Primary structure of the mouse glycerol-3-phosphate dehydrogenase gene

Effects of rosiglitazone and linoleic acid on human preadipocyte differentiation

BACKGROUND

Peroxisome proliferator activated receptor gamma (PPARgamma) is a ligand-activated transcription factor known to be central to both adipose tissue development and insulin action. Growth of adipose tissue requires differentiation of preadipocytes with acquisition of specific cellular functions including insulin sensitivity, leptin secretion and the capacity to store triglyceride. Dietary fatty acids and members of the thiazolidinedione class of compounds have been reported to influence adipogenesis at the transcriptional level. Here, we compare the effects of a dietary fatty acid, linoleic acid, and a thiazolidinedione, rosiglitazone, on biochemical and functional aspects of human preadipocyte differentiation in vitro.

MATERIALS AND METHODS

Human omental and subcutaneous preadipocytes were subcultured 2-3 times and subsequently differentiated for 21 days in the presence of either linoleic acid or rosiglitazone. Differentiation was assessed using a number of biochemical and functional parameters.

RESULTS

Omental and subcutaneous preadipocytes differentiated in the presence of linoleic acid showed marked cytoplasmic triacylglycerol accumulation however, no biochemical markers of differentiation (LPL expression, G3PDH gene expression and enzyme activity and leptin expression or secretion) were detected. In contrast, treatment of these cells with rosiglitazone induced full biochemical differentiation as judged by all markers assessed, despite comparatively little lipid accumulation. The rosiglitazone effects were subcutaneous depot-specific. Cells treated with linoleic acid showed decreased glucose uptake cf rosiglitazone-treated cells. A luciferase reporter assay demonstrated that rosiglitazone potently activates h-peroxisome proliferator activated receptor gamma while linoleic acid had no effect.

CONCLUSIONS

These studies demonstrate that (a) human preadipocytes have the potential to accumulate triacylglycerol irrespective of their stage of biochemical differentiation; (b) while omental preadipocytes are refractory to biochemical differentiation in vitro, they are able to accumulate triacylglycerol; and (c) rosiglitazone and linoleic acid may exert their effects via different biochemical pathways.

Induction of glycerol phosphate dehydrogenase gene expression during seizure and analgesia

Using mRNA differential display, we found that the gene for NAD(+)-dependent glycerol phosphate dehydrogenase (GPDH; EC 1.1.1.8) is induced in rat brain following seizure activity. Northern blot and in situ hybridization analysis confirmed the differential display results; they also showed, in a separate model of neuronal activation, that after thermal noxious stimulation of the hind-paws, a similar increase in GPDH mRNA occurs in the areas of somatotopic projection in the lumbar spinal cord. Surprisingly, administration of analgesic doses of morphine or the nonsteroidal antiinflammatory drugs aspirin, metamizol (dipyrone), and indomethacin also increased GPDH mRNA levels in rat spinal cord. The opioid receptor antagonist naloxone completely blocked morphine induction of GPDH but had no effect on GPDH induction by noxious heat stimulation or metamizol treatment, implicating different mechanisms of GPDH induction. Nevertheless, in all cases, induction of the GPDH gene requires adrenal steroids and new protein synthesis, as the induction was blocked in adrenalectomized rats and by cycloheximide treatment, respectively. Our results suggest that the induction of the GPDH gene upon peripheral noxious stimulation is related to the endogenous response to pain as it is mimicked by exogenously applied analgesic drugs.

In vitro induction of UCP1 mRNA in preadipocytes from rabbit considered as a model of large mammals brown adipose tissue development: importance of PPARgamma agonists for cells isolated in the postnatal period

In mammals with a lower mass-specific metabolic rate than small laboratory rodents, the brown adipose tissue (BAT) loses its thermogenic activity after birth and undergoes a transformation into white adipose tissue (WAT). Rabbit is a model of these mammals of larger body mass. Preadipocytes from cervical BAT of foetal or newborn rabbits differentiated in a chemically-defined medium and expressed low levels of uncoupled protein-1 (UCP1) mRNA, greatly increased by beta3-adrenergic or retinoic acid stimulations. On the contrary, preadipocytes from 1-month-old animals differentiated in the same conditions with no detectable,expression of UCP1. Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists were necessary to induce UCP1 in these cells from older animals, a synergistic increase being noted in the presence of beta3-adrenergic agonists. In contrast to these results, preadipocytes from perirenal WAT stimulated by PPARgamma agonists never expressed UCPI.

CONCLUSION

preadipocytes in the postnatal period are determined as brown or white preadipocytes. PPARgamma agonists induce UCP1 expression in brown postnatal preadipocytes, but they are unable to trigger the gene in white preadipocytes.

Expression of specific white adipose tissue genes in denervation-induced skeletal muscle fatty degeneration

Denervation of skeletal muscle results in rapid atrophy with loss of contractile mass and/or progressive degeneration of muscle fibers which are replaced to a greater or lesser degree by connective and fatty tissues. In this study, we show that denervated rabbit muscles are transformed into a white adipose tissue, depending on their fiber types. This tissue does express LPL, G3PDH and particularly the ob gene, a white adipose tissue-specific marker, and does not express the brown adipose tissue molecular marker UCP1 mRNA.

gas7: A gene expressed preferentially in growth-arrested fibroblasts and terminally differentiated Purkinje neurons affects neurite formation

Growth arrest-specific (gas) genes are expressed preferentially in cells that enter a quiescent state. gas7, which we identified in serum-starved murine fibroblasts, is reported here to be expressed in vivo selectively in neuronal cells of the mature cerebral cortex, hippocampus, and cerebellum. gas7 transcripts encode a 48-kDa protein containing a structural domain that resembles sequences of OCT2, a POU transcription factor implicated in neuronal development, and synapsins, which have a role in modulating neurotransmitter release. Using in situ hybridization and immunocytochemical analysis, we show that GAS7 expression occurs prominently in cerebellar Purkinje cells and that inhibition of production in terminally differentiating cultures of embryonic murine cerebellum impedes neurite outgrowth from maturing Purkinje cells. Conversely, GAS7 overexpression in undifferentiated neuroblastoma cell cultures dramatically promotes neurite-like outgrowth. Collectively, our results provide evidence for an association between expression of this gas gene and neuronal development.

