Identification of multiple genes in bovine retinal pericytes altered by exposure to elevated levels of glucose by using mRNA differential display

Use of messenger RNA differential display to identify interleukin-11-responsive genes in human umbilical cord blood mononuclear cells: IL-11 upregulates the expression of the hMAL gene

Human umbilical cord blood (HUCB) mononuclear cells represent a source of hematopoietic stem and progenitor cells, including cells responsive to interleukin-11 (IL-11). To investigate the molecular mechanisms associated with IL-11 action, we have used HUCB mononuclear cells as a model system to identify genes that are transcriptional targets of IL-11. Using the technique of messenger RNA differential display, we have identified 17 candidate cDNA differentially expressed in mononuclear cells incubated without and with IL-11. Fifteen of these cDNA were recovered, and 11 were sequenced. DNA sequence analysis has identified one of these cDNA as being the human MAL gene, originally identified as a marker for intermediate stages of T cell differentiation. Northern analysis using a MAL-specific probe confirms the upregulation of MAL by IL-11 in HUCB cells.

The role of hyperglycaemia and hyperinsulinaemia in causing vascular dysfunction in diabetes

Hyperglycaemia and insulin abnormality are the cause of all vascular diseases in diabetes. Recent studies have narrowed down the pathways by which hyperglycaemia can cause the various complications observed in the vasculature. Insulin resistance and hyperglycaemia have been associated with cardiovascular disease. New ideas are presented on how selective insulin resistance of the vasculature may be responsible for the increased incidence of hypertension and cardiovascular disease.

Isolation of differentially expressed cDNAs during ferret tracheal development: application of differential display PCR

The technique of differential display polymerase chain reaction (DD-PCR) was used to identify cDNA sequences, which are temporally expressed during ferret tracheal airway development. Such differentially expressed cDNAs may ultimately prove to be useful markers in elucidating mechanisms of epithelial differentiation and submucosal gland development in the airway. Using two sets of oligonucleotide primers 15 differentially amplified cDNAs were isolated by comparative reverse transcriptase (RT) PCR of 6-h and 3-day postnatal tracheal poly-A mRNA. In situ hybridization was used to assess the reliability of this method and confirm the differential mRNA expression patterns of cloned cDNAs. Results of in situ hybridization analysis demonstrated that 10 of the 15 cDNA sequences gave a temporally regulated pattern of expression, which was concordant with that of the differential display. Furthermore, sequence analysis of the 15 isolated cDNAs revealed that the majority of clones were amplified from two inverted decamer primers. These findings demonstrate the lack of poly-T priming in the differential display reaction, which suggests that this method may yield substantially more information regarding the coding sequence of cloned genes. In support of this observation, 6 of the 15 cDNA sequences contained one complete open reading frame. Although the majority of cDNAs demonstrated no homology to sequence data bases at the DNA or amino acid level, clone FT-4, which demonstrated a differential expression pattern limited to 3-day tracheal time points, was composed of a 10-amino acid repeat domain that was structurally similar to neuropeptide anthoRFamide and barley D hordein seed protein. A second interesting clone, FT-3, demonstrated an infrequent pattern of expression within a subset of epithelial cells limited to early developmental time points (6 h) and was dramatically reduced by 3 days postnatally. Several additional clones with no homologies to previously cloned genes demonstrated expression patterns that were also temporally regulated throughout tracheal development. Although the function of these temporally regulated genes has not been determined, these genes may ultimately prove to be useful markers of cellular differentiation during tracheal development.

The cellular and molecular mechanisms of diabetic complications

In this article, the cellular and molecular mechanisms of diabetic complications have been reviewed. Hyperglycemia-induced mechanisms that may induce vascular dysfunction in specific sites of diabetic microvascular damage include increased polyol pathway flux, altered cellular redox state, increased formation of diacylglycerol and the subsequent activation of specific PKC isoforms, and accelerated nonenzymatic formation of advanced glycation endproducts. Several of these mechanisms may be responsible for the potentially damaging overproduction of reactive oxygen species observed with hyperglycemia. Each of these mechanisms may contribute to the known pathophysiologic features of diabetic complications by a number of mechanisms, including the upregulation of cytokines and growth factors. Diabetic macrovascular disease may arise more from insulin resistance than from hyperglycemia, and the authors speculate that this may reflect a selective loss of insulin-dependent vascular homeostasis.

