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Biomedical subjects

R Jaenisch

Publications and source records attributed to R Jaenisch.

At least 253 records · Page 14Linked to original sources
PubMed1981

Effects of murine leukemia virus infection on long-term hematopoiesis in vitro emphasized by increased survival of bone marrow cultures derived from BALB/Mo mice.

The effect of infection with Moloney murine leukemia virus (Mo-MuLV) on long-term bone marrow cultures was studied. Cultures were derived from the bone marrow of BALB/Mo mice, which carry Mo-MuLV as an endogenous virus, or from BALB/c, 129/J, or balb/c X 129/J mice that were infected with Mo-MuLV in vitro. The following parameters were tested: longevity of generation of granulocytes; biological properties of nonadherent cells in colony-forming assays for pluripotential stem cells and committed granulocyte-macrophage colony-forming unit culture, erythroid, or metachromasia-positive mast cell-basophil colony-forming cells; differentiation of nonadherent cells following cocultivation with thymic or bone marrow stromal cells; and generation of WEHI-3 dialyzed conditioned medium-dependent permanent cell lines. Granulocytes were generated for 65 weeks in BALB/Mo marrow cultures, 31 weeks for BALB/c, 22 weeks in 129/J, and 28 weeks in balb/c X 129/J cultures. Exogenous infection of BALB/c cultures with Mo-MuLV increased the longevity of hematopoiesis to 41 weeks. Granulocyte-macrophage colony-forming unit cultures were produced for 61 weeks in BALB/Mo cultures, 25 to 40 weeks in Mo-MuLV-infected cultures, and 19 to 33 weeks in uninfected control cultures. Nonadherent cells harvested from BALB/Mo marrow cultures generated cloned permanent WEHI-3 dialyzed conditioned medium-dependent, nonleukemogenic granulocyte-macrophage colony-forming unit culture cell lines at greater efficiency than did Mo-MuLV-infected or uninfected BALB/c cultures. The cell lines differentiated to mature granulocytes following cocultivation with purified marrow or thymic stromal cells. There was no detectable differentiation of nonadherent cells to lymphocytes or mast cells. Thus, Mo-MuLV does not detectably transform granulocyte progenitor cells in vitro to granulocytic leukemia. However, Mo-MuLV replication stimulates self-renewal of granulocyte progenitor cells in both primary marrow culture and in suspension culture in WEHI-3 dialyzed conditioned medium.

Animals↗
PubMed1980

Integration of Moloney leukaemia virus into the germ line of mice: correlation between site of integration and virus activation.

Endogenous avian and murine C-type viruses are genetic elements which are transmitted at several distinct chromosomal loci. Different patterns of virus activation have been observed in a variety of different mouse strains. However, because there are multiple copies of closely related endogenous viruses in every mouse strain, the genetic basis of the differential expression of these genes is poorly understood. A new substrain of mice, BALB/Mo, was derived previously carrying the exogenous Moloney leukaemia virus (M-MuLV) genome on chromosome 6 (ref. 14). Virus activation occurs in lymphatic tissues of all BALB/Mo mice soon after birth. We report here the derivation of three new substrains of mice each carrying a single M-MuLV genome on different chromosomal integration sites. Each locus was associated with a distinct phenotype of virus expression. Evidence is presented that apparently identical viral genomes show differences in spontaneous virus activation and that defective viral genomes can be carried in the germ line of mice.

Animals↗
PubMed1980

Passive immunotherapy prevents expression of endogenous Moloney virus and amplification of proviral DNA in BALB/Mo mice.

BALB/Mo mice carrying the Moloney murine leukemia virus (M-MuLV) as an endogenous virus become viremic soon after birth and develop leukemia at a later age. M-MuLV-specific gene expression and an increase of virus-specific DNA copies in lymphatic target organs are characteristics of the preleukemic phase. Passive immunotherapy of new born BALB/Mo mice with anti-gp70 glycoprotein or anti-M-MuLV serum prevented viremia and delayed significantly the subsequent development of leukemia. Molecular hybridization experiments showed that both virus-specific genome transcription and virus-specific DNA amplification could be completely suppressed by antiserum treatment. Thus virus-specific RNA concentrations in target organs of immunized BALB/Mo mice of 6 months or older were as low as in normal BALB/c mice. This is an age at which untreated BALB/Mo mice have already developed malignant lymphoma. Our experiments demonstrate that treatment with antiserum interferes with the early events of virus expression and thus prevents the subsequent steps leading to leukemia.

Age Factors↗
PubMed1980

Chromatin conformation of integrated Moloney leukemia virus DNA sequences in tissues of BALB/Mo mice and in virus-infected cell lines.

