deoxynucleotidyltransferase gene (TdT; DNA nucleotidylexotransferase, nucleosidetriphosphate: DNA deoxynucleotidylexotransferase, EC 2.7.7.31) were used to screen a panel of mouse X human somatic cell hybrid DNAs to determine the chromosomal location of the human TdT gene. The results of the Southern transfer analysis of hybrid DNAs indicate that the gene for TdT is located on human chromosome 10. The in situ hybridization technique was then used to further localize the gene for TdT to region q23-q25 of human chromosome 10.
We hybridized Raji Burkitt lymphoma cells, which carry a t(8;14) chromosome translocation, with human lymphoblastoid cells to study the expression of the translocated cellular myc oncogene (c-myc) in the hybrid cells. In Raji cells the c-myc oncogene is translocated to a switch region of the gamma heavy chain locus (S gamma). Because of sequence alterations in the 5' exon of the translocated c-myc oncogene in this cell line, it is possible to distinguish the transcripts of the translocated c-myc gene and of the normal c-myc gene. S1 nuclease protection experiments with a c-myc first exon probe indicate that Raji cells express predominantly the translocated c-myc gene, while the level of expression of the normal c-myc gene is less than 2% of that of the translocated c-myc gene. Somatic cell hybrids between Raji and human lymphoblastoid cells retain the lymphoblastoid phenotype and express only the normal c-myc oncogene. This result indicates that the activation of a c-myc oncogene translocated to a S region depends on the stage of B-cell differentiation of the cells harboring the translocated c-myc gene and not on alterations in the structure of the translocated c-myc oncogene.
We have cloned and sequenced the translocated c-myc gene from the Burkitt's lymphoma CA46 cell line that carries a reciprocal translocation between chromosomes 8 and 14. The breakpoint lies within the first intron of c-myc, so that the first noncoding exon of the gene remains on the 8q- chromosome. The second and third coding exons are translocated to the 14q+ chromosome into the switch region of C-alpha 1. The orientation of the c-myc gene with relationship to alpha 1 is 5' to 5', with directions of transcription in opposite orientation. DNA sequencing studies predict five changes in the amino acid sequence of the myc protein, two of which occur in a region within the second exon which is highly conserved in evolution. Southern blotting data indicate that the first exon of c-myc is rearranged 3' to 3' with the pseudo-epsilon gene. Because CA46 cells contain two rearranged mu genes, the translocation must have occurred after immunoglobulin rearrangement. The position of the breakpoint in CA46 occurs within a 20-base-pair region of the first intron of c-myc to which breakpoints have been mapped for two additional B-cell lymphomas with the t(8;14) translocation, ST486 and the Manca cell line. The region of the heavy chain locus to which c-myc has translocated is different in each case. Comparisons have been made of the levels of transcripts of the translocated c-myc gene in ST486 and CA46, where the gene is not associated with the heavy chain enhancer, with its expression in the Manca cell, in which it is. The c-myc gene is transcribed at similar levels in all three cases.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
From an acute B-cell leukemia cell line, a DNA probe was obtained that was specific for chromosome 18 and flanked the heavy chain joining region of the immunoglobulin heavy chain locus on chromosome 14. This probe detected rearrangement of the homologous DNA segment in the leukemic cells and in follicular lymphoma cells with the t(14:18) chromosome translocation but not in other neoplastic or normal B or T cells. The probe appears to identify bcl-2, a gene locus on chromosome 18 (band q21) that is unrelated to known oncogenes and may be important in the pathogenesis of B-cell neoplasms with this translocation.
We have cloned a human V lambda cDNA sequence from an Ig lambda-producing human Burkitt lymphoma cell line (BL2) by taking advantage of a cloned constant region gene as a primer for cDNA synthesis instead of an oligo(dT) primer. The amino acid sequence deduced from the nucleotide sequence of V lambda clones is highly related to that of the NEW V lambda protein of subgroup I. Southern blot hybridization of human DNAs with the V lambda I probe showed at least 12 hybridizing V lambda fragments. These fragments are amplified in K562 cells which derive from a case of chronic myelogenous leukemia and contain an amplified c-abl oncogene and amplified C lambda sequences.
The chromosomal breakpoint of chronic lymphocytic leukemia (CLL) cells of the B-cell type carrying the translocated long arms of chromosomes 11 and 14 [t(11;14) (q13;q32)] was cloned. The breakpoint was found to be within the joining segment of the human heavy chain locus on the translocated long arm of chromosome 14. A probe that is specific for chromosome 11 and that maps immediately 5' to the breakpoint on the 14q+ chromosome was isolated. The probe detected a rearrangement of the homologous genomic DNA segment in the parental CLL cells and also in DNA from a diffuse large cell lymphoma with the t(11;14) translocation. This rearranged DNA segment was not present in Burkitt lymphoma cells with the t(8;14) translocation or in nonneoplastic human lymphoblastoid cells. The probe can thus be used to identify and characterize a gene located on band q13 of chromosome 11 that appears to be involved in the malignant transformation of human B cells carrying the t(11;14) translocation. This gene, named bcl -1, appears to be unrelated to any of the known retrovirus oncogenes described to date.
The productively rearranged immunoglobulin mu chain gene and the translocated cellular oncogene c-myc are transcribed at high levels both in human Burkitt lymphoma cells carrying the t(8;14) chromosome translocation and in mouse plasmacytoma X Burkitt lymphoma cell hybrids. In the experiments reported here these genes were found to be repressed in mouse 3T3 fibroblast X Burkitt lymphoma cell hybrids. Such repression probably occurs at the transcriptional level since no human mu- and c-myc messenger RNA's are detectable in hybrid clones carrying the corresponding genes. It is therefore concluded that the ability to express these genes requires a differential B cell environment. The results suggest that the 3T3 cell assay may not be suitable to detect oncogenes directly involved in human B cell oncogenesis, since 3T3 cells apparently are incapable of transcribing an oncogene that is highly active in malignant B cells with specific chromosomal translocations.