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A Leder

Publications and source records attributed to A Leder.

At least 19 recordsLinked to original sources
PubMed1998

Rapid genotyping of mice with hemoglobinopathies and globin transgenes.

The hematology of the laboratory mouse has been well characterized. Normal genetic differences at the alpha- and beta-globin gene loci serve as useful markers for a wide variety of types of experimental studies. There are a number of naturally occurring or induced mutations that disrupt globin expression and produce thalassemic phenotypes. In addition, much has been learned of the workings of the globin locus control region from studies of transgenic mice, including those with mutations induced by targeted site-specific modifications. After a new mutation or transgene has been created, it must be maintained in living mice, and the genotypes of the offspring must be ascertained. While it is possible to determine genotypes by DNA analyses, such assays are time consuming and relatively expensive. An osmotic challenge test--originally developed for the genotyping of large-deletion alpha-thalassemia mutations in mice--has proven useful in detecting both severe and milder alpha- and beta-thalassemias, as well as some transgenic genotypes in mice carrying human globin genes. Reliable genotyping can, in some cases, be completed within a few minutes with minimal expense. Quantification of red cell fragility for a variety of thalassemic and transgenic mice is described here, along with a simplified test suitable for rapid, routine genotyping. The osmotic challenge test is perfectly reliable for distinguishing genotypes that cause significantly decreased release of hemoglobin from the red cells, but it is also useful for some of the conditions in which overall erythrocyte osmotic fragility is essentially normal.

Animals↗
PubMed1997

Mouse zeta- and alpha-globin genes: embryonic survival, alpha-thalassemia, and genetic background effects.

A classical notion regarding the expression of murine embryonic zeta- and adult alpha-globin genes holds that there is a switch in globin production from the embryonic to the adult form during fetal development. Our previous in situ hybridization studies challenged this view, since both zeta- and alpha-globin mRNAs can be detected simultaneously in the earliest erythrocyte populations. This finding raises the possibility that zeta-globin production might be wholly or partially redundant in embryos in which the adult alpha-globin is also expressed. To test this possibility, we created a null mutation of the zeta-globin gene using homologous recombination in embryonic stem cells. Many outbred mice homozygous for the zeta-null mutation were able to develop normally, undermining the notion that there is an absolute need for zeta-globin and indicating that alpha-globin alone can serve the survival needs of the fetus. Interestingly, insertion of the PGK-Neo cassette (used to create the null mutation) into the zeta-globin gene appears to influence the expression of the nearby alpha-globin genes, giving rise to reduced alpha-globin production and to an alpha-thalassemia-like syndrome. There is also evidence indicating the strong influence of genetic background on the zeta-null and alpha1-null phenotypes, both of which are much more severe in the 129/SvEv inbred genetic background. These quantitative differences can potentially be exploited to identify genes important for erythropoiesis.

Alleles↗
PubMed1993

Multiple tumor types appear in a transgenic mouse with the ras oncogene.

A transgenic mouse strain with the zeta-globin promoter and the vHa-ras oncogene develops an array of mesenchymal and epithelial neoplasms described here. The predominate mesenchymal tumors were dermal spindle cell tumors, which resembled malignant fibrous histiocytomas found in humans. They were associated with hepatosplenomegaly and developed beneath squamous papillomas. The hepatosplenomegaly was associated with infiltrates of cells that tended toward myelocytic or monocytic differentiation. Other epithelial tumors included keratoacanthomas and squamous cell carcinomas. Squamous cysts, some with squamous cell carcinomas, of the salivary glands and mammary carcinomas were also found. Odontogenic tumors, which sometimes differentiated into ameloblastomas, were one of the more unusual tumor types observed. Other, less frequent tumors were also noted. The tumors described here are a potentially valuable experimental resource that may lead to an understanding of malignant fibrous histiocytoma-like lesions, odontogenic tumors, and tumor progression.

Animals↗
PubMed1992

An embryonically expressed gene is a target for c-Myc regulation via the c-Myc-binding sequence.

