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At least 649 records · Page 36Linked to original sources
PubMed1991

Transgenic mice carrying a murine amylase 2.2/SV40 T antigen fusion gene develop pancreatic acinar cell and stomach carcinomas.

The mouse pancreatic amylase Amy-2.2 gene was fused to the structural gene for SV40 T antigen, and 51 independent transgenic founder mice carrying the fusion gene were generated. The majority of the founders and 100% of their offspring in the derived transgenic lines developed pancreatic acinar cell carcinomas and stomach carcinomas. Transgenic animals also had a high incidence of metastatic carcinomas in other tissues. The development of stomach carcinomas was unexpected because the Amy-2.2 promoter was not previously known to be expressed in stomach. Northern blot analyses and ribonuclease protection assays showed that Amy-2.2 is expressed in stomach, at approximately 0.05% of the level in pancreas. Expression of the fusion gene in stomach, therefore, appears to represent a previously unrecognized activity of the Amy-2.2 promoter. Examination of young transgenic mice demonstrated that preneoplastic lesions were present in pancreas and stomach before the development of neoplastic lesions in either tissue, consistent with the notion that stomach neoplasms are primary neoplasms and not metastases from the pancreas. Ribonuclease protection assays demonstrated that properly initiated large T and small t antigen transcripts were present in pancreas and stomach during tumorigenesis. T antigen protein was also detected in pancreas and stomach by immunohistochemistry. A time course for tumorigenesis was established for several transgenic mouse lines in which distinct types of lesions appeared at predictable times. This study provides the basis for future analysis of the role of SV40 T antigen in the progression and maintenance of pancreatic and stomach carcinomas.

Amylases↗
PubMed1991

Influence of a V kappa 8 L chain transgene on endogenous rearrangements and the immune response to the HA(Sb) determinant on influenza virus.

A rearranged murine V kappa 8/J kappa 5 L chain gene that codes for the L chain of most antibodies generated in the primary response of BALB/c mice to the antigenic site, Sb, of the hemagglutinin (HA) molecule of influenza virus A/PR/8/34 (PR8) has been cloned. Three transgenic lines were generated by microinjecting the gene. Lines Ga and L each contain a single copy of the transgene whereas line Gb contains three complete copies. Mice of the Ga lineage showed increased V kappa 8-specific mRNA levels only in spleen, but not in nonlymphoid organs and therefore displayed apparently normal lymphoid-specific regulation of the Ig transgene. B cell hybridomas generated from these mice were analyzed for rearrangements of endogenous V kappa genes. Greater than 90% of the C kappa alleles were retained in germ-line configuration in the Ga line, compared with only 0 to 18% in the L line. Thus, a wide variation in the frequency of endogenous rearrangements is seen among mice of different lineages using the same transgene construct. None of more than 150 hybridomas derived from LPS-stimulated splenic B cells of Ga mice exhibited HA-binding activity although they expressed the transgene and, in most cases, excluded endogenous V kappa rearrangements. In contrast, a large fraction of hybridomas isolated after primary immunization with PR8 were HA(Sb)-specific. This indicated that the transgene was functional but formed HA-specific antibodies with a more restricted set of H chains than previously hypothesized. The primary anti-HA response to immunization with PR8 was diminished in all lines compared with normal mice except for a slightly accelerated but transient burst of anti-HA antibody formation in two out of three lines (Ga and Gb). This early response in G lineage mice was largely specific for HA(Sb) and thus appeared to be composed of transgene-expressing antibodies. No differences in serum titers were observed in the secondary anti-HA responses to booster inoculation with PR8 between transgenic and normal mice.

Animals↗
PubMed1999

Testicular wild-type p53 expression in transgenic mice induces spermiogenesis alterations ranging from differentiation defects to apoptosis.