Inhibition of PI 3-kinase and RAS blocks IGF-I and insulin-induced uncoupling protein 1 gene expression in brown adipocytes

Fetal brown adipocytes expressed uncoupling protein 1 (UCP1) mRNA, this expression being blunted throughout culture for 24 h in a serum-free medium. At physiological doses, either insulin-like growth factor I (IGF-I) or insulin turned out to be as potent as dibutyryl cAMP (dbcAMP) in increasing UCP1 gene transcription rate (1 h) and also UCP1 mRNA accumulation (3 h), their maximal effect (15-fold increase) reached upon treatment for 24 h. Upon treatment with either IGF-I or insulin for 48 h, a 7-fold increase in the UCP1 protein content relative to levels in the control cells was found, this induction being abolished in the presence of cycloheximide. Moreover, either IGF-I or insulin transactivates the UCP1-chloramphenicol acetyl transferase (CAT) fusion gene after transient transfection of primary brown adipocytes, these effects being tissue-specific. Transient transfection of dominant-negative form of phosphatidylinositol (PI) 3-kinase completely blocked the transactivation of the fusion gene UCP1-CAT induced by either IGF-I or insulin, although inhibition of p70S6kinase with rapamycin does not preclude transactivation of the UCP1 promoter by insulin. Furthermore, transient transfection of dominant-negative form of p21-ras or treatment of cells with a mitogen-activated protein kinase kinase (MEK-1) inhibitor (PD098059) completely abolished insulin-induced UCP1-CAT transactivation. Cotransfection with dominant-negative p85 or with dominant-negative Ras also produced down-regulation of the insulin or IGF-I-induced 12-O-tetradecanoylphorbol-13-acetate response element (TRE)-CAT (five AP-1, activating protein-1, binding sites arranged in tandem) transactivation. In addition, insulin induced AP-1 DNA binding activity, this effect being totally prevented in the presence of MEK-1 inhibitor. These results strongly suggest that either IGF-I or insulin induced thermogenic-differentiation through AP-1 activity in a PI 3-kinase and Ras/MAPK dependent manner in brown adipocytes.

Glial- and fat-specific expression of the rat glycerol phosphate dehydrogenase-luciferase fusion gene in transgenic mice

Glycerol phosphate dehydrogenase (GPDH) is a metabolic enzyme that catalyzes the conversion of dihydroxyacetone phosphate to glycerol-3-phosphate. It provides phospholipid precursors for lipid biosynthesis and energy metabolism. In the brain, GPDH enzymatic activity, protein, mRNA are exclusively associated with oligodendroglial and Bergmann glial cells. Expression of GPDH in the brain increases dramatically during the active period of myelination, and is regulated by extracellular signals. In an effort to understand the mechanism that confers glial-specific expression of GPDH, we have examined the role of the 5' flanking sequence of the rat GPDH gene in conferring cell-specific expression of reporter gene in transgenic mice. Luciferase reporter constructs containing either the full-length GPDH 5' flanking region (p4.3), or a distally truncated version (p2.6), were injected into mouse zygotes. Three independent lines of transgenic mice containing the p4.3, and seven lines of mice containing the p2.6 constructs, were analyzed. Luciferase enzyme activity was detectable only in brain and fat, not in other GPDH-positive organs such as liver, muscle, and kidney. Both the full-length and the distally deleted transgenes were expressed similarly in these two organs, indicating that the distal portion of the 5' flanking region was not required for brain- and fat-specific expression. Immunocytochemical analyses revealed that luciferase immunoreactivity colocalized with glial fibrillary acidic protein (GFAP)-positive Bergmann glia in the cerebellum, and myelin basic protein (MBP)-positive oligodendroglia in the cerebral cortex and the brainstem. Results here suggest that the rat GPDH 5' flanking region directs glial-specific expression of GPDH transcription in the brain, and provide a good model for analyses of changes in glial metabolism in response to extracellular perturbations in vivo.

Dramatic enhancement of the specific expression of the heart-type fatty acid binding protein in rat brown adipose tissue by cold exposure

To understand the difference in energy metabolisms in brown (BAT) and white (WAT) adipose tissues, we examined the steady-state transcript levels of the heart-type and adipose-type fatty acid binding proteins (H-FABP and A-FABP, respectively) by Northern blot analysis. The transcript of H-FABP in rat BAT was increased about 100-fold by cold exposure, whereas that in WAT was negligible, and was increased only slightly by cold exposure. The transcript of A-FABP was observed in both BAT and WAT, the level being slightly greater in WAT. However, its transcript level was not affected by cold exposure in either adipose tissue. In addition, on treatment with norepinephrine (NE), transcript level of H-FABP was elevated markedly but that of A-FABP was not changed in rat brown adipocytes. Therefore, the stimulatory effect of cold exposure on the transcript of H-FABP in BAT was concluded to be mediated by NE, like that of the uncoupling protein (UCP). Thus, the expressions of H-FABP and UCP may be controlled by the same mechanism.

