Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Transgene”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed2004

Transgenic mouse model for breast cancer: induction of breast cancer in novel oncogene HCCR-2 transgenic mice.

Transgenic mice containing novel oncogene HCCR-2 were generated to analyse the phenotype and to characterize the role of HCCR-2 in cellular events. Mice transgenic for HCCR-2 developed breast cancers and metastasis. The level of p53 in HCCR-2 transgenic mice was elevated in most tissues including breast, brain, heart, lung, liver, stomach, kidney, spleen, and lymph node. We examined whether stabilized p53 is functional in HCCR-2 transgenic mice. Defective induction of p53 responsive genes including p21WAF1, MDM2, and bax indicates that stabilized p53 in HCCR-2 transgenic mice exists in an inactive form. These results suggest that HCCR-2 represents an oncoprotein that is related to breast cancer development and regulation of the p53 tumor suppressor.

Animals↗
PubMed2003

The capacity of transgenic tobacco to send a systemic RNA silencing signal depends on the nature of the inducing transgene locus.

RNA silencing is a conserved eukaryotic pathway in which double-stranded RNA (dsRNA) triggers destruction of homologous target RNA via production of short-interfering RNA (siRNA). In plants, at least some cases of RNA silencing can spread systemically. The signal responsible for systemic spread is expected to include an RNA component to account for the sequence specificity of the process, and transient silencing assays have shown that the capacity for systemic silencing correlates with the accumulation of a particular class of small RNA. Here, we report the results of grafting experiments to study transmission of silencing from stably transformed tobacco lines in the presence or absence of helper component-proteinase (HC-Pro), a viral suppressor of silencing. The studied lines carry either a tail-to-tail inverted repeat, the T4-IR transgene locus, or one of two different amplicon transgene loci encoding replication-competent viral RNA. We find that the T4-IR locus, like many sense-transgene-silenced loci, can send a systemic silencing signal, and this ability is not detectably altered by HC-Pro. Paradoxically, neither amplicon locus effectively triggers systemic silencing except when suppressed for silencing by HC-Pro. In contrast to results from transient assays, these grafting experiments reveal no consistent correlation between capacity for systemic silencing and accumulation of any particular class of small RNA. In addition, although all transgenic lines used to transmit systemic silencing signals were methylated at specific sites within the transgene locus, silencing in grafted scions occurred without detectable methylation at those sites in the target locus of the scion.

DNA Methylation↗
PubMed1988

Divergent disease patterns in granulocyte-macrophage colony-stimulating factor transgenic mice associated with different transgene insertion sites.

A comparison was made of disease development in two lines of transgenic mice in which the granulocyte-macrophage colony-stimulating factor (GM-CSF) transgene was inserted in different chromosomal locations. Female-line mice (X chromosome insertion) had equivalent elevations of serum GM-CSF levels to those in male-line mice (autosomal insertion) but a shorter survival (median survival, 95 versus 145 days) and a significantly higher incidence of large inflammatory foci in skeletal muscle and gut congestion. Male-line transgenic mice had higher levels of cells in the peritoneal cavity and a higher frequency of spleen enlargement with excess erythropoiesis than female-line mice and uniquely developed fibrotic nodules in the abdominal and pleural cavities. The various diseases in GM-CSF transgenic mice are likely to have been induced by GM-CSF-stimulated products of macrophages, and in the two transgenic lines the macrophages exhibit characteristic differences in morphology and possibly functional activity.

Animals↗
PubMed1993

Generation of a transgenic model for retrovirus-mediated gene therapy for hepatocellular carcinoma is thwarted by the lack of transgene expression.

