Impaired differentiation of endocrine and exocrine cells of the pancreas in transgenic mouse expressing the truncated type II activin receptor.
(57/7369)
Activin A is expressed in endocrine precursor cells of the fetal pancreatic anlage. To determine the physiological significance of activins in the pancreas, a transgenic mouse line expressing the truncated type II activin receptor under the control of beta-actin promoter was developed. Histological analyses of the pancreas revealed that the pancreatic islets of the transgenic mouse were small in size and were located mainly along the pancreatic ducts. Immunoreactive insulin was detected in islets, some acinar cells, and in some epithelial cells in the duct. In addition, there were abnormal endocrine cells outside the islets. The shape and the size of the endocrine cells varied and some of them were larger than islets. These cells expressed immunoreactive insulin and glucagon. In the exocrine portion, there were morphologically abnormal exocrine cells, which did not form a typical acinar structure. The cells lacked spatial polarity characteristics of acinar cells but expressed immunoreactive amylase, which was distributed diffusely in the cytoplasm. Plasma glucose concentration was normal in the transgenic mouse before and after the administration of glucose. The insulin content of the pancreas in transgenic and normal mice was nearly identical. These results suggest that activins or related ligands regulate the differentiation of the pancreatic endocrine and exocrine cells. (+info)
Morphological, histochemical, immunohistochemical, and ultrastructural characterization of tumors and dysplastic and non-neoplastic lesions arising in BK virus/tat transgenic mice.
(58/7369)
To study the role in AIDS pathogenesis of the human immunodeficiency virus type 1 (HIV-1) Tat protein, a transactivator of viral and cellular genes, we generated transgenic mice with a recombinant DNA containing BK virus (BKV) early region and the HIV-1 tat gene, directed by its own promoter-enhancer. DNA hybridization revealed that the transgene is stably maintained in all organs of transgenic mice as a tandem insertion in a number of copies ranging from 5 to 20 per cell. In addition, tat and BKV RNA were expressed in all tissues. Transgenic mice developed three types of lesions: 1) tumors, 2) hyperplastic and dysplastic lesions, and 3) non-neoplastic lesions. Tumors of different histotypes, such as lymphomas, adenocarcinomas of skin glands, leiomyosarcomas, skin squamous cell carcinomas, hepatomas, hepatocarcinomas, and cavernous liver hemangiomas, developed in 29% of transgenic animals. The majority of tumors were malignant, invasive, and producing metastases. Conversely, tumors of only two histotypes (lymphomas and adenocarcinomas of skin glands) appeared in control mice. Hyperplastic and dysplastic lesions were more frequent in transgenic than in control mice and involved the skin or its adnexes, the liver and the rectum, indicating multiple targets for the activity of the transgene. Pyelonephritis, frequently complicated with hydronephrosis, inflammatory eye lesions, and amyloid depositions represented the most frequent non-neoplastic lesions detected in transgenic mice. Many of the pathological findings observed in this animal model are comparable to similar lesions appearing in AIDS patients, suggesting a relevant role for Tat in the pathogenesis of such lesions during the course of AIDS. (+info)
Implication of interfering antibody formation and apoptosis as two different mechanisms leading to variable duration of adenovirus-mediated transgene expression in immune-competent mice.
