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Use of multimetric statistical analysis to characterize and discriminate between the performance of four Alzheimer's transgenic mouse lines differing in Abeta deposition.

Behavioral assessment of genetically-manipulated mouse lines for Alzheimer's disease has become an important index for determining the efficacy of therapeutic interventions and examining disease pathogenesis. However, the potential for higher level statistical analyses to assist in these goals remains largely unexplored. The present study thus involved multimetric statistical analyses of behavioral and beta-amyloid (Abeta) deposition measures from four PDAPP-derived transgenic mouse lines that differ in extent of Abeta deposition. For all four lines, multiple behavioral measures obtained from a comprehensive task battery administered at 15-16 months of age were collectively examined by correlation, factor, and discriminant function analyses. In addition, both compact and total beta-amyloid (Abeta) histologic measures were determined from the same animals. Widespread intra- and inter-task correlations were evident, with impairment in all three water tasks (Morris maze, platform recognition, and radial arm water maze) correlating extensively with Abeta deposition in hippocampus and cerebral cortex. By elucidating the underlying relationships among measures, factor analysis revealed a single primary factor (Factor 1) that loaded most cognitive measures, particularly those for working memory and recognition. Abeta deposition measures loaded exclusively on this primary factor. In individual animals, only factor scores derived from this primary factor were correlated with Abeta deposition. Both of these findings again underscore the association between cognitive impairment and Abeta deposition. Finally, discriminant function analysis (step-wise forward method) was able to distinguish between all four AD transgenic lines based on behavioral performance alone, as well as when Abeta deposition measures were included. Our results demonstrate the utility of higher level, multimetric analysis of behavioral measures from AD transgenic mice. Analyses such as these will be very beneficial for the functional evaluation of therapeutic interventions against AD and for finding behavioral measures that can serve as predictors of pathology.

Alzheimer Disease↗

Overexpression of mouse follistatin causes reproductive defects in transgenic mice.

Follistatin is an activin-binding protein that can act as an activin antagonist in vitro. Follistatin also binds heparin sulfate proteoglycans and may function as a reservoir for activins in vivo. In the mouse, follistatin mRNA is first detected in the deciduum on embryonic day 5.5 and later in the developing hindbrain, somites, vibrissae, teeth, epidermis, and muscle. We have previously shown that follistatin-deficient mice have numerous embryonic defects including shiny, taut skin, growth retardation, and cleft palate leading to death within hours of birth. To further define the roles of follistatin during mammalian reproduction and development, we created gain-of-function mutant mice in which mouse follistatin is overexpressed. The mouse metallothionein (MT)-I promoter was placed upstream of the six-exon mouse follistatin (FS) gene. To distinguish wild-type and transgenic follistatin mRNA, the 3'-untranslated region of the mouse follistatin gene was replaced with the SV40 untranslated and polyA sequences. Three male and two female founder transgenic mice were produced, were fertile, and transmitted the transgene to offspring. Northern blot analysis demonstrated that the transgene mRNA was expressed at varying levels in the livers of offspring from four of five of the transgenic lines and was expressed in the testes in all five lines. In MT-FS line 4, which had the highest expression of the transgene mRNA in the liver, the transgene transcripts were also present in multiple other tissues. Phenotypically, the MT-FS transgenic lines had defects in the testis, ovary, and hair. Mice from MT-FS lines 7 and 10 had slightly decreased testis size, whereas mice from lines 4, 5, and 9 had much smaller testes and shiny, somewhat irregular, fur. Histological analysis of the adult testes from line 5 and 9 males showed variable degrees of Leydig cell hyperplasia, an arrest of spermatogenesis, and seminiferous tubular degeneration leading to infertility. Female transgenic mice from lines 4 and 9 had thin uteri and small ovaries due to a block in folliculogenesis at various stages. Many of the line 9 female mice eventually became infertile, and all of the line 4 female mice were infertile. Suppressed serum FSH levels were seen in only the line 4 transgenic male and female mice, the line with widespread expression of the transgene. Serum FSH levels were not significantly different in gonadectomized wild-type and line 5 transgenic male mice despite high levels of the follistatin transgene mRNA in the liver of these transgenic mice. These results suggest that follistatin exerts its effects at the levels of the gonads and pituitary as a local regulator of activin and possibly other transforming growth factor-beta family members.