Transgenic mice have been generated to determine the tissue-specific expression, safety, and efficacy of a novel chimeric gene that is being investigated as a test system for virus-directed enzyme prodrug therapy (VDEPT). The chimeric gene consists of the transcriptional regulatory sequences of the albumin gene and the protein-coding sequence of the varicella-zoster virus thymidine kinase (VZV-TK) gene inserted into a retroviral vector. Eight founders were obtained from microinjection of a nearly full-length proviral fragment containing the chimeric gene. Liver extracts of the founders and 12 G1 mice were analyzed by enzymatic and Western blot analysis for the presence of VZV-TK. No VZV-TK enzymatic activity or protein was detected. Methylation analysis indicated that both the chimeric gene and retroviral sequences were methylated. Treatment of newborn mice with 5-azacytidine or backcrossing into a DBA/2 genetic background did not result in detectable VZV-TK expression or a change in transgene methylation. The poor transgene expression reported here appears to reflect an inherent, continuing problem of transgenic technology with transgenes that are essentially intact retroviral shuttle vectors. These methylation and expression problems are generally applicable to other animal models for retroviral-mediated gene therapy and should be of interest to researchers as they design and evaluate preclinical safety and efficacy studies.

Albumins↗
PubMed1999

Tamoxifen induces G:C-->T:A mutations in the cII gene in the liver of lambda/lacI transgenic rats but not at 5'-CpG-3' dinucleotide sequences as found in the lacI transgene.

Tamoxifen, a rat liver carcinogen, can induce mutations in the lacI gene in the livers of lambda/lacI transgenic rats. However, the presence of persistent tamoxifen adducts on the liver DNA raises the possibility that some contribution to the mutagenesis from ex vivo mutations during the in vitro lacI assay cannot be ruled out. To address this issue, mutagenesis at the cII gene of the transgenic shuttle vector was determined using a selection based assay which is unaffected by the presence of tamoxifen-DNA adducts. Female lambda/lacI transgenic rats were dosed orally with tamoxifen (20 mg/kg body wt) daily for 6 weeks, causing a 3.2-fold increase in the mutant frequency (MF) in the cII gene compared with that obtained with solvent treated animals. This was similar to the MF found previously at the lacI gene and confirms that tamoxifen is mutagenic in vivo. The major class of mutation induced by tamoxifen in the cII gene was G:C-->T:A transversions as was found previously in the lacI gene. However, in the one unreplicated study of mutations in the p53 gene of liver tumours induced by tamoxifen, no G:C-->T:A transversions were found; possible differences between mutagenesis in normal and tumour tissues are explored. The major proportion of the G:C-->T:A transversions occurred at 5'-CpG-3' dinucleotide (CpG) sites in the lacI gene, but not at such sites in the cII gene. The methylation of CpG sites greatly enhances the targeting of deoxyguanosine by carcinogens, thus this finding might be explained by differences in the methylation patterns at their respective CpG sites; however, nothing is known about the methylation status of either the lacI nor the cII gene in this transgenic rat. This study raises the important issue of which target genes (mammalian or transgenic) should be used as endpoints in mammalian mutagenesis assays.

Aflatoxin B1↗
PubMed1993

A high frequency of hybridomas from M54 mu heavy chain transgenic mice initially co-express transgenic and rearranged endogenous mu genes.

The M54 transgenic mouse line, which carries the 17.2.25 Ig mu heavy chain gene, rearranges Ig heavy chains and expresses both transgenic and endogenous mu. B cell lineage development is selectively impaired in these mice and cells that simultaneously express transgenic and endogenous mu ('double-producers') are common amongst the B cells and plasma cells that do develop. Weaver, Imanishi-kari, Baltimore and colleagues failed to obtain double-producing hybridomas from M54 mice; however, molecular and serologic studies presented here show that such hybridomas are readily generated. These hybridomas are extremely unstable and rapidly yield variants producing either transgenic or endogenous mu. Therefore the stable cloned lines we obtained, like Weaver et al., were almost all single or non-producers. We also found that the VH gene usage in our hybridomas was skewed towards the JH proximal (VHQ52, VH81X) families, supporting the idea that the expression of the M54 transgene alters the endogenous Ig repertoire.

