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R D Palmiter

Publications and source records attributed to R D Palmiter.

At least 19 recordsLinked to original sources
PubMed1992

DNA rearrangement causes hepatocarcinogenesis in albumin-plasminogen activator transgenic mice.

Hepatocyte-directed production of urokinase-type plasminogen activator (uPA) in transgenic mice is hepatotoxic. Infrequently, hepatocytes arise that do not express uPA, due to physical loss of transgene DNA, and these cells clonally repopulate the entire liver within 3 months of birth. Surprisingly, hepatic tumors appear in these mice beginning at 8 months of age despite the fact that uPA is not oncogenic or genotoxic. Analysis of the transgene locus reveals that tumors arise only from a particular subclass of transgene-deficient cells in which the entire transgene array, and possibly a significant amount of flanking DNA, is deleted. Considering that all transgene-deficient regenerative nodules undergo extensive replication but only a subset gives rise to tumors, we propose that loss of genomic DNA, not mitogenesis per se, is a primary carcinogenic determinant in this model of hepatocarcinogenesis.

Alanine Transaminase↗
PubMed1992

MT-III, a brain-specific member of the metallothionein gene family.

A third member of the metallothionein (MT) gene family, designated MT-III, was cloned by virtue of its homology to a human protein that was shown previously to inhibit neuronal survival in culture and to be deficient in the brains of people with Alzheimer disease. Human and mouse MT-IIIs have two insertions relative to all other known mammalian MTs: a threonine after the fourth amino acid and a block of six amino acids near the carboxyl terminus. The genes encoding MT-III resemble all other mammalian MT genes in their small size and exon/intron organization. The MT-III genes are closely linked to the other functional MT genes on human chromosome 16 and mouse chromosome 8. Mouse MT-III gene expression appears to be restricted to brain; in addition, it fails to respond to zinc, cadmium, dexamethasone, or bacterial endotoxin in vivo, thereby distinguishing MT-III from other known MTs.

Amino Acid Sequence↗
PubMed1992

Peripheral tolerance to an islet cell-specific hemagglutinin transgene affects both CD4+ and CD8+ T cells.

To study the basis for immunological tolerance of peripheral tissue-specific antigens, a transgenic mouse line was established that expresses the influenza hemagglutinin (HA) on pancreatic islet beta cells (Ins-HA transgenic mice). When followed up to 14 months of age, Ins-HA transgenic mice did not develop spontaneous autoimmune disease. Upon immunization with HA-expressing viruses, high titers of HA-specific circulating antibody were detected; however, T cell responses by both the T helper and T cytolytic compartment were markedly reduced as compared with transgene-negative littermates, and no evidence could be found for islet infiltrates. Adoptive transfer of histocompatible lymphocytes from transgene-negative mice plus virus into irradiated Ins-HA hosts resulted in islet inflammation dominated by CD4+ T cells, indicating that the HA antigen was accessible to activated T cells. These results suggest that T cells can be rendered tolerant of antigens expressed outside the thymus.

Amino Acid Sequence↗
PubMed1992

P0 promoter directs expression of reporter and toxin genes to Schwann cells of transgenic mice.

We generated transgenic mice that specifically express foreign genes in myelinating Schwann cells. A 1.1 kb segment of 5' flanking sequence from the rat P0 gene was used to drive expression of the genes encoding human growth hormone (hGH) and bacterial diphtheria toxin A chain (DT-A). The P0-hGH mice expressed hGH in myelinating Schwann cells, but not in nonmyelinating Schwann cells, the central nervous system, or any other tissue assayed. This expression was activated on a developmental schedule comparable to that of endogenous myelin gene expression. One line of P0-DT-A mice developed a generalized hypomyelinating peripheral neuropathy, with Schwann cell deficiency apparent in newborn animals. Peripheral nerves from adult mice of this line displayed morphological alterations ranging from completely denuded axons to myelinated Schwann cells undergoing degeneration, although occasional Schwann cells were able to form apparently normal myelin sheaths. Pronounced secondary changes, including proliferation and retraction of processes, occurred in the nonmyelinating Schwann cells of these P0-DT-A mice.