Animals↗

Interleukin-5-mediated allergic airway inflammation inhibits the human surfactant protein C promoter in transgenic mice.

Allergen challenge in the lung of humans and animals is associated with surfactant dysfunction, but the mechanism of this effect has not been established. By using a murine model of asthma we now report the effect of allergen-induced airway inflammation on the expression of transgenes regulated by the human surfactant protein (hSP)-C promoter. The hSP-C 3.7-kilobase pair promoter was used to direct the expression of eotaxin, an eosinophil-selective chemokine, into the lungs of several transgenic lines. As expected, the transgenic mice expressed increased amounts of eotaxin mRNA and protein compared with wild-type mice. Surprisingly, following allergen challenge, there was a marked down-regulation of transgene mRNA in three independent transgenic lines. The down-regulation was in contrast to other related proteins such as endogenous eotaxin and surfactant protein D levels, which were both increased following allergen challenge. Consistent with specific down-regulation of the eotaxin transgene, there was no increase in pulmonary eosinophil levels in the transgenic mice above that found in wild-type mice. Analysis of hSP-C transgenic mice with distinct reporter genes and 3'-untranslated regions revealed that allergen challenge was directly affecting the hSP-C promoter. We hypothesized that allergen-induced down-regulation of the hSP-C promoter was related to the eosinophilic inflammation. To test this, we blocked eosinophilic inflammation in the lungs by treating mice with neutralizing antiserum against interleukin-5. Interestingly, this treatment also blocked allergen-induced inhibition of the hSP-C promoter. These results establish that allergic airway inflammation is associated with up-regulation of the surfactant proteins primarily involved in immunity, whereas down-regulation of the surfactant protein primarily involved in maintaining airway patency. Furthermore, the marked down-regulation of the hSP-C promoter is interleukin-5-dependent, implying a critical role for eosinophilic inflammation. These results suggest that alterations in surfactant protein levels may contribute to immune and airway dysfunction in asthma.

3' Untranslated Regions↗

Relationship between expression of epidermal growth factor and simian virus 40 T antigen in a line of transgenic mice.

The pattern of expression of the simian virus 40 (SV40) T antigen gene and resultant dysplasia were re-examined in a line of transgenic mice in which the T antigen gene was under the control of the SV40 early promoter. We found that T antigen expression in the kidney, and resulting dysplastic lesions, occurred exclusively in the distal convoluted tubules and the ascending limbs of Henle. Epidermal growth factor (EGF) expression in the kidney of normal mice was similarly immunolocalized. The correlation between high EGF immunoreactivity in normal mouse tissues and T antigen expression in the transgenic counterpart was also seen in the choroid plexus epithelium and in the submandibular glands of male mice. T antigen was not found in the submandibular gland of transgenic females. Similarly, EGF was only rarely detected in the normal female submandibular gland. In contrast to the correlation between T antigen expression in the transgenic mice and EGF expression in the corresponding tissues of the normal mice, within the dysplastic lesions of the transgenic mice EGF expression was severely diminished. Adenocarcinomas of the male submandibular gland from another line of transgenic mice that expresses the Int-1 transgene, showed similarly reduced levels of immunostaining for EGF. Thus, reduced expression of EGF might be a general feature of dysplasia and tumorigenesis in those tissues that normally express EGF.

Adenocarcinoma↗

Transgenic tobacco plants overexpressing cotton glutathione S-transferase (GST) show enhanced resistance to methyl viologen.

A GST (EC 2.5.1.18) gene (Gst-cr 1) from cotton was introduced into Nicotiana tabacum by Agrobacterium tumefaciens-mediated transformation. Transgenic tobacco plants overexpressing Gst-cr1 were normal in growth and mature compared with control, but had much higher levels of GST and GPx activities and showed an enhanced resistance to oxidative stress induced by a low concentration of methyl viologen (MV). Six antioxidant enzymes, glutathione S-transferase, glutathione peroxidase (EC 1.11.1.9), superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), and ascorbate peroxidase (EC 1.11.1.11) were monitored in transgenic lines and non-transgenic control during MV treatments. When they were treated with 0.03 mmol/L of MV, both transgenic lines and control showed a rapid increase in the activities of GST, GPx, SOD, POD, APx, while the activity of CAT seemed to be irregular. The percent of the increase in SOD and POD activities was much higher in control than in transgenic plants. When treated with 0.05 mmol/L of MV, both control and transgenic plants were severely damaged, and the activities of the six enzymes decreased sharply.

