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At least 631 records · Page 35Linked to original sources
PubMed2005

Ectopic expression of a soybean phytase in developing seeds of Glycine max to improve phosphorus availability.

A transgenic approach was used to alter soybean seed phytate content by expressing a soybean phytase gene (GmPhy) during seed development to degrade accumulating phytic acid (IP6). An expression vector containing the soybean phytase cDNA controlled by the seed-specific beta-conglycinin promoter (alpha'-subunit) was used to transform embryogenic soybean cultures. Plants from four independent transgenic lines were analyzed for transgene integration and seed IP6 levels. The reduction in IP6 levels in transgenic seeds compared to control 'Jack' soybeans ranged from 12.6 to 24.8 as determined by HPLC. A low copy transformant was propagated to the T4 generation and examined in more detail for phytase expression and enzyme activity during seed development. Expression of phytase mRNA and phytase activity increased during seed development, consistent with the use of an embryo-specific promoter. Ectopic phytase expression during seed development offers potential as an effective strategy for reducing phytate content in soybean seed.

6-Phytase↗
PubMed1994

Spermatocyte-specific transcription by calmodulin gene II promoter in transgenic mice.

Transgenic mice carrying a fused gene of the 294-base upstream and 68-base leader sequences of a rat calmodulin gene, CaMII, and beta-galactosidase gene were made. Only spermatocytes expressed the transgene mRNA in the testes of four independent transgenic lines. The localization of transgene mRNA was consistent with that of the mouse endogenous CaMII analyzed by in situ hybridization with the probe of 3'-noncoding region of mouse CaMII. Thus, this short promoter of CaMII evidently conferred the expression of transgene only on spermatocytes but not on spermatogonia nor on spermatids of the testis. The rat CaMII promoter up to -294 contained no sequences that corresponded to any of the reported sequence features of genes expressed in the testis. Therefore, this short promoter region of CaMII seemed to carry a certain novel machinery for the spermatocyte-specific gene expression.

Animals↗
PubMed2000

Impaired brain development and hydrocephalus in a line of transgenic mice with liver-specific expression of human insulin-like growth factor binding protein-1.

Insulin-like growth factors (IGFs) produced in the brain are known to participate in brain development via activation of the type 1 IGF receptor. IGF binding proteins (IGFBPs) modulate the cellular action of IGFs and some are expressed in the fetal brain. Under normal conditions IGFBP-1 is not one of these, but IGFBP-1 expression obtained via transgenesis using ubiquitous promoters affects brain development. In earlier work, we established a model of transgenic mouse in which liver-specific IGFBP-1 expression begins during fetal life. The repercussions of this IGFBP-1 over-expression include reproductive defects, ante- and perinatal mortality and post-natal growth retardation, the extent of which is related to the degree of transgene expression. Unexpectedly, during the first 2 months of postnatal life, there were some cases of head enlargement revealing hydrocephalus among homozygotes, frequently associated with motor disorders. Brain sections showed dilatation of the lateral ventricles in 10 out of 15 homozygotes examined. Histologically, dilatation was evident in four out of nine heterozygotes. Brain weight in transgenics was relatively less reduced than the weights of other organs. Hence, brain weight/body weight ratios were normal in heterozygotes and on average higher than normal in homozygotes. The width of the cerebral cortex was reduced in homozygotes, with disorganized neuronal layers. The corpus callosum was underdeveloped, particularly in homozygotes. The area of the hippocampus was reduced in homozygotes and one-third of the heterozygotes, with a short and thick dentate gyrus in the former. Similar anomalies have been reported in mice with disruption of the igf-I gene and in a model of transgenic mice over-expressing IGFBP-1 in all tissues, including the brain. Hydrocephalus was not mentioned in these reports, raising the possibility that insertional mutagenesis may have been involved in our mice. Nevertheless, our observations indicate that hepatic over-expression of IGFBP-1 may have endocrine effects on brain development.

Animals↗
PubMed2004

Altered amyloid-beta metabolism and deposition in genomic-based beta-secretase transgenic mice.

