Biomedical subjects

Yong-Sung Lee

Publications and source records attributed to Yong-Sung Lee.

At least 19 recordsLinked to original sources

PubMed2006

Acquisition of in vitro and in vivo functionality of Nurr1-induced dopamine neurons.

Neural precursor cells provide an expandable source of neurons and glia for basic and translational applications. However, little progress has been made in directing naive neural precursors toward specific neuronal fates such as midbrain dopamine (DA) neurons. We have recently demonstrated that transgenic expression of the nuclear orphan receptor Nurr1 is sufficient to drive dopaminergic differentiation of forebrain embryonic rat neural precursors in vitro. However, Nurr1-induced DA neurons exhibit immature neuronal morphologies and functional properties and are unable to induce behavioral recovery in rodent models of Parkinson's disease (PD). Here, we report on the identification of key genetic factors that drive morphological and functional differentiation of Nurr1-derived DA neurons. We show that coexpression of Nurr1, Bcl-XL, and Sonic hedgehog (SHH) or Nurr1 and the proneural bHLH factor Mash1 is sufficient to drive naive rat forebrain precursors into neurons exhibiting the biochemical, electrophysiological, and functional properties of DA neuron in vitro. On transplantation into the striatum of Parkinsonian rats, precursor cells engineered with Nurr1/SHH/Bcl-XL or Nurr1/Mash1 survived in vivo and differentiated into mature DA neurons that can reverse the behavioral deficits in the grafted animals.

Animals↗

PubMed2006

Comprehensive analysis of differential gene expression profiles on D-galactosamine-induced acute mouse liver injury and regeneration.

Microarray analysis of RNA from d-galactosamine (GalN)-administered mouse livers was performed to establish a global gene expression profile during injury and regeneration stages at two different doses. A single dose of GalN at 266 or 26.6 mg/kg body weight was given intraperitoneally, and the liver samples were obtained after 6, 24, and 72 h. Histopathologic studies enabled the classification of the D-galactosamine effect into injury (6, 24 h) and regeneration (72 h) stages. By using the Applied Biosystems mouse genome survey microarray, a total of 7267 out of 33,315 (21.8%) genes were found to be statistically reliable at p<0.05 by two-way ANOVA, and 1469 (4.4%) probes at false discovery rate <5% by significance analysis of microarray. Among the statistically reliable clones by both analytical methods, 389 genes were differentially expressed when compared with non-treated control, with more than a 1.625-fold difference (which equals 0.7 in log(2) scale) at one or more GalN treatment conditions and with less than 1.625-fold difference at all three vehicle-treated conditions. Three hundred thirty six genes and 13 genes were identified as injury- and regeneration-specific genes, respectively, showing that most of the transcriptomic changes were seen during the injury stage. Furthermore, multiple genes involved in protein synthesis and degradation, mRNA processing and binding, and cell cycle regulation showed variable transcript levels upon acute GalN administration.

Acute Disease↗

PubMed2006

Comprehensive analysis of differential gene expression profiles on diclofenac-induced acute mouse liver injury and recovery.

Microarray analysis of RNA from diclofenac-administered mouse livers was performed to establish a global gene expression profile during injury and recovery stages at two different doses. A single dose of diclofenac at 9.5 mg/kg or 0.95 mg/kg body weight was given orally, and the liver samples were obtained after 6, 24, and 72 h. Histopathologic studies enabled the classification of the diclofenac effect into injury (6, 24 h) and recovery (72 h) stages. By using the Applied Biosystems Mouse Genome Survey Microarray, a total of 7370 out of 33,315 (22.1%) genes were found to be statistically reliable at p<0.05 by two-way ANOVA, and 602 (1.8%) probes at false discovery rate <5% by Significance Analysis of Microarray. Among the statistically reliable clones by both analytical methods, 49 genes were differentially expressed with more than a 1.625-fold difference (which equals 0.7 in log(2) scale) at one or more treatment conditions. Forty genes and two genes were identified as injury- and recovery-specific genes, respectively, showing that most of the transcriptomic changes were seen during the injury stage. Furthermore, multiple genes involved in oxidative stress, eicosanoid synthesis, apoptosis, and ATP synthesis showed variable transcript levels upon acute diclofenac administration.