Animals↗
PubMed2004

Comparison of HLA-DR1-restricted T cell response induced in HLA-DR1 transgenic mice deficient for murine MHC class II and HLA-DR1 transgenic mice expressing endogenous murine MHC class II molecules.

Transgenic mice expressing human HLA class II molecules provide a useful model for identifying HLA-restricted CD4+ epitopes. However, the influence of endogenous murine H-2-restricted T cell responses on HLA-restricted responses is not known. In the present study, we show that HLA-DR1 transgenic mice deficient for H-2 class II expression (HLA-DR1+/+/IAbeta0/0) exhibit an equivalent expression level of the transgene HLA-DR1 and a similar diversity in the TCR repertoire, but a slightly different number of CD4+ peripheral T cells, when compared to HLA-DR1 transgenic mice in which H-2 class II molecules were retained (HLA-DR1+/+/IAbeta+/+). More importantly, a strong antigen-specific HLA-DR1-restricted response was observed in nearly all HLA-DR1+/+/IAbeta0/0 mice immunized with HBV envelope protein (HBs) or capsid protein (HBc), whereas weak HBs- or HBc-specific HLA-DR1-restricted responses were detected in half of the immunized HLA-DR1+/+/IAbeta+/+ mice. Conversely, strong HBs- or HBc-specific H-2-restricted T cell responses were detected in HLA-DR1+/+/IAbeta+/+ mice but not in HLA-DR1+/+/IAbeta0/0 mice. Our results indicate that the coexpression of endogenous H-2 class II molecules reduces the intensity of HLA-DR1-restricted antigen-specific responses in transgenic mice, by favoring murine over human MHC recognition and education. Thus, HLA-DR1+/+/IAbeta0/0 mice represent a better model for identifying and characterizing HLA-DR1-restricted epitopes relevant for human disease.

Animals↗
PubMed2004

Silencing of the aleurone-specific Ltp2-gus gene in transgenic rice is reversed by transgene rearrangements and loss of aberrant transcripts.

An Ltp2 promoter was isolated from barley as an aleurone-specific promoter, and its tissue specificity was maintained in transgenic rice. Expression of the Ltp2-gus gene in rice could be detected by X-gluc staining of the seeds. Previously, we reported the isolation of silenced plants in the R2 generation and the involvement of antisense gus transcripts in aleurone-specific Ltp2-gus gene silencing in transgenic rice, the L3.3 line. In the current study, we analyzed the L0.1 line, a sibling of the L3.3 line, and the partially revertant line from the L0.1 line accompanied by a transgene structural change. Strong silencing of the Ltp2-gus gene was detected over five generations in the L0.1 line. DNA and RNA analysis revealed that there were incomplete transgenes and that several aberrant RNAs that carried an antisense gus region were expressed in the L0.1 line. Determination of the transgene structure in the L0.1 line revealed that the partial antisense gus gene and the partial Ltp2 promoter region fused to the Ltp2 promoter were lacking in the revertants. RNA analysis demonstrated that the antisense gus and the promoter transcripts were produced and found in the poly(A)- fraction. Results of these analyses suggested that the observed aberrant transcripts, including antisense and promoter transcripts, were associated with Ltp2-gus silencing in the L0.1 line.

Carrier Proteins↗
PubMed1993

Effect of maternal aging on transgene heritability in transgenic founder mice derived from zygotes microinjected with retroviral long terminal repeat-containing recombinant deoxyribonucleic acid.

To determine the stability of artificially introduced recombinant DNA in the mouse germline throughout the reproductive life, founder mice derived from fertilized eggs injected with retroviral long-terminal-repeat-containing recombinant DNAs were mated with congenic FVB/N mice. Tail DNA of all progeny were screened and restriction fragment patterns of the transgenes were examined. Litter size and percentage of transgene transmission at various reproductive age periods were analyzed. Microinjection of 1737 eggs with four different recombinant DNAs resulted in 12 female and 11 male transgenic mice; 2 males were sterile and the remaining 21 mice served as founders to produce 1087 F1 progeny. With increasing parental age, litter size decreased generally. The percentage of progeny inheriting the transgenes declined markedly with increasing aging of 4 female founders; this aging effect was not observed in male founders (p < 0.005). No apparent change in transgenes was detected in progeny from late reproductive stages.