Ascorbate Peroxidases↗

Expression by transgenesis of a constitutively active mutant form of the prolactin receptor induces premature abnormal development of the mouse mammary gland and lactation failure.

Prolactin (PRL) initiates signal transduction by inducing homodimerization of PRL receptor (PRL-R). We have previously developed a mutant form of the PRL-R in which a part of the extracellular domain is deleted. This receptor constitutively activates protein gene transcription. We examined the oligomerization of the mutant PRL-R using two differently epitope-tagged receptors in a coimmunoprecipitation assay. It was shown that mutant receptor dimers were formed in a ligand-independent manner, which may explain the constitutive activity on milk protein gene expression. To study the biological activity of this mutant PRL-R on mammary gland development, we generated two lines of transgenic mice expressing the corresponding cDNA specifically in the mammary epithelial cells. For both transgenic lines, the mammary gland of 8-wk-old virgin mice was overdeveloped with numerous dilated ductal and alveolar structures, whereas only a limited duct network was present in wild-type animals at the same age. During pregnancy, the ducts and alveoli of transgenic mice were more developed than those of control animals. At parturition, the transgenic animals failed to lactate and nourish their offspring, and the involution of the mammary gland was strongly delayed. In conclusion, the expression of a constitutively active PRL-R by transgenesis induces a premature and abnormal mammary development and impairs terminal differentiation and milk production at the end of pregnancy.

Animals↗

Developmental regulation and complex organization of the promoter of the non-coding hsr(omega) gene of Drosophila melanogaster.

The nucleus-limited large non-coding hsr(omega)-n RNA product of the 93D or the hsr(omega) gene of Drosophila melanogaster binds to a variety of RNA-binding proteins involved in nuclear RNA processing. We examined the developmental and heat shock induced expression of this gene by in situ hybridization of nonradioactively labelled riboprobe to cellular transcripts in intact embryos, larval and adult somatic tissues of wild type and an enhancer-trap line carrying the hsr(omega) 05241 allele due to insertion of a P-LacZ-rosy+ transposon at -130 bp position of the hsr(omega) promoter. We also examined LacZ expression in the enhancer-trap line and in two transgenic lines carrying different lengths of the hsr(omega) promoter upstream of the LacZ reporter. The hsr(omega) gene is expressed widely at all developmental stages; in later embryonic stages, its expression in the developing central nervous system was prominent. In spite of insertion of a big transposon in the promoter, expression of the hsr(omega) 05241 allele in the enhancer-trap line, as revealed by in situ hybridization to hsr(omega) transcripts in cells, was similar to that of the wild type allele in all the embryonic, larval and adult somatic tissues examined. Expression of the LacZ gene in this enhancer-trap line was similar to that of the hsr(omega) RNA in all diploid cell types in embryos and larvae but in the polytene cells, the LacZ gene did not express at all, neither during normal development nor after heat shock. Comparison of the expression patterns of hsr(omega) gene and those of the LacZ reporter gene under its various promoter regions in the enhancer-trap and transgenic lines revealed a complex pattern of regulation, which seems to be essential for its dynamically varying expression in diverse cell types.

Animals↗

Fruit-specific V-ATPase suppression in antisense-transgenic tomato reduces fruit growth and seed formation.