Phosphatidylinositol 3-kinase is a requirement for insulin-like growth factor I-induced differentiation, but not for mitogenesis, in fetal brown adipocytes

In the present study we have examined the role of phosphatidylinositol 3-kinase (PI 3-kinase) in the insulin-like growth factor I (IGF-I)-signaling pathways involved in differentiation and in mitogenesis in fetal rat brown adipocytes. Activation of PI 3-kinase in response to IGF-I was markedly inhibited by two PI 3-kinase inhibitors (wortmannin and LY294002) in a dose-dependent manner. IGF-I-stimulated glucose uptake was also inhibited by both compounds. The expression of adipogenic-related genes such as fatty acid synthase, malic enzyme, glycerol 3-phosphate dehydrogenase, and acetylcoenzyme A carboxylase induced by IGF-I was totally prevented in the presence of IGF-I and any of those inhibitors, resulting in a marked decrease of the cytoplasmic lipid content. Moreover, the expression of the thermogenic marker uncoupling protein induced by IGF-I was also down-regulated in the presence of wortmannin/LY294002. IGF-I-induced adipogenic- and thermogenic-related gene expression was only partly inhibited by the p70S6k inhibitor rapamycin. In addition, pretreatment of brown adipocytes with either wortmannin or LY294002, but not with rapamycin, blocked protein kinase C zeta activation by IGF-I. In contrast, IGF-I-induced fetal brown adipocyte proliferation was PI 3-kinase-independent. Our results show for the first time an essential requirement of PI 3-kinase in the IGF-I-signaling pathways leading to fetal brown adipocyte differentiation, but not leading to mitogenesis. In addition, protein kinase C zeta seems to be a signaling molecule also involved in the IGF-I differentiation pathways downstream from PI 3-kinase.

Cloning and characterization of the NAD-linked glycerol-3-phosphate dehydrogenases of Trypanosoma brucei brucei and Leishmania mexicana mexicana and expression of the trypanosome enzyme in Escherichia coli

A polyclonal antiserum raised against the purified glycosomal glycerol-3-phosphate dehydrogenase of Trypanosoma brucei brucei has been used to identify the corresponding cDNA clone in a T.b. brucei expression library. This cDNA was subsequently used to obtain genomic clones containing glycerol-3-phosphate dehydrogenase genes. Two tandemly arranged genes were detected in these clones. Characterization of one of the genes showed that it codes for a polypeptide of 353 amino acids, with a molecular mass of 37,651 Da and a calculated net charge of +8. Using the T.b. brucei gene as a probe, a corresponding glycerol-3-phosphate dehydrogenase gene was also identified in a genomic library of Leishmania mexicana mexicana. The L.m. mexicana gene codes for a polypeptide of 365 amino acids, with a molecular mass of 39,140 Da and a calculated net charge of +8. The amino-acid sequences of both polypeptides are 63% identical and carry a type-1 peroxisomal targeting signal (PTS1) SKM and -SKL at their respective C-termini. Moreover, the L.m. mexicana polypeptide also carries a short N-terminal extension reminiscent of a mitochondrial transit sequence. Subcellular localisation analysis showed that in L.m. mexicana the glycerol-3-phosphate dehydrogenase activity co-fractionated both with mitochondria and with glycosomes. This is not the case in T. brucei, where the enzyme is predominantly glycosomal. The two trypanosomatid sequences resemble their prokaryotic homologues (32-36%) more than their eukaryotic counterparts (25-31%) and carry typical prokaryotic signatures. The possible reason for this prokaryotic nature of a trypanosomatid glycerol-3-phosphate dehydrogenase is discussed.

Fatty acids and fibrates are potent inducers of transcription of the phosphenolpyruvate carboxykinase gene in adipocytes

Cytosolic phosphoenolpyruvate carboxykinase (PEPCK) plays a critical role in adipose tissue glyceroneogenesis. We have previously shown that transcription of the PEPCK gene was stimulated by isoprenaline and retinoic acid in 3T3-F442A adipocytes. We also showed that oleate increased PEPCK mRNA. Here, we analysed the effect that fatty acids of various chain lengths and unsaturation degrees exerted on PEPCK gene expression in 3T3-F442A adipocytes. When maintained in serum-free, glucose-free medium, differentiated cells responded to unsaturated long-chain fatty acids by a large increase in PEPCK mRNA whereas saturated fatty acids were inefficient. A maximum fivefold stimulation by oleate was attained at 4 h of treatment with 1 mM fatty acid bound to albumin in a 6:1 ratio. The poly-unsaturated very long-chain fatty acid all-cis-4,7,10,13,16,19-docosahexaenoic acid (C22:6) was even more potent and produced a tenfold increase. The expression of the genes encoding glycerol-3-phosphate dehydrogenase, hormone-sensitive lipase or actin remained unaffected by oleate exposure. A 4-h treatment by the hypolipidemic drug clofibrate, 0.5-2 mM, also produced a large (3-9-fold) increase in PEPCK mRNA. When used at non-saturating concentrations, oleate and clofibrate acted in an additive manner. At maximally effective concentrations, additivity was lost, suggesting that fatty acids and fibrates might act through similar mechanisms. Nuclear transcription experiments showed that oleate and clofibrate stimulated the transcription rate of the gene. 3T3-F442A cells were stably transfected with a plasmid containing the base pairs -2100 to +69 of the PEPCK gene promoter fused to the chloramphenicol acetyltransferase gene. These differentiated stable transfectants responded to oleate and clofibrate by a specific increase in chloramphenicol acetyltransferase activity. Adipocytes express various isoforms of peroxisome-proliferator-activated receptors that can be activated by fibrates and fatty acids. Potential recognition sequences for peroxisome-proliferator-activated receptors are present in the -2100 to +69 fragment of the PEPCK gene promoter. Thus, this gene represents an ideal molecular target for understanding the complex transcriptional control exerted by fatty acids and peroxisome proliferators.

Sequence evolution of the Gpdh gene in the Drosophila virilis species group

The nucleotide sequence of the Gpdh gene from six taxa, D. virilis, D. lummei, D. novamexicana, D. a. americana, D. a. texana and D. ezoana, belonging to the virilis species group was determined to examine details of evolutionary change in the structure of the Gpdh gene. The Gpdh gene is comprised of one 5' non-translated region, eight exons, seven introns and three 3' non-translated regions. Exon/intron organization was identical in all the species examined, but different from that of mammals. Interspecific nucleotide divergence in the entire Gpdh gene followed the common pattern: it was low in the exon, high in the intron and intermediate in the non-translated regions. The degree of nucleotide divergence differed within these regions, suggesting that selection exerts constraints differentially on nucleotide change of the Gpdh gene. A phylogenetic tree of the virilis phylad constructed from nucleotide variation of total sequence was consistent with those obtained from other data.