While p53 is dispensable for development, an excess of p53 has dramatic consequences on the embryogenesis and on the cell differentiation. In an attempt to analyse in vivo the effects of p53 activity, we have generated transgenic mice expressing the wild-type p53 under the control of the metallothionein I promoter. In the three transgenic lines established, exogenous p53 is expressed constitutively in the postmeiotic cells of transgenic males and two lines are subfertile. Transgenic males expressing the upper level of p53 produce few spermatozoa since the majority of developing spermatids undergo apoptosis. In the subfertile males exhibiting an intermediate amount of p53, teratozoospermia is obvious suggesting an altered terminal differentiation of postmeiotic cells. In contrast lower level of p53 does not lead the third line to sterility. These results suggest that the activity of p53 is dependent in vivo on the amount of p53 present within cells, as it has been already demonstrated in vitro.

Animals↗
PubMed2005

Matrix attachment region from the chicken lysozyme locus reduces variability in transgene expression and confers copy number-dependence in transgenic rice plants.

Matrix-attachment regions (MARs) may function as domain boundaries and partition chromosomes into independently regulated units. In this study, BP-MAR, a 1.3-kb upstream fragment of the 5'MAR flanking the chicken lysozyme locus, was tested for its effects on integration and expression of transgenes in transgenic rice plants. Using the Agrobacterium-mediated method, we transformed rice with nine different constructs containing seven and six different promoters and coding sequences, respectively. Genomic Southern blot analyses of 357 independent transgenic lines revealed that in the presence of BP-MAR, 57% of the lines contained a single copy of the transgene, whereas in its absence, only 20% of the lines contained a single copy of the transgene. RNA gel-blot and immunoblot experiments demonstrated that in the presence of BP-MAR, transgene expression levels were similar among different lines. These data were in direct contrast to those derived from transgenes expressed in the absence of BP-MAR, which varied markedly with the chromosomal integration site . Thus, it can be concluded that BP-MAR significantly reduces the variability in transgene expression between independent transformants. Moreover, the presence of BP-MAR appears to confer a copy number-dependent increase in transgene expression, although it does not increase expression levels of individual transgenes. These data contrast with results previously obtained with various MARs that increased expression levels of transgene significantly. Therefore, we conclude that the incorporation of BP-MAR sequences into the design of transformation vectors can minimize position effects and regulate transgene expression in a copy number-dependent way.

5' Flanking Region↗
PubMed1990

Polyomavirus large T-antigen expression in heart of transgenic mice causes cardiomyopathy.

One of the early genes of polyomavirus, large T-antigen (PVLT), has been classified in vitro as an immortalizing gene. In order to determine the ability of PVLT to cause the formation of hyperplasia or tumors in vivo, we generated transgenic mice harboring the cDNA for PVLT linked to the heavy-metal responsive metallothionein-1 promoter (MT). The transgene was primarily expressed in testes and seminal vesicles, but expression was also detected in heart of a single transgenic line. The expression of the transgene in the heart of MT-PVLT line 8 mice was correlated with cardiomyopathy and atrial thrombus formation leading to premature death at approximately 160 days due to cardiac failure. The heart of affected animals was from 1.5 to 5.2 fold greater in weight and 2 fold greater in dimensions than normal nontransgenic mice. Affected hearts fell short of frank tumor phenotype and no macroscopic nor microscopic focal growth was found. Histologically the heart has a heterogenous cardiomyocyte population with markedly enlarged cells mixed with relatively normal cells. Both cell types express PVLT protein. The primary cell type affected is the cardiomyocyte however, as heart proportions are maintained, interstitial and non-myocyte cells must be affected either directly or indirectly. Expression of PVLT has upset normal strict control of cell growth in these hearts to result in a new model of congestive cardiomyopathy.

Animals↗
PubMed1998

Accelerated Alzheimer-type phenotype in transgenic mice carrying both mutant amyloid precursor protein and presenilin 1 transgenes.