Animals↗

PubMed2006

Differential actions of the proneural genes encoding Mash1 and neurogenins in Nurr1-induced dopamine neuron differentiation.

The steroid receptor-type transcription factor Nurr1 has a crucial role in the development of the mesencephalic dopamine (DA) neurons. Although ectopic expression of Nurr1 in cultured neural precursor cells is sufficient in establishing the DA phenotype, Nurr1-induced DA cells are morphologically and functionally immature, suggesting the necessity of additional factor(s) for full neuronal differentiation. In this study, we demonstrate that neurogenic basic helix-loop-helix (bHLH) factors Mash1, neurogenins (Ngns) and NeuroD play contrasting roles in Nurr1-induced DA neuronal differentiation. Mash1, but not Ngn2, spatially and temporally colocalized with aldehyde dehydrogenase 2 (AHD2), a specific midbrain DA neuronal progenitor marker, in the early embryonic ventral mesencephalon. Forced expression of Mash1 caused immature Nurr1-induced DA cells to differentiate into mature and functional DA neurons as judged by electrophysiological characteristics, release of DA, and expression of presynaptic DA neuronal markers. By contrast, atonal-related bHLHs, represented by Ngn1, Ngn2 and NeuroD, repressed Nurr1-induced expression of DA neuronal markers. Domain-swapping experiments with Mash1 and NeuroD indicated that the helix-loop-helix domain, responsible for mediating dimerization of bHLH transcription factors, imparts the distinct effect. Finally, transient co-transfection of the atonal-related bHLHs with Nurr1 resulted in an E-box-independent repression of Nurr1-induced transcriptional activation of a reporter containing Nurr1-binding element (NL3) as well as a reporter driven by the native tyrosine hydroxylase gene promoter. Taken together, these findings suggest that Mash1 contributes to the generation of DA neurons in cooperation with Nurr1 in the developing midbrain whereas atonal-related bHLH genes inhibit the process.

Aldehyde Dehydrogenase↗

PubMed2006

Expression profiles of 4-nonylphenol-exposed medaka (Oryzias latipes) analyzed with a 3.4 K microarray.

Changes in gene expression in liver of medaka in response to 4-nonylphenol (4-NP) were investigated with a microarray consisting of 3.4 K medaka-specific cDNA probes. Upon exposure to 4-NP at two different concentrations (20 and 100 microg/L) for 24 h, we found 44 different genes that were up- or downregulated with statistically significant changes. Digestive enzyme genes were downregulated but vitellogenin, choriogenin and novel biomarker genes were upregulated. Additionally an analysis of the changes of gene expression with respect to time was conducted at 100 microg/L of 4-NP with samples at 0, 24, 48 and 96 h. The expression of 75 genes was altered and these were categorized into four different clusters. The validity of the results was checked by semi-quantitative PCR with 12 representative genes and this confirmed the microarray data. Therefore, we suggest that this medaka 3.4 K chip would be useful in generating gene expression profiles for studies of ecotoxicogenomics in medaka.

Animals↗

PubMed2005

Differential gene expression profiles in the steatosis/fibrosis model of rat liver by chronic administration of carbon tetrachloride.

Global gene expression profile was analyzed by microarray analysis of rat liver RNA after chronic carbon tetrachloride (CCl(4)) administration. Rats received 0.5 ml CCl(4)/kg three times a week, and the liver samples were obtained after 0, 30, 60, and 90 days of injection. Histopathologic studies of liver tissues enabled the classification of the CCl(4) effect into mild and severe fatty liver/steatosis (30 and 60 days, respectively) and fibrosis/cirrhosis (90 days) stages. The expression levels of 4,900 clones on a custom rat gene microarray were analyzed and the results were confirmed by semi-quantitative RT-PCR. Four hundred thirty-eight clones were differentially expressed with more than a 1.625-fold difference (which equals 0.7 in log2 scale) at one or more time points. Multiple genes involved in lipid metabolism and ribosome biogenesis showed differential transcript levels upon chronic CCl(4) administration, which was previously seen in acute rat model as well. In addition, a total of 149 clones were identified as fibrosis/cirrhosis-specific genes by either fold changes or Significance Analysis of Microarrays. In conclusion, we report microarray analysis results in rat liver upon chronic CCl(4) administration with a full chronological profile that not only covered fatty liver/steatosis but also later points of fibrosis/cirrhosis. These data will provide the insight of specific gene expression profiles that is implicated in the multistep process of fatty liver/steatosis and fibrosis/cirrhosis after chronic hepatotoxin exposure.