The vacuole is a large, multifunctional organelle related to the processes of cell expansion, solute accumulation, regulation of cytoplasmic ion concentrations, pH homeostasis and osmoregulation, which are directly or indirectly achieved by vacuolar H+-pumps: vacuolar H+-ATPase (V-ATPase; EC 3.6.1.3) and vacuolar H+-pyrophosphatase (V-PPase; EC 3.6.1.1). In this study, we produced antisense-transgenic tomatoes (Lycopersicon esculentum L.) of the V-ATPase A subunit, which is under the control of the fruit-specific 2A11 promoter. One beta-glucuronidase (GUS)-transgenic line (GUS control) and seven A subunit antisense-transgenic lines were obtained. The amount of V-ATPase A subunit mRNA in fruit decreased in all antisense-transgenic lines, but in leaves showed no difference compared with the GUS control line and the nontransformant, suggesting that suppression of the V-ATPase A subunit by a 2A11 promoter is limited to fruit. The antisense-transgenic plants had smaller fruits compared with the GUS control line and the nontransformant. Surprisingly, fruits from the antisense-transgenic plants, except the fruit that still had relatively high expression of A subunit mRNA, had few seeds. Sucrose concentration in fruits from the antisense-transgenic plants increased, but glucose and fructose concentrations did not change. These results show the importance of V-ATPase, not only in fruit growth, but also in seed formation and in sugar composition of tomato fruit.

Antisense Elements (Genetics)↗

Effects of simultaneous over-expression of Cu/ZnSOD and MnSOD on Drosophila melanogaster life span.

The FLP-out technique, based on yeast FLP recombinase, allows induced over-expression of transgenes in Drosophila adults. With FLP-out control and over-expressing flies have identical genetic backgrounds and therefore differences in life span must result from transgene induction. The amount of over-expression achieved varies between independent transgenic lines, and previously for both Cu/ZnSOD and MnSOD life span was found to be increased in proportion to the increase in enzyme activity. To determine if greater increases in enzyme and life span could be achieved with FLP-out, enzyme over-expression and life span were analyzed in eight lines containing two MnSOD transgenes, three lines containing three MnSOD transgenes, and three lines containing a MnSOD transgene plus a Cu/ZnSOD transgene. Life span was again found to be increased in proportion to the increase in MnSOD enzyme activity, with increases of up to 40% in mean and maximum life span. However the increases in enzyme activity and life span conferred per transgene were reduced when more than one transgene was present at the same time. When the reduced efficiency of enzyme over-expression per transgene was taken into account, simultaneous over-expression of MnSOD and Cu/ZnSOD was found to have partially additive effects on life span.

Animals↗

In vivo properties of monocyte chemoattractant protein-1.

Monocyte chemoattractant protein-1 (MCP-1) attracts monocytes, memory T lymphocytes, and natural killer (NK) cells in vitro. Its expression has been documented in disorders characterized by mononuclear cell infiltrates, suggesting that it may contribute to the inflammatory component of such diseases as atherosclerosis, multiple sclerosis, or rheumatoid arthritis. To prove a causal association, the in vivo properties of MCP-1 must be understood. Several lines of transgenic mice have been constructed to address this question. A transgenic line in which MCP-1 expression is controlled by the MMTV-LTR expressed high levels of MCP-1 in multiple organs but showed no evidence for monocyte infiltration. Instead, these mice were more susceptible to infection by the intracellular pathogens, Listeria monocytogenes and Mycobacterium tuberculosis. These mice had high serum levels of MCP-1, suggesting that their circulating monocytes may have been desensitized or that MCP-1 stimulated a Th2-dominant response. In contrast, another model in which MCP-1 expression was controlled by the insulin promoter demonstrated a monocytic infiltrate in pancreatic islets. These results indicate that MCP-1 expression at low levels in an anatomically confined area results in monocyte infiltration, suggesting that when properly expressed, MCP-1's in vitro properties are reproduced in vivo. This justifies the examination of MCP-1-deficient mice in disease models in order to explore MCP-1's role in pathogenesis.

Animals↗

Insulin-like growth factor-binding protein 5 (Igfbp5) compromises survival, growth, muscle development, and fertility in mice.