Age Factors↗
PubMed1992

Alteration of neurotransmitter phenotype in noradrenergic neurons of transgenic mice.

The normal complement of neurotransmitters in noradrenergic neurons was altered by expressing the structural gene for the enzyme phenylethanolamine-N-methyltransferase (PNMT) under the control of the dopamine-beta-hydroxylase gene promoter in transgenic mice. This resulted in accumulation of large amounts of epinephrine in neurons of the sympathetic nervous system (SNS) and central nervous system (CNS) but did not reduce norepinephrine levels. Adrenalectomy reduced PNMT levels in the SNS and CNS, suggesting that the transgene is positively regulated by adrenal steroids. Epinephrine levels were unaffected by this treatment in the CNS, suggesting that PNMT is not rate limiting for epinephrine synthesis. However, catecholamines were elevated in a sympathetic ganglion and a target tissue of the SNS, perhaps due to up-regulation of tyrosine hydroxylase in response to adrenalectomy. These transgenic mice also reveal a marked difference in the ability of chromaffin cells and neurons to synthesize epinephrine.

Adaptation, Physiological↗
PubMed1992

Directed expression of an oncogene to Sertoli cells in transgenic mice using mullerian inhibiting substance regulatory sequences.

Mullerian inhibiting substance (MIS) is a glycoprotein hormone expressed by Sertoli cells that induces the regression of Mullerian ducts during development of the male reproductive tract. Transgenic mice carrying a fusion gene composed of human MIS transcriptional regulatory sequences linked to the SV40 T-antigen gene specifically develop testicular tumors composed of a cell type histologically resembling the Sertoli cell. The lack of pathology at other sites suggests tissue-restricted expression of the transgene. A cell line derived from one of the testicular tumors has been established that continues to express markers associated with Sertoli cells, such as transferrin, sulfated glycoprotein-2, and inhibin-beta B. The cell line does not express detectable levels of inhibin-alpha, MIS, or FSH receptor. However, the cells have retained forskolin responsiveness. As adult Sertoli cells cannot be propagated in vitro, the availability of an immortal cell line displaying features characteristic of normal Sertoli cells should aid in subsequent analyses of the biology of this cell type.

Animals↗
PubMed1992

A transgenic model for studying development of the enteric nervous system in normal and aganglionic mice.

The dopamine beta-hydroxylase promoter has been shown to direct expression of the reporter gene product, beta-galactosidase, to enteric neurons and putative embryonic neuroblasts in transgenic mice (Mercer et al., 1991; Kapur et al., 1991). In this paper, expression of the transgene, D beta H-nlacZ, in the gastrointestinal tract is characterized in more detail in wild-type mice and mice which are also homozygous for the lethal spotted allele (ls). Expression of the transgene in wild-type embryos was first detected in scattered mesenchymal cells in the proximal foregut on embryonic day 9.5, and progressed distally until embryonic day 13.5 when the entire length of the gut was colonized by such cells. Several observations suggest that the mesenchymal cells which express the transgene (MCET) are, in fact, enteric neuroblasts, probably derived from the vagal neural crest. (1) The presence of MCET in progressively more caudal portions of the embryonic gut correlated with the neurogenic potential of isolated gastrointestinal segments grafted under the renal capsule. (2) Mitotic activity of MCET was demonstrated by incorporation of [3H]thymidine in utero. (3) The migratory behavior of MCET and/or their precursors was revealed in anastomotic subcapsular grafts of gut from transgenic and non-transgenic embryos; enteric ganglia of the latter were populated by MCET from the former. (4) Enteric expression of the transgene postnatally was restricted to intrinsic neurons that coexpressed other phenotypic markers of neuronal differentiation. The pattern of transgene expression in ls/ls mice was identical to that seen in ls/+ and +/+ mice until embryonic day 12.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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↗
PubMed1991

Retrotransposition of a mouse L1 element.