(59/7369)
This study explores the genetic and immunologic factors involved in the differences in duration of transgene expression following in vivo transduction with recombinant adenoviruses. Different strains of mice (C3H/HeJ [C3H], C57BL/6J [B6], BALB/cJ [Balb/c], C. B10-H2(b)/LiMcdJ [Balb.B], CB6F1/J [(Balb/c x B6)F1], B6C3F1/J [(B6 x C3H)F1], and BALB/cj SCID) received 5 x 10(9) PFU of the first-generation adenovirus, which expresses human alpha1-antitrypsin (Ad/RSVhAAT). While all strains studied showed similar patterns of anti-adenovirus antibody formation, only Balb/c and C3H mice developed significant levels of anti-hAAT antibodies by 8 weeks posttransduction. In addition, while all strains had quantitatively comparable amounts of adenovirus genomes and hAAT mRNA transcripts in the liver 9 days posttransduction, only Balb/c mice had undetectable adenovirus vector genomes and hAAT mRNA in the liver 40 days posttransduction. Terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling staining of liver sections from control and Ad/RSVhAAT-infected mice 5, 9, and 40 days posttransduction suggested that apoptosis was involved in the rapid elimination of transduced hepatocytes in Balb/c mice. Persistent expression of hAAT protein observed in BALB/cj SCID mice suggests that antigen-dependent immunity was essential for this apoptotic process in transduced Balb/c hepatocytes. In contrast to Balb/c mice, the loss of expression in C3H mice did not correlate with the loss of vector genomes or hAAT mRNA. Instead, the anti-hAAT antibodies in C3H but not Balb/c mice were found to interfere with detection of hAAT in the serum. In Balb. B and B6 mice, vector genome, hAAT mRNA transcripts, and hAAT protein levels persisted for at least 40 days posttransduction. This persistence correlated with poor anti-hAAT antibody formation and minimal hepatocyte toxicity. The expression of hAAT in (Balb/c x B6)F1 pups was found to be intermediate between the duration observed in the parental strains, while in (C3H x B6)F1 pups hAAT expression was similar to that seen in the B6 parents, which together support polygenic control of the immune responses in these mice. In summary, these findings suggest that there are three different profiles and at least two defined immune system-mediated mechanisms resulting in the loss of hAAT expression in mice and that different strains differ in the capacity to utilize these mechanisms. (+info)
Inhibition of tumor necrosis factor alpha by an adenovirus-encoded soluble fusion protein extends transgene expression in the liver and lung.
(60/7369)
The cellular and humoral immune responses to adenovirus (Ad) remain a major barrier to Ad-mediated gene therapy. We recently reported that mice deficient in tumor necrosis factor alpha (TNF-alpha) or Fas (APO-1, CD95) have prolonged expression of an Ad transgene expressing a foreign protein in the liver. To determine whether blockade of TNF-alpha or Fas would have the same effect in normal mice, we created transgenes that expressed soluble murine CD8 or CD8 fused to the extracellular regions of TNF receptor 1 (TNFR) or Fas and inserted into the left-end region of first-generation (E1/E3-) Ad vectors. Consistent with the results observed in TNF-deficient mice, expression of the TNFR-CD8 fusion protein was prolonged in vivo compared to that of control proteins. Not only did expression of TNFR-CD8 persist in the liver and the lung, but when coadministered with another first-generation vector, the protein provided "transprotection" for the companion vector and transgene. In addition, TNFR-CD8 attenuated the humoral immune response to the Ad. Together, these findings demonstrate that blockade of TNF-alpha is likely to be useful in extending the expression of an Ad-encoded transgene in a gene therapy application. (+info)
Retinoid kinetics in eye tissues of VPP transgenic mice and their normal littermates.