Alanine Transaminase↗

PubMed2005

In vitro and in vivo analyses of human embryonic stem cell-derived dopamine neurons.

Human embryonic stem (hES) cells, due to their capacity of multipotency and self-renewal, may serve as a valuable experimental tool for human developmental biology and may provide an unlimited cell source for cell replacement therapy. The purpose of this study was to assess the developmental potential of hES cells to replace the selectively lost midbrain dopamine (DA) neurons in Parkinson's disease. Here, we report the development of an in vitro differentiation protocol to derive an enriched population of midbrain DA neurons from hES cells. Neural induction of hES cells co-cultured with stromal cells, followed by expansion of the resulting neural precursor cells, efficiently generated DA neurons with concomitant expression of transcriptional factors related to midbrain DA development, such as Pax2, En1 (Engrailed-1), Nurr1, and Lmx1b. Using our procedure, the majority of differentiated hES cells (> 95%) contained neuronal or neural precursor markers and a high percentage (> 40%) of TuJ1+ neurons was tyrosine hydroxylase (TH)+, while none of them expressed the undifferentiated ES cell marker, Oct 3/4. Furthermore, hES cell-derived DA neurons demonstrated functionality in vitro, releasing DA in response to KCl-induced depolarization and reuptake of DA. Finally, transplantation of hES-derived DA neurons into the striatum of hemi-parkinsonian rats failed to result in improvement of their behavioral deficits as determined by amphetamine-induced rotation and step-adjustment. Immunohistochemical analyses of grafted brains revealed that abundant hES-derived cells (human nuclei+ cells) survived in the grafts, but none of them were TH+. Therefore, unlike those from mouse ES cells, hES cell-derived DA neurons either do not survive or their DA phenotype is unstable when grafted into rodent brains.

Animals↗

PubMed2005

Retrovirally transduced NCAM140 facilitates neuronal fate choice of hippocampal progenitor cells.

Neural cell adhesion molecule (NCAM) influences proliferation and differentiation of neuronal cells. However, only a little is known about the downstream effects of NCAM signalling, such as alterations in gene transcription, which are associated with cell fate choice. To examine whether NCAM plays a role in cell fate choice during hippocampal neurogenesis, we performed a gain-of-function study, using a retroviral vector which contained full-length NCAM140 cDNA and the marker gene EGFP, and found that NCAM140 promoted neurogenesis by activating proneural transcription activators with concurrent inhibition of gliogenesis. The enhanced transcript levels of proneural transcription factors in NCAM140-transduced cells were down-regulated by treatment of the cells with mitogen-activated protein kinase kinase (MEK) inhibitor PD098059. Overall, these findings suggest that NCAM140 may facilitate hippocampal neurogenesis via regulation of proneurogenic transcription factors in an extracellular signal-regulated kinase (ERK)-dependent manner.

Animals↗

PubMed2004

Feature genes of hepatitis B virus-positive hepatocellular carcinoma, established by its molecular discrimination approach using prediction analysis of microarray.