Transforming growth factor beta 1 induces differentiation-specific gene expression in fetal rat brown adipocytes

Fetal rat brown adipocytes show a low number of transforming growth factor beta 1 (TGF-beta 1) binding sites of high affinity, revealing the presence of type I, II and III TGF-beta 1 receptors and a minor-labeled species of approximately 140 kDa. The culture of cells in the presence of TGF-beta 1 induced the expression of the tissue-specific gene uncoupling protein in a dose- and time-dependent manner. In addition, TGF-beta 1 up-regulates the expression of genes involved in adipogenesis such as fatty acid synthase, glycerol 3-phosphate dehydrogenase, malic enzyme and glucose 6-phosphate dehydrogenase, as well as induces the expression of fibronectin (specific target gene for TGF-beta 1). Our results suggest that TGF-beta 1 is a major signal involved in initiating and/or maintaining the thermogenic and adipogenic differentiation of rat fetal brown adipocytes.

Regulation of the uncoupling protein gene (Ucp) by beta 1, beta 2, and beta 3-adrenergic receptor subtypes in immortalized brown adipose cell lines

Immortalized brown adipocyte cell lines derived from a mouse hibernoma express all three beta-adrenergic receptor subtypes, including beta 3-adrenergic receptor (AR). In response to norepinephrine, cAMP production by plasma membranes from four clonal cell lines was stimulated to levels comparable with brown adipocytes isolated from interscapular brown adipose tissue (72.8-89.6 versus 97.8 pmol cAMP/min/mg of protein, respectively). All cell lines responded to the highly selective beta 3-adrenergic receptor agonist CL316,243 by stimulating adenylyl cyclase activity (3-10-fold over basal). beta 1-, beta 2-, and beta 3-adrenergic receptor mRNA was detected by Northern blotting and/or reverse transcriptase-polymerase chain reaction. Competition binding assays with the antagonists CGP20712A and 125I-cyanopindolol showed the proportions of beta 1AR and beta 2AR in immortalized cells to be similar to brown adipocytes from tissue (cells: 35% beta 1AR, 65% beta 2AR; brown adipocytes from tissue: beta 1AR 41%, 59% beta 2AR). Expression of brown fat-specific mitochondrial uncoupling protein (Ucp) was stimulated by beta-adrenergic agonists in two of the four cell lines. The ability of individual beta AR subtypes to regulate Ucp expression was examined with combinations of selective beta-adrenergic agonists and antagonists. Expression of Ucp could be induced by any of the beta-adrenergic receptor subtypes. However, the greatest response was obtained by stimulating all three beta-adrenergic receptor subtypes simultaneously (100 microM isoproterenol). Incubation of membranes from cultured cells or brown adipocytes from tissue with CL316,243 at an optimal concentration (5 microM) did not prevent norepinephrine from further stimulating adenylyl cyclase activity, suggesting that the combined activation of beta 1AR/beta 2AR, plus beta 3AR, together produced an additive cAMP response. Multiple forms of adenylyl cyclase were identified in brown and white adipocyte cell lines and tissues. Northern blot analysis detected adenylyl cyclase types 5, 6, and 10. Screening of reverse transcriptase-PCR products by DNA sequencing confirmed the identities of these forms and lower levels of additional isoforms, raising the possibility that beta-adrenergic receptor subtypes in adipocytes couple to distinct adenylyl cyclases. Because these cell lines display functional and phenotypic similarities to interscapular brown adipocytes, they will be a useful model to study the regulation of beta-adrenergic receptor expression and function, and the control of Ucp expression and activity.

Glucocorticoid regulation of glycerolphosphate dehydrogenase expression in the developing rat brain

Glucocorticoid regulation of glycerolphosphate dehydrogenase (GPDH) activity and gene expression in the developing rat brain appears complex throughout the postnatal developmental period and attains the adult pattern after the first month of life. GPDH enzyme activity is higher in the limbic system than in the cerebral cortex of intact young animals. Adrenalectomy of young rats, before the first month of life, does not affect GPDH enzyme activity in the brain areas mentioned above, while in the adult animals it results in a statistically significant decrease in activity. Furthermore, "adult type" glucocorticoid responsivity of GPDH enzyme activity is attained in the developing limbic system earlier--by day 40 of life--than in the cerebral cortex. During the first month of life, GPDH basal mRNA levels are increased in the absence of glucocorticoids, in both the limbic system and the cortex, in contrast to the effect of adrenalectomy in the adults, where GPDH mRNA levels are decreased in the absence of the adrenals. The observed pattern of glucocorticoid regulation of GPDH during development in the rat is discussed in relation to the possible existence of various levels of regulation of GPDH gene and enzyme activity.

Cloning, sequence, and disruption of the Saccharomyces diastaticus DAR1 gene encoding a glycerol-3-phosphate dehydrogenase

The Saccharomyces diastaticus DAR1 gene was cloned by complementation in an Escherichia coli strain auxogrophic for glycerol-3-phosphate. DAR1 encodes an NADH-dependent dihydroxyacetone phosphate reductase (sn-glycerol-3-phosphate dehydrogenase [G3PDase; EC 1.1.1.8]) homologous to several other eukaryotic G3PDases. DAR1 is distinct from GUT2, which encodes a glucose-repressed mitochondrial G3PDase, but is identical to GPD1 from S. cerevisiae, a close relative of S. diastaticus. The level of DAR1-encoded G3PDase was increased about threefold in a medium of high osmolarity. Disruption of DAR1 in a haploid S. cerevisiae was not lethal but led to a decrease in cytoplasmic NADH-dependent G3PDase activity, an increase in osmotic sensitivity, and a 25% reduction in glycerol secretion from cells grown anaerobically on glucose.

