Kwang H. Choi

Gene Expression and Genetic Variation Data Implicate PCLO in Bipolar Disorder

BACKGROUND Genetic variation may contribute to differential gene expression in the brain of individuals with psychiatric disorders. To test this hypothesis, we identified genes that were differentially expressed in individuals with bipolar disorder, along with nearby single nucleotide polymorphisms (SNPs) that were associated with expression of the same genes. We then tested these SNPs for association with bipolar disorder in large case-control samples. METHODS We used the Stanley Genomics Database to extract gene expression and SNP microarray data from individuals with bipolar disorder (n = 40) and unaffected controls (n = 43). We identified 367 genes that were differentially expressed in the prefrontal cortex of cases vs. controls (fold change > 1.3 and FDR q-value < .05) and 45 nearby SNPs that were associated with expression of those same genes (FDR q-value < .05). We tested these SNPs for association with bipolar disorder in a meta-analysis of genome-wide association studies (GWAS) including 4,936 cases and 6,654 healthy controls. RESULTS We identified 45 SNPs that were associated with expression of differentially expressed genes, including HBS1L (15 SNPs), HLA-DPB1 (15 SNPs), AMFR (8 SNPs), PCLO (2 SNPs) and WDR41 (2 SNPs). Of these, one SNP (rs13438494), in an intron of the piccolo (PCLO) gene, was significantly associated with bipolar disorder (FDR adjusted p < .05) in the meta-analysis of GWAS. CONCLUSIONS These results support the previous findings implicating PCLO in mood disorders and demonstrate the utility of combining gene expression and genetic variation data to improve our understanding of the genetic contribution to bipolar disorder.

Analysis of Copy Number Variations in Brain DNA from Patients with Schizophrenia and Other Psychiatric Disorders

BACKGROUND Clinical studies have identified several regions of the genome with copy number variations (CNVs) associated with diverse neurodevelopmental behavioral disorders. METHODS We analyzed 1 million (M) single nucleotide polymorphism genotype arrays for evidence of previously reported recurrent CNVs and enriched genome-wide CNV burden in DNA from 600 brains, including 441 individuals with various psychiatric diagnoses. We explored gene expression in the dorsolateral prefrontal cortex in selected cases with CNVs and in other subjects with Illumina BeadArrays (568 subjects in total) and additionally in 66-92 subjects with quantitative real-time polymerase chain reaction. RESULTS The CNVs in previously reported genomic regions were identified in 4 of 193 patients with the diagnosis of schizophrenia (1q21.1, 11q25, 15q11.2, 22q11), 4 of 238 patients with mood disorders (11q25, 15q11.2, 22q11), and 1 of 10 patients with autism (2p16.3). No evidence of increased genome-wide CNV burden was observed in cases with schizophrenia or mood disorders, although the study is underpowered to observe rare events. Messenger RNA expression patterns suggested incomplete molecular penetrance of observed CNVs. CONCLUSIONS Our data confirm in brain DNA the presence of certain recurrent CNVs in a small percentage of patients with psychiatric diagnoses.

Effects of typical and atypical antipsychotic drugs on gene expression profiles in the liver of schizophrenia subjects

BackgroundAlthough much progress has been made on antipsychotic drug development, precise mechanisms behind the action of typical and atypical antipsychotics are poorly understood.MethodsWe performed genome-wide expression profiling to study effects of typical antipsychotics and atypical antipsychotics in the postmortem liver of schizophrenia patients using microarrays (Affymetrix U133 plus2.0). We classified the subjects into typical antipsychotics (n = 24) or atypical antipsychotics (n = 26) based on their medication history, and compared gene expression profiles with unaffected controls (n = 34). We further analyzed individual antipsychotic effects on gene expression by sub-classifying the subjects into four major antipsychotic groups including haloperidol, phenothiazines, olanzapine and risperidone.ResultsTypical antipsychotics affected genes associated with nuclear protein, stress responses and phosphorylation, whereas atypical antipsychotics affected genes associated with golgi/endoplasmic reticulum and cytoplasm transport. Comparison between typical antipsychotics and atypical antipsychotics further identified genes associated with lipid metabolism and mitochondrial function. Analyses on individual antipsychotics revealed a set of genes (151 transcripts, FDR adjusted p < 0.05) that are differentially regulated by four antipsychotics, particularly by phenothiazines, in the liver of schizophrenia patients.ConclusionTypical antipsychotics and atypical antipsychotics affect different genes and biological function in the liver. Typical antipsychotic phenothiazines exert robust effects on gene expression in the liver that may lead to liver toxicity. The genes found in the current study may benefit antipsychotic drug development with better therapeutic and side effect profiles.