Recent introduction of a learning algorithm for cDNA microarray analysis has permitted to select feature set to accurately distinguish human cancers according to their pathological judgments. Here, we demonstrate that hepatitis B virus-positive hepatocellular carcinoma (HCC) could successfully be identified from non-tumor liver tissues by supervised learning analysis of gene expression profiling. Through learning and cross-validating HCC sample set, we could identify an optimized set of 44 genes to discriminate the status of HCC from non-tumor liver tissues. In an analysis of other blind-tested HCC sample sets, this feature set was found to be statistically significant, indicating the reproducibility of our molecular discrimination approach with the defined genes. One prominent finding was an asymmetrical distribution pattern of expression profiling in HCC, in which the number of down-regulated genes was greater than that of up-regulated genes. In conclusion, the present findings indicate that application of learning algorithm to HCC may establish a reliable feature set of genes to be useful for therapeutic target of HCC, and that the asymmetric expression pattern may emphasize the importance of suppressed genes in HCC.

Carcinoma, Hepatocellular↗

PubMed2004

Comprehensive analysis of differential gene expression profiles on carbon tetrachloride-induced rat liver injury and regeneration.

Microarray analysis of RNA from carbon tetrachloride (CCl4)-administered rat livers was performed at various time points to establish a global gene expression profile during injury and regeneration stages. A single dose of 1 ml/kg of CCl4 was given by ip injection, and the liver samples were obtained after 6, 24, 48 h, and 2 weeks. Histopathologic, biochemical, and immunohistochemical studies enabled the classification of the CCl4 effect into injury (6 and 24 h) and regeneration (48 h and 2 weeks) stages. The expression levels of 5180 clones on a custom rat gene microarray were analyzed and 587 clones yielded changeable gene expression on at least single time point. One hundred seventy-nine clones were classified as injury-specific clones, while 38 clones as regeneration-specific clones. Characteristic gene expression profiles could be associated with CCl4-induced gene expression with the disruption of lipid metabolism, which is known to cause the fatty liver induced by CCl4 treatment. In addition, induction of the transcripts for many ribosomal proteins was detected during the injury stage, particularly at the 24-h time point, despite the previous report of decreased protein synthesis rate upon CCl4 treatment. Several genes with known functions were also identified as CCl4-regulated genes. In conclusion, we established a global gene expression profile utilizing microarray analysis in rat liver upon acute CCl4 administration with a full chronological profile that not only covers injury stage but also later points of regeneration stage.

Animals↗

PubMed2004

Dexamethasone inhibits proliferation of adult hippocampal neurogenesis in vivo and in vitro.

Activation of glucocorticoid receptor (GR) induces a reduction of adult hippocampal neurogenesis found in dentate gyrus (DG). However, the nature of specific effects by glucocorticoid in hippocampal neurogenesis is not known. In this report, we show differential effects of dexamethasone (DEX), a glucocorticoid receptor agonist, on proliferation and functional differentiation of adult hippocampal progenitor cells in DG. Two-month-old adult rats received daily injections of DEX for 9 days and were sacrificed 12 h and 28 days after the ninth injection. Proliferation assays showed that DEX inhibited proliferation of neural progenitor cells and the inhibitory effects of DEX was not detected 28 days after recovery. Functional differentiation studies using B-cell lymphoma protein-2 (Bcl-2), brain-derived neurotrophic factor (BDNF), p-ERK, and neuronal nuclear protein (NeuN) antibodies revealed that the expressions of Bcl-2 and BDNF were not significantly different between control and DEX-treated rats. In contrast, however, the activation of extracellular signal-regulated kinase (ERK) was downregulated 12 h, but not 28 days, after the DEX treatment. When adult hippocampal progenitor cell cultures were treated with subchronic DEX, proliferation of the progenitor cells was suppressed. Taken these in vitro and in vivo results together, it is concluded that glucocorticoid receptor activation blocks only proliferation, but not differentiation, in hippocampal neurogenesis.

Animals↗

PubMed2004

Temporal expression changes during differentiation of neural stem cells derived from mouse embryonic stem cell.