The nucleotide sequence of the murine Hox-D3 (Hox-4.1) gene reveals extensive identity with the human protein

We report the sequence of the murine Hox-D3 gene, formerly referred to as Hox-4, Hox-4.1 and Hox-4A. This gene is located on murine chromosome 2 in the Hox-D complex. The predicted Hox-D3 protein comprises 417 amino acids and displays 95% identity to the human protein. We have demonstrated that Hox-D3 is expressed in the skin, kidney and thymus, but not in lung, liver, spleen or stomach.

A novel, conserved gene of the rat that is developmentally regulated in the testis

From a rat testis library three overlapping cDNA clones were isolated that represent a novel single-copy gene, designated Tegt. Two transcripts of 2.8 and 1.0 kb were found in each organ tested. The shorter transcript was highly abundant in adult testis. A similar expression pattern was found in the mouse. Analysis of rat RNA from different stages of spermatogenesis indicated that accumulation of the short transcript occurred mainly postmeiotically. The rat Tegt gene maps to Chromosome (Chr) 7, and its mouse homolog to Chr 15.

A gene encoding sn-glycerol 3-phosphate dehydrogenase (NAD+) complements an osmosensitive mutant of Saccharomyces cerevisiae

Osmoregulatory mutants of Saccharomyces cerevisiae with a defect in their capacity to readjust the cell volume/buoyant density after osmotically induced dehydration were enriched by density gradient centrifugation. Colonies derived from cells that remained dense after dehydration were screened for sensitivity to high concentrations of NaCl and defects in their osmotically induced production and intracellular accumulation of glycerol. The isolated osg (osmosensitive glycerol defective) mutants were recessive in heterozygous diploids and fell into four complementation groups (osg1-osg4). The osg1-1 mutant, described in this work, is unable to grow at low water potential and shows a decreased capacity for glycerol production and a strongly reduced activity of NAD(+)-dependent sn-glycerol 3-phosphate dehydrogenase (GPD), an enzyme in the glycerol-producing pathway. Complementation of the osg1-1 salt sensitivity defect with a low copy yeast genomic library led to the cloning of GPD1, encoding an S. cerevisiae GPD consisting of 391 amino acids and sharing 47-50% identity with GPD from other sources. Micro-sequencing of the N-terminus of purified S. cerevisiae GPD revealed a 20-amino-acid sequence that was identical to a nucleotide-deduced amino acid sequence in GPD1, but indicated that the enzyme is produced with an N-terminal extension that is removed from the functional enzyme. Subcellular fractionation does not indicate, however, that the putative pre-sequence targets GPD to any organelle; the enzyme appears to be located in the cytoplasm. Chromoblot and tetrad analysis were used to position the GPD1 gene to chromosome IV, with a distance of about 18 cM from trp1.

Mapping of the mouse Rar loci encoding retinoic acid receptors RAR alpha, RAR beta and RAR gamma

Nuclear retinoic acid receptors RAR alpha, RAR beta and RAR gamma are transcription factors that bind all-trans retinoic acid as their ligand and mediate its action by activating particular set of genes that contain retinoic acid responsive elements in their promoter-enhancers. We have mapped genetic loci for these genes using restriction fragment length variants (RFLVs) in interspecific backcross mice. None of the Rar loci cosegregated with each other or with the new subclass of retinoid receptors, Rxr loci. Rara mapped to mChr 11, Rarb mapped to mChr 14, and Rarg mapped to mChr 15. The results are consistent with the previous reports and the human data in terms of syntenic homology between mouse and human chromosomes.

Gene order and genetic distance of 13 loci spanning murine chromosome 15

Thirteen genetic loci spanning murine chromosome 15 from 15A2 (Mlvi-2) to 15F2-3 (Gdc-1) have been mapped. The genetic distance extends to 55.4 cM. Among 151 animals, only 1 animal with a double cross-over was found. The linear order is unambiguous, with the exception of the distal end on 15F1-3. Our analysis favors the order cen-Ela-1/Hox-3-Wnt-1-Gdc-1-ter. This ordering makes necessary the introduction of three tightly spaced double recombination events around and within the Hox-3 locus. Alternatively, Hox-3 may be most distal, and several double recombinations at the telomere lead to map expansion. Despite the unequal distribution along chromosome 15 of G-versus R-bands, a comparison of distances determined by physical and genetic mapping does not indicate an overt difference in distance between both mapping techniques.

Molecular analysis of the aberrant replication banding pattern on chromosome 15 in murine T-cell lymphomas

Cytogenetic techniques revealed an altered early replication banding pattern on the distal part of chromosome 15 in some murine T-cell lymphomas. This pattern reverted back to normal replication in somatic cell hybrids that had become non-tumorigenic after fusion of leukemic cells with normal fibroblasts. The altered banding pattern was correlated with malignancy. To investigate the molecular basis of the aberrant pattern in more detail, centrifugal elutriation of cells containing bromodeoxyuridine labeled DNA was used to prepare newly replicated DNA from selected intervals of the S-phase from tumor cells, as well as from hybrid cells with the revertant phenotype. These different DNA fractions were probed for DNA sequences distributed over the distal half of chromosome 15. Only two out of ten chromosome 15 specific genes tested showed a clear change in replication timing between the two different cell lines tested. These two genes were the lymphocyte antigen-6, Ly-6, and the neighboring thyroglobulin gene, Tgn, which replicated at the beginning of S in the tumor cells and later in S in the non-tumorigenic hybrid cells.

