Biomedical subjects

Garry Wong

Publications and source records attributed to Garry Wong.

7 recordsLinked to original sources

PubMed2003

Microarray analysis of nonhuman primates: validation of experimental models in neurological disorders.

Nonhuman primates (NHPs) have provided robust experimental animal models for many human-related diseases due to their similar physiologies. Nonetheless, profound differences remain in the acquisition, progression, and outcome of important diseases such as AIDS and Alzheimer's, for which the underlying basis remains obscure. We explored the utility of human high-density oligonucleotide arrays to survey the transcription profile of NHP genomes. Total RNA from prefrontal cortices of human (Homo sapiens), common chimpanzee (Pan troglodytes), cynomolgous macaque (Macaca fascicularis), and common marmoset (Callithrix jacchus) was labeled and hybridized to Affymetrix U95A GeneChip probe arrays. Corresponding data obtained previously from common chimpanzee and orangutan (Pongo pygmaeus) were added for comparison. Qualitative (present or not detected) and quantitative (expression level) analysis indicated that many genes known to be involved in human neurological disorders were present and regulated in NHPs. A gene involved in dopamine metabolism (catechol-O-methyltransferase) was absent in macaque and marmoset. Glutamate receptor 2 was up-regulated, and transcription-associated genes were down-regulated in NHPs compared with humans. We demonstrate that transcript profiling of NHPs could provide comparative genomic data to validate and better focus experimental animal models of human neurological disorders.

Adult↗

PubMed2003

Dopaminergic neuronal loss and motor deficits in Caenorhabditis elegans overexpressing human alpha-synuclein.

Overexpression of human alpha-synuclein in model systems, including cultured neurons, drosophila and mice, leads to biochemical and pathological changes that mimic synucleopathies including Parkinson's disease. We have overexpressed both wild-type (WT) and mutant alanine53-->threonine (A53T) human alpha-synuclein by transgenic injection into Caenorhabditis elegans. Motor deficits were observed when either WT or A53T alpha-synuclein was overexpressed with a pan-neuronal or motor neuron promoter. Neuronal and dendritic loss were accelerated in all three sets of C. elegans dopaminergic neurons when human alpha-synuclein was overexpressed under the control of a dopaminergic neuron or pan-neuronal promoter, but not with a motor neuron promoter. There were no significant differences in neuronal loss between overexpressed WT and A53T forms or between worms of different ages (4 days, 10 days or 2 weeks). These results demonstrate neuronal and behavioral perturbations elicited by human alpha-synuclein in C. elegans that are dependent upon expression in specific neuron subtypes. This transgenic model in C. elegans, an invertebrate organism with excellent experimental resources for further genetic manipulation, may help facilitate dissection of pathophysiologic mechanisms of various synucleopathies.

Animals↗

PubMed2002

Regulation of TRKB surface expression by brain-derived neurotrophic factor and truncated TRKB isoforms.

Brain-derived neurotrophic factor (BDNF) signaling through its receptor TRKB modulates survival, differentiation, and activity of neurons. BDNF activates TRKB on the cell surface, which leads to the initiation of intracellular signaling cascades and different biological responses in neurons. Neuronal activity has been shown to regulate TRKB levels on the plasma membrane of neurons, but little is known about other factors affecting TRKB surface expression levels. We report here that BDNF regulates the cell surface levels of transfected or endogenously expressed full-length TRKB, depending on the exposure time in neuroblastoma cells and primary hippocampal neurons. BDNF rapidly increases TRKB surface expression levels in seconds, whereas treatment of cells with BDNF for a longer time (minutes to hours) leads to decreased TRKB surface levels. Coexpression of the full-length TRKB together with the truncated TRKB.T1 isoform results in decreased levels of full-length TRKB on the cell surface. This effect is specific to the T1 isoform, because coexpression of a kinase-dead TRKB mutant or another kinase domain-lacking TRKB form, truncated T-Shc, leads to increased TRKB surface levels. Our results suggest that regulation of TRKB surface expression levels by different factors is tightly controlled by complex mechanisms in active neurons.

Animals↗

PubMed2002

Chronic antipsychotic drug treatment induces long-lasting expression of fos and jun family genes and activator protein 1 complex in the rat prefrontal cortex.