Temporal analysis in gene expression during differentiation of neural stem cells (NSCs) was performed by using in-house microarrays composed of 10,368 genes. The changes in mRNA level were measured during differentiation day 1, 2, 3, 6, 12, and 15. Out of 10,368 genes analyzed, 259 genes were up-regulated or down-regulated by 2-fold or more at least at one time-point during differentiation, and were classified into six clusters based on their expression patterns by K-means clustering. Clusters characterized by gradual increase have large numbers of genes involved in transport and cell adhesion; those which showed gradual decrease have much of genes in nucleic acid metabolism, cell cycle, transcription factor, and RNA processing. In situ hybridization (ISH) validated microarray data and it also showed that Fox M1, cyclin D2, and CDK4 were highly expressed in CNS germinal zones and ectonucleotide pyrophosphatase/phosphodiesterase 2 (Enpp2) was highly expressed in choroid plexus where stem/progenitor cells are possibly located. Together, this clustering analysis of expression patterns of functionally classified genes may give insight into understanding of CNS development and mechanisms of NSCs proliferation and differentiation.

Animals↗

PubMed2004

Changes of gene expression profiles during neuronal differentiation of central nervous system precursors treated with ascorbic acid.

Ascorbic acid (AA) has been shown to increase the yield of dopaminergic (DA) neurons derived from basic fibroblast growth factor (bFGF)-expanded mesencephalic precursors. To understand the molecular mechanisms underlying this phenomenon, we used cDNA microarray analysis to examine differential expression of neuronal genes following AA treatment. The putative precursor cells were isolated from E13 rat ventral mesencephalons and expanded in the presence of bFGF. Cells were incubated in mitogen-free media supplemented with 200 microM AA or were left untreated as a control, and total RNA was isolated at different time points (expansion stage and 1, 3, and 6 days after induction of differentiation) and subjected to cDNA microarray analysis. Differentiation was evaluated by Western blot analysis and immunocytochemistry of neuron-specific markers. AA treatment of the mesencephalic precursors increased the expression of neuronal (MAP2) and astrocytic (glial fibrillary acidic protein) markers and the percentage of tyrosine hydroxylase (TH)-positive cells. The microarray analysis revealed that 12 known genes were up-regulated and 20 known genes were down-regulated in expansion-stage AA-treated cells. Six days after the induction of differentiation, AA-treated cells showed up-regulation of 48 known genes and down-regulation of 5 known genes. Our results identified several proteins, such as transferrin, S-100, and somatostatin, as being differentially regulated in AA-treated mesencephalic precursors. This novel result may lead to a better understanding of the molecular mechanisms underlying the AA-induced differentiation of mesencephalic precursors into DA neurons and may form the basis for improved DA neuronal production for treatment of Parkinson's disease patients.

Animals↗

PubMed2004

Ascorbic acid responsive genes during neuronal differentiation of embryonic stem cells.

Ascorbic acid has been reported to enhance differentiation of embryonic stem (ES) cells into neurons, however, the specific functions of ascorbic acid have not been defined yet. To address this issue, gene expression profiling was performed using cDNA microarray. Ascorbic acid increased the expressions of genes involved in neurogenesis, maturation, and neurotransmission. Furthermore, statistical analysis using Fisher's exact test revealed ascorbic acid significantly modulated the genes involved in cell adhesion and development category. These results provide information on the role for ascorbic acid during neuronal differentiation of ES cells and might contribute to large-scale generation of neurons for future clinical treatment.

Animals↗

PubMed2004

The complete mitochondrial genome of the javeline goby Acanthogobius hasta (Perciformes, Gobiidae) and phylogenetic considerations.

We isolated Acanthogobius hasta mitochondrial DNA by long-polymerase chain reaction (long-PCR) with conserved primers, and sequenced this mitogenome with primer walking. The resultant A. hasta mitochondrial DNA sequence was found to consist of 16,663 bp with a structural organization conserved relative to that of other fish. In this paper, we report the basic characteristics of the A. hasta mitochondrial genome including structural organization, base composition of rRNAs and the tRNAs and protein-encoding genes, and characteristics of mitochondrial tRNAs. These findings are applicable to molecular phylogenetics in the suborder Gobioidei.

Animals↗

PubMed2004

Differential effects of corticosterone and dexamethasone on hippocampal neurogenesis in vitro.

