Chromosomal location of the structural gene cluster encoding murine immunoglobulin heavy chains

Effect of the mouse scid mutation on meiotic recombination

The goal of this study was to determine the effect of the mouse severe combined immunodeficiency (scid) mutation on the rate of meiotic recombination, by standard backcross linkage analysis. For this purpose, we examined four crosses that involved F1 hybrid animals heterozygous for the strain C57BL/6 and BALB/c genomes. In one set of reciprocal crosses, F1 animals were homozygous scid/scid, and in a second set of reciprocal crosses, F1 mice were homozygous wild-type (+/+) at the scid locus. Backcross progeny were typed for recombination between selected genetic markers on mouse Chromosomes (Chrs) 1, 4, 6, 7, 9, 15, and 17. Although some differences in recombination were observed over some intervals, the expression of the SCID phenotype did not appear to have a major or consistent effect on meiotic recombination.

Rapid physical mapping of cloned DNA on banded mouse chromosomes by fluorescence in situ hybridization

Physical mapping of DNA clones by nonisotopic in situ hybridization has greatly facilitated the human genome mapping effort. Here we combine a variety of in situ hybridization techniques that make the physical mapping of DNA clones to mouse chromosomes much easier. Hybridization of probes containing the mouse long interspersed repetitive element to metaphase chromosomes produces a Giemsa-like banding pattern which can be used to identify individual Mus musculus, Mus spretus, and Mus castaneus chromosomes. The DNA binding fluorophore, DAPI, gives quinacrine-like bands that can complement the hybridization banding data. Simultaneous hybridization of a differentially labeled clone of interest with the banding probe allows the assignment of a mouse clone to a specific cytogenetic band. These methods were validated by first mapping four known genes, Cpa, Ly-2, Cck, and Igh-6, on banded chromosomes. Twenty-seven additional clones, including twenty anonymous cosmids, were then mapped in a similar fashion. Known marker clones and fractional length measurements can also provide information about chromosome assignment and clone order without the necessity of recognizing banding patterns. Clones hybridizing to each murine chromosome have been identified, thus providing a panel of marker probes to assist in chromosome identification.

Mapping and conservation of the group-specific component gene in mouse

The group-specific component (GC), also known as the vitamin D-binding protein, transports vitamin D and its metabolites in plasma to target tissues throughout the body. The GC gene shares an evolutionary origin with genes encoding albumin (ALB) and alpha-fetoprotein (AFP). All three genes are descendants of an evolutionary ancestor that arose from an intragenic triplication. As a result, each gene is composed of three homologous domains. The study described here characterizes and compares mouse GC to the corresponding nucleotide and amino acid sequences of GC from human and rat. The deduced amino acid sequence of mouse GC was 78% identical to human and 91% identical to rat GC. The results suggest that, unlike the corresponding sequences in the ALB and AFP genes, chromosomal sequences encoding the first domain and the leader sequence of the GC gene have specifically been conserved throughout vertebrate evolution. Protection of domain I during evolution may correlate with an important functional aspect of its sequence. The mouse GC gene was mapped to chromosome 5, where the ALB and AFP genes are also located, demonstrating conservation of the three genes in vertebrate species.

Chromosomal evolution in secretory and nonsecretory subline of MOPC 21

Murine myeloma cell lines are noted for the instability of their immunoglobulin genes and the production of nonsynthesizing variants. In this study, the synthesizing line P3-X63-Ag8 (P3) and its nonsynthesizing subline X63-Ag8-653 (653) were karyotyped and rearrangements of the immunoglobulin carrying chromosomes were investigated. Loss of immunoglobulin synthesis was associated with a reduction in the number of immunoglobulin-carrying chromosomes. When these findings were analyzed in light of published molecular data, it appeared that loss of immunoglobulin synthesis in 653 probably occurred as a result of immunoglobulin gene loss. An unusual finding was the absence of the t(12;15) chromosome in both P3 and 653 cell lines. It was concluded that the t(12;15) chromosome, carried by MOPC 21, has evolved into an unrecognizable form.