An Integrative Genomic Study Implicates the Postsynaptic Density in the Pathogenesis of Bipolar Disorder.

Genome-wide association studies (GWAS) have identified several common variants associated with bipolar disorder (BD), but the biological meaning of these findings remains unclear. Integrative genomics—the integration of GWAS signals with gene expression data—may illuminate genes and gene networks that have key roles in the pathogenesis of BD. We applied weighted gene co-expression network analysis (WGCNA), which exploits patterns of co-expression among genes, to brain transcriptome data obtained by sequencing of poly-A RNA derived from postmortem dorsolateral prefrontal cortex from people with BD, along with age- and sex-matched controls. WGCNA identified 33 gene modules. Many of the modules corresponded closely to those previously reported in human cortex. Three modules were associated with BD, enriched for genes differentially expressed in BD, and also enriched for signals in prior GWAS of BD. Functional analysis of genes within these modules revealed significant enrichment of several functionally related sets of genes, especially those involved in the postsynaptic density (PSD). These results provide convergent support for the hypothesis that dysregulation of genes involved in the PSD is a key factor in the pathogenesis of BD. If replicated in larger samples, these findings could point toward new therapeutic targets for BD.

Expression Profiles of Mitochondrial Genes in the Frontal Cortex and the Caudate Nucleus of Developing Humans and Mice Selectively Bred for High and Low Fear

A growing body of evidence suggests that mitochondrial function may be important in brain development and psychiatric disorders. However, detailed expression profiles of those genes in human brain development and fear-related behavior remain unclear. Using microarray data available from the public domain and the Gene Ontology analysis, we identified the genes and the functional categories associated with chronological age in the prefrontal cortex (PFC) and the caudate nucleus (CN) of psychiatrically normal humans ranging in age from birth to 50 years. Among those, we found that a substantial number of genes in the PFC (115) and the CN (117) are associated with the GO term: mitochondrion (FDR qv <0.05). A greater number of the genes in the PFC (91%) than the genes in the CN (62%) showed a linear increase in expression during postnatal development. Using quantitative PCR, we validated the developmental expression pattern of four genes including monoamine oxidase B (MAOB), NADH dehydrogenase flavoprotein (NDUFV1), mitochondrial uncoupling protein 5 (SLC25A14) and tubulin beta-3 chain (TUBB3). In mice, overall developmental expression pattern of MAOB, SLC25A14 and TUBB3 in the PFC were comparable to the pattern observed in humans (p<0.05). However, mice selectively bred for high fear did not exhibit normal developmental changes of MAOB and TUBB3. These findings suggest that the genes associated with mitochondrial function in the PFC play a significant role in brain development and fear-related behavior.