Prenatal stress during fetal development results in the blockade of neurogenesis in the dentate gyrus in adulthood. Present study was undertaken to investigate the dominant role of the glucocorticoid receptors in corticosterone actions on the neurogenesis of fetal hippocampal progenitor cells. For that purpose, expressions of key molecules affected by corticosterone and dexamethasone were compared during proliferation and differentiation of the hippocampal progenitor cells. Corticosterone (2 microM) significantly decreased the number of bromodeoxyuridine-labeled cells (about 50%) and caused the dendritic atrophy in microtubule-associated protein 2-labeled cells. The expressions of NeuroD, BDNF, and NR1 mRNA levels and protein levels of p-ERK and p-CREB were remarkably decreased by corticosterone in a dose-dependent manner. In contrast, dexamethasone, a glucocorticoid receptor (GR) specific agonist, had an inhibitory effect on proliferation, but not differentiation. It is concluded that corticosterone elicits its effects on neurogenesis including proliferation and differentiation whereas stimulation of the glucocorticoid receptor is sufficient to decrease only proliferation.

Animals↗

PubMed2004

Enhanced in vitro midbrain dopamine neuron differentiation, dopaminergic function, neurite outgrowth, and 1-methyl-4-phenylpyridium resistance in mouse embryonic stem cells overexpressing Bcl-XL.

Embryonic stem (ES) cells provide a potentially unlimited source of specialized cells for regenerative medicine. The ease of inducing stable genetic modifications in ES cells allows for in vitro manipulations to enhance differentiation into specific cell types and to optimize in vivo function of differentiated progeny in animal models of disease. We have generated mouse ES cells that constitutively express Bcl-XL, an antiapoptotic protein of Bcl-2 family. In vitro differentiation of Bcl-XL overexpressing ES (Bcl-ES) cells resulted in higher expression of genes related to midbrain dopamine (DA) neuron development and increased the number of ES-derived neurons expressing midbrain DA markers compared with differentiation of wild-type ES cells. Moreover, DA neurons derived from Bcl-ES cells were less susceptible to 1-methyl-4-phenylpyridium, a neurotoxin for DA neurons. On transplantation into parkinsonian rats, the Bcl-ES-derived DA neurons exhibited more extensive fiber outgrowth and led to a more pronounced reversal of behavioral symptoms than wild-type ES-derived DA neurons. These data suggest a role for Bcl-XL during in vitro midbrain DA neuron differentiation and provide an improved system for cell transplantation in a preclinical animal model of Parkinson's disease.

1-Methyl-4-phenylpyridinium↗

PubMed2004

Human zinc finger protein 161, a novel transcriptional activator of the dopamine transporter.

The dopamine transporter (DAT) terminates dopaminergic neurotransmission via reuptake of released dopamine into presynaptic neurons. We have cloned 2.5 kb of the regulatory region upstream of human DAT (hDAT) and constructed a series of deletion mutants to test promoter activity. A comparison of promoter activity between non-neural and neuronal cell lines reveals an interesting difference in pattern. In the PC12 cell line, activity of the proximal promoter is strongly silenced by one or more unidentified elements spanning positions -395 to -2465 of the hDAT gene. Our studies focus on identifying and characterizing the activating factor for hDAT transcription in the sequence between -2511 and -2492 (5(')-CTA CCT GCA CAG TTC ACG GA-3('), termed HY1). In this investigation, we cloned the zinc finger protein 161 (ZFP161) gene as a HY1-binding factor, using the yeast one-hybrid screen. Recombinant ZFP161 was produced to evaluate the DNA-binding properties of the protein. The ability of ZFP161 to directly bind HY1 was examined in an electrophoretic mobility shift assay. RT-PCR analyses revealed that transfection of ZFP161 induced hDAT mRNA expression in HEK293 cells. We additionally confirmed the expression and localization of the DAT protein, using a specific antibody. Both the HY1 sequence and the downstream region were necessary for activation of the hDAT promoter by ZFP161. This finding suggests that the site of cofactor interaction with ZFP161 may exist downstream of HY1.

Animals↗