Mapping of gene encoding mouse placental alkaline phosphatase to chromosome 4

The gene encoding the mouse placental alkaline phosphatase (ALP; orthophosphoric-monoester phosphohydrolase, alkaline optimum, EC 3.1.3.1) is mapped to chromosome 4, based on Southern blot hybridization of the mouse cDNA with DNAs from mouse-Chinese hamster somatic cell hybrids. This assignment is consistent with the genetic analysis of the Akp-2 locus, which is responsible for the genetic variation of alkaline phosphatase enzyme in placenta as well as in liver, kidney, and bone.

The endogenous retrovirus Mtv-8 on mouse chromosome 6 maps near several kappa light chain markers

Endogenous retroviruses are known to affect expression of cellular genes in the vicinity of their integration sites. The endogenous mouse mammary tumor provirus (Mtv-8) previously has been reported to reside on mouse chromosome 6 near the immunoglobulin kappa chain locus. Using pairs of mouse strains on the BALB/c (Mtv-8 positive) and C58 (Mtv-8 negative) backgrounds which are congenic for chromosome 6 genetic markers, we have confirmed the chromosome assignment of this provirus. Moreover, we have analyzed the N1 progeny of a (B6 X C58) X C58 backcross to determine the segregation of the Mtv-8 provirus with respect to polymorphisms in the Igk-VSer and Igk-J loci. The results with congenic and backcross mice together with results of others suggest that Mtv-8 is located approximately 0.52 cM from several closely linked kappa markers on chromosome 6.

Chromosomal locations of the gene coding for the CD3 (T3) gamma subunit of the human and mouse CD3/T-cell antigen receptor complexes

The gene coding for the Mr 26000 gamma chain of the human CD3 (T3) antigen/T-cell antigen receptor complex was mapped to chromosome band 11q23 by using a cDNA clone (pJ6T3 gamma-2), by in situ hybridization to metaphase chromosomes and by Southern blot analysis of a panel of human-rodent somatic cell hybrids. The mouse homolog, here termed Cdg-3, was mapped to chromosome 9 using the mouse gamma cDNA clone pB10.AT3 gamma-1 and a panel of mouse-hamster somatic cell hybrids. Similar locations for the CD3 delta genes have been described previously. Thus, the corporate results indicate that the CD3 gamma and delta genes have remained together since they duplicated about 200 million years ago.

A complementary DNA clone for a macrophage-lymphocyte Fc receptor

Macrophages, granulocytes and many lymphocytes express or secrete receptors for the Fc domain of immunoglobulins (Ig). These Fc receptors (FcRs) are heterogeneous and can be distinguished on the basis of their cellular distribution and specificities for different immunoglobulin isotypes. Although their functions are not completely understood, FcRs are known to be involved in triggering various effector cell functions and in regulating differentiation and development of B-cells. One of the best characterized is the mouse macrophage-lymphocyte receptor for IgG1 and IgG2b (ref. 5). On macrophages, this FcR mediates the endocytosis of antibody-antigen complexes via coated pits and coated vesicles, the phagocytosis of Ig-coated particles, and the release of various inflammatory and cytotoxic agents. It is possible that the receptor possesses an intrinsic ligand-activated ion channel activity responsible for some of these functions. The IgG1/IgG2b FcR has been isolated and shown to be a transmembrane glycoprotein of relative molecular mass (Mr) 47,000-60,000 (47-60 K) containing four N-linked oligosaccharide chains and a large (greater than 10K) cytoplasmic domain. It is also immunologically indistinguishable from the murine Ly-17 alloantigen which, in turn, is tightly linked to the Mls lymphocyte activation locus. Here we describe the isolation and characterisation of a complementary DNA clone encoding the whole of the IgG1/IgG2b FcR expressed by the mouse macrophage-like cell line P388D1. The receptor is a member of the immunoglobulin superfamily and, like Ly-17, maps to the distal portion of chromosome 1. cDNA probes detect one or two mRNA species in FcR+ macrophage and B-cell lines, but not in FcR- cells or a receptor-deficient variant derived from a FcR+ B-cell line. Finally, DNA hybridization analysis indicates the receptor gene is partially deleted or rearranged in the FcR- variant.