Long interspersed elements (LINEs) of the L1 family represent a major class of mammalian repetitive DNA and are present at copy numbers of between 10(4) and 10(5) elements per genome. Structural similarities between L1 elements and known retrotransposons have led to the suggestion that a subset of L1 elements may function as mobile genetic elements and have thus gained their prominent place in the mammalian genome. We describe a consensus mouse L1 element that was tagged with a heterologous intron and shown to transpose by way of an RNA intermediate when transfected into baby hamster kidney cells, formally establishing L1 elements as retrotransposons. When the putative reverse transcriptase-encoding region of this L1 element was deleted, the element still underwent retrotransposition in hamster cells, suggesting that reverse transcriptase activity can be supplied by an endogenous enzyme.

Animals↗
PubMed1991

Complete hepatic regeneration after somatic deletion of an albumin-plasminogen activator transgene.

We previously demonstrated that expression of an albumin-urokinase-type plasminogen activator (Alb-uPA) fusion construct in transgenic mice resulted in elevated plasma uPA concentration, hypofibrinogenemia, and neonatal hemorrhaging. Two lines of Alb-uPA mice were established in which only one half of the transgenic pups died at birth; surprisingly, plasma uPA concentrations in survivors gradually returned to normal by 2 months of age. The basis for this phenomenon is DNA rearrangement within hepatocytes that affects the transgene tandem array and abolishes transgene expression. Transgene-deficient cells selectively proliferate relative to surrounding liver, and this process culminates in replacement of the entire liver by clonal hepatic nodules derived from transgene-deficient progenitor cells. In some cases as few as two nodules can reconstitute over 90% of liver mass, highlighting the remarkable regenerative capacity of individual liver cells.

Animals↗
PubMed1991

Human beta-globin locus control region: analysis of the 5' DNase I hypersensitive site HS 2 in transgenic mice.

The human beta-globin locus control region (LCR) is essential for high-level expression of human epsilon-, gamma-, and beta-globin genes. Developmentally stable DNase I hypersensitive sites (designated HS) mark sequences within this region that are important for LCR activity. A 1.9-kilobase (kb) fragment containing the 5' HS 2 site enhances human beta-globin gene expression 100-fold in transgenic mice and also confers position-independent expression. To further define important sequences within this region, deletion mutations of the 1.9-kb fragment were introduced upstream of the human beta-globin gene, and the constructs were tested for activity in transgenic mice. Although enhancer activity was gradually lost with deletions of both 5' and 3' sequences, a 373-base-pair (bp) fragment retained the ability to confer relative position-independent expression. Three prominent DNase I footprints were observed in this region with extracts from the human erythroleukemia cell line K-562, one of which contained duplicated binding sites for transcription factor AP-1 (activator protein 1). When the 1.9-kb fragment containing an 18-bp deletion of the AP-1 binding sites was tested in transgenic mice, enhancer activity decreased 20-fold but position-independent expression was retained.

Animals↗
PubMed1991

Heterologous introns can enhance expression of transgenes in mice.

In a previous study we showed that genomic constructs were expressed more efficiently in transgenic mice than constructs that were identical except for the lack of introns. Using the mouse metallothionein promoter-rat growth hormone gene construct as a model, we show that the first intron of the rat growth hormone gene is essential for high-level expression, whereas the other three introns are less effective. Several heterologous introns placed 3' of the coding region of an intronless rat growth hormone gene are also ineffective. However, insertion of some heterologous introns between the metallothionein promoter and the growth hormone gene improves expression. To determine whether addition of heterologous introns would provide a general strategy for improving expression, we have tested them in conjunction with other intronless genes and with different promoters.

Animals↗
PubMed1991

Pancreatic tumor pathogenesis reflects the causative genetic lesion.

Transgenic mice in which c-myc expression is targeted to pancreatic acinar cells develop mixed acinar/ductal pancreatic adenocarcinomas between 2 and 7 months of age. This contrasts with the effect on pancreas of the simian virus 40 tumor antigen or activated ras, which in adult mice causes lesions composed exclusively of acinar-like cells. Furthermore, during an early stage of myc-induced pathology, transformed acinar-derived cells appear within islets, suggesting that islet hormones may influence the progression of these exocrine pancreatic tumors. These findings demonstrate that the initial oncogenic alteration can influence the pattern of subsequent tumor pathogenesis and, given that human exocrine pancreatic tumors are predominantly ductal adenocarcinomas, support the suggestion that transformed acinar cells may contribute to the genesis of this serious disease in man.