Regulation of rodent myelin proteolipid protein gene expression

The regulation of rodent proteolipid protein (PLP) gene expression was studied during rat development and in cultured cells. Nuclear run-on assays demonstrate a strong transcriptional component associated with the developmental regulation of the PLP mRNA. Transcription rates of the PLP and MBP genes parallel their respective steady-state mRNA levels throughout rat brain development. In addition, a moderate 25-h half-life was measured for PLP mRNA in 37-day-old cultured oligodendrocytes, suggesting that regulation of PLP expression occurs predominantly at the transcriptional level. Finally, 5400 and 1400 bp of mouse PLP 5'-flanking sequence demonstrate transcriptional activity 13-fold and 5-fold above background, respectively, in hamster glial cells. Far upstream elements are clearly involved in transcription of the PLP gene. The 5400 bp sequence demonstrates no more activity than the 1400 bp in a mouse hepatoma cell line suggesting that elements involved in the glial cell-specific expression of PLP lie between 1400 and 5400 bp upstream of the gene.

The recombinant congenic strains--a novel genetic tool applied to the study of colon tumor development in the mouse

The development of tumors in mice is under multigenic control, but, in spite of considerable efforts, the identification of the genes involved has so far been unsuccessful, because of the insufficient resolution power of the available genetic tools. Therefore, a novel genetic tool, the RC (Recombinant Congenic) strains system, was designed. In this system, a series of RC strains is produced from two inbred strains, a "background" strain and a "donor" strain. Each RC strain contains a different small subset of genes from the donor strain and the majority of genes from the background strain. As a consequence, the individual genes of the donor strain which are involved in the genetic control of a multigenic trait, become separated into different RC strains, where they can be identified and studied individually. One of the RC strains series which we produced is made from the parental strains BALB/cHeA (background strain) and STS/A (donor strain). We describe the genetic composition of this BALB/cHeA-C-STS/A (CcS/Dem) series and show, using 45 genetic autosomal markers, that it does not deviate from the theoretical expectation. We studied the usefulness of the CcS/Dem RC strains for analysis of the genetics of colon tumor development. The two parental strains, BALB/cHeA and STS/A, are relatively resistant and highly susceptible, respectively, to the induction of colon tumors by 1,2-dimethylhydrazine (DMH). The individual RC strains differ widely in colon tumor development after DMH treatment; some are highly susceptible, while others are very resistant. This indicates that a limited number of genes with a major effect are responsible for the high susceptibility of the STS strain. Consequently, these genes can be mapped by further analysis of the susceptible RC strains. The differences between the RC strains were not limited to the number of tumors, but the RC strains differed also in size of the tumors and the relative susceptibility of the two sexes. Our data indicate that the number of tumors and the size of tumors are not controlled by the same genes. The genetics of these different aspects of colon tumorigenesis can also be studied by the RC strains. The DMH-treated mice of the parental strains and the RC strains also developed anal tumors and haemangiomas in varying numbers. The strain distribution pattern (SDP) of susceptibility for each of the three types of tumors induced by DMH is different, indicating that development of these tumors is under control of different, largely non-overlapping, sets of genes.(ABSTRACT TRUNCATED AT 400 WORDS)

Cloning and characterisation of the Saccharomyces cerevisiae glycerol-3-phosphate dehydrogenase (GUT2) promoter

The Saccharomyces cerevisiae glycerol-3-phosphate dehydrogenase (GUT2) promoter and part of the protein-coding region have been isolated on a 6.3-kb genomic DNA fragment. Nucleotide sequence analysis shows that the promoter has many structural features in common with yeast glycolytic enzyme promoters. Chromosomal mapping indicates that this genomic fragment is located on chromosome XII. The GUT2 promoter has been used to construct a recombinant human albumin (reHA) secretion vector; yeast transformed with this vector secrete reHA into the culture supernatant.

The mouse Col2a-1 gene is highly conserved and is linked to Int-1 on chromosome 15

Type II collagen is the major extracellular matrix component of cartilage and correct expression of the alpha 1(II) collagen gene is important for vertebrate skeletal development. In order to provide the basis for studying the control of type II collagen gene expression in embryogenesis and in mouse models of human connective tissue disease, the complete mouse Col2-a1 gene has been isolated in a single cosmid clone, cosMco1.2, and partially characterized. The gene is approximately 30 kb and is highly conserved in exon/intron structure and nucleotide and amino acid sequence (greater than 80% homology) when compared with the human, rat, bovine and chicken equivalents. A high degree of conservation was also found in the 5' flanking region of the rat, human and mouse alpha 1(II) collagen genes, including the presence of several G + C and C + T rich, direct repeat motifs. The sites of transcription start, termination codon and polyadenylation have also been identified. Unlike chicken, bovine and human, where polyA attachment is at a single site, for the mouse Col2a-1 gene two polyadenylation sites are utilized. Col2a-1 has also been localized by interspecies backcross analysis to the central portion of mouse Chromosome (Chr) 15, approximately 8 centiMorgans (cM) proximal of Int-1 and 18 cM distal of Myc. Col2a-1 is therefore included in a linkage group which is conserved on human Chr 12q.

Differentiation of newborn rat preadipocytes in culture: effects of insulin and dexamethasone

A preadipocyte cell population isolated from the inguinal tissue of 3-day-old rats converts at confluence into mature adipocytes when cultured with insulin (10(-9) M). Insulin is necessary only from Day 4 postplating. If the addition of insulin is further delayed, the proportion of cells which will undergo adipose conversion decreases. A loss of the differentiation competence is also observed when the cells are allowed to proliferate (seeding at a low density in a serum containing medium). A preexposure of the primary cells to dexamethasone during the insulin-insensitive period (Days 0-4) accelerates the subsequent "insulin-dependent" adipose conversion. In order to produce its effect, dexamethasone needs only to be present for 4 h on Day 2 postplating. The effect of dexamethasone is probably due neither to inhibition of cell proliferation nor to induction of the cell content of insulin receptors. The evolution of G3PDH enzyme activity as well as of G3PDH protein and mRNA was used as an indicator of the differentiation process. The enzyme accumulates to a low extent during culture in the absence of insulin. When insulin is present, the enzyme level is dramatically increased (maximum on Day 11). Dexamethasone pretreatment (Days 0-4, or 4 h on Day 2) accelerated the G3PDH enzyme activity increase as well as protein and mRNA accumulation. This was also true in cells maintained in insulin-free medium; however, in this case, the increase in the enzyme activity was limited to the first 8 days of culture and full differentiation did not take place. We conclude that: (1) the rat preadipocytes are committed to differentiate, requiring insulin as a sufficient physiological stimulus; (2) the differentiation program is progressively lost after greater than 4 days of culture without insulin and more rapidly if the cells are allowed to undergo divisions; and (3) dexamethasone accelerates the insulin-dependent adipose conversion but alone does not ensure the complete differentiation process.