Double isotype production by a neoplastic B cell line. II. Allelically excluded production of mu and gamma 1 heavy chains without CH gene rearrangement

In our accompanying paper, we described a switch variant (BCL1.2.58) that expresses membrane and secreted forms of IgM and IgG1. Both IgM and IgG1 share the same idiotype and use the same VDJ rearrangement. Here, a detailed Southern blot analysis of the entire constant region of the Ig heavy chain (Ig CH) locus of parental (BCL1.B1) and variants (BCL1.B2) DNA showed no detectable rearrangement. Similar analysis of the JH-C mu region led to the conclusion that two heavy chain alleles present in the IgM/IgG1-producing variants carried the same VDJ rearrangement but differed in their 3' flanking regions. One chromosome 12 did not carry any Ig CH genes, whereas, the other chromosome 12 carried one copy of CH genes. In BCL1.B1, however, each of the chromosome 12 alleles carried a full copy of CH genes. Karyotypic analysis confirmed the presence of two translocated t(12;16) chromosomes in both BCL1.2.58 and BCL1.B1 cells, with a break 5' to the VH locus at the distal region (12F2) of chromosome 12, and at the proximal region below the centromere (16B3) of chromosome 16. We conclude that double production of IgM and IgG1 in BCL1.B2 is accomplished by transcription of the corresponding CH genes in germline configuration using a single VDJ on the same chromosome 12.

Molecular analysis of membrane immunoglobulin-negative variants

The mouse B-cell lymphoma WEHI 279.1 is a tumor which synthesizes both membrane and secreted immunoglobulin M (IgM). We have immunoselected variants which fail to express the membrane form (mIgM-); the most frequently isolated phenotype is a complete loss of both membrane expression and synthesis of the mu heavy chain within the cells. We have chosen four of these mIgM- mutants for detailed molecular investigation. One of these has suffered a large deletion which covers the region of chromosome 12 containing the expressed mu gene, but three have no detectable changes in the DNA arrangement of the mu gene. All of the mutants, including the deletion mutant, synthesize 10-30% of the wild-type level of cytoplasmic mu RNA; however, none is the appropriate size for membrane mu (mu m) or secreted mu (mu s) message. Based on our studies of the deletion mutant, which retains its nonproductively arranged allele, at least some of these RNAs may be 'sterile' transcripts from the nonproductively arranged allele. However, if all of these mRNAs derive from the other allele, they represent a substantial elevation of these sterile messages relative to the wild-type level. Furthermore, the three nondeletion mutants transcribe mu RNA at a level indistinguishable from the wild type. It is likely that their defects lie in the stability, processing, or transport of the mu RNA within the nucleus. Somatic cell hybrids between P3X and the IgM- variants produced mostly mIgM- hybrids. However, a few mIgM+ hybrids were produced, suggesting that the mu- defects may be partly complemented by the P3X fusion partner.

Regional location of alpha 1-antichymotrypsin and alpha 1-antitrypsin genes on human chromosome 14

The human protease inhibitor genes alpha 1 antitrypsin (alpha 1-PI) and alpha 1-antichymotrypsin (alpha 1-ACT) are acute-phase proteins which are induced in response to inflammation. These inhibitors function to limit the activity of serine proteases in vivo. alpha 1-PI acts as an inhibitor of neutrophil elastase to protect the elastin fibers of the lung. Genetic deficiencies of alpha 1-PI result in development of chronic pulmonary emphysema. The physiologic role of alpha 1-ACT has not been clearly defined, but it also appears to function in the maintenance of protease-protease inhibitor equilibrium in the lung. Nucleic acid and protein sequence homologies detected between alpha 1-PI and alpha 1-ACT suggested an evolutionary relationship. Gene mapping experiments were performed to determine if these protease inhibitor genes reside at the same chromosomal locus in man. In situ hybridization data demonstrate that both alpha 1-PI and alpha 1-ACT map to the same region, q31-q32.3, on chromosome 14.