Genetic causes of Alzheimer's disease (AD) include mutations in the amyloid precursor protein (APP), presenilin 1 (PS1), and presenilin 2 (PS2) genes. The mutant APP(K670N,M671L) transgenic line, Tg2576, shows markedly elevated amyloid beta-protein (A beta) levels at an early age and, by 9-12 months, develops extracellular AD-type A beta deposits in the cortex and hippocampus. Mutant PS1 transgenic mice do not show abnormal pathology, but do display subtly elevated levels of the highly amyloidogenic 42- or 43-amino acid peptide A beta42(43). Here we demonstrate that the doubly transgenic progeny from a cross between line Tg2576 and a mutant PS1M146L transgenic line develop large numbers of fibrillar A beta deposits in cerebral cortex and hippocampus far earlier than their singly transgenic Tg2576 littermates. In the period preceding overt A beta deposition, the doubly transgenic mice show a selective 41% increase in A beta42(43) in their brains. Thus, the development of AD-like pathology is substantially enhanced when a PS1 mutation, which causes a modest increase in A beta42(43), is introduced into Tg2576-derived mice. Remarkably, both doubly and singly transgenic mice showed reduced spontaneous alternation performance in a "Y" maze before substantial A beta deposition was apparent. This suggests that some aspects of the behavioral phenotype in these mice may be related to an event that precedes plaque formation.

Alzheimer Disease↗
PubMed1988

Fast skeletal muscle-specific expression of a quail troponin I gene in transgenic mice.

We have produced seven lines of transgenic mice carrying the quail gene encoding the fast skeletal muscle-specific isoform of troponin I (TnIf). The quail DNA included the entire TnIf gene, 530 base pairs of 5'-flanking DNA, and 1.5 kilobase pairs of 3'-flanking DNA. In all seven transgenic lines, normally initiated and processed quail TnIf mRNA was expressed in skeletal muscle, where it accumulated to levels comparable to that in quail muscle. Moreover, in the three lines tested, quail TnIf mRNA levels were manyfold higher in a fast skeletal muscle (gastrocnemius) than in a slow skeletal muscle (soleus). We conclude that the cellular mechanisms directing muscle fiber type-specific TnIf gene expression are mediated by cis-regulatory elements present on the introduced quail DNA fragment and that they control TnIf expression by affecting the accumulation of TnIf mRNA. These elements have been functionally conserved since the evolutionary divergence of birds and mammals, despite the major physiological and morphological differences existing between avian (tonic) and mammalian (twitch) slow muscles. In lines of transgenic mice carrying multiple tandemly repeated copies of the transgene, an aberrant quail TnIf transcript (differing from normal TnIf mRNA upstream of exon 2) also accumulated in certain tissues, particularly lung, brain, spleen, and heart tissues. However, this aberrant transcript was not detected in a transgenic line which carries only a single copy of the quail gene.

Animals↗
PubMed2000

Transgenic mouse models for lung cancer.

Transgenic technology allows the ability to target regulatory genes to the lungs in a cell-specific fashion. Using this technology, we have generated a model to investigate the phenotypic consequences of targeting oncogenes to particular cell types in the lungs and are developing a second model for the regulated expression of oncogenes in the lung. The transgenic model involves the constitutive expression of simian virus 40 large T antigen in the Clara cells of mouse lungs. This model has been used to investigate changes in expression of cell cycle regulatory genes in the Clara cells during the transformation process, as well as the expression of the transcription factors regulating the expression of Clara cell differentiation markers. The second model we are developing investigates the regulated expression of the genes in the lungs. This system is based on the establishment of two types of transgenic lines. The regulator line consists of a chimeric transcriptional factor placed under the control of a lung-specific SPC (surfactant protein C) promoter. This chimeric regulator is composed of a transcription activation domain, the GAL4 DNA-binding domain, and a truncated progesterone receptor that is responsive to RU 486, but not to endogenous progesterone. The second transgenic mouse line contains the silent target transgene under the control of a minimal promoter with upstream activating sequences (UAS) that are recognized by the regulator transgene. Upon breeding these two lines, the resulting bitransgenic mice can then be induced to express the target transgene only with the administration of RU 486. Two generations of regulators have been evaluated on their ability to regulate the expression of a growth hormone reporter gene. This system demonstrated the inducible expression of the reporter genes in the distal airways of the lungs.

Adenocarcinoma↗
PubMed2005

[The study of transformation of tobacco with the stress responsible gene BoRS1 from Brassica oleracea var. acephala].