Dose-response characteristics of intravenous ketamine on dissociative stereotypy, locomotion, sensorimotor gating, and nociception in male Sprague-Dawley rats

ABSTRACT Clinicians administer subanesthetic intravenous (IV) ketamine infusions for treatment of refractory depression, chronic pain, and post‐traumatic stress disorder in humans. However, ketamine is administered via the subcutaneous (SC) or intraperitoneal (IP) routes to rodents in most pre‐clinical research, which may limit translational application. The present study characterized the dose‐response of a subanesthetic IV ketamine bolus (2 and 5 mg/kg) and 1‐h infusion (5, 10, and 20 mg/kg/h) on dissociative stereotypy, locomotion, sensorimotor gating, and thermal nociception in male Sprague‐Dawley rats. The secondary aim was to measure ketamine and norketamine plasma concentrations following IV ketamine bolus at 1, 20, and 50 min and at the conclusion of the 1‐h infusion using liquid chromatography/mass spectrometry. The results showed that ketamine bolus and infusions produced dose‐dependent dissociative stereotypy. Bolus (2 and 5 mg/kg) and 20 mg/kg/h infusion increased locomotor activity while 5 mg/kg/h infusion decreased locomotor activity. Both 10 and 20 mg/kg/h infusions reduced the acoustic startle reflex, while 5 mg/kg bolus and 20 mg/kg/h infusion impaired pre‐pulse inhibition. Ketamine 5 mg/kg bolus and the 10 and 20 mg/kg/h infusions induced significant and prolonged antinociception to the hotplate test. Plasma concentrations of ketamine decreased quickly after bolus while norketamine levels increased from 1 to 20 min and plateaued from 20 to 50 min. The peak ketamine plasma concentrations [ng/ml] were similar between 5 mg/kg bolus [4100] vs. 20 mg/kg/h infusion [3900], and 2 mg/kg bolus [1700] vs. 10 mg/kg/h infusion [1500]. These results support the findings from previous ketamine injection studies and further validate the feasibility of administering subanesthetic doses of IV ketamine infusion to rats for neuropharmacological studies. HighlightsIntravenous (IV) ketamine is a valid administration route for rat behavior studies.Ketamine IV bolus induced hyper‐locomotion, impaired PPI, and antinociception.Ketamine IV infusion induced hypo & hyper‐locomotion and extended antinociception.A high‐dose ketamine infusion reduced acoustic startle and impaired PPI.Plasma ketamine concentrations rapidly declined after bolus and infusion administration.

Effects of isoflurane anesthesia and intravenous morphine self‐administration on regional glucose metabolism ([18F]FDG PET) of male Sprague‐Dawley rats

Although certain drugs of abuse are known to disrupt brain glucose metabolism (BGluM), the effects of opiates on BGluM are not well characterized. Moreover, preclinical positron emission tomography (PET) studies anesthetize animals during the scan, which limits clinical applications. We investigated the effects of (i) isoflurane anesthesia and (ii) intravenous morphine self‐administration (MSA) on BGluM in rats. Jugular vein cannulated adult male Sprague‐Dawley rats self‐administered either saline (SSA) or morphine (0.5 mg/kg/infusion, 4 h/day for 12 days). All animals were scanned twice with [18F]‐fluoro‐deoxy‐glucose (FDG)‐PET/CT at a baseline and at 2‐day withdrawal from self‐administration. After the IV injection of FDG, one batch of animals (n = 14) was anesthetized with isoflurane and the other batch (n = 16) was kept awake during the FDG uptake (45 min). After FDG uptake, all animals were anesthetized in order to perform a PET/CT scan (30 min). Isoflurane anesthesia, as compared to the awake condition, reduced BGluM in the olfactory, cortex, thalamus, and basal ganglia, while increasing BGluM in the midbrain, hypothalamus, hippocampus, and cerebellum. Morphine self‐administered animals exhibited withdrawal signs (piloerection and increased defecation), drug seeking, and locomotor stimulation to morphine (0.5 mg/kg) during the 2 day withdrawal. The BGluM in the striatum was increased in the MSA group as compared to the SSA group; this effect was observed only in the isoflurane anesthesia, not the awake condition. These findings suggest that the choice of the FDG uptake condition may be important in preclinical PET studies and increased BGluM in the striatum may be associated with opiate seeking in withdrawal.