Chromosomal distribution of genes coding for fast twitch skeletal muscle myosin light chains

The mouse fast twitch skeletal muscle myosin light chains are encoded by a multigene family which comprises the gene coding for the myosin light chain 2 (Myl2f), and the gene coding for both myosin light chains 1 and 3 (Myl1f/Myl3f). In addition, a Myl1f/Myl3f-related pseudogene is present in the domestic mouse Mus musculus. The members of this gene family were assigned to chromosomes by molecular hybridization, using DNA extracted from a panel of cloned mouse-Chinese hamster somatic hybrid cells and specific DNA probes. The genes coding for the light chains of the myosin molecule are dispersed on several chromosomes, while genes coding for the heavy chain of myosin are located on a single, different chromosome.

Regional location of T cell receptor gene Ti alpha on human chromosome 14

The chromosomal location of Ti alpha was determined by hybridization of a radiolabeled cDNA for the alpha chain of human T cell receptor with 12 human X mouse cell hybrid DNAs cleaved with BamHI. Seven hybrids contained human Ti alpha, while the remaining five lacked it. Only human chromosome 14 matched the distribution of human Ti alpha signal across the mapping panel. Hybrids segregating a chromosome 14 translocation were used to demonstrate that Ti alpha is in the region 14pter greater than 14q21. Thus, the alpha and beta chain genes that contribute structural components to the Ti moiety of the human T cell receptor lie on different chromosomes. In humans, the immunoglobulin heavy chain locus and Ti alpha are in different regions of chromosome 14, with Ti alpha more proximal and the immunoglobulin heavy chain locus more distal.

Chromosomal locations of the murine T-cell receptor alpha-chain gene and the T-cell gamma gene

Two independent methods were used to identify the mouse chromosomes on which are located two families of immunoglobulin (Ig)-like genes that are rearranged and expressed in T lymphocytes. The genes coding for the alpha subunit of T-cell receptors are on chromosome 14 and the gamma genes, whose function is yet to be determined, are on chromosome 13. Since genes for the T-cell receptor beta chain were previously shown to be on mouse chromosome 6, all three of the Ig-like multigene families expressed and rearranged in T cells are located on different chromosomes, just as are the B-cell multigene families for the Ig heavy chain, and the Ig kappa and lambda light chains. The findings do not support earlier contentions that genes for T-cell receptors are linked to the Ig heavy chain locus (mouse chromosome 12) or to the major histocompatibility complex (mouse chromosome 17).

A genetic map of mouse chromosome 12 composed of polymorphic DNA fragments

Mouse chromosome 12 encodes the heavy chains of immunoglobulins (Igh), a family of T cell surface molecules, and a tumor antigen that may be homologous to immunoglobulins. To refine and extend the genetic map of this chromosome, a procedure has been developed to isolate chromosome 12-specific DNA fragments from a somatic cell hybrid carrying the chromosome on a Chinese hamster background. Five fragments have been isolated and characterized in detail. All are polymorphic, defining loci D12-1, 2, 3, 4, and 5. Using recombinant inbred mouse strains, a tentative linkage map of chromosome 12 has been worked out that incorporates these markers, the c-fos oncogene, Igh, and Pre-1/alpha 1 antitrypsin. This strategy should be applicable to any mouse chromosome or chromosomal region that can be isolated in a somatic cell hybrid.

Murine T cell receptor beta chain is encoded on chromosome 6

Southern blot analysis of somatic cell hybrid lines indicates that the beta chain of the T cell receptor for antigen maps to chromosome 6 of the mouse. An experiment testing hybridization of the constant region of this gene to DNA from a hybrid cell line containing a translocation of chromosome 6 supports the localization of this gene to the proximal (centromeric) one-third of chromosome 6, in the same general region as the immunoglobulin kappa chain locus. This may be another indication of the shared evolutionary origins of the genes encoding both T and B cell antigen recognition.

Glutathione S-transferase Ya subunit is coded by a multigene family located on a single mouse chromosome

A cloned DNA probe of Ya, the major glutathione S-transferase subunit in rat liver, was used to study the organization of Ya genes in the mouse genome. Southern blot analysis of mouse genomic DNA indicates that the Ya subunit is encoded by a multigene family. The chromosomal distribution of Ya genes was determined by analysis of DNA from a panel of mouse-Chinese hamster somatic cell hybrids. All detectable Ya genes were found to be located on chromosome 9. At least some of the Ya-specific DNA sequences are clustered since, by screening a mouse genomic library, two recombinant phages, each containing two different Ya DNA sequences in the same insert, have been isolated. The finding that Ya is encoded by a cluster of different genes raises the question of the specificity of the different Ya DNA sequences.