(61/7369)
PURPOSE: VPP mice, which possess a mutant transgene for opsin (V20G, P23H, P27L), exhibit a progressive rod degeneration that resembles one form of human autosomal dominant retinitis pigmentosa. In the present study the association of the development of VPP rod degeneration with abnormal operation of the retinoid visual cycle was examined. METHODS: Dark-adapted VPP mice and normal littermates were anesthetized and the pupils dilated. One eye of each animal was illuminated for 2 minutes; the other eye was shielded from the light and served as a control. Each animal was then dark adapted for a defined period (0-300 minutes) and killed. Retinoids contained in the retina, retinal pigment epithelium (RPE), and extracellular medium were recovered by means of formaldehyde-, isopropanol- and ethanol-based extractions and analyzed by high-performance liquid chromatography. RESULTS: Total amounts of retinoid recovered from unilluminated eyes of 2-month-old normal and VPP mice were 425 +/- 90 picomoles per eye and 115 +/- 33 picomoles per eye, respectively (mean +/- SD). Relative distributions of retinoids within normal and VPP eyes were similar. In normal and VPP animals, illumination for 2 minutes produced a similar immediate reduction in the molar percent of total retinoid represented by 11-cis retinal in the retina (average reduction of 34% and 28% in normal and VPP animals, respectively) and a similar transient increase of all-trans retinal in the retina. In both groups the decline of all-trans retinal was accompanied by an increase in total retinyl ester. In normal and VPP animals, a period of approximately 40 minutes or more preceded initiation of the recovery of 11-cis retinal in the retina, and the time course of this recovery was generally similar to that for the decline of retinyl ester. The overall dark-adaptation period required for half-completion of 11-cis retinal recovery was approximately 150 minutes. In neither group did illumination produce a substantial peak of all-trans retinol in the retina. CONCLUSIONS: The evident approximately fourfold reduction of total retinoid in the eyes of 2-month-old VPP mice is consistent with histologic and electroretinographic abnormalities determined in previous studies. Despite this marked abnormality in retinoid content, retinoid cycling in the VPP is remarkably similar to that in normal littermates. The data place constraints on the functional consequences of any abnormality in retinoid processing that may be present at this stage of the VPP rod degeneration. (+info)
Evidence that intramolecular associations between presenilin domains are obligatory for endoproteolytic processing.
(62/7369)
Mutations in genes encoding presenilins (PS1 and PS2) cosegregate with the majority of early onset cases of familial Alzheimer's disease. PS1 and PS2 are polytopic membrane proteins that undergo endoproteolytic cleavage to generate stable NH2- and COOH-terminal derivatives (NTF and CTF, respectively). Several lines of evidence suggest that the endoproteolytic derivatives are likely the functional units of PS in vivo. In the present report, we examine the disposition of PS NTF and CTF assemblies in stable mouse N2a neuroblastoma cell lines expressing human PS polypeptides. We show that exogenous expression of PS1 NTFs neither assemble with endogenous CTF nor exhibit dominant negative inhibitory effects on the endogenous PS1 cleavage and the accumulation of derivatives. In cells co-expressing PS1 and PS2, PS1- and PS2-derived fragments do not form mixed assemblies. In contrast, cells expressing a chimeric PS1/PS2 polypeptide form stable PS1 NTF-PS2 CTF assemblies. Moreover, expression of chimeric PS1/PS2 polypeptides harboring a familial early onset AD-linked mutation (M146L) elevates the production of Abeta42 peptides. Our results provide evidence that assembly of structural domains contained within NH2- and COOH-terminal regions of PS occur prior to endoproteolytic cleavage. (+info)
Breaking colinearity in the mouse HoxD complex.
(63/7369)
Vertebrate Hox genes are activated in a spatiotemporal sequence that reflects their clustered organization. While this colinear relationship is a property of most metazoans with an anterior to posterior polarity, the underlying molecular mechanisms are unknown. Previous work suggested that Hox genes were made progressively available for transcription in the course of gastrulation, implying the existence of an element capable of initiating a repressive conformation, subsequently relieved from the clusters sequentially. We searched for this element by combining a genomic walk with successive transgene insertions upstream of the HoxD complex followed by a series of deletions. The largest deficiency induced posterior homeotic transformations coincidentally with an earlier activation of Hoxd genes. These data suggest that a regulatory element located upstream of the complex is necessary for setting up the early pattern of Hox gene colinear activation. (+info)
Mammalian transgenesis by intracytoplasmic sperm injection.
(64/7369)
Coinjection of unfertilized mouse oocytes with sperm heads and exogenous DNA encoding either a green fluorescent protein (GFP) or beta-galactosidase reporter produced 64 to 94 percent transgene-expressing embryos, reflecting DNA-sperm head association before coinjection. Nonselective transfer to surrogate mothers of embryos in the GFP series generated about 20 percent offspring expressing the integrated transgene. These data indicate that exogenous DNA can reproducibly be delivered into an oocyte by microinjected spermatozoa and suggest an adaptable method of transgenesis. (+info)