Amyloid-beta (Abeta) the primary component of the senile plaques found in Alzheimer's disease (AD) is generated by the rate-limiting cleavage of amyloid precursor protein (APP) by beta-secretase followed by gamma-secretase cleavage. Identification of the primary beta-secretase gene, BACE1, provides a unique opportunity to examine the role this unique aspartyl protease plays in altering Abeta metabolism and deposition that occurs in AD. The current experiments seek to examine how modulating beta-secretase expression and activity alters APP processing and Abeta metabolism in vivo. Genomic-based BACE1 transgenic mice were generated that overexpress human BACE1 mRNA and protein. The highest expressing BACE1 transgenic line was mated to transgenic mice containing human APP transgenes. Our biochemical and histochemical studies demonstrate that mice overexpressing both BACE1 and APP show specific alterations in APP processing and age-dependent Abeta deposition. We observed elevated levels of Abeta isoforms as well as significant increases of Abeta deposits in these double transgenic animals. In particular, the double transgenics exhibited a unique cortical deposition profile, which is consistent with a significant increase of BACE1 expression in the cortex relative to other brain regions. Elevated BACE1 expression coupled with increased deposition provides functional evidence for beta-secretase as a primary effector in regional amyloid deposition in the AD brain. Our studies demonstrate, for the first time, that modulation of BACE1 activity may play a significant role in AD pathogenesis in vivo.

Alzheimer Disease↗
PubMed1999

A new mouse insertional mutation that causes sensorineural deafness and vestibular defects.

This article describes a new recessive insertional mutation in the transgenic line TgN2742Rpw that causes deafness and circling behavior in mice. Histologic analysis revealed virtually complete loss of the cochlear neuroepithelium (the organ of Corti) in adult mutant mice. In association with the neuroepithelial changes, there is a dramatic reduction of the cochlear nerve supply. Adult mutants also show morphological defects of the vestibular apparatus, including degeneration of the saccular neuroepithelium and occasional malformation of utricular otoconia. Audiometric evaluations demonstrated that the mice displaying the circling phenotype are completely deaf. Molecular analysis of this mutant line revealed that the transgenic insertion occurred without creating a large deletion of the host DNA sequences. The mutant locus was mapped to a region on mouse chromosome 10, where other spontaneous, recessive mutations causing deafness in mice have been mapped.

Animals↗
PubMed2006

Arabidopsis mutants by activation tagging in which photosynthesis genes are expressed in dedifferentiated calli.

In an effort to delineate the precise mechanisms underlying the organ-specific expression of photosynthesis genes, Arabidopsis lines homozygous for each transgene construct made with the gene for hygromycin B phosphotransferase or beta-glucuronidase (GUS) placed under control of the promoter of the nuclear gene for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (RBCS-3B) were constructed. Furthermore, activation tagging with T-DNA possessing quadruply repeated enhancers derived from the cauliflower mosaic virus 35S promoter was applied to a transgenic line of Arabidopsis. Mutants resistant to hygromycin B during the growth of calli generated from non-green roots on callus-inducing medium resulted from the expression of hygromycin B phosphotransferase driven by the RBCS-3B promoter. Three mutant lines, ces101 to ces103 (callus expression of RBCS), were obtained from approximately 4,000 calli resistant to a selectable marker for transformation. The active transcription driven by the RBCS-3B promoter in all the calli of ces mutants was confirmed by expression of both the GUS reporter gene and endogenous RBCS-3B. Chlorophyll and carotenoids, as well as light-dependent O(2) evolution, have been detected in the calli of all ces mutants. The loci where T-DNA was integrated in the ces101 line were determined by thermal asymmetric interlaced (TAIL)-PCR. The introduction of a DNA fragment harboring the gene for receptor-like kinase placed under the influence of enhancers into the parental line reproduced the phenotype of ces mutants. We have thus concluded that CES101 is a receptor-like kinase. The strategy presented in this investigation may promise to select a greater number of ces mutants.

Arabidopsis↗
PubMed2000

Construction of transgenic pea lines with modified expression of diamine oxidase and modified nodulation responses with exogenous putrescine.

Diamine oxidase (DAO) might influence pea nodule development either by regulating the peroxide-driven cross-linking of glycoproteins in the infection thread matrix or by modifying the metabolism of diamines and polyamines in host cells. Transformed lines of pea (Pisum sativum) with the coding sequence for DAO (PSAO-1) in sense orientation behind a tissue-specific promoter (pENOD12A) showed strong co-suppression of DAO activity in extracts from nodules and epicotyls, whereas the antisense constructs were relatively unaffected. No difference in nodule number was observed between transformed lines and controls, suggesting that DAO does not normally have an essential role in nodule initiation. However, lines showing co-suppression of DAO were less sensitive to the inhibitory effects of exogenous putrescine and less active in the cross-linking of matrix glycoprotein, indicating that putrescine-derived products of DAO activity could retard nodule development. Inoculation of co-suppressed lines with Rhizobium strain B661 (a lipopolysaccharide-defective mutant) resulted in more extreme impairment of nodule development and nitrogen fixation capacity, relative to lines with normal levels of DAO, which suggests that DAO may serve to reduce the endogenous level of inhibitory diamines or polyamines in nodules under physiological stress. We conclude that the most critical role of DAO in pea nodule development is apparently in the regulation of diamine levels in host tissues.