The induction of adipose conversion by bezafibrate in 3T3-L1 cells. Synergism with dibutyryl-cAMP

The induction of adipose conversion in 3T3-L1 cells by bezafibrate (Brandes, R., Hertz, R. Arad R., Naishtat S., Weil, S. and Bar-Tana, J. (1987) Life Sci., 40, 935-941) was enhanced by dibutyryl-cAMP as well as forskolin, theophylline or isobutylmethylxanthine added to the incubation medium together with the bezafibrate inducer. The synergistic effect of bezafibrate and dibutyryl-cAMP resulted in enhancing the expression of late markers of adipose conversion, e.g., lipid accumulation or glycerol-3-phosphate dehydrogenase activity and its mRNA. This enhanced expression of late markers was reflected in shortening the time period required for their first appearance as well as increasing their yield during the course of adipose conversion. By following the accumulation of glutamine synthetase mRNA serving as an early marker for adipose conversion, the synergistic effect of bezafibrate and dibutyryl-cAMP was already evident as early as 5 h following their addition to confluent 3T3-L1 cells. Hence, the induction of adipose conversion by bezafibrate in 3T3-L1 cells appears to involve an early event which is rate-limited by the availability of intracellular cAMP.

Genomic structure of the human cytosolic aldehyde dehydrogenase gene

We have isolated and characterized several overlapping clones from two human genomic libraries constructed in cosmid and bacteriophage vectors. They span about 80 kbp and include the entire human cytosolic aldehyde dehydrogenase (ALDH1) gene. Restriction endonuclease mapping, Southern blotting with cDNA and specific oligonucleotide probes, and DNA sequencing were performed to analyze the cloned genomic DNA. The ALDH1 gene is about 53 kbp long and is divided into 13 exons which encode 501 amino acid residues. Primer extension results defined the transcription initiation site to 53 bp upstream from the A of the initiation codon ATG. The promoter region of the gene contains an ATA box and a CCAAT box, which are located 32 and 74 bp upstream, respectively, from the transcription initiation site. The possible functional domains of the protein encoded by exons are discussed. A similar intron-exon organization between the genes of cytosolic ALDH1 and its mitochondrial ALDH2 isozyme in which both enzymes are encoded by 13 exons and 9 of the 12 introns interrupt the coding sequence at homologous positions was observed. This is consistent with the model that the two isozyme genes evolved after the duplication of a common ancestor gene.

In developing brown adipose tissue c-myc protooncogene expression is restricted to early differentiation stages

The expression pattern of the c-myc protooncogene during fetal development of the mouse was studied by RNA in situ hybridization to tissue sections. In day 15.5 post coitum (p.c.) and day 16.5 p.c. embryos, distinct c-myc expression was observed at the site of brown adipose tissue development. High c-myc expression at this site coincides with expression of the NADH-dependent, cytosolic form of glycerol-3-phosphate dehydrogenase (GPDH). Fat deposition in the form of single small droplets occurs as early as day 15.5 p.c. At earlier stages (day 14.5 p.c. and earlier) the mesenchymal precursor cells at this site show neither c-myc nor GPDH expression. During fetal development the brown adipose tissue increases enormously in size. GPDH expression increases concomitantly as does multilocular fat deposition. However, c-myc expression is not detectable in brown adipose tissue later than day 16.5 p.c.

Tissue-specific expression, developmental regulation, and genetic mapping of the gene encoding CCAAT/enhancer binding protein

This paper presents the results of experiments that determine the chromosomal location of the mouse gene encoding CCAAT/enhancer binding protein (C/EBP) and measure its expression as a function of tissue type and temporal period of development in mice and rats. Three alleles of the C/EBP gene were identified according to restriction fragment length polymorphisms. The strain distribution pattern of the three alleles was determined in recombinant inbred mouse strains and compared to that of other mouse genes. These results mapped the gene to a position within 2.5 centimorgans (cM) of the structural gene encoding glucose phosphate isomerase on chromosome 7 of the mouse. The expression pattern of the C/EBP gene was studied by a combination of nucleic acid hybridization and antibody staining assays. High levels of C/EBP mRNA were observed in tissues known to metabolize lipid and cholesterol-related compounds at uncommonly high rates. These included liver, fat, intestine, lung, adrenal gland, and placenta. More detailed analysis of two of these tissues, liver and fat, showed that C/EBP expression was limited to fully differentiated cells. Moreover, analysis of the temporal pattern of expression of C/EBP mRNA in two tissues, liver and intestine, revealed a coordinated induction just prior to birth. These observations raise the possibility that the synthesis of C/EBP may be responsive to humoral factors and that modulation in C/EBP expression might mediate coordinated changes in gene expression that facilitate adaptive challenges met during development or during the fluctuating physiological states of adult life.

