Enhanced growth performance in transgenic swine.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
C A Pinkert
Publications and source records attributed to C A Pinkert.
Immunobiology and pathogenesis of hepatocellular injury in hepatitis B virus transgenic mice.
The role of the immune response to hepatitis B virus (HBV)-encoded antigens in the pathogenesis of liver cell injury has not been defined because of the absence of appropriate experimental models. HBV envelope transgenic mice were used to show that HBV-encoded antigens are expressed at the hepatocyte surface in a form recognizable by major histocompatibility complex (MHC) class I-restricted, CD8+ cytotoxic T lymphocytes specific for a dominant T cell epitope within the major envelope polypeptide and by envelope-specific antibodies. Both interactions led to the death of the hepatocyte in vivo, providing direct evidence that hepatocellular injury in human HBV infection may also be immunologically mediated.
Amino Acid Sequence↗
Characterization of transgenic livestock production.
The objective of transgenic livestock improvement projects is to develop and bring to market superior breeding stock, as well as germplasm for the artificial insemination and embryo transfer industries. Livestock animal biotechnology programs hold the promise of achieving, in a single generation, improvements in commercially important livestock species previously possible only through long-term traditional selective breeding practices or by chance mutation. Transgenic farm animals harboring growth hormone or metabolically related structural genes have been created. Studies of these animals demonstrate the effects of inadequate regulation of transgene expression. Research continues to explore the intricacies of developmental regulation of such genes and phenotypic consequences of mammalian gene transfer. Ultimately, genetically engineered livestock will provide producers with the benefit of increased production efficiencies while the consumer will have healthier animal food products. Conceivably, products will be produced with lower levels of fat, cholesterol, feed additives and pharmaceutical residues from animals with altered carcass composition that will result in greater nutritional benefit for the consumer.
Animals↗
Infertility in male transgenic mice: disruption of sperm development by HSV-tk expression in postmeiotic germ cells.
Previous experiments revealed that male transgenic mice bearing a cosmid that included the Class II E alpha gene, about 35 kb of 5' flanking DNA, and the cosmid vector sequences were sterile. To ascertain the cause of the sterility, various subfragments of the cosmid were tested in transgenic mice. Only those pieces of DNA that included some of the E alpha flanking chromosomal DNA and the herpes simplex virus (HSV)-thymidine kinase (tk) gene that was in the vector resulted in male sterility. Histological analysis revealed abnormalities in nuclear morphology of elongating spermatids and retention of mature spermatids within the seminiferous epithelium. Immunocytochemical studies showed that the HSV-tk gene was expressed at low levels in postmeiotic round spermatids and at higher levels in more mature elongating spermatids. To determine whether expression of HSV-tk in spermatids might be responsible for the sterility, the protamine gene promoter was used to direct the expression of HSV-tk to postmeiotic germ cells. Since the mice so treated were also sterile, the data suggest that expression of this enzyme in spermatids is responsible for the sterility phenotype.
Animals↗
Expression and performance in transgenic pigs.
Recent research clearly shows that fusion genes can be microinjected into a pronucleus of an ovum and integrate into the pig genome. Animals with such fusion genes are called 'transgenic'. The percentage of injected ova that developed into transgenic pigs varied among experiments from 0.31% to 1.73%. The percentage of transgenic pigs that expressed the fusion gene ranged from 17% to 100%. Eleven different regulatory sequences have been used for fusion genes transferred into pigs. Some of these regulatory sequences directed strong gene expression, but control over level of expression was inadequate. Other regulatory sequences directed weak expression, but imparted only brief spikes of induced expression. The predominant gene coding sequences transferred were for growth-related hormones. Elevation of growth hormone (GH) in expressing transgenic pigs enhanced plasma concentrations of insulin-like growth factor-I (IGF-I), insulin, and glucose, improved feed efficiency about 15%, and markedly reduced subcutaneous fat compared to nontransgenic siblings. Growth rate was enhanced in some transgenic GH pigs but not in others, possibly due to dietary limits. The 'over-expression' of GH was detrimental to the general health of most transgenic pigs. The most prevalent problems were lethargy, lameness, and gastric ulcers. Gilts that expressed foreign GH genes were anoestrous. Boars that expressed foreign GH genes lacked libido, but their semen was fertile when used by artificial insemination. Six different fusion genes have been transmitted from transgenic founders to progeny. Most of the transgenic pigs that produced progeny transmitted the fusion gene as an autosomal dominant trait to about half of their progeny. Regulatory sequences that will permit full control of gene expression must be developed before the full potential of gene transfer in pigs can be realized.