Chromosomal location of mouse gene 202 which is induced by interferons and specifies a 56.5 kD protein

The 202 gene which specifies a 56.5 kD protein can be induced in Ehrlich ascites tumor cells by treatment with mouse beta interferon. This treatment increases the level of the gene 202-specific mRNA at least 12-fold. For determining the chromosomal location of this gene a 1.5 kb fragment of the gene was hybridized to EcoR1 digested DNA samples from a set of mouse-hamster somatic cell hybrids. Each of the cell hybrids used contained a complete array of hamster chromosomes and one or more mouse chromosomes. The 202 gene fragment hybridized to every DNA sample from cell hybrids containing mouse chromosome 1 (8 hybrids in total) and to none of the DNA samples from hybrids lacking this chromosome (7 hybrids in total). These and other data indicate that the 202 gene is located on mouse chromosome 1.

Rat c-myc oncogene is located on chromosome 7 and rearranges in immunocytomas with t(6:7) chromosomal translocation

Two B-cell-derived tumours, human Burkitt's lymphoma (BL) and murine plasmacytoma (MPC), are regularly associated with a distinctive form of chromosomal translocation (for reviews see refs 1, 2). In BL, the distal portion of chromosome 8 breaks off and is transposed, in most cases, to chromosome 14, known to carry the immunoglobulin heavy-chain locus. In about 5% of the cases the same distal part of the chromosome 8 has moved to either chromosome 2 or 22, to the neighbourhood of the kappa or the lambda locus, respectively. In MPC the distal region of chromosome 15 is transposed to the chromosome 12, known to carry the immunoglobulin heavy-chain locus, or enters into reciprocal exchange with the kappa locus-carrying chromosome 6 (ref. 7). Several laboratories have located c-myc, the cellular homologue of the MC29 retroviral oncogene v-myc, to human chromosome 8 (refs 8-10) and mouse chromosome 15 (refs 11-13). It has also been shown that the BL- and MPC-associated translocations remove the c-myc gene from its original site and transpose it into or close to one of the immunoglobulin gene clusters. In view of the above findings we also looked for possible involvement of the c-myc gene in a B-cell-derived tumour of a third species, the rat. Rat immunocytomas of spontaneous origin carry a reciprocal translocation between chromosomes 6 and 7 (ref. 17). Here we have localized the c-myc locus to chromosome 7 of the rat. Moreover, we have found that the c-myc gene was rearranged in four of five immunocytomas carrying the characteristic chromosomal translocation.

Somatic cell genetics and flow cytometry

Human genes coding cell surface molecules can be introduced into mouse host cells using a variety of somatic cell genetic techniques. Because these human gene products can be detected using indirect immunofluorescence on viable cells, the genes themselves can be monitored and manipulated using flow cytometry and sorting. In this paper, we review ways that we have used cell sorting to develop a somatic cell genetic analysis of the human cell surface.

Multigene family for sarcomeric myosin heavy chain in mouse and human DNA: localization on a single chromosome

Cloned myosin heavy chain DNA probes from rat and human were hybridized to restriction endonuclease digests of genomic DNA from somatic cell hybrids and their parental cells. The mouse myosin heavy chain genes detectable by this assay were located on chromosome 11, and three different human sarcomeric myosin heavy chain genes were mapped to the short arm of chromosome 17. A synteny between myosin heavy chain and two unrelated markers, thymidine kinase and galactokinase, was found to be preserved in the rodent and human genomes.

Somatic cell genetics and gene families

The utility of somatic cell genetic analysis for the chromosomal localization of genes in mammals is well established. With the development of recombinant DNA probes and efficient blotting techniques that allow visualization of single-copy cellular genes, somatic cell genetics has been extended from the level of phenotypes expressed by whole cells to the level of the cellular genome itself. This extension has proved invaluable for the analysis of genes not readily expressed in somatic cell hybrids and for the study of multigene families, especially pseudogenes dispersed in different chromosomes throughout the genome.