Amine Oxidase (Copper-Containing)↗
PubMed2006

Expression and functional analyses of the plastid lipid-associated protein CHRC suggest its role in chromoplastogenesis and stress.

Chromoplastogenesis during flower development and fruit ripening involves the dramatic overaccumulation of carotenoids sequestered into structures containing lipids and proteins called plastid lipid-associated proteins (PAPs). CHRC, a cucumber (Cucumis sativus) PAP, has been suggested to be transcriptionally activated in carotenoid-accumulating flowers by gibberellin (GA). Mybys, a MYB-like trans-activator identified here, may represent a chromoplastogenesis-related factor: Its expression is flower specific and parallels that of ChrC during flower development; moreover, as revealed by stable ectopic and transient-expression assays, it specifically trans-activates ChrC promoter in flowers accumulating carotenoids and flavonoids. A detailed dissection of ChrC promoter revealed a GA-responsive element, gacCTCcaa, the mutation of which abolished ChrC activation by GA. This cis-element is different from the GARE motif and is involved in ChrC activation probably via negative regulation, similar to other GA-responsive systems. The GA responsiveness and MYBYS floral activation of the ChrC promoter do not overlap with respect to cis-elements. To study the functionality of CHRC, which is activated in vegetative tissues similar to other PAPs by various biotic and abiotic stresses, we employed a tomato (Lycopersicon esculentum) plant system and generated RNAi-transgenic lines with suppressed LeCHRC. Transgenic flowers accumulated approximately 30% less carotenoids per unit protein than controls, indicating an interrelationship between PAPs and flower-specific carotenoid accumulation in chromoplasts. Moreover, the transgenic LeCHRC-suppressed plants were significantly more susceptible to Botrytis cinerea infection, suggesting CHRC's involvement in plant protection under stress conditions and supporting the general, evolutionarily preserved role of PAPs.

Adaptation, Physiological↗
PubMed2007

Varietal effects of eight paired lines of transgenic Bt maize and near-isogenic non-Bt maize on soil microbial and nematode community structure.

A glasshouse experiment was undertaken to provide baseline data on the variation between conventional maize (Zea mays L.) varieties and genetically modified maize plants expressing the insecticidal Bacillus thuringiensis protein (Bt, Cry1Ab). The objective was to determine whether the variation in soil parameters under a range of conventional maize cultivars exceeded the differences between Bt and non-Bt maize cultivars. Variations in plant growth parameters (shoot and root biomass, percentage carbon, percentage nitrogen), Bt protein concentration in shoots, roots and soil, soil nematode abundance and soil microbial community structure were determined. Eight paired varieties (i.e. varieties genetically modified to express Bt protein and their near-isogenic control varieties) were investigated, together with a Bt variety for which no near-isogenic control was available (NX3622, a combined transformant expressing both Bt and herbicide tolerance) and a conventional barley (Hordeum vulgare L.) variety which was included as a positive control. The only plant parameter which showed a difference between Bt varieties and near-isogenic counterparts was the shoot carbon to nitrogen ratio; this was observed for only two of the eight varieties, and so was not attributable to the Bt trait. There were no detectable differences in the concentration of Bt protein in plant or soil with any of the Bt-expressing varieties. There were significant differences in the abundance of soil nematodes, but this was not related to the Bt trait. Differences in previously published soil nematode studies under Bt maize were smaller than these varietal effects. Soil microbial community structure, as determined by phospholipid fatty acid (PLFA) analysis, was strongly affected by plant growth stage but not by the Bt trait. The experimental addition of purified Cry1Ab protein to soil confirmed that, at ecologically relevant concentrations, there were no measurable effects on microbial community structure.

Animals↗
PubMed1998

Galanin in normal and hyperplastic anterior pituitary cells. From pituitary tumor cell lines to transgenic mice.

Studies on the regulation of galanin expression in the epithelial cells of the anterior pituitary gland have provided a wealth of insight into the cellular and molecular biology of this unique peptide. Galanin is localized within subpopulations of specific pituitary cell types, and hypothalamic as well as gonadal factors including dopamine, somatostatin, thyrotropin-releasing hormone, growth hormone-releasing hormone (GHRH), estrogen, and progesterone dynamically regulate its expression and release. Galanin gene expression and peptide secretion are markedly increased in estrogen-induced prolactinomas, wherein galanin serves as both an autocrine and paracrine hormone regulating prolactin secretion. Galanin mRNA and peptide levels are also dramatically elevated in somatotroph adenomas of human GHRH transgenic mice. Moreover, galanin secretion is increased from the hyperplastic somatotrophs of hGHRH transgenic mice. However, not all pituitary adenomas are associated with increased galanin gene expression; galanin synthesis is repressed in 131I-induced thyrotroph adenomas. Thus, galanin acts locally to regulate pituitary hormone secretion and appears to act as a mitogenic factor to increase the proliferation of pituitary cells in a cell-type specific manner.