Transgenic tobacco plants expressing a stress responsive gene BoRS1, isolated from Brassica oleracea var. acephala, under the control of the 35S promoter of the Cauliflower mosaic virus were produced. Some plants were further used to test the effect of high level BoRS1 expression on drought stress resistance. The presence of transgene in putative transgenic plants was confirmed by PCR analysis. Thirty-six among 130 transformants showed amplification of predicted fragment of BoRS1 while no amplification was observed in the control. Some transgenic lines confirmed by PCR analysis were analyzed through semi-quantitative one-step RT-PCR for the expression of BoRS1 gene. Amplification of 1.4 kb cDNA product revealed transcription of BoRS1 gene. Meanwhile, differential intensity of the cDNA band indicated variable expression levels of the transgene among different transformed lines. The water loss of detached leaves from the transgenic plants was slower than that of the control. Transgenic tobaccos and the non-transgenic controls were used for further drought stress experiments by using different concentration of mannitol. The transformants showed higher tolerance to drought stress than non-transgenic plants and different transgenic lines exhibited different tolerance during drought stress. These results showed that the BoRS1 gene probably play role in enhancing the ability to drought stress.

Adaptation, Physiological↗
PubMed2004

Expression of UDP-glucose dehydrogenase reduces cell-wall polysaccharide concentration and increases xylose content in alfalfa stems.

The primary cell-wall matrix of most higher plants is composed of large amounts of uronic acids, primarily D-galacturonic acid residues in the backbone of pectic polysaccharides. Uridine diphosphate (UDP)-glucose dehydrogenase is a key enzyme in the biosynthesis of uronic acids. We produced transgenic alfalfa (Medicago sativa) plants expressing a soybean UDP-glucose dehydrogenase cDNA under the control of two promoters active in alfalfa vascular tissues. In initial greenhouse experiments, enzyme activity in transgenic lines was up to seven-fold greater than in nontransformed control plants; however, field-grown transgenic plants had only a maximum of 1.9-fold more activity than the control. Cell-wall polysaccharide content was lower and Klason lignin content was higher in transgenics compared to the nontransformed control. No significant increase in pectin or uronic acids in the polysaccharide fraction was observed in any line. Xylose increased 15% in most transgenic lines and mannose concentration decreased slightly in all lines. Because of the complexity of pectic polysaccharides and sugar biosynthesis, it may be necessary to manipulate multiple steps in carbohydrate metabolism to alter the pectin content of alfalfa.

Biomass↗
PubMed2004

Analysis of imprinted murine Peg3 locus in transgenic mice.

Peg3 is an imprinted gene exclusively expressed from the paternal allele. It encodes a C(2)H(2) type zinc-finger protein and is involved in maternal behavior. It is important for TNF-NFkB signaling and p53-mediated apoptosis. To investigate the imprinting mechanism and gene expression of Peg3 and its neighboring gene(s), we used a 120 kb Peg3-containing BAC clone to generate transgenic mice. The BAC clone contains 20 kb of 5' and 80 kb of 3' flanking DNA, and we obtained three transgenic lines. In one of the lines harboring one copy of the transgene, Peg3 was imprinted properly. In the other two lines, Peg3 was expressed upon both maternal and paternal transmission. Imprinted expression was linked to the differential methylation of a region (DMR) upstream of the Peg3 gene. A second, maternally expressed gene, Zim1, present on the transgene was expressed irrespective of parental inheritance in all lines. These data suggest that, similar to other imprinted genes within domains, Peg3 and Zim1 are regulated by one or more elements lying at a distance from the genes. The imprinting of Peg3 seen in one line may reflect the presence of a responder sequence. Concerning the expression of the Peg3 transgene, we detected appropriate expression in the adult brain. However, this was not sufficient to rescue the maternal behavior phenotype seen in Peg3 deficient animals.

Animals↗
PubMed1992

Pattern of somatic transposition in a high copy Ac tomato line.