Animals↗
A rapid procedure to evaluate foreign DNA transfer into mammals.
Explore the source record for details and available documents.
Animals↗
Production of transgenic pigs harbouring a rat phosphoenolpyruvate carboxykinase-bovine growth hormone fusion gene.
Over the past 5 years, reports detailing the production of transgenic pigs have focussed on enhanced growth performance. Phenotypic side-effects observed in pigs harbouring chimaeric constructs containing metallothionein or Moloney murine leukaemia virus transcriptional activators fused to growth hormone (GH) structural genes have been attributed to chronic overexpression of GH. In an effort to regulate a transgene product more effectively, a liver specific 460 bp 5' flanking sequence of the rat phosphoenolpyruvate carboxykinase (PEPCK) gene was ligated to a BamHI site of the first exon of the genomic bovine GH (bGH) structural gene. Following micro-injection of the PEPCK/bGH construct into 1- and 2-cell pig zygotes. 124 offspring were produced of which 7 pigs were determined to be transgenic by dot-blot and Southern analysis. The PEPCK gene expression, in terms of tissue and developmental specificity, appears similar to that observed in PEPCK/bGH transgenic mice. Germ-line transmission was identified in 1 of 3 mated founders. Dramatic influences on backfat thickness were observed including a 41% reduction in backfat depth when compared to non-transgenic sex-matched littermate control pigs. Both the regulation and characterization of gene expression in PEPCK/bGH transgenic pigs are under investigation.
Animals↗
Molecular pathogenesis of hepatocellular carcinoma in hepatitis B virus transgenic mice.
Transgenic mice that overproduce the hepatitis B virus large envelope polypeptide and accumulate toxic quantities of hepatitis B surface antigen (HBsAg) within the hepatocyte develop severe, prolonged hepatocellular injury that initiates a programmed response within the liver, characterized by inflammation, regenerative hyperplasia, transcriptional deregulation, and aneuploidy. This response inexorably progresses to neoplasia. The incidence of hepatocellular carcinoma in this model corresponds to the frequency, severity, and age of onset of liver cell injury, which itself corresponds to the intrahepatic concentration of HBsAg and is influenced by genetic background and sex. Thus, the inappropriate expression of a single structural viral gene is sufficient to cause malignant transformation in this model. These results suggest that severe, prolonged cellular injury induces a preneoplastic proliferative response that fosters secondary genetic events that program the cell for unrestrained growth.
Aging↗
Genetic engineering of livestock.
Genetic engineering of livestock is expected to have a major effect on the agricultural industry. However, accurate assessment of the consequences of transgene expression is impossible without multigenerational studies. A systematic study of the beneficial and adverse consequences of long-term elevations in the plasma levels of bovine growth hormone (bGH) was conducted on two lines of transgenic pigs. Two successive generations of pigs expressing the bGH gene showed significant improvements in both daily weight gain and feed efficiency and exhibited changes in carcass composition that included a marked reduction in subcutaneous fat. However, long-term elevation of bGH was generally detrimental to health: the pigs had a high incidence of gastric ulcers, arthritis, cardiomegaly, dermatitis, and renal disease. The ability to produce pigs exhibiting only the beneficial, growth-promoting effects of growth hormone by a transgenic approach may require better control of transgene expression, a different genetic background, or a modified husbandry regimen.
Agriculture↗
Elevated PC responsive B cells and anti-PC antibody production in transgenic mice harboring anti-PC immunoglobulin genes.
The rearrangement of heavy and light chain immunoglobulin genes is necessary for the production of functional antibody molecules. The myeloma MOPC 167 produces specific antibodies to the antigen phosphorylcholine (PC), which is present on bacterial surfaces, fungi and other environmental contaminants. Rearranged heavy and light chain immunoglobulin genes cloned from MOPC 167 were microinjected into mouse eggs. Within the resulting transgenic mice, expression of the transgenes were limited to lymphoid tissues. Transgenic mice produced elevated levels of anti-PC antibodies constitutively, at 16 days of age, when normal non-transgenic mice were not fully immunocompetent. A triggering antigenic stimulus was not necessary to evoke anti-PC immunoglobulin production. Additionally, the frequency of PC-responsive B cells in these transgenic mice was further increased upon specific immunization.
Animals↗
Histopathology associated with elevated levels of growth hormone and insulin-like growth factor I in transgenic mice.