Animals↗
PubMed2003

Progressive adult-onset emphysema in transgenic mice expressing human MMP-1 in the lung.

Mice with lung-specific expression of human matrix metalloproteinase-1 (MMP-1) develop emphysematous changes similar to those seen in smoking-induced emphysema in humans. Morphometric analyses of three transgenic lines [homozygous colony (Col) 34, Col 50, and Col 64] with varying temporal expression of MMP-1 were undertaken to determine the validity of this animal as a model of adult-onset emphysema. Line 50 mice, which have early expression of MMP-1 (14 days postconception), exhibited morphometric changes by 5 days of age. In contrast, homozygous line 34 and 64 with delayed expression (birth and 2 wk of age) were normal up until 4 wk of age when progressive changes in their mean linear intercept were first noted. In contrast, heterozygous mice from line 34 with lower transgene expression did not develop emphysema until 1 yr of age. The changes in mean linear intercept coincided with an increase in lung compliance. Emphysema in these mice was associated with decreased immunostaining for type III collagen within the alveolar septa. This study provides evidence that MMP-1 induces progressive adult-onset emphysema by the selective degradation of type III collagen within the alveolar wall.

Acute Disease↗
PubMed2001

Elevated blood pressure in transgenic mice with brain-specific expression of human angiotensinogen driven by the glial fibrillary acidic protein promoter.

In addition to the circulatory renin (REN)-angiotensin system (RAS), a tissue RAS having an important role in cardiovascular function also exists in the central nervous system. In the brain, angiotensinogen (AGT) is expressed in astrocytes and in some neurons important to cardiovascular control, but its functional role remains undefined. We generated a transgenic mouse encoding the human AGT (hAGT) gene under the control of the human glial fibrillary acidic protein (GFAP) promoter to experimentally dissect the role of brain versus systemically derived AGT. This promoter targets expression of transgene products to astrocytes, the most abundant cell type expressing AGT in brain. All transgenic lines exhibited hAGT mRNA expression in brain, with variable expression in other tissues. In one line examined in detail, transgene expression was high in brain and low in tissues outside the central nervous system, and the level of plasma hAGT was not elevated over baseline. In the brain, hAGT protein was mainly localized in astrocytes, but was present in neurons in the subfornical organ. Intracerebroventricular (ICV) injection of human REN (hREN) in conscious unrestrained mice elicited a pressor response, which was abolished by ICV preinjection of losartan. Double-transgenic mice expressing the hREN gene and the GFAP-hAGT transgene exhibited a 15-mm Hg increase in blood pressure and an increased preference for salt. Blood pressure in the hREN/GFAP-hAGT mice was lowered after ICV, but not intravenous losartan. These studies suggest that AGT synthesis in the brain has an important role in the regulation of blood pressure and electrolyte balance.

Angiotensinogen↗
PubMed2001

Targeted antizyme expression in the skin of transgenic mice reduces tumor promoter induction of ornithine decarboxylase and decreases sensitivity to chemical carcinogenesis.

To directly evaluate the role of increased ornithine decarboxylase (ODC) and polyamines in mouse skin carcinogenesis, we used bovine keratin 5 (K5) and keratin 6 (K6) promoter elements to direct the expression of antizyme (AZ) to specific skin cell populations. AZ is a multifunctional regulator of polyamine metabolism that inhibits ODC activity, stimulates ODC degradation, and suppresses polyamine uptake. K5-AZ mice treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) at 0 and 24 h exhibit increases in epidermal and dermal ODC activity that are reduced in magnitude. K6-AZ mice treated similarly do not show any increased ODC activity or protein after a second application due to TPA-induced expression of AZ protein. Epidermal and dermal polyamine content, particularly spermidine, is reduced in untreated K5-AZ mice and TPA-treated K5-AZ and K6-AZ mice. Susceptibility to 7,12-dimethylbenz(a)anthracene/TPA carcinogenesis was also investigated for two K6-AZ transgenic lines [K6-AZ(52) and K6-AZ(18)] and a single K5-AZ line. K6-AZ(52) mice had a substantial delay in tumor onset and a >80% reduction in tumor multiplicity compared with normal littermates. K6-AZ(18) and K5-AZ mice also developed fewer papillomas than littermate controls (35% and 50%, respectively), and the combination of these lines to produce double transgenic animals yielded an additive decrease (70%) in tumor multiplicity. These mice demonstrate for the first time that AZ suppresses tumor growth in an animal cancer model and provide a valuable model system to evaluate the role of ODC and polyamines in skin tumorigenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

[Restriction analysis of autonomously replicating molecules containing exogenous DNA in a transgenic silkworm line].