The insulin-like growth factors (IGFs) are essential for development; bioavailable IGF is tightly regulated by six related IGF-binding proteins (IGFBPs). Igfbp5 is the most conserved and is developmentally up-regulated in key lineages and pathologies; in vitro studies suggest that IGFBP-5 functions independently of IGF interaction. Genetic ablation of individual Igfbps has yielded limited phenotypes because of substantial compensation by remaining family members. Therefore, to reveal Igfbp5 actions in vivo, we generated lines of transgenic mice that ubiquitously overexpressed Igfbp5 from early development. Significantly increased neonatal mortality, reduced female fertility, whole-body growth inhibition, and retarded muscle development were observed in Igfbp5-overexpressing mice. The magnitude of the response in individual transgenic lines was positively correlated with Igfbp5 expression. Circulating IGFBP-5 concentrations increased a maximum of only 4-fold, total and free IGF-I concentrations increased up to 2-fold, and IGFBP-5 was detected in high M(r) complexes; however, no detectable decrease in the proportion of free IGF-I was observed. Thus, despite only modest changes in IGF and IGFBP concentrations, the Igfbp5-overexpressing mice displayed a phenotype more extreme than that observed for other Igfbp genetic models. Although growth retardation was obvious prenatally, maximal inhibition occurred postnatally before the onset of growth hormone-dependent growth, regardless of Igfbp5 expression level, revealing a period of sensitivity to IGFBP-5 during this important stage of tissue programming.

Animals↗

Cytoplasmic beta-actin promoter produces germ cell and preimplantation embryonic transgene expression.

The cytoplasmic beta-actin promoter, commonly used as strong promoter in many gene regulation studies, produces a pattern of male germ cell and preimplantation, embryonic gene expression in transgenic mice. In seven of ten expressing transgenic lines, a chicken beta-actin-lacZ fusion gene was expressed in adult testes. In addition, five of the ten lines demonstrated transgene expression in the preimplantation mouse embryo. This is the first example of transgene expression at the stages of both gamete and early embryo. Overall, the site or transgene integration appeared to influence transgene expression in adult tissues.

Actins↗

Tyrosinase-related protein 2 promoter targets transgene expression to ocular and neural crest-derived tissues.

In an effort to identify a promoter suitable for studying early ocular development, we generated transgenic mice carrying the lacZ reporter gene linked to the tyrosinase-related protein 2 (TRP2) promoter. TRP2-lacZ was expressed in early retinal pigment epithelium (RPE) and early neural crest cells in embryos. The promoter activity was robust and consistent in independent transgenic lines. The transgene was also expressed in the optic nerve and neural crest-derived neuronal cells in which the endogenous TRP2 gene is not expressed. This suggests that repressor elements may be missing in the promoter used in this study. To test whether this promoter can be used to study melanocyte development, we cross-mated TRP2-lacZ transgenic mice with mice heterozygous for the Patch (Ph) mutation. The pattern of beta-galactosidase activity in the embryos correlates well with the pigmentation phenotype in postnatal and adult Ph/+ mice. We also generated transgenic mice expressing fibroblast growth factor 9 (FGF9) directed by the TRP2 promoter and examined the effect on ocular development. Ectopic expression of FGF9 in the early embryonic RPE switched its differentiation pathway to a neuronal fate, resulting in formation of a duplicated neural retina in transgenic mice. These studies demonstrate that the TRP2 promoter is valuable for transgenic studies of ocular differentiation and development of neural crest cells.

Animals↗

Gene transfer into zebrafish by sperm nuclear transplantation.

A technique for fertilizing zebrafish eggs by injection of sperm nuclei is described. Eggs that cleave normally can develop into swimming larvae and give rise to fertile adults. If sperm nuclei are preincubated for 20 min with DNA encoding the green fluorescent protein, transgene expression can be detected in all cells of the embryo. The use of condensed sperm nuclei allows injection with a small bore pipette, which is critical for successful injection of the relatively small zebrafish egg. This technique enables the generation of ubiquitously expressing transgenic zebrafish directly by microinjection. Hence, experiments involving transgenic fish can be completed in days, without the need for growing and breeding founders. This technique may also be used to generate transgenic lines, as transgene expression was visible in the offspring of transgenic founders. The method described here is likely to be applicable to other teleosts, such as medaka and salmon.

Animals↗

Sensitivity of different vascular beds in the eye to neovascularization and blood-retinal barrier breakdown in VEGF transgenic mice.