Aging↗
PubMed1993

Development of B cells secreting endogenous or transgene-encoded immunoglobulins in H-chain transgenic mice.

The development of splenic B cells secreting transgene-encoded or endogenous immunoglobulin (Ig) was analysed in the mu heavy (H-)chain transgenic mouse line M54. The results show that cells secreting endogenous Ig are not detectable during the perinatal period, even after lipopolysaccharide stimulation in vitro. At this time, transgene-secreting cells are readily detectable and keep increasing with age of the animals. After a few weeks of age cells secreting endogenous Ig appear in the spleen and keep increasing with age, reaching numbers comparable to non-transgenic littermates by 5 weeks of age. Thereafter, the proportion of transgene-secreting B cells decreases. We conclude that the preferential expression of endogenous Igs by secreting B cells in the adult does not result from peculiar genetic features of those cells, but from age-dependent cellular selection operating on all B cells.

Age Factors↗
PubMed1997

Transgenic medaka fish bearing the mouse tyrosinase gene: expression and transmission of the transgene following electroporation of the orange-colored variant.

Transgenic fish bearing the mouse tyrosinase gene (mg-Tyrs-J) were produced by transfection into fertilized eggs of the homozygous normal orange-colored variant of medaka fish, Oryzias latipes, by means of electroporation. Of 589 eggs transfected, 38 fish (6%) exhibited brownish wild-type skin pigmentation, which was discernible from control siblings. Light microscopy of the skin from the founders thus generated disclosed that 1) melanization occurred and was restricted to melanophores formed presumably from pre-existing amelanotic melanophores, 2) there was a wide variation in the degree of melanization observed among melanophores, and 3) no melanin deposition was recognized in xanthophores or leucophores. Immunofluorescence using an antibody raised against mouse tyrosinase disclosed that melanophores at varying stages of maturation were reactive. Thus, it was shown that the transgene in medaka fish expressed its action in a cell type-specific manner. Crossing of transgenic founders with homozygous orange-colored variant fish yielded two groups of offspring expressing either the wild-type or the orange-colored skin pigmentation at an approximate ratio of 1:1. Crossing between founders exhibiting wild-type pigmentation yielded only offspring with melanized skin. Skin melanophores in these offspring formed vertical stripes, which are rare in this species. The hereditary basis of melanized skin was demonstrated in matings of F1 progenies, which resulted in similar degrees of melanization over whole skin melanophores. The sum of these findings implied that the transgene is expressed as a dominant character gene and is transmitted through germ cell lines according to the Mendelian law. PCR analysis combined with nested PCR technique strongly suggested that the transgene was integrated into the medaka genome, even though the copy number deduced from gel banding was largely diminished, possibly as a result of fragmentation or instability within the medaka genome.

Animals↗
PubMed1995

A rat gastrin-human gastrin chimeric transgene directs antral G cell-specific expression in transgenic mice.

Gastrin gene expression in the gastrointestinal tract is under both developmental and spatial regulation. In the mature animal, gastrin, an important regulator of parietal acid secretion, is expressed primarily in G cells of the antrum. To determine whether specific promoter elements can direct expression to the gastric antrum in vivo, 450 nucleotides of the proximal rat gastrin promoter were cloned and used to construct a rat gastrin-human gastrin reporter chimeric transgene, which was injected into the mouse germ line. Northern blot analysis, in situ hybridization, and double-label immunocytochemistry studies demonstrated expression of the transgene specifically in antral G cells. Low levels of transgene expression were observed in the ileum and colon, where immunohistochemical studies demonstrated colocalization in enteroendocrine cells expressing peptide YY. The same 450-nucleotide rat gastrin promoter, when joined to the human growth hormone gene, did not result in antral expression. Similarly, a human gastrin-human gastrin reporter transgene also did not achieve antral expression, although it did express in the liver. These results suggest that cis-acting elements present in both the basal 450-nucleotide rat gastrin promoter and the intragenic sequences of the human gastrin gene are necessary to direct expression of a transgene specifically to antral G cells.