Serum levels of GH and insulin-like growth factor I (IGF-I) were genetically increased to investigate the physiological activities of these proteins. Lines of mice expressing chimeric genes composed of bovine GH, human GRF, or human IGF-I coding sequences fused to the mouse metallothionein I promoter were examined for consequences of chronic exposure to high levels of these peptides. Animals with elevated serum levels of GH (either bovine GH or mouse GH) have selective splanchnomegaly coupled with glomerular sclerosis and hepatocellularmegaly. Serum levels of insulin and cholesterol are increased. In contrast (with the exception of selective enlargement of organs), the chronic expression of IGF-I results in a different pattern of abnormalities. These findings suggest that the pathogenesis of GH-related disorders is not mediated solely by IGF-I.
Animals↗
In-vitro development of zygotes from superovulated prepubertal and mature gilts.
Ten prepubertal and 8 mature gilts were superovulated with PMSG and hCG, and inseminated with fresh boar semen. Zygotes were surgically recovered from oviducts 54-60 h after hCG. One and 2-cell zygotes were randomly allotted to Medium PL (modified BMOC-3 supplemented with 0.1 mM-EDTA and 1.5% BSA) or Medium G (Medium PL without pyruvate or lactate). Eggs were washed twice in medium, and placed in microdrops of medium overlaid with silicon oil for culture in an humidified 5% CO2, 5% O2, 90% N2 environment, then observed daily for 6 days. Development of eggs was dependent (P less than 0.001) on the interactive effects of age of gilt (prepubertal versus mature) and medium type (PL versus G) used in culture. A greater proportion of eggs cultured in Medium G developed further than did eggs in Medium PL (P less than 0.001). Additionally, a greater proportion of eggs from mature gilts developed further than did eggs from prepubertal gilts (P less than 0.02). We suggest that these results provide evidence that zygotes resulting from superovulation regimens of prepubertal gilts do not possess the same capacity for in-vitro development as do zygotes from pubertal gilts.
Animals↗
Expression of human or bovine growth hormone gene with a mouse metallothionein-1 promoter in transgenic swine alters the secretion of porcine growth hormone and insulin-like growth factor-I.
Endocrine profiles were examined in swine that had integrated and expressed a fusion gene consisting of mouse metallothionein-1 (MT) promoter fused to either a human (h) or bovine (b) GH structural gene. Eleven of 18 pigs that had integrated MT-hGH and eight of nine pigs that had integrated MT-bGH expressed the genes. The level of expression varied widely among pigs (14-4551 micrograms/l for MT-hGH and 23-1578 micrograms/l for MT-bGH). The level of expression varied over time within each pig with no general pattern. Concentrations of porcine GH (pGH) were lower in MT-hGH pigs that expressed the gene than in non-expressors or in littermate controls. Insulin-like growth factor-I (IGF-I) concentrations increased with age in all pigs and were raised threefold in pigs expressing either the MT-hGH or MT-bGH genes. Measurement of the foreign GH in samples taken at 15-min intervals failed to reveal any short-term fluctuations in concentration. Administration of hGH releasing factor (GRF) to pigs expressing MT-bGH resulted in attenuated release of pGH compared with that of contemporary controls. Concentrations of bGH did not change after GRF injection. Human and bovine GH expressed in transgenic pigs appear to be biologically active in that they induce IGF-I and suppress endogenous pGH secretion. The failure to find short-term fluctuations and the lack of response to GRF injections are consistent with a non-pituitary and non-GRF regulatable site of production.
Animals↗
Oncogene-induced liver neoplasia in transgenic mice.
Models of hepatocarcinogenesis were generated by directing the expression of SV40 T-antigens, an oncogenic mutant of c-H-ras, or c-myc to the liver of transgenic mice using the albumin enhancer/promoter. The majority of mice carrying the ras transgene (group A) were born with enlarged livers and atypical hepatic architecture, and these all died within several days of birth. The remaining ras transgenic mice (group B) had lower levels of hepatic ras expression, exhibited mild hepatic dysplasia but no liver enlargement, and all ultimately died from development of lung tumors. In contrast, the livers of mice expressing T-antigens were relatively normal at birth, by one month displayed marked dysplasia, and by three to seven months developed multiple nodular adenomas and carcinomas. Myc expression caused mild to severe hepatic dysplasia in young mice, and focal hepatic adenomas in some mice over fifteen months of age. Lines of mice expressing ras (group B), T-antigen, or myc were established and crossed with each other to generate dual transgenic mice expressing oncogene pairs. Each combination resulted in accelerated tumor development, suggesting that these oncoproteins can cooperate with one another during multistep hepatic transformation.