Neovascularization (NV) causes visual deficits in ocular disorders such as diabetic retinopathy, age-related macular degeneration, and retinopathy of prematurity. An understanding of the angiogenic factors promoting this abnormal vascular growth is necessary to devise a therapeutic approach to inhibit NV. One factor known to promote NV is vascular endothelial growth factor (VEGF), which can also induce a breakdown of the blood-retinal barrier (BRB) leading to macular edema, another major cause of visual loss in a variety of ocular disorders. To investigate the role of VEGF on ocular NV, transgenic mice have been produced that over-express VEGF in the photoreceptors under control of the rhodopsin promoter. Eyes from these mice and from littermates not expressing the transgene were examined using immunohistochemistry, griffonia simplicifolia isolectin-B4 (GSA) staining to clearly visualize vessels, and electron microscopy. Levels of transgene expression were determined by the polymerase chain reaction. In normal mice, retinal vessels are organized into a superficial and a deep capillary bed with some vessels forming a shunt between both beds. In a transgenic line of mice that over-expresses VEGF (V-6), NV originates from the deep capillary bed at about postnatal day 10 (P10) and extends through the photoreceptor layer to form vascular complexes in the subretinal space with BRB breakdown occurring only in the area of NV. The superficial capillary bed and the choroidal vasculature are unaffected. In another line of transgenic mice with a higher expression rate of VEGF (V-24), photoreceptor degeneration begins at P7-8, soon after the onset of transgene expression, without widespread NV, as was observed in V-6 mice. In conclusion, overexpression of VEGF in transgenic mice is sufficient to cause retinal NV, but only the deep capillary bed is responsive. Increasing the expression of VEGF does not necessarily increase the amount of NV. A better understanding of the specific factors and conditions that result in a particular pattern of ocular NV may provide clues regarding the pathogenesis of ocular neovascular disease.

Animals↗

Sex- and tissue-specific expression of a cytochrome P450 2C2-luciferase transgene.

To study the transcriptional regulation of the rabbit cytochrome P450 2C2 gene (CYP2C2), transgenic mice were generated using a DNA fragment containing the CYP2C2 5'-flanking region fused to a luciferase reporter gene. In one of three transgenic lines, this transgene was expressed in the liver and at a lower level in the kidney, similar to the tissue-specific pattern of this gene in rabbits. Unlike expression in rabbits, the transgene was expressed in a male-specific pattern in liver and kidney, and in the brain of both sexes. Expression of the transgene in male mice was repressed after castration, while expression in females was stimulated after testosterone treatment and periodic injection of rat growth hormone (GH). The expression of this transgene was also regulated developmentally in the liver. These results suggest that this 3500 bp of CYP2C2 5'-flanking region contains the basal transcriptional regulation elements for tissue-specific and developmental expression. Although a position effect can not be ruled out, this transgene may also include the cis-regulatory element for sexual dimorphic expression.

Animals↗

An update on in vitro test methods in human hepatic drug biotransformation research: pros and cons.

The liver is the predominant organ in which biotransformation of foreign compounds takes place, although other organs may also be involved in drug biotransformation. Ideally, an in vitro model for drug biotransformation should accurately resemble biotransformation in vivo in the liver. Several in vitro human liver models have been developed in the past few decades, including supersomes, microsomes, cytosol, S9 fraction, cell lines, transgenic cell lines, primary hepatocytes, liver slices, and perfused liver. A general advantage of these models is a reduced complexity of the study system. On the other hand, there are several more or less serious specific drawbacks for each model, which prevents their widespread use and acceptance by the regulatory authorities as an alternative for in vivo screening. This review describes the practical aspects of selected in vitro human liver models with comparisons between the methods.

Animals↗

Gibberellins signal nuclear import of PHOR1, a photoperiod-responsive protein with homology to Drosophila armadillo.

S. tuberosum ssp. andigena potato plants require short days (SD) for tuberization. We have isolated PHOR1 (photoperiod-responsive 1), which shows upregulated expression in induced leaves (SD). PHOR1 encodes an arm repeat protein with homology to the Drosophila segment polarity protein armadillo. Antisense inhibition of PHOR1 produces a semidwarf phenotype similar to that of GA-deficient plants, and the antisense lines show reduced GA responsiveness combined with a higher endogenous GA content than wild-type plants. Feedback regulation of GA biosynthetic genes is also altered in these lines. Conversely, transgenic lines overexpressing PHOR1 show an enhanced response to GA. GA application induces rapid migration of PHOR1-GFP protein to the nucleus. Thus, PHOR1 appears to be a general component of GA signaling pathways that relocalizes to the nucleus in the presence of GA.

Active Transport, Cell Nucleus↗