Early embryos of the silkworm, Bombyx mori, were injected with plasmid p1,5LTR, harboring DNA copies of the Rous sarcoma long terminal repeats (LTR). Three generations of insects were obtained whose total DNA carried DNA sequences of the injected plasmid. Plasmid rescue method revealed that exogenous DNA was present in extrachromosomal molecules that harbored also cellular DNA sequences. A restriction map of the plasmid rescued from the F2 generator was constructed.

Animals↗
PubMedDate not supplied

Abnormalities in secondary cartilages in four lines of transgenic mice harboring two different types of mutations in the cartilage-specific type II collagen gene.

A histological analysis was performed on two secondary cartilages, the mandibular condyle and the medial end of clavicle, in transgenic mice harboring two different types of mutations in the cartilage-specific type II collagen gene. Considerable differences were observed in the maturation zone of the chondrocytes and the hypertrophic cells of the growth regions of the two secondary cartilages examined between the transgenic mice and their transgene-negative littermates, which served as controls. Looseness of the perichondrium/periosteum was a distinct feature seen in both mutations. However, phenotypic consequences of the mutations in secondary cartilages were less severe than those in primary cartilages. We propose that the differences between primary and secondary cartilages are due to differences in their origin, mode of growth, architecture and behavior under extrinsic factors.

Amino Acid Sequence↗
PubMed1998

Conditional transgene expression in endothelial cells.

The ability to tightly control transgene expression in vivo provides an opportunity to determine the role of certain gene products at different times during development and/or in response to different stimuli. We have characterized and evaluated a tetracycline-responsive endothelial-specific binary system during mouse development, by engineering several transgenic lines which drive the expression of a tetracycline-controlled transactivator (tTA) under the control of either the Tek or Tie promoters (driver lines). We have also generated a responder line which carries multiple copies of the tTA DNA binding element (tetOS) upstream of a reporter gene coding for a nuclear targeted beta-galactosidase (responder lines). No expression of the target transgene was detected in mice homozygous for the reporter transgene. On mating the driver lines with the responder line, expression of beta-galactosidase from the reporter transgene was detected within the endothelium. Responder transgene expression was repressed rapidly upon addition of doxycycline to the drinking water. Importantly, this repression was reversible upon withdrawal of the drug. This approach should be useful to deliver the expression of potentially toxic gene products or rescue embryonic mutations that affect either the endothelial lineage or production of growth factors which are secreted systemically.

Animals↗
PubMed2005

Molecular composition of leaves and stems of genetically modified Bt and near-isogenic non-Bt maize--characterization of lignin patterns.

Transformation of crops, including maize (Zea mays L.), with the cry1Ab gene from Bacillus thuringiensis to combat lepidopteran pests results in pleiotropic effects regarding lignin biosynthesis. Lignin patterns in stems and leaves of two genetically modified Bt-maize varieties (Novelis T and Valmont T) were studied along with their non-Bt near-isolines (Nobilis and Prelude, respectively). Molecular-level based thermochemolysis using tetramethylammonium hydroxide (TMAH) in combination with gas chromatography-mass spectrometry (GC-MS) was used to quantitate the total lignin contents and to identify monomeric lignin subunits including p-hydroxyphenyl (P), guaiacyl (G), and syringyl (S) moieties. The results were supplemented and confirmed by cupric oxide oxidation. The stems of the transgenic lines had higher concentrations of total lignin than the respective isogenic lines: Valmont T/Prelude by 18% and Novelis T/Nobilis by 28%. In contrast, differences in the total lignin concentration of leaves between the transgenic and the respective near-isogenic lines were marginal. There were significant modifications in the ratio of p-hydroxyphenyl/guaiacyl/syringyl molecular marker units of stem lignin between transgenic and isogenic lines. The guaiacyl units (in particular the G18 marker) accounted chiefly for the higher total lignin contents in the transgenic lines. The leaf lignin patterns did not show significant differences in molecular markers between isogenic and transgenic lines. TMAH-induced thermochemolysis--conducted in both the on-line and off-line modes--provided detailed information on the molecular composition of lignin, thus proving superior to the established "wet chemistry" methods of lignin determination.

Analysis of Variance↗