We have used a subtraction/coexpression strategy involving two different tumors derived from c-myc-bearing transgenic mice to identify a gene that is a target for c-Myc regulation. The gene, expressed in certain embryonic and adult tissues and in several (but not all) c-myc-based tumors, bears a functional c-Myc-binding sequence located 3' to its transcription start site. This sequence is required for the binding of a nuclear protein complex which, by antibody analysis, includes c-Myc. This site is also required for expression of a reporter gene in chimeric constructs transfected into c-myc-overexpressing cells and, conversely, requires c-myc cotransfection for its enhanced expression in COS cells. Furthermore, transfection of c-myc blocks the normal down-regulation of this gene, which occurs in embryonic stem cells as they undergo differentiation. This target gene encodes an anonymous cDNA (ECA39) found previously to be amplified in a teratocarcinoma cell line.

Animals↗
PubMed1992

In situ hybridization reveals co-expression of embryonic and adult alpha globin genes in the earliest murine erythrocyte progenitors.

Murine erythropoiesis begins with the formation of primitive red blood cells in the blood islands of the embryonic yolk sac on day 7.5 of gestation. By analogy to human erythropoiesis, it has been thought that there is a gradual switch from the exclusive expression of the embryonic alpha-like globin (zeta) to the mature adult form (alpha) in these early mouse cells. We have used in situ hybridization to assess expression of these two globin genes during embryonic development. In contrast to what might have been expected, we find that there is simultaneous expression of both zeta and alpha genes from the very onset of erythropoiesis in the yolk sac. At no time could we detect expression of embryonic zeta globin mRNA without concomitant expression of adult alpha globin mRNA. Indeed, adult alpha transcripts exceed those of embryonic zeta in the earliest red cell precursors. Moreover, the pattern of hybridization reveals co-expression of both genes within the same cells. Even in the fetal liver, which supersedes the yolk sac as the major site of murine fetal erythropoiesis, there is a brief co-expression of zeta and alpha genes followed by the exclusive expression of the adult alpha genes. These data indicate an important difference in hematopoietic ontogeny between mouse and that of human, where zeta expression precedes that of alpha. In addition to resolving the embryonic expression of these globin genes, our results suggest that the embryonic alpha-like globin gene zeta may be physiologically redundant, even during the earliest stages of embryonic development.

Animals↗
PubMed1990

v-Ha-ras transgene abrogates the initiation step in mouse skin tumorigenesis: effects of phorbol esters and retinoic acid.

Experimental carcinogenesis has led to a concept that defines two discrete stages in the development of skin tumors: (i) initiation, which is accomplished by using a mutagen that presumably activates a protooncogene, and (ii) promotion, which is a reversible process brought about most commonly by repeated application of phorbol esters. We have created a transgenic mouse strain that carries the activated v-Ha-ras oncogene fused to the promoter of the mouse embryonic alpha-like, zeta-globin gene. Unexpectedly, these animals developed papillomas at areas of epidermal abrasion and, because abrasion can also serve as a tumor-promoting event in mutagen-treated mouse skin, we tested these mice for their ability to respond to phorbol ester application. Within 6 weeks virtually all treated carrier mice had developed multiple papillomas, some of which went on to develop squamous cell carcinomas and, more frequently, underlying sarcomas. We conclude that the oncogene "preinitiates" carrier mice, replacing the initiation/mutagenesis step and immediately sensitizing them to the action of tumor promoters. In addition, treatment of the mice with retinoic acid dramatically delays, reduces, and often completely inhibits the appearance of promoter-induced papillomas. This strain has use in screening tumor promoters and for assessing antitumor and antiproliferative agents.

Animals↗
PubMed1989

Perinatal lethality (ple): a mutation caused by integration of a transgene into distal mouse chromosome 15.

We have used cytogenetic and recombinational analysis to determine the position of a transgene integrated into the mouse genome. The transgene maps to band F on the physical map of mouse chromosome 15 by in situ analysis and is tightly linked genetically to a cluster of loci that include the mutations caracul (Ca) and microcytic anemia (mk). Genetic analysis of the offspring of noninbred animals carrying the transgene and marker loci demonstrates a significant deficiency of homozygous progeny at weaning. When inbred mice heterozygous for the transgene are mated, about one-quarter of their offspring are homozygous; none of these animals survives more than 1 day after birth. It appears likely that a recessive insertional mutation has occurred as a result of transgene integration into a locus required for postnatal viability. We call this mutation transgenic perinatal lethality (Tg.ple).