The technique of preferential DNase I digestion of transcriptionally active chromatin regions was used to study the structural organization of integrated Moloney murine leukemia virus (M-MuLV) proviral sequences in various cells carrying integrated viral genomes. BALB/Mo mice, which carry M-MuLV as an endogenous virus at a single Mendelian locus, were used to examine the genetically transmitted viral genome copy and additional M-MuLV sequences acquired somatically during leukemogenesis. It has been shown previously that M-MuLV genome expression in these mice is restricted to lymphatic target tissues. In young homozygous BALB/Mo mice carrying one M-MuLV genome copy per haploid mouse genome in all cells we found that the genetically transmitted viral genome copy was in a preferentially DNase I-sensitive conformation in lymphatic target tissues, whereas in nontarget tissues the same sequence was not preferentially DNase I sensitive. This suggests that the chromatin conformation and the transcriptional activity of the integrated proviral genome are related to and probably determined by the state of cellular differentiation. In target tissues from BALB/Mo mice examined at different ages and in different stages of leukemogenesis the majority of the new somatically acquired M-MuLV sequences were preferentially DNase I digestible. A very similar pattern of DNase I digestibility was observed in target tissues from BALB/c mice exogenously infected with M-MuLV. This shows that in these tissues somatically acquired proviral sequences integrate preferentially or exclusively at sites of the host genome in which they are in a transcriptionally active chromatin conformation. Alternatively, the chromatin structure of the respective host genome region may be changed after the integration of viral DNA. In nontarget tissues from BALB/Mo mice the M-MuLV-specific sequences remained DNase I resistant throughout the lives of the animals. A different pattern of DNase I digestibility was observed in virus-infected cell lines which had been produced by low-multiplicity infection, cloned, and selected for virus production. When cell lines harboring different numbers of M-MuLV proviral copies were examined, it was found that a minority of the proviral sequences (on the average only one M-MuLV genome copy per haploid mouse genome) were preferentially digestible by DNase I, independent of the total number of proviral genome copies present. This suggests that the chromatin conformation of newly acquired proviral sequences is influenced by the state of differentiation of the infected cell or the way infected cells are selected or both.

Aging↗
PubMed1979

Genetic transmission of Moloney leukemia virus: mapping of the chromosomal integration site.

Mice genetically transmitting the exogenous Moloney leukemia virus (Balb/Mo) have been previously derived. These animals carried one copy of Moloney virus DNA (M-MuLV) in their germ line and transmitted the virus as a single Mendelian gene to the next generation. Homozygous BALB/Mo mice were used to genetically map the M-MuLV locus. Embryo fibroblasts were fused to established Chinese hamster cells and somatic cell hybrids were selected. Segregation of mouse chromosomal markers in the hybrids was correlated to the loss of M-MuLV-specific sequences as detected by molecular hybridization. Of 15 isozymes located on different mouse chromosomes only triosephosphate isomerase segregated syntenic with the M-MuLV gene, suggesting that the virus was integrated on chromosome No. 6. This was confirmed by sexual genetic experiments analyzing segregation of Moloney viremia and two markers on chromosome 6 and 15, respectively. The results show that M-MuLV expression is linked to wa-1 on chromosome 6 at a distance of about 30 map units. These data define a new genetic locus, Mov-1, representing the structural gene of M-MuLV in BALB/Mo mice.

Animals↗
PubMed1979

The integration sites of endogenous and exogenous Moloney murine leukemia virus.

Specific cDNA probes of Moloney and AKR murine leukemia viruses have been prepared to characterize the proviral integration sites of these viruses in the genomes of Balb/Mo and Balb/c mice. The genetically transmitted Moloney provirus of Balb/Mo mice was detected in a characteristic Eco RI DNA fragment of 16 x 10(6) daltons. No fragment of this size was detected in tissue DNAs from Balb/c mice infected as newborns with Moloney virus. We conclude that a viral integration site, occupied in preimplantation mouse embryos, is not necessarily occupied when virus infects cells in post-natal animals. Balb/Mo and Balb/c mice do carry the AkR structural gene in an Eco RI DNA fragment of 12 x 10(6) daltons. Further restriction analysis of this fragment indicated that both mouse lines carry one AKR-type provirus. Leukemogenesis in Balb/Mo and newborn infected Balb/c mice is accompanied by reintegration of Moloney viral sequences in new chromosomal sites of tumor tissues. Part of the reintegrated Moloney viral sequences are of subgenomic size. The AKR viral sequences, however, are not found in new sites. Further restriction analysis revealed that the development of Moloney virus-induced leukemia in Balb/Mo mice does not lead to detectable structural alteration of the genetically transmitted Moloney and AKR structural genes. Possible mechanisms of the reintegration process are also discussed.

AKR murine leukemia virus↗
PubMed1979

Germ line integration of Moloney leukemia virus: identification of the chromosomal integration site.