Molecular basis of a mouse strain-specific anti-hapten response

The response of C57BL/6 and BALB/c mice to immunization with proteins coupled to (4-hydroxy-3-nitrophenyl)acetyl (NP) is dominated by distinctly different sets of antibodies. The VH gene family previously shown to be involved in the C57BL/6 response has now been shown to have highly homologous counterparts in BALB/c but of five sequenced BALB/c VH regions, none appeared likely to be able to encode an NP-binding protein. The active VH region from a BALB/c hybridoma making a characteristic anti-NP antibody was recovered and sequenced and shown to be quite different from the VH gene family involved in the C57BL/6 response. Comparison of the variation of the closely related VH regions between the two mouse strains showed that there are separate types of evolutionary pressures on the framework and complementarity-determining regions. The molecular basis for strain-specific immune responses appears to be that the structural divergence of VH regions between mouse strains is great enough that different strains use different VH regions for making the predominant class of antibodies to a specific hapten.

Induction of lambda 1-immunoglobulin is determined by a regulatory gene (r lambda 1) linked (or identical) to the structural (c lambda 1) gene

The cis-acting gene regulating specifically the inducibility of lambda 1-bearing B cells has been mapped within 2.9 cM of the structural gene. If the lambda 1lo-phenotype is due to the gly leads to val interchange in C lambda 1, then an argument can be made that (a) the lambda 1lo-phenotype is due to inefficient induction of lambda 1lo-bearing B cells and (b) B cell triggering is dependent upon a conformational change in the Ig receptor upon interaction with antigen. If the lambda 1lo-phenotype is due to a regulatory sequence linked to the structural C lambda 1-gene, then it must control the expression of the lambda 1-locus during development into adulthood, e.g., by an effect on methylation.

Somatic generation of antibody diversity

In the genome of a germ-line cell, the genetic information for an immunoglobulin polypeptide chain is contained in multiple gene segments scattered along a chromosome. During the development of bone marrow-derived lymphocytes, these gene segments are assembled by recombination which leads to the formation of a complete gene. In addition, mutations are somatically introduced at a high rate into the amino-terminal region. Both somatic recombination and mutation contribute greatly to an increase in the diversity of antibody synthesized by a single organism.

Characterization of superoxide dismutase (SOD-1 and SOD-2) activities in inbred mice: evidence for quantitative variability and possible nonallelic SOD-1 polymorphism

Liver Cu/Zn (SOD-1) and Mn (SOD-2) superoxide dismutase activities were determined in 12 inbred mouse lines. SOD-2 activity varied from 5 to 8 U/mg protein but was never more than 5% of the total. SOD-1 activity varied from 112 (SJL/J) to 155 (RF/J) U/mg protein, with the 12 strains falling into three activity classes. No correlation between SOD-1 activity and H-2 histocompatibility phenotype was observed, i.e., these two loci do not appear linked as previously suggested [Novak, R., Bosze, Z., Matkovics, B. and Fachet, J. (1980). Science 207:86]. Several tissues in all strains exhibited three SOD-1 charge electromorphs which did not differ in relative proportions between strains or tissues. The pI values of these three isozymes were 4.0, 4.5, and 5.0, respectively. The pI value of SOD-2 was 7.7. Both SOD-1 and SOD-2 were sensitive to CHCl3/EtOH extraction, but this sensitivity was not electromorph specific. Quantitation of the SOD-1 isozymic pattern indicated that the electromorphs were present at a ratio of 1:6:23 in order of increasing pI. Fitting of these data to a binomial distribution showed that they were consistent with the presence of two SOD-1 subunits (chains) of unequal pI. The mole fractions of the two chains were calculated to be 0.14 (lower-pI chain) and 0.86 (higher-pI chain). Since the mice used were highly inbred, this pattern could be due to unequal rates of transcription of linked, nonallelic SOD-1 loci, although other explanations are possible. The activity differences between SJL/J and RF/J appear large enough and the data precise enough to make genetic studies on the control of SOD-1 expression in the mouse practicable.