A transgenic tomato line containing between eight and ten copies per genome of an exceptionally active maize transposable element Ac has previously been described. Southern analyses indicated that these elements are somatically active in these plants. In order to characterize further the pattern of somatic transposition in this line, 24 independent Ac insertion events from a single plant were cloned. In 21 cases, Ac inserted into single copy genomic DNA while in three cases Ac inserted into sequences present at two to four copies per genome; none of the insertions occurred into more highly repetitive DNA. The chromosomal locations of 20 insertion sites were determined by RFLP mapping and a pattern of small dispersed clusters emerged. Thirteen of the 20 insertion sites were linked to at least one other insertion site but these were distributed over nine of the 12 tomato chromosomes. Only one Ac insertion was linked to the T-DNA locus. The structural integrity of these Ac elements was examined and no evidence of deletions or other rearrangements suggestive of Ds elements was found. The implications of these findings with respect to the use of Ac as a transposon tag in heterologous species are discussed.

Base Sequence↗
PubMed1992

A recessive defect in lymphocyte or granulocyte function caused by an integrated transgene.

A line of transgenic mice has been identified with a recessive defect in lymphocyte or granulocyte function, presumably as a result of insertional mutagenesis by the integrated transgene. Transgenic mice homozygous for the transgene integrant showed nearly complete absence of lymphocytes in peripheral lymph nodes and Peyer's patches, a severely diminished thymus medulla, and a greatly enlarged spleen. These animals also developed a syndrome characterized by granulocyte and mononuclear infiltrates in numerous tissues, including skin, liver, and lung, and immunoglobulin deposits in kidney glomeruli. Lung infiltrates were specifically localized around large blood vessels and bronchi, accompanied in some cases by destruction of arterial walls. The light scatter profile of spleen lymphocytes suggested an extremely high percentage of blast cells. Because tissue development and morphology appears to be normal in all other tissues observed, the genetic lesion appears to specifically affect the regulation of lymphocyte or granulocyte activation.

Animals↗
PubMed1994

A distal tyrosinase upstream element stimulates gene expression in neural-crest-derived melanocytes of transgenic mice: position-independent and mosaic expression.

We have assessed the importance of a melanocyte-specific DNase I hypersensitive site and matrix attachment region situated 15 kb upstream of the mouse tyrosinase gene by analysis in transgenic mice. Transgenes containing all, part, or none of this region linked to the tyrosinase promoter and human tyrosinase cDNA were introduced into genetically albino mice, and pigmentation and transgene message levels were analyzed in the resulting transgenic lines. The effect of the upstream region was to enhance significantly gene expression in melanocytes, and to provide position-independent expression of the transgene. Two exceptions to complete position independence were seen; these lines displayed a mosaic expression pattern in which the transgene was expressed fully in some melanocyte clones but less so in others, resulting in transverse stripes of colours ranging from near white to dark grey. Unexpectedly, pigmentation in the eye of all transgenic lines containing the upstream region was nonuniform, in that the neural-crest-derived melanocytes of the choroid and anterior iris contained significantly more pigment than those derived from the optic cup (retinal pigment epithelium and posterior iris). Transgenes containing a small part or none of the upstream region were expressed poorly and in a position-dependent manner; of those lines that were visibly pigmented, expression was equal in the neural crest and optic-cup-derived cells of the eye.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Characterization of resistance in transgenic Nicotiana benthamiana encoding N-terminal deletion and assembly mutants of the tobacco etch potyvirus coat protein.

The resistance of transgenic Nicotiana benthamiana plants encoding wild type, truncated and point mutants of the tobacco etch virus (TEV) coat protein (CP) was analyzed. After R1 plants from 45 transgenic lines were challenged with TEV, six percent of the lines exhibited high resistance, 38% exhibited low resistance, and the remainder were susceptible. The phenomenon of recovery and delay in symptom development was observed in 65% and 56% of the resistant and susceptible lines, respectively. Plants containing genes that encode sequences of two assembly-deficient mutants of TEV-CPDelta1-63 exhibited resistance to infection, suggesting that self-assembly of the CP is not responsible for resistance. Highly resistant lines accumulated low levels of transgene mRNA and non-detectable amounts of protein, and tissues accumulated lower amounts of transgene mRNA following recovery than before infection. In addition, co-suppression of replication of a recombinant tobamovirus containing the TEV-CPDelta1-63 sequence was observed in several lines, suggesting homology-dependent degradation of RNA, most likely through induction of post-transcriptional gene silencing. Plants not exhibiting high resistance via gene silencing exhibited moderate levels of resistance that is attributed to and/or affected by the CP molecule.