Altered Acoustic Startle Reflex, Prepulse Inhibition, and Peripheral Brain-Derived Neurotrophic Factor in Morphine Self-Administered Rats

Abstract Background: Previous studies suggested that opiate withdrawal may increase anxiety and disrupt brain-derived neurotrophic factor function, but the effects of i.v. morphine self-administration on these measures remain unclear. Methods: Adult male Sprague-Dawley rats were implanted with a catheter in the jugular vein. After 1 week of recovery, the animals were allowed to self-administer either i.v. morphine (0.5 mg/kg per infusion, 4 h/d) or saline in the operant conditioning chambers. The acoustic startle reflex and prepulse inhibition were measured at a baseline and on self-administration days 1, 3, 5, and 7 (1- and 3-hour withdrawal). Blood samples were collected on self-administration days 3, 5, and 7 from separate cohorts of animals, and the levels of brain-derived neurotrophic factor and corticosterone were assayed using the enzyme-linked immunosorbent assay method. Results: Compared with the saline group, the morphine self-administration group showed hyper-locomotor activity and reduced defecation during the self-administration. The morphine self-administration increased acoustic startle reflex at 1-hour but not 3-hour withdrawal from morphine and disrupted prepulse inhibition at 3-hour but not 1-hour withdrawal. The blood brain-derived neurotrophic factor levels were decreased in the morphine self-administration group at self-administration days 3 and 5, while the corticosterone levels remained unchanged throughout the study. Conclusions: The current findings suggest that spontaneous withdrawal from i.v. morphine self-administration may have transient effects on acoustic startle, sensorimotor gating, and peripheral brain-derived neurotrophic factor levels, and these changes may contribute to the adverse effects of opiate withdrawal.

Individual differences in initial morphine sensitivity as a predictor for the development of opiate addiction in rats

Individuals report a wide range of analgesia to similar doses of opiates, and not all opiate users become addicted. This suggests that there may be certain predispositions that influence one to develop opiate addiction. We investigated the relationship between the individual differences in initial morphine sensitivity and the subsequent development of opiate addiction-like behavior using a hot plate test and an intravenous morphine self-administration (MSA) paradigm in rats. Using a median split of initial morphine antinociception, animals were defined as low antinociception (LA) and high antinociception (HA) groups. Thus, the LA group represents the animals that were less sensitive to initial morphine antinociception as compared to those of the HA group. The animals were allowed to self-administer either saline or morphine (0.5mg/kg/infusion, 4hr/day) 5days per week for 3 weeks. Spontaneous locomotor activity was measured on self-administration days 10 and 15. Individual differences in initial morphine sensitivity were not correlated with the amount of morphine self-administered by the animals on day 1. In the second-week of MSA, the LA group exhibited increased morphine intake and locomotor hyperactivity as compared to those of the HA group. Therefore, certain animals that are less sensitive to initial morphine antinociception may be susceptible to developing opiate addiction. The current findings may have clinical implications for future research on the biological mechanisms of opiate addiction and preclinical medication development.

The role of endocannabinoid function in posttraumatic stress disorder: Modulating the risk phenotype and rendering effects of trauma

Posttraumatic stress disorder (PTSD) is a debilitating consequence of trauma in military and civilian settings. Substantial evidence implicates endocannabinoid function in three dimensions associated with risk for the disorder and in the etiology of essential symptoms. Negative (fear-avoidance) and positive (approach-reward) systems, and a dispositional dimension of control, modulate risk for PTSD and rely heavily on endocannabinoid function. Moreover, animal models associate an exaggerated fear response, characteristic of PTSD, with compromised endocannabinoid signaling, while plasticity in the same system renders effects of trauma in early life, fundamentally altering the stress response. Further implicating the endocannabinoid system, PTSD often co-occurs with cannabis use. Cannabis appears to alleviate negative affect states and symptoms of PTSD, possibly by normalizing endocannabinoid function. While this diverse evidence recommends the endocannabinoid system as a therapeutic target, it also reveals complexities that complicate efforts to develop such therapies. Scientific analysis of endocannabinoid function in PTSD will facilitate these efforts, while also informing a developing discussion on medical and recreational use of marijuana.