Stable antibody-producing murine hybridomas

A method is described for obtaining antibody-producing hybridomas that are preferentially retained in cultures of fused mouse spleen and myeloma cells. Hybridomas are produced by fusing mouse myeloma cells that are deficient in adenosine phosphoribosyltransferase (APRT) with mouse spleen cells containing Robertsonian 8.12 translocation chromosomes. The cell fusion mixtures are exposed to a culture medium that can be utilized only by APRT-positive cells, which results in the elimination of both unfused APRT-deficient myeloma cells and non-antibody-producing APRT-deficient hybridomas that arise by segregation of the 8.12 translocation chromosomes containing the APRT genes and the active heavy chain immunoglobulin gene.

Mouse c-myc oncogene is located on chromosome 15 and translocated to chromosome 12 in plasmacytomas

Hybridization studies with viral oncogene probes indicate that c-myc, the cellular gene homologous to the transforming gene of avian myelocytomatosis virus, resides on mouse chromosome 15 and in many plasmacytomas is translocated to the antibody heavy chain gene locus on chromosome 12. The transcriptional orientation of the translocated c-myc sequence is opposite the orientation of the adjacent C alpha gene that codes for the heavy chain of immunoglobulin A. The translocated c-myc sequence is not the same oncogene detected in urine plasmacytomas by the NIH-3T3 cell transformation assay.

Novel myc oncogene RNA from abortive immunoglobulin-gene recombination in mouse plasmacytomas

We have found that the myc oncogene has been modified by abortive recombination with the alpha heavy-chain immunoglobulin constant-region (C alpha) gene in five different mouse plasmacytoma lines. Recombination occurred approximately 0.8-2.0 kb to the 5' side of two distinct coding regions, defined by sequence homology between the chicken cellular and plasmacytoma myc genes. The myc and C alpha genes were always in opposite transcriptional orientation, with the recombination site within the C alpha switch region sequences. DNA recombination was found to correlate with the production of a novel 2.1 kb species of myc RNA that was 0.4 kb shorter than the normal cellular transcript. No elevated levels of myc RNA were evident, suggesting that DNA rearrangements have altered the myc oncogene product. This oncogene activation corresponds to the chromosomal translocations found in nearly all plasmacytomas.

DNA sequence associated with chromosome translocations in mouse plasmacytomas

A DNA sequence that generates aberrantly rearranged immunoglobulin heavy chain constant region genes in murine plasmacytomas is shown to participate in a chromosome translocation. We have previously termed this DNA sequence NIARD for non-immunoglobulin-associated rearranging DNA. NIARD rearrangements were found frequently in murine plasmacytomas but were not detected in normal lymphocytes. These rearrangements occasionally involve the switch region of the C alpha gene. In this study, DNA samples obtained from mouse-Chinese hamster somatic cell hybrid lines were digested with various restriction endonucleases and analyzed by the Southern transfer technique with a NIARD hybridization probe. These experiments show that NIARD resides on chromosome 15 in the mouse germ line. Since NIARD is found adjacent to the C alpha gene (located on chromosome 12) in some plasmacytomas, it is apparent that a translocation involving these two chromosomes has occurred. We have proposed a rcpT(12;15) model to explain our data. The implications of NIARD rearrangements for malignant transformation are discussed.

Autoimmune diseases: immunopathology and etiopathogenesis

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Chromosomal mapping of the simian sarcoma virus onc gene analogue in human cells

The primate cell-derived transforming gene (v-sis) of simian sarcoma virus (SSV) is represented as a single copy marker within cellular DNAs of mammalian species including human. The human analogue of v-sis can be distinguished from its rodent counterparts by Southern blotting analysis of EcoRI-restricted DNAs. By testing for the presence of the human v-sis-related fragment, c-sis (human), in somatic cell hybrids possessing varying numbers of human chromosome, as well as in segregants of such hybrids, it was possible to assign c-sis to human chromosome 22.

Structural genes of the mouse major urinary protein are on chromosome 4

The major urinary proteins (MUPs) of mouse are a family of at least three major proteins which are synthesized in the liver of all strains of mice. The relative levels of synthesis of these proteins with respect to each other in the presence of testosterone is regulated by the Mup-a locus located on chromosome 4. In an effort to determine the mechanism of this regulation in molecular terms, a cDNA clone containing most of the coding region of a MUP protein has been isolated and identified by partial DNA sequence analysis. Using a combination of hybridization analysis and somatic cell genetics, the structural gene family has been unambiguously mapped to mouse chromosome 4. These data suggest that Mup-a regulation operates in a cis fashion and that models proposing trans regulation of MUP protein synthesis are unlikely.