Amino Acid Sequence↗
PubMed1994

Apoptosis defects analyzed in TcR transgenic and fas transgenic lpr mice.

Although autoreactive T cells are thought to play a prominent role in autoimmune disease in MRL-lpr/lpr mice, it has been difficult to directly determine if autoreactive T cells escape from the thymus and react with self-antigens in the periphery. Defective expression of the Fas apoptosis antigen in MRL-lpr/lpr mice results from the insertion of the ETn retrotransposon. The fas defect can be partially corrected in CD2-fas transgenic mice in which the expression of fas is corrected in T cells. To identify a possible defect in clonal deletion or clonal anergy induction of auto-specific T cells, we have studied C57BL/6-lpr/lpr transgenic mice that express TcR genes that recognize a known self-antigen, the male H-Y antigen. In addition, we have analyzed clonal deletion and tolerance induction after neonatal tolerance induction and superantigen-induced arthritis with the class II MHC reactive superantigen staphylococcal enterotoxin B (SEB) in V beta 8 TcR transgenic and non-transgenic MRL-lpr/lpr mice. Neonatal tolerance induction to SEB was normal in lpr/lpr mice. However, over time a loss of tolerance (thymic or peripheral) was observed in lpr/lpr mice but not in +/+ TcR transgenic mice. This defect in lpr/lpr mice was thymic-dependent and was due to increased CD28/CTLA4 signaling. These results suggest that an apoptosis defect involving both thymocytes and peripheral lymphoid cells leads to autoimmune disease in lpr/lpr mice. The challenge in the future will be to determine the role of defective apoptosis in other autoimmune diseases.

Animals↗
PubMed2003

Co-influence of transgene expression in mammalian cells. Mutual influence of transgenes on their expression in mammalian cells.

It becomes increasingly clear that therapeutic gene delivery should provide not only for the sustained high level of gene expression but also, in most cases, for the regulated expression of transgenes as much as it occurs under natural conditions. Over the past few years a variety of different systems have been developed in order to regulate the amounts of transcribed RNA upon administration of exogenous agents, or in autoregulated manner. While efforts were focused on optimizing gene expression at the transcriptional level, other levels are still overlooked. In the meantime, regulation of gene expression is not restricted to transcription, but is also executed at the post-transcriptional level, i.e. mRNA stability, processing, transport, translation, protein stability, and modification. Codon usage is considered to be one of the critical factors that limit the expression rate of heterologous genes in different organisms at the posttranscriptional level. HIV-1 structural genes gag, pol, and env represent one of the most extensively utilized models for studying codon usage-mediated effects on transgene expression. In the current work we demonstrate that the codon content affects not only CMV-driven HIV-1 gag expression but also the expression of luciferase reporter gene transcribed independently from the SV40 promoter. The expression levels of both transgenes co-transfected into the human H1299 were inversely co-dependent. The observed phenomenon may be described as sequence-independent post-transcriptional gene silencing, which reflects the existing limitation of transgene expression in mammalian cells at the post-transcriptional level. Optimization of the codon usage may provide for the additional level of regulation of transgene expression in gene transfer experiments in order to maintain the concentration of the protein at the therapeutic levels.

Cell Line, Tumor↗
PubMed1990

[The transgenic characteristics of mice with the gene for the surface antigen of human hepatitis B virus. II. The inheritance of the transgene and its expression in the liver].