FOG1 and FOG2 genes, required for the transcriptional activation of glucose-repressible genes of Kluyveromyces lactis, are homologous to GAL83 and SNF1 of saccharomyces cerevisiae

The fog1 and fog2 mutants of the yeast Kluyveromyces lactis were identified by inability to grow on a number of both fermentable and non-fermentable carbon sources. Genetic and physiological evidences suggest a role for FOG1 and FOG2 in the regulation of glucose-repressible gene expression in response to a glucose limitation. The regulatory effect appears to be at the transcriptional level, at least for beta-galactosidase. Both genes have been cloned by complementation and sequenced. FOG1 is a unique gene homologous to GAL83, SIP1 and SIP2, a family of regulatory genes affecting glucose repression of the GAL system in Saccharomyces cerevisiae. However, major differences exist between fog1 and gal83 mutants. FOG2 is structurally and functionally homologous to SNF1 of S. cerevisiae and shares with SNF1 a role also in sporulation.

Altered hepatic gene expression of enzymes involved in energy metabolism in the growth-retarded fetal rat

Intrauterine growth retardation (IUGR) resulting from placental insufficiency is a common complication of pregnancy. Bilateral uterine artery ligation of the pregnant rat is a model which mimics intrauterine growth retardation in the human. IUGR rat fetuses have altered hepatic energy and redox states, with reduced fetal hepatic ATP/ADP ratio, increased cytosolic NAD+/NADH ratio, and decreased mitochondrial NAD+/NADH ratio. These critical changes in energy metabolism contribute to IUGR. The effects of these changes at the molecular level are largely unknown. To address these effects we compared hepatic mRNA populations of IUGR and normal fetuses and neonates using mRNA differential display, a polymerase chain reaction-based method for assaying transcriptional differences under various conditions. We isolated and sequenced 18 cDNA products whose mRNA levels were elevated in IUGR compared with normal fetal and neonatal liver. These analyses demonstrated that NADH-ubiquinone oxireductase subunit 4L mRNA (ND-4L) was significantly increased in liver of IUGR fetuses and neonates. This suggested that IUGR may be associated with altered expression of genes involved in the generation of ATP and NADH. Therefore, we measured mRNA levels of adenine-nucleotide translocator-2 (ANT-2), glucose-6-phosphate dehydrogenase (G6PD), mitochondrial malate dehydrogenase (MMD), ornithine transcarbamylase (OTC), and phosphofructokinase-2 (PFK-2) using a semiquantitative reverse transcriptase-polymerase chain reaction-based technique. In the IUGR fetus, ND-4L, ANT-2, G6PD, and MMD mRNA levels were significantly elevated; PFK-2 mRNA levels were unchanged, and OTC levels were decreased. In the IUGR newborn rat, mRNA levels of all 6 enzymes were increased suggesting that the metabolic state of the growth retarded newborn remains abnormal after birth. Uteroplacental insufficiency affects the immediate and long-term metabolic milieu of the growth retarded animal, and forces specific adjustments, including the expression of mRNA encoding enzymes involved with hepatic energy production.

Specific co-ordinated regulation of PC3 and PC2 gene expression with that of preproinsulin in insulin-producing beta TC3 cells

Short-term (less than 2 h) glucose stimulation of isolated pancreatic islets specifically increases the biosynthesis of proinsulin and its converting enzymes PC2 and PC3 at the translation level. To determine whether gene expression of PC2 and PC3 was also regulated by longer-term (more than 6 h) glucose stimulation along with that of preproinsulin, studies were performed with the beta TC3 insulin-producing cell line. By Northern blot analysis, glucose maintained PC2 and PC3 mRNA levels in parallel with those of preproinsulin. After 48 h, mRNA levels of preproinsulin, PC2 and PC3 were, respectively, 2.9 (P < 0.05), 3.0 (P < 0.005) and 5.3 (P < 0.001) times greater in the presence of glucose than in beta TC3 cells cultured in the absence of glucose. Glucose-regulated PC2 and PC3 gene expression, like that of preproinsulin, was maximal at glucose concentrations above 5.5 mM. Studies of mRNA stability showed that the half-lives of PC2 (9 h) and PC3 (5 h) mRNA were much shorter than that of preproinsulin mRNA (over 24 h), but little effect of glucose on stability of these mRNAs was observed. Nuclear run-off analysis indicated that transcription of preproinsulin, PC2 and PC3 was modestly induced after 1 h exposure to 16.7 mM glucose. Therefore preproinsulin, PC2 and PC3 mRNA levels in beta TC3 cells were most probably maintained at the level of gene transcription. In contrast, elevation of cyclic AMP by forskolin had no effect on mRNA levels or gene transcription of preproinsulin, PC2 and PC3, despite a cyclic-AMP-induced phosphorylation of the cyclic AMP response element binding protein that correlated with a marked increase in cJun and cFos gene transcription in the same beta-cells. These results suggest that preproinsulin, PC2 and PC3 gene transcription can be specifically glucose-regulated in a mechanism that is unlikely to involve a key role for cyclic AMP. The co-ordinate increase in PC2 and PC3 mRNA levels with that of preproinsulin mRNA in response to chronic glucose represents a long-term means of catering for an increased demand on proinsulin conversion.