Continuous culture of human/mouse lymphoid hybridomas: pattern of immunoglobulin secretion

Fusion of human and mouse cells leads to preferential loss of human chromosomes. In this study the loss of human immunoglobulin heavy and light chain production by human/mouse lymphoid hybridomas has been followed longitudinally. A sensitive quantitative ELISA method has been used for measuring human immunoglobulins. The pattern of loss of heavy and light chain production suggests that the genes for human heavy and light chains are on separate chromosomes.

Non-immunoglobulin-associated DNA rearrangements in mouse plasmacytomas

We have characterized a class of DNA rearrangements in plasmacytomas. These recombination events involve a DNA sequence whose origin is outside of the locus of the heavy chain constant region genes, CH. Therefore, we choose to refer to this sequence as non-immunoglobulin-associated rearranging DNA (NIARD). We have isolated two abortively rearranged C alpha genes, generated by NIARD events from the alpha-producing J558 myeloma. Restriction endonuclease maps of these sequences reveal two possible recombination sites in NIARD that are separated by approximately 6.5 kilobase pairs of DNA (defined as 5' and 3' sites). A NIARD rearrangement occurs in 15 out of 20 plasmacytomas tested, including gamma 3-, gamma 1-, gamma 2b-, gamma 2a-, and alpha-producers, but this event usually does not involve a CH switch (S) region. In fact, only S alpha appears to accept NIARD. However, NIARD did not undergo a rearrangement in eight IgA-producing hybridomas tested. One germ-line copy of NIARD (a 22-kilobase pair EcoRI fragment) is retained in all plasmacytomas. NIARD does not appear to possess repetitive DNA sequences homologous to S mu or S alpha. We discuss the possible role and implications of NIARD-like sequence rearrangements in allelic exclusion and chromosomal translocation events in plasmacytomas.

Somatic cell genetic analysis of HLA-A, B, C and human beta 2-microglobulin expression

We have examined the cell surface expression of the human histocompatibility antigens HLA-A, B, C and beta 2-microglobulin (beta 2m) on a human-mouse somatic cell hybrid line. Using specific antibodies and the fluorescence-activated cell sorter (FACS), we viably fractionated and characterized four separate hybrid subpopulations (HLA+,beta 2m+; HLA+,beta 2m-; HLA-,beta 2m+; HLA-,beta 2m-). Hybrid selection based on surface antigen expression resulted in corresponding genetic selection for and against human chromosomes 6 and 15. Studies of the homogeneous hybrid sublines revealed that the presence of human beta 2m in a hybrid cell dramatically increased the surface expression of human HLA-A, B, C and mouse H-2Kk antigens. The results demonstrate the importance of human chromosome-specific surface markers and the fluorescence-activated cell sorter in somatic cell genetic analysis.

Chromosomal location of human kappa and lambda immunoglobulin light chain constant region genes

The chromosomal location of human constant region light chain immunoglobulin (Ig) genes has been determined by analyzing a group of human fibroblast/rodent somatic cell hybrids with nucleic acid probes prepared from cloned human kappa and lambda constant region genes. Human chromosomes in each cell line were identified by isoenzyme analysis. The DNA from hybrid cells was digested with restriction endonucleases, size fractionated by gel electrophoresis, transferred to nitrocellulose or DBM paper, and hybridized with (32)P-labeled nucleic acid probes. The C(kappa) gene was assigned to human chromosome 2 and the C(lambda) genes to chromosome 22, based upon analysis of these hybrid cell lines, and these assignments were confirmed by analysis of subclones. A group of previously unassigned loci can be mapped to chromosome 2 by virtue of their close linkage to C(kappa). The lambda and kappa light chain and heavy chain Ig genes have now been assigned to all three human chromosomes that are involved in translocations with chromosome 8 in human B cell neoplasms. These techniques and probes provide a means to study the detailed arrangement of human Ig genes and their pseudogenes.