Adenocarcinoma↗
PubMed1991

Expression of mouse IgA by transgenic mice, pigs and sheep.

The development of transgenic animal technology allows the introduction of desired traits into the germ line of mice and other animals. Since the production of antibody to various polysaccharide antigens can be protective against pathogenic bacteria, we generated transgenic mice, sheep and pigs carrying genes encoding the mouse alpha and kappa chains for antibodies against phosphorylcholine (PC) to determine whether transgene antibody might be used to influence susceptibility to disease. High serum levels of mouse IgA were detected in transgenic mice and pigs but not in transgenic sheep. It has been noted that transgene immunoglobulin expression can suppress endogenous immunoglobulin gene rearrangement and expression, and indeed, in one mouse line, expression of the transgene resulted in less than 10% of spleen B cells expressing endogenous IgM. Despite this suppression, significant levels of endogenous IgM were still secreted into the serum. Suppression of endogenous IgM expression was not seen in other mouse lines, nor was it seen in transgenic pigs. In the transgenic pigs, the mouse IgA was detected in the serum despite the absence of an intact mouse kappa transgene, so the secreted antibody presumably included pig light chains. Little if any of the mouse IgA in these sera showed binding specificity for PC. In one of the founder sheep, mouse IgA was detectable in peripheral lymphocytes but not in serum. Mouse kappa expression was not detected in the transgenic sheep harboring an intact kappa transgene. These results illustrate the potential of introducing beneficial traits such as germ-line-encoded immunity into large mammalian species.

Animals↗
PubMed1991

Effect of bovine growth hormone gene expression, sex and age on plasma gonadotropins, estrone and testosterone in prepuberal pigs.

Chronic supraphysiological blood levels of growth hormone (GH) may retard sexual maturation in swine. Pigs used in this study included four founder transgenic pigs (two gilts and two boars) expressing a mouse transferrin (TF) promoter fused to a bovine (b) GH structural gene, 13 second- or third- generation transgenic pigs (seven gilts and six boars) expressing a mouse metallothionein (MT) promoter fused to a bGH structural gene and 16 control littermates (eight gilts and eight boars). Blood plasma levels of LH, FSH, estrone and testosterone were measured to determine whether expression of bGH genes altered secretion of hormones between 80 and 180 days of age. Presence of a bGH gene was detected by hybridization of DNA in dot blots of tail biopsies. Expression of a bGH gene was detected by radioimmunoassay of plasma bGH. In four TFbGH founder transgenic pigs bGH ranged from 164 to 1948 ng/ml; in one MTbGH transgenic boar of line 3104 bGH was 1211 ng/ml; and in 12 pigs of line 3706 bGH ranged from 25 to 190 ng/ml. Expression of bGH in transgenic pigs lowered (P = .0192) plasma LH with no significant differences between sexes, had no significant effect on plasma FSH and lowered plasma estrone (P = .0001) and testosterone (P = .0269) in boars (but not gilts). Plasma estrone and testosterone were higher (P = .0001) in boars than in gilts. Plasma FSH was higher (P = .0001) in gilts than boars and decreased (P = .0001) with advancing age in gilts but not in boars.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1991

The dopamine beta-hydroxylase gene promoter directs expression of E. coli lacZ to sympathetic and other neurons in adult transgenic mice.

Dopamine beta-hydroxylase (DBH) catalyzes the final step in the biosynthesis of norepinephrine, the principal classic neurotransmitter of peripheral sympathetic neurons. We have shown that 5.8 kb of 5' upstream region from a cloned human DBH gene promoter is sufficient to direct expression of the E. coli lacZ gene in transgenic mice to neurons of the locus ceruleus and other classic noradrenergic brain stem nuclei, sympathetic ganglion neurons, and adrenal chromaffin cells. lacZ expression was also observed in neurons of the enteric system, the retina, some sensory and all cranial parasympathetic ganglia, and some diencephalic and telencephalic brain nuclei. The expression pattern of the transgene in DBH-immunonegative sites overlapped with many sites where expression of tyrosine hydroxylase or phenylethanolamine N-methyltransferase, two other catecholamine biosynthetic enzymes, has been reported.

Animals↗