The inheritance of the MT-1sAg transgene (a gene of the major envelope polypeptide of human hepatitis B virus under the control of the metallothionein I gene promoter) and its expression in mouse liver cells have been studied. The Mendel inheritance of the transgene for three generations of mice was established. The analysis of transgenic mouse F2 chromosomal DNA by the Southern hybridization revealed the tandem copy insertion of the MT-1sAg plasmid. The expression of the transgene in liver cells, both with MT-1 promoter induction by Cd++ and without it, has been observed. The decrease in mouse liver cell parts containing viral protein HBsAg was observed as well as a reliable decrease in the share of mice with detectable MT-1sAg expression in the liver during the ontogenesis. The MT-1sAg-transgenic mice may be useful for studying the human chronic HBsAg state.

Animals↗
PubMed1995

Transgenic mouse model for estrogen-regulated lipoprotein metabolism: studies on apoVLDL-II expression in transgenic mice.

We have produced transgenic mice that express an estrogen-responsive avian apolipoprotein, apoVLDL-II. An apoVLDL-II natural gene construct containing 4.7 kb of 5' flanking and 19 bp of 3' flanking sequences together with the 4 exon/3 intron structural gene was expressed in a liver-specific manner in transgenic mice. A single injection of estrogen caused a 5.9- to 7.5-fold stimulation of apoVLDL-II mRNA in the liver. The transgene mRNA had the same initiation sites of transcription as the native mRNA isolated from laying hen liver, and the same sites were used before and after estrogen treatment. The number of hepatocytes that stain positive for immunoreactive apoVLDL-II increased from < 1% to 40-60% in 24 h after estrogen treatment. Thus, in trangenic mice as in the cockerel, hepatocytes are biochemically heterogeneous and induction of apoVLDL-II synthesis occurs by recruitment of hepatocytes. In the plamsa compartment, compared to controls, transgenic mice have a 3- to 5-fold higher basal total plasma triglyceride which was accounted for by a 5.4-fold high basal VLDL triglyceride. Estrogen treatment results in a approximately 2-fold increase in the VLDL triglycerides over basal levels and 8.5-fold increase over nontransgenic mice, which did not show any change in VLDL in response to estrogen. Transgenic mice with the integrated apoVLDL-II gene provide a useful model for the study of the regulation of lipoprotein metabolism by estrogen.

Animals↗
PubMed2006

Comparative field performance over 3 years and two sites of transgenic wheat lines expressing HMW subunit transgenes.

A series of transgenic wheat lines expressing additional high molecular weight (HMW) subunit genes and the corresponding control lines were grown in replicate field trials at two UK sites (Rothamsted Research, approximately 50 km north of London and Long Ashton, near Bristol) over 3 years (1998, 1999, 2000), with successive generations of the transgenic lines (T3, T4, T5) being planted. Four plots from each site were used to determine grain dry weight, grain nitrogen, dough strength (measured as peak resistance by Mixograph analysis) and the expression levels of the endogenous and "added" subunits. Detailed statistical analyses showed that the transgenic and non-transgenic lines did not differ in terms of stability of HMW subunit gene expression or in stability of grain nitrogen, dry weight or dough strength, either between the 3 years or between sites and plots. These results indicate that the transgenic and control lines can be regarded as substantially equivalent in terms of stability of gene expression between generations and environments.

Breeding↗
PubMed2006

Synthesis of minus-strand copies of a viral transgene during viral infections of transgenic plants.

Viral transgenes designed to provide resistance to specific plant viruses frequently consist of the coat protein gene and a contiguous 3' untranslated region (3'UTR) of viral origin. In many RNA viruses the viral 3'UTR establishes a recognition and initiation site for viral RNA replication. Thus the transgenic transcript may contain a functional virus replication site. Experiments were designed to determine if a challenging virus would recognize this replication site on a nuclear derived transcript and synthesize the complementary RNA. These data demonstrate that upon infection by a virus that recognizes the viral replication site, a full-length complement of the transgenic transcript is produced. In these experiments the replication complex of Brome Mosaic bromovirus recognized the transgenic transcript derived from a Cowpea Chlorotic Mottle bromovirus transgene. The resulting RNA may contribute to RNA recombination events.

Bromovirus↗