Capsid Proteins↗
PubMed1992

Parent-specific expression of a human keratin 18/beta-galactosidase fusion gene in transgenic mice.

Insertion of a human keratin 18 (K18)-bacterial beta-galactosidase (LacZ) fusion gene into mice has led to a unique transgenic line in which expression of the transgene is subject to unusual germ line-specific, genomic imprinting effects. Fetal expression of the LacZ reporter gene depends on the gender of the transmitting parent, with appropriate expression in liver after maternal inheritance, and ectopic expression in retina and mesodermal tissues after paternal inheritance. This tissue-specific imprinting pattern is superimposed upon a basic expression pattern which is unaffected by parental inheritance. Insertion of the transgene has led to a recessive-lethal phenotype, with no parent-of-origin effects on viability, suggesting that the transgene has not inserted into an imprinted region of the genome. HpaII and HhaI methylation sensitive restriction sites within the bacterial LacZ reporter gene are completely methylated when activity of the maternally inherited transgene is detected in the fetal liver, and not methylated when the paternally inherited transgene is silent. Thus DNA methylation of LacZ is correlated with maternal inheritance and may be implicated in the genomic imprinting mechanism as others have suggested. However, in contrast to the commonly found correlation of expression and low DNA methylation, the LacZ gene was expressed in fetal liver when fully methylated. This result may imply the existence of negative regulatory activities that recognize the unmethylated LacZ gene.

Animals↗
PubMed1995

Increased tyrosine-phosphorylation of 55KDa proteins in beta-actin/Tec transgenic mice.

Protein-tyrosine kinases are considered to play important roles in cell proliferation and differentiation. Tec is a cytoplasmic protein-tyrosine kinase expressed in liver and hematopoietic tissues. To better understand Tec function in vivo, we generated transgenic mice expressing tec driven by the cytomegarovirus enhancer and beta-actin promoter. Among six transgenic lines generated, a particular line, named 2-11, expressed tec transgene product more widely and abundantly than the other lines. In the tissues of 2-11, the kinase activity of Tec was enhanced in accordance with the high expression of tec transgene product. Interestingly, tyrosine-phosphorylation of approximately 55KDa proteins in the tissues was induced. These results suggest that cellular proteins of 55KDa might be potential substrates of Tec in vivo.

Actins↗
PubMed2001

Emergence during development of the white-adipocyte cell phenotype is independent of the brown-adipocyte cell phenotype.

In mammals, two types of adipose tissue are present, brown and white. They develop sequentially, as brown fat occurs during late gestation whereas white fat grows mainly after birth. However, both tissues have been shown to have great plasticity. Thus an apparent transformation of brown fat into white fat takes place during post-natal development. This observation raises questions about a possible conversion of brown into white adipocytes during development, although indirect data argue against this hypothesis. To investigate such questions in vivo, we generated two types of transgenic line. The first carried a transgene expressing Cre recombinase specifically in brown adipocytes under the control of the rat UCP1 promoter. The second corresponded to an inactive lacZ gene under the control of the human cytomegalovirus promoter. This dormant gene is inducible by Cre because it contains a Stop sequence between two loxP sequences, separating the promoter from the coding sequence. Adipose tissues of progeny derived by crossing independent lines established from both constructs were investigated. LacZ mRNA corresponding to the activated reporter gene was easily detected in brown fat and not typically in white fat, even by reverse transcriptase PCR experiments. These data represent the first direct experimental proof that, during normal development, most white adipocytes do not derive from brown adipocytes.

Adipocytes↗