The chromosomal integration site of the structural gene of Moloney murine leukemia virus (M-MuLV) in the genome of BALB/Mo mice was mapped genetically. These mice transmit the exogenous M-MuLV as an endogenous virus at a single Mendelian locus. Two independent experimental approaches were used: (i) Non-virus-producing fibroblasts prepared from homozygous BALB/Mo embryos were fused to Chinese hamster Wg3-h-o cells. In an analysis of 30 independent mouse-Chinese hamster cell hybrid clones, the segregation of the viral genome measured by molecular hybridization and enzymes assigned to 16 different mouse chromosomes were compared. We found a highly concordant segregation of M-MuLV sequences and the mouse enzyme triosephosphate isomerase (TPI, EC 5.3.1.1), whose gene has been assigned to chromosome 6. A further karyotype analysis of 9 clones, in which the chromosomes were identified cytochemically, supported this result. (ii) The segregation of the viral genome was studied in backcrosses of BALB/Mo with ABP/J mice. In the backcross ABP/Jx(ABP/JxBALB/Mo) a linkage of the M-MuLV genome to the morphological marker wa-1 on mouse chromosome 6 was found. This confirmed the conclusion that the M-MuLV genome is integrated in mouse chromosome 6. These experiments define the genetic locus Mov-1, denoting the genetically transmitted structural gene of M-MuLV in BALB/Mo mice.

Animals↗
PubMed1979

Highly inducible cell lines derived from mice genetically transmitting the Moloney murine leukemia virus genome.

Permanent, non-virus-producing cell lines have been established from a mouse embryo carrying an endogenous, genetically transmitted Moloney murine leukemia virus (M-MuLV) genome. These cells carry the M-MuLV genome, as demonstrated by hybridization of cellular DNA to M-MuLV complementary DNA, but do not express it at the levels of virus production, accumulation of intracellular viral p30, or M-MuLV-specific RNA. Treatment with bromodeoxyuridine (50 microgram/ml for 24 h) resulted in induction of XC-positive NB-tropic virus, although only a small fraction of the cells released virus (less than 0.1% after 48 h). Immunofluorescent staining and flow microfluorometry indicated that a wave of p30 accumulation occurs in the induced cells, with a maximum at 24 to 48 h after the addition of bromodeoxyuridine. Furthermore, most, if not all, cells were induced to produce p30 protein. Similar kinetics were found for the accumulation of M-MuLV-specific RNA in the cytoplasm of induced cells. This rapid induction of virus expression in a majority of cells was dependent on the presence of the M-MuLV genome and probably represents primarily the expression of this endogenous virus since induction was not observed in cells similarly derived from a sibling embryo lacking the M-MuLV genome.

Animals↗
PubMed1978

Low-multiplicity infection of Moloney murine leukemia virus in mouse cells: effect on number of viral DNA copies and virus production in producer cells.

Mouse cells infected with Moloney murine leukemia virus (M-MuLV) were prepared by two methods, and the number of M-MuLV-specific DNA copies in the infected cells was measured. The number of M-MuLV-specific DNA copies detected varied from one to eight per infected cell in different cell lines. Cells in which multiple rounds of viral infection occurred during establishment had on the average more viral DNA copies than cells in which infection at low multiplicity was performed, followed by cloning of the cells. However, even in cells derived by the low multiplicity of infection method, most cell lines carried more than one copy of M-MuLV-specific DNA. Virus production per cell was also measured, and no strict correlation was observed between the number of M-MuLV DNA copies present and the amount of virus produced.

Cell Line↗
PubMed1977

Germ line integration of moloney leukemia virus: effect of homozygosity at the m-mulV locus.

Mice genetically transmitting the exogenous Moloney leukemia virus (M-MuLV) have been previously derived. These animals carried one copy of M-MuLV DNA in their germ line and were heterozygous for the M-MuLV locus (Jaenisch, 1976). Experiments were performed to investigate whether homozygosity at the M-MuLV locus would be compatible with normal development. Animals heterozygous for the M-MuLV locus were mated [female (+/-) X male(+/-)] and the genotype of the offspring was analyzed. Molecular hybridization experiments revealed three classes of offspring carrying two copies (++), one copy (+/-) and no (--) M-MuLV-specific DNA sequences, respectively, in their liver DNA. Genetic experiments indicated that males of the first class transmitted the virus to 100% of their offspring, males of the second class to 50% and males of the third class not at all when mated with normal females. These results demonstrated that homozygosity at the M-MuLV locus has no detectable effect on normal development of the animals and that the M-MuLV gene is transmitted from one generation to the next strictly according to Mendelian expectations. Development of M-MuLV-induced leukemia is not influenced by the genotype of these animals--that is, animals carrying two or one copies of M-MuLV in their germ line or animals congenitally infected from the mother developed disease at similar rates.

Animals↗