Animals↗
The E mu-myc transgenic mouse. A model for high-incidence spontaneous lymphoma and leukemia of early B cells.
Mice transgenic for a c-myc gene driven by the IgH enhancer (E mu-myc) were shown to almost invariably develop lymphomas, 90% succumbing in the first 5 mo of life. The tumors typically presented as rapidly progressive lymphadenopathy with thymic involvement and were highly malignant by transplantation assay. Morphologically, they were lymphoblastic lymphomas, usually accompanied by lymphoid leukemia and granulocytosis, and were distinct from the tumors that arose much later in 37% of nontransgenic mice of the same (C57BL/6 x SJL)F2 genetic background. Cell-surface markers on 31 E mu-myc tumors identified 52% as pre-B lymphomas, 29% as mixed pre-B and B lymphomas, and 19% as B lymphomas. The tumors appeared to arise at random from a population of pre-B cells expanded by constitutive expression of the myc transgene. A majority of the animals initiated malignancy at the rate of 17% per week. The rate at which the cycling, benign pre-B cells spontaneously convert to malignancy was estimated to about 10(-10) per cell per generation. A transient leukocytosis identified in young E mu-myc mice was developed into a rapid assay for inheritance of the transgene.
Animals↗
Glomerular epithelial, mesangial, and endothelial cell lines from transgenic mice.
The culture of glomerular cells has represented an important tool in the understanding of individual glomerular cell functions. However, the complexity of the glomerulus has made it difficult to obtain pure cell populations. It has also been difficult to culture glomerular endothelial cells, even as mixed cell populations. At present there are no established glomerular cell lines from any source. We have established permanent cell lines of cloned glomerular epithelial, mesangial, and endothelial cells from a line of mice transgenic for the early region of simian virus 40 (SV40). These mice appear normal at birth but by three to four months of age have sclerosis affecting a variable percentage of their glomeruli. The cells maintain features characteristic of their normal counterparts despite their transformed phenotype. These cell lines could be useful tools in understanding the pathogenesis of glomerulosclerosis in this transgenic mouse model and in studying those features of normal glomerular cell biology which are not altered by a transformed phenotype.
Animals↗
Serum concentrations of prolactin, oestrogen and LH during the perioestrous period in prepubertal gilts induced to ovulate and mature gilts.
The temporal relationships of serum prolactin, oestrogen and LH concentrations during the perioestrous period were compared in prepubertal gilts induced to ovulate by PMSG and hCG and in mature gilts. In Exp. 1, 2 sustained prolactin surges, beginning 4 days and 1 day before the preovulatory LH surge, occurred in all mature gilts. A single preovulatory prolactin surge occurred in 3 prepubertal gilts, starting just before the preovulatory LH surge, but 4 prepubertal gilts had neither a prolactin nor an LH surge. A status (prepubertal or mature) versus time interaction (P less than 0.01) was detected for serum prolactin concentrations. A preovulatory oestrogen surge occurred in all gilts but was of lesser magnitude (P less than 0.01) and duration (P less than 0.05) in the prepubertal gilts without prolactin and LH surges compared to mature gilts and of lesser magnitude (P less than 0.01) compared to prepubertal gilts with prolactin and LH surges. The relative timing of the oestrogen surge in prepubertal gilts corresponded with that of mature gilts when adjusted to the LH surge (if present) but was delayed (P less than 0.01) in all prepubertal gilts if standardized to the hCG injection. In Exp. 2, mature gilts were examined to determine whether 2 perioestrous prolactin surges were characteristic of all cycling gilts. Of 9 gilts, 8 exhibited an initial prolactin surge 4-5 days before oestrus and 5/9 gilts exhibited a periovulatory prolactin surge. The presence of 2 perioestrous serum prolactin surges was not a requirement for subsequent pregnancy maintenance.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Developmental study of SV40 large T antigen expression in transgenic mice with choroid plexus neoplasia.
Expression of SV40 large T antigen was correlated with the development of pathology in three lines of transgenic mice. Immunohistochemical detection of large T revealed positive cells only in subsets of choroid plexus epithelium, thymus and renal tubular epithelium, which was first observed during the first month of post-natal life. Morphologic abnormalities became apparent several weeks later. Only some of the choroid plexus cells which expressed T antigen progressed to form neoplasms, suggesting the need for one or more secondary events to effect transformation. Tumors did not develop in thymus and kidney.
Animals↗