Regulation of gene expression by insulin in adipose cells: opposite effects on adipsin and glycerophosphate dehydrogenase genes

Insulin is known to play the role of a positive effector both in vitro on the adipose conversion process and in vivo on the fatty acid synthesis and esterification processes in adipose tissue. The effects of insulin on the expression of two genes activated during adipose conversion, glycerol-3-phosphate dehydrogenase (GPDH) and adipsin genes, have been investigated in 3T3 F442A adipose cells. Within a physiological range of concentrations, insulin exerts opposite effects on the levels of GPDH (EC50 approximately 0.2 nM) and adipsin (EC50 approximately 1 nM) mRNAs. Its negative effect on the abundance of adipsin mRNA involves primarily a rapid inhibition of the transcriptional rate (less than 2 h). Its positive effect on the abundance of GPDH mRNA is due to a stimulation of the transcriptional rate accompanied by a delayed stabilization of GPDH mRNA. In addition, insulin exerts a specific effect on the length of the poly(A) tract of the adipsin mRNA. These results show that a single mechanism for the regulation of adipose-related genes by insulin can be excluded but rather suggest a complex phenomenon in which various levels of regulation take place.

Suppression of SV40-promoted gene expression by differentiation of preadipose cells

When a plasmid bearing the chloramphenicol acetyltransferase (CAT) gene under the control of an SV40 early promoter is introduced into preadipose or adipose cells of line 3T3-F442A, the promoter directs high levels of transient expression of CAT. However, when the plasmid is introduced into preadipose cells and the cells are then allowed to differentiate into adipose cells, the expression of the CAT gene is suppressed. In this process, the plasmid is not changed detectably in amount, topology, or state of methylation. Stably transformed preadipose cells bearing an integrated plasmid express the transferase, but if the cells are allowed to differentiate, the expression of the gene is similarly suppressed. The decline in CAT activity is associated with a decrease in the transcription rate of the gene. Transcription of a gene coding for neomycin phosphotransferase driven by the SV40 promoter is also greatly diminished by differentiation. Because suppression of CAT does not occur when the gene is under control of a retroviral long terminal repeat (LTR), a specific mechanism exists for the recognition and inactivation of the SV40 early promoter during differentiation.

Structural organization of the mouse mitochondrial malate dehydrogenase gene

Structural organization of the mouse mitochondrial malate dehydrogenase (EC 1.1.1.37) gene was determined by analyzing a genomic DNA fragment isolated from a cosmid library. The gene is 12,000 base-pairs long and contains nine exons interrupted by eight introns of various sizes. The 5' and 3'-flanking regions, and the exact sizes and boundaries of the exon blocks including the transcription-initiation sites were determined. In the 5'-flanking region, there is neither a TATA box nor a CAAT box. Instead of these sequences, there are six copies of the GGGCGG or CCGCCC sequence, which is a potential binding site for the transcription factor, Sp1. The 5'-flanking region up to about 600 nucleotides is G + C-rich (65%) and contains sequences compatible with the formation of a number of potentially stable stem-loop structures. S1 nuclease mapping and primer extension analysis demonstrated that transcription of the mitochondrial malate dehydrogenase gene initiates at multiple sites. Comparison of the nucleotide sequence of the promoter region of the mitochondrial malate dehydrogenase gene with that of the mitochondrial aspartate aminotransferase gene, revealed that there are several highly conserved regions between these two mitochondrial enzyme genes participating in the malate-aspartate shuttle.

Genomic structure of the human mitochondrial aldehyde dehydrogenase gene

We have isolated and characterized four overlapping clones from two cosmid human genomic libraries, which span about 90 kilobase pairs (kbp) and contain the entire human mitochondrial aldehyde dehydrogenase (ALDH2) gene. Restriction maps of the genomic clones were elucidated utilizing cDNA probes and specific oligonucleotide probes. The organization of exons and introns was established by DNA sequencing of each exon and splicing junctions. The ALDH2 gene is about 44 kbp in length and contains at least 13 exons which encode 517 amino acid residues. Except for the signal NH2-terminal peptide, which is absent in the mature enzyme, the amino acid sequence deduced from the exons coincided with the reported primary structure of human liver ALDH2 (J. Hempel, R. Kaiser, and H. Jörnvall, 1985, Eur. J. Biochem. 153: 13-28). Several introns contain Alu repetitive sequences. A TATA-like sequence (TTATAAAA) and a CAAT-like sequence (GTCATCAT) are located 473 and 515 bp, respectively, upstream from the translation initiation codon. Primer extension and S1 nuclease mapping were performed to characterize the 5'-region of the gene.

Rat glycine methyltransferase. Complete amino acid sequence deduced from a cDNA clone and characterization of the genomic DNA

The amino terminus of glycine methyltransferase from rat liver is blocked. A hexapeptide containing the blocked amino-terminal residue was obtained from a tryptic digest of the purified enzyme and its amino acid sequence was determined to be Ac-Val-Asp-Ser-Val-Tyr-Arg by Edman degradation and fast-atom-bombardment mass spectrometry after fragmentation with Staphylococcus aureus protease V8. A full-length cDNA clone for the enzyme was isolated from a lambda gt11 rat liver cDNA library using the previously obtained pGMT A56 cDNA [Ogawa, H., Gomi, T., Horii, T., Ogawa, H. & Fujioka, M. (1984) Biochem. Biophys. Res. Commun. 124, 44-50] as a probe. The amino acid sequence deduced from the nucleotide sequence contained both amino- and carboxyl-terminal sequences. The predicted amino acid composition and molecular mass were also in agreement with the published data obtained with the purified protein. Five clones for the glycine methyltransferase gene were isolated from a Charon 4A library containing EcoRI digest of rat liver DNA by in situ plaque hybridization. All clones had inserts of 6500 base pairs, consistent with the size of EcoRI genomic DNA fragment determined by Southern blot hybridization. Sequence analysis of a 5400-bp fragment of the insert DNA lacking a 1100-bp 5' region and comparison of the sequence with that of the cDNA showed that the insert DNA entirely encoded glycine methyltransferase and the gene consisted of six exons and five introns. S1 nuclease protection mapping and primer extension analysis allowed us to propose that the A residue located 19 bp upstream from the translation initiation codon is the site of transcription initiation. TATA, CAAT and GC sequences, and the complementary sequence to the enhancer core element, were located upstream of the transcription initiation site.