Animals↗
PubMed1989

Animal models of human disease. Pathology and molecular biology of spontaneous neoplasms occurring in transgenic mice carrying and expressing activated cellular oncogenes.

This present review focuses on spontaneous neoplasms occurring in transgenic mice carrying and expressing activated cellular oncogenes. The historical development of transgenic mice as in vivo disease models is briefly traced, followed by a brief description of the actual technology in such systems. Additional emphasis is placed on the concept of targeting activated cellular oncogenes to specific tissues in transgenic mice. Cumulative experience with activated (Vmyc, ras, and neu (erb-B2] oncogenes in transgenic mice is considered in detail, with particular attention paid to the observed pathology, as well as to the kinetics of disease occurrence. It is concluded that transgenic mice offer the interested investigator(s) an excellent prospective, in vivo model of oncogenesis.

Animals↗
PubMed1988

[HIV transmission via blood transfusions: a study by the Swiss Red Cross blood bank service].

An inquiry amongst blood transfusion services served to establish at 19 the number of known transfusion associated HIV infections in Switzerland. In 12 cases the transfusion of an anti-HIV positive blood unit could be proven retrospectively, while in 7 cases an HIV-infected blood donor could not be found but the association of the infection with blood transfusion is highly probable by exclusion of other risk factors. All these infections occurred before introduction of anti-HIV screening in Switzerland in November 1985. After this date no new transfusion associated HIV infections have been reported. It is estimated that there are fewer than 170 transfusion associated HIV infections in Switzerland. The probability of infection with AIDS by blood transfusion is less than 1:500,000. Blood transfusion today appears to be as safe as before the emergence of the AIDS epidemic.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Consequences of widespread deregulation of the c-myc gene in transgenic mice: multiple neoplasms and normal development.

We have constructed a transgenic mouse strain in which a mammary tumor virus LTR/c-myc fusion gene is anomalously expressed in a wide variety of tissues. The deregulated c-myc transgene, now glucocorticoid inducible, contributes to an increased incidence of a variety of tumors, including those of testicular, breast, lymphocytic (B cell and T cell), and mast cell origin. The deregulated gene does not, however, otherwise disturb cell proliferation, nor does it interfere with normal development in these animals. Moreover, since not all tissues that express the transgene develop neoplasms, these results begin to define the transforming spectrum of the c-myc oncogene. They also extend to several organ systems the notion that elements in addition to an activated c-myc gene are required to induce malignancy in the living organism.

Adenocarcinoma↗
PubMed1986

Induction of growth alterations in factor-dependent hematopoietic progenitor cell lines by cocultivation with irradiated bone marrow stromal cell lines.

We studied the production of hemopoietins by x-irradiated plateau-phase cultures of cloned marrow stromal cell lines derived from C3H/HeJ marrow, termed D2XRII and clone 11. The production of CSF in agar overlay of control or 10,000 rad irradiated stromal cultures was quantitated by induction of colonies in: overlaid fresh marrow, IL-3-dependent cell line 32D cl 3, or GM-CSF/IL-3-dependent cell lines FDCP-1 or bg/bg cl 1. Conditioned media were tested for CSF by bioassay using fresh marrow cells, for M-CSF (CSF-1) by RIA, and for IL-3 and GM-CSF by microwell proliferation assay with 32D cl 3 and FDCP-1 cells, respectively. X-irradiation to doses that decreased CSF-1 to 40% of control levels (greater than 5,000 rad) resulted in a 30-fold increase in growth of FDCP-1 or bg/bg cl 1 cells in liquid co-culture or agar culture overlay with no detectable growth of 32D cl 3. The frequency of subculture of nonautocrine, factor independent (FI) variant clonal lines of FDCP-1 or bg/bg cl 1 cells was increased over 1000-fold by 15 weeks cocultivation with irradiated stromal cell cultures. FI subclonal lines formed tumors in syngeneic mice and contained no detectable poly A messenger RNA for GM-CSF or IL-3, and no elevation in c-myc, c-abl, c-src, or erb-B onc gene-specific messenger RNA compared to parent factor-dependent lines. These data indicate that x-irradiated plateau phase marrow stromal cells produce increased levels of cell contact-mediated biologically active hemopoietin(s) other than M-CSF, GM-CSF, or IL-3 and induce nonautocrine factor-independent malignant cell lines in vitro.