We have characterized the effects of chronic clozapine and haloperidol treatments on the expression of fos (c-fos, fosB, fra-2) and jun (c-jun, junB, junD) family genes in the rat forebrain. The effects of chronic (17d) clozapine and haloperidol on mRNA expression were determined two hours, 24 hours, and six days after the last drug injection, and the DNA-binding activity of the activator protein-1 (AP-1) complex was studied after washout periods of 24 hours and six days. Chronic clozapine treatment with a 6 d washout period induced the expression of several fos and jun family genes in cortical regions, including the prefrontal cortex (PFC), and in the caudate putamen and nucleus accumbens. Moreover, the DNA-binding activity of the AP-1 complex was greatly increased in the anterior cingulate cortex-PFC in mobility shift assays already after 24 h, and remained increased after a 6d washout period. Chronic administration of haloperidol upregulated fos and jun family mRNA expression that was detectable 24 h and 6 d after cessation of the treatment mainly in the cortex. However, the DNA-binding activity of the AP-1 complex was not altered in the anterior cingulate cortex-PFC by chronic haloperidol administration at any of the time points studied. Thus, chronic treatments with clozapine and haloperidol induce a long-lasting enhancement of fos and jun family transcription factors that continues for several days after the cessation of the treatments in the cortex. These lasting effects might represent events that are potentially involved in the mechanisms of antipsychotic drug action.

Animals↗

PubMed2002

Expression profiling to understand actions of NMDA/glutamate receptor antagonists in rat brain.

Agents acting as noncompetitive N-methyl-D-aspartate (NMDA)/glutamate receptor antagonists induce the expression of several genes in limbic cortical regions, such as the cingulate, retrosplenial, and entorhinal cortices. These include important regulatory genes such as the neurotrophin brain-derived neurotrophic factor (BDNF), its receptor trkB, and c-fos. We applied expression profiling methods to find genes coregulated with BDNF following treatment with the prototypical NMDA/glutamate receptor antagonist MK-801. Expression profiling provides a useful technique for describing the molecular and transcriptional level events that follow various processes. We illustrate the utility of microarrays to find novel ESTs regulated by MK-801. We also used expression profiling with microarrays to characterize the levels of transcription factor cAMP response element modulator (CREM) and inducible cAMP early repressor (ICER) isoforms that are induced by MK-801. These factors may act as the eventual repressors for BDNF expression via competition and heterodimerization with phosphorylated CREB, a transcription factor important for BDNF expression. Finally, we find and confirm the regulation of Erp29, RTNI, and an ABC transporter by antagonism of NMDA/glutamate receptors as potential stress related molecules in brain. The emerging picture generated by using these expression profiling approaches, identifies several of what likely will be many molecules that take part in the complex events that occur during BDNF signaling mediated by blockade of NMDA/ glutamate receptors.

Animals↗

PubMed2002

Antipsychotic drug treatment induces differential gene expression in the rat cortex.

Antipsychotic drug treatment is known to modulate gene expression in experimental animals. In this study, candidate target genes for antipsychotic drug action were searched using microarrays after acute clozapine treatment (1, 6 and 24 h) in the rat prefrontal cortex. Microarray data clustering with a self-organizing map algorithm revealed differential expression of genes involved in presynaptic function following acute clozapine treatment. The differential expression of 35 genes most profoundly regulated in expression arrays was further examined using in situ hybridization following acute clozapine, and chronic clozapine and haloperidol treatments. Acute administration of clozapine regulated the expression of chromogranin A, synaptotagmin V and calcineurin A mRNAs in the cortex. Chronic clozapine treatment induced differential cortical expression of chromogranin A, son of sevenless (SoS) and Sec-1. Chronic treatment with haloperidol regulated the mRNA expression of inhibitor of DNA-binding 2 (ID-2) and Rab-12. Furthermore, the expression of visinin-like proteins-1, -2 and -3 was regulated by chronic drug treatments in various brain regions. Our data suggest that acute and chronic treatments with haloperidol and clozapine modulate the expression of genes involved in synaptic function and in regulation of intracellular Ca2+ in cortex.

Animals↗

PubMedDate not supplied

Analysis and visualization of gene expression data using self-organizing maps.

Cluster structure of gene expression data obtained from DNA microarrays is analyzed and visualized with the Self-Organizing Map (SOM) algorithm. The SOM forms a non-linear mapping of the data to a two-dimensional map grid that can be used as an exploratory data analysis tool for generating hypotheses on the relationships, and ultimately of the function of the genes. Similarity relationships within the data and cluster structures can be visualized and interpreted. The methods are demonstrated by computing a SOM of yeast genes. The relationships of known functional classes of genes are investigated by analyzing their distribution on the SOM, the cluster structure is visualized by the U-matrix method, and the clusters are characterized in terms of the properties of the expression profiles of the genes. Finally, it is shown that the SOM visualizes the similarity of genes in a more trustworthy way than two alternative methods, multidimensional scaling and hierarchical clustering.

Cluster Analysis↗