Identification and characterization of a gene regulating enzymatic glycosylation which is induced by diabetes and hyperglycemia specifically in rat cardiac tissue

Primary cardiac abnormalities have been frequently reported in patients with diabetes probably due to metabolic consequences of the disease. Approximately 2,000 mRNA species from the heart of streptozotocin-induced diabetic and control rats were compared by the mRNA differential display method, two of eight candidate clones thus isolated (DH1 and 13) were confirmed by Northern blot analysis. The expression of clone 13 was increased in the heart by 3.5-fold (P < 0.05) and decreased in the aorta by twofold (P < 0.05) in diabetes as compared to control. Sequence analysis showed that clone 13 is a rat mitochondrial gene. DH1 was predominantly expressed in the heart with an expression level 6.8-fold higher in the diabetic rats than in control (P < 0.001). Insulin treatment significantly (P < 0.001) normalized the expression of DH1 in the hearts of diabetic rats. DH1 expression was observed in cultured rat cardiomyocytes, but not in aortic smooth muscle cells or in cardiac derived fibroblasts. The expression in cardiomyocytes was regulated by insulin and glucose concentration of culture media. The full length cDNA of DH1 had a single open-reading frame with 85 and 92% amino acid identity to human and mouse UDP-GlcNAc:Gal beta 1-3GalNAc alpha R beta 1-6 N-acetylglucosaminyltransferase (core 2 GlcNAc-T), respectively, a key enzyme determining the structure of O-linked glycosylation. Transient transfection of DH1 cDNA into Cos7 cells conferred core 2 GlcNAc-T enzyme activity. In vivo, core 2 GlcNAc-T activity was increased by 82% (P < 0.05) in diabetic hearts vs controls, while the enzymes GlcNAc-TI and GlcNAc-TV responsible for N-linked glycosylation were unchanged. These results suggest that core 2 GlcNAc-T is specifically induced in the heart by diabetes or hyperglycemia. The induction of this enzyme may be responsible for the increase in the deposition of glycoconjugates and the abnormal functions found in the hearts of diabetic rats.

Cataloging altered gene expression in young and senescent cells using enhanced differential display

Recently, a novel PCR-based technique, differential display (DD), has facilitated the study of differentially expressed genes at the mRNA level. We report here an improved version of DD, which we call Enhanced Differential Display (EDD). We have modified the technique to enhance reproducibility and to facilitate sequencing and cloning. Using EDD, we have generated and verified a catalog of genes that are differentially expressed between young and senescent human diploid fibroblasts (HDF). From 168 genetags that were identified initially, 84 could be sequenced directly from PCR amplified bands. These sequences represent 27 known genes and 37 novel genes. By Northern blot analysis we have confirmed the differential expression of a total of 23 genes (12 known, 11 novel), while 19 (seven known, 12 novel) did not show differential expression. Several of the known genes were previously observed by others to be differentially expressed between young and senescent fibroblasts, thereby validating the technique.

Isolation of genes differentially expressed at the downstream anastomosis of prosthetic arterial grafts with use of mRNA differential display

PURPOSE

Downstream anastomotic intimal hyperplasia in prosthetic arterial grafts remains a major cause of delayed graft failure. The new method of messenger RNA (mRNA) differential display was used to screen numerous genes to gain insight into the molecular mechanisms of intimal hyperplasia.

METHODS

Fifty-centimeter-long 8 mm expanded polytetrafluoroethylene grafts were placed in four mongrel dogs from the carotid artery to the distal abdominal aorta. At 3 months the distal anastomoses and adjacent normal aortas were harvested; a portion was taken for histologic examination, and total RNA was isolated from the remainder. Differential mRNA display was used to identify candidate cDNA clones whose expression differed in anastomotic intimal hyperplasia as compared with adjacent unaffected aorta. The clones were sequenced, and national gene databases were searched. Northern blot analysis confirmed alteration of gene expression.

RESULTS

Approximately 5000 mRNA species were screened, and 11 candidate clones were obtained. DNA sequence revealed homology of five clones to known gene sequences. Homologous genes included an interferon-gamma-induced human gene, (IGUP I-5111), alpha-1 protease inhibitor gene, human retinoblastoma susceptibility gene, and human creatine kinase gene (two clones). Northern blot analysis revealed altered gene expression in 4 of 11, nonregulation in 1 of 11, and undetectable signals in 6 of 11. Expression of the clone representing IGUP I-5111 in the segment of intimal hyperplasia was found to be decreased over threefold to only 31% +/- 16.4% SE of the level seen in normal aorta.

CONCLUSIONS

The technique of mRNA differential display has identified differences in gene expression in an in vivo model of anastomotic intimal hyperplasia. Expression of RNA with homology to an interferon-gamma-induced human gene was consistently decreased within the hyperplastic region at the downstream polytetrafluoroethylene arterial anastomosis.