Animals↗
PubMed1985

Characterization, expression, and evolution of the mouse embryonic zeta-globin gene.

We have determined the complete sequence of the embryonic alpha-like, zeta (zeta)-globin gene of the BALB/c mouse. The structure of this gene establishes the amino acid sequence of the mouse embryonic zeta-globin polypeptide chain and allows us to identify sequences within the gene that may be important for its expression. One of these is a 300-base segment that is tightly conserved between mice and humans and is located at the 5' end of the zeta-globin gene. By introducing the cloned gene into permanently transfected mouse erythroleukemic cell lines and comparing its transcript with that of zeta-globin mRNA derived from embryonic yolk sac erythrocytes, we are able to show that the cloned gene is transcriptionally active and that its transcript is correctly initiated and processed. Interestingly, the zeta-globin gene is also active when permanently transfected into an immunoglobulin-producing B-cell, a cell that presumably has tissue-specific requirements for gene expression. Further, a comparison of the amino acid coding sequence of the mouse zeta-globin gene to that of zeta-like globin genes of other species supports a revised evolutionary lineage in which goats and humans are closely related, whereas mice are further removed.

Amino Acid Sequence↗
PubMed1982

Globin genes: a paradigm of gene structure, function, and evolution.

Access to the detailed structure of the globin (and other) genes has taught us at least three valuable, but not necessarily expected, lessons regarding the structure and evolution of the genes. Foremost, at least in terms of its surprising nature, is the fact that many genes are interrupted, i.e., they contain discontinuous blocks of coding and noncoding information. No less surprising are the accompanying facts that chromosomal DNA changes by the movement and rearrangement of large pieces of DNA and that genetic loci are highly and unexpectedly complex, consisting of arrays of related genes and pseudo (or apparently nonfunctional) genes. Here we review some of the evidence upon which these conclusions rest, and we try to form a coherent picture of gene evolution. The evidence that we shall use is based on studies of the mouse globin. Evidence from various other genetic systems leads us to believe that these genes serve as an instructive general model rather than an idiosyncratic one.

Animals↗
PubMed1981

The organization and evolution of cloned globin genes.

The globin genes represent a complex set of sequences that are expressed in a coordinate fashion during the development of red blood cells. while this complex family of genes may consist of as many as ten to fourteen members [34], three of these genes have now been cloned and their entire nucleotide sequence determined. As was initially observed in the case of beta globin major gene, all are encoded in three distinct coding blocks separated by two intervening sequences of DNA. Their intervening sequences of DNA are preserved, with respect to location, but are widely divergent, with respect to size and sequence. The divided information in each gene is edited and spliced together at the level of its initial RNA transcript which is complementary to the entire gene sequence including its intervening sequences. Structural correlation analyses have allowed us to identify sites in all three genes that might be responsible for the initiation of transcription, RNA splicing, and poly A addition. The function of these sites has been tested by cloning these genes in an animal virus vector SV40. Such animal virus hybrids have been used to infect tissue culture cells and have directed the synthesis of both alpha and beta mouse globin in cells of monkey origin. These studies indicate that such signals operate across species barriers and further indicate that the animal virus vector system will be useful in elucidating their function.

Amino Acid Sequence↗
PubMed1980

Mouse globin system: a functional and evolutionary analysis.

Structural and functional analysis of the mouse alpha-globin and beta-globin genes reveals that the globin genes are encoded in discontinous bits of coding information and that each gene locus is much more complex than was originally supposed. Each seems to consist of an array of several authentic genes as well as several apparently inactive pseudogenes. Comparison of the sequences of some of these genes to one another indicates that chromosomal DNA is a dynamic structure. Flanking and intervening sequences change in two ways: quickly, by duplication and extensive insertions and deletions, and slowly, by point mutation. Active coding sequences are usually limited to the slower mode of evolution. In addition to identifying fast and slow modes of evolution, it has also been possible to test the function of several signals that surround these genes and to identify those that appear to play a role in gene expression.

Animals↗