European Neuropsychopharmacology (v.21, #1)

Shared changes in gene expression in frontal cortex of four genetically modified mouse models of depression by D. Hoyle; G. Juhasz; E. Aso; D. Chase; J. del Rio; V. Fabre; M. Hamon; L. Lanfumey; K.-P. Lesch; R. Maldonado; M.-A. Serra; T. Sharp; R. Tordera; C. Toro; J.F.W. Deakin (3-10).
This study aimed to identify whether genetic manipulation of four systems implicated in the pathogenesis of depression converge on shared molecular processes underpinning depression-like behaviour in mice. Altered 5HT function was modelled using the 5-HT transporter knock out mouse, impaired glucocorticoid receptor (GR) function using an antisense-induced knock down mouse, disrupted glutamate function using a heterozygous KO of the vesicular glutamate transporter 1 gene, and impaired cannabinoid signalling using the cannabinoid 1 receptor KO mouse. All 4 four genetically modified mice were previously shown to show exaggerated helpless behaviour compared to wild-type controls and variable degrees of anxiety and anhedonic behaviour. mRNA was extracted from frontal cortex and hybridised to Illumina microarrays. Combined contrast analysis was used to identify genes showing different patterns of up- and down-regulation across the 4 models. 1823 genes were differentially regulated. They were over-represented in gene ontology categories of metabolism, protein handling and synapse. In each model compared to wild-type mice of the same genetic background, a number of genes showed increased expression changes of > 10%, other genes showed decreases in each model. Most of the genes showed mixed effects. Several previous array findings were replicated. The results point to cellular stress and changes in post-synaptic remodelling as final common mechanisms of depression and resilience.
Keywords: Depression;; Gene expression;; Cellular stress;; Remodelling;

Genes differentially expressed in CB1 knockout mice: Involvement in the depressive-like phenotype by Ester Aso; Andrés Ozaita; Miquel-Àngel Serra; Rafael Maldonado (11-22).
Recent hypotheses to explain the neurobiology of depression underline the role played by stress in mood disorders. The endocannabinoid system is one of the major physiological substrates involved in emotional responses and stress. Thus, mice lacking CB1 receptor exhibit a depressive-like phenotype and an increased vulnerability to deleterious effects of stress. In order to identify possible molecular pathways contributing to this phenotype, we have examined the gene expression profile of mutants at basal conditions and after the exposure to repeated stress. Several genes coding for neurotransmitter receptors, neurotrophic factors, neuropeptides and hormones receptors were differentially expressed in CB1 knockout mice.
Keywords: CB1 cannabinoid receptor; Depression; Stress; Gene expression;

Chronic stress and impaired glutamate function elicit a depressive-like phenotype and common changes in gene expression in the mouse frontal cortex by R.M. Tordera; A.L. Garcia-García; N. Elizalde; V. Segura; E. Aso; E. Venzala; M.J. Ramírez; J. Del Rio (23-32).
Major depression might originate from both environmental and genetic risk factors. The environmental chronic mild stress (CMS) model mimics some environmental factors contributing to human depression and induces anhedonia and helplessness. Mice heterozygous for the synaptic vesicle protein (SVP) vesicular glutamate transporter 1 (VGLUT1) have been proposed as a genetic model of deficient glutamate function linked to depressive-like behaviour. Here, we aimed to identify, in these two experimental models, gene expression changes in the frontal cortex, common to stress and impaired glutamate function.Both VGLUT1+/− and CMS mice showed helpless and anhedonic-like behavior. Microarray studies in VGLUT1+/− mice revealed regulation of genes involved in apoptosis, neurogenesis, synaptic transmission, protein metabolic process or learning and memory. In addition, RT-PCR studies confirmed gene expression changes in several glutamate, GABA, dopamine and serotonin neurotransmitter receptors. On the other hand, CMS affected the regulation of 147 transcripts, some of them involved in response to stress and oxidoreductase activity. Interestingly, 52 genes were similarly regulated in both models. Specifically, a dowregulation in genes that promote cell proliferation (Anapc7), cell growth (CsnK1g1), cell survival (Hdac3), and inhibition of apoptosis (Dido1) was observed. Genes linked to cytoskeleton (Hspg2, Invs), psychiatric disorders (Grin1, MapK12) or an antioxidant enzyme (Gpx2) were also downregulated. Moreover, genes that inhibit the MAPK pathways (Dusp14), stimulate oxidative metabolism (Eif4a2) and enhance glutamate transmission (Rab8b) were upregulated.We suggest that these genes could form part of the altered “molecular context” underlying depressive-like behaviour in animal models. The clinical relevance of these findings is discussed.
Keywords: Chronic mild stress; VGLUT1; Major depression; Animal models; Gene expression;

Differential gene expression in mutant mice overexpressing or deficient in the serotonin transporter: A focus on urocortin 1 by Véronique Fabre; Renaud Massart; Adeline Rachalski; Katie Jennings; Andrew Brass; Trevor Sharp; Klaus-Peter Lesch; Laurence Lanfumey; Michel Hamon (33-44).
Transcriptome analyses were performed in the anterior raphe area of mutant mice deficient in the serotonin transporter (5-HTT KO) or overexpressing this protein (5-HTT TG), which exhibit opposite changes in anxiety-related behavior. Among genes with altered expression, the gene encoding the neuropeptide urocortin 1 was down-regulated in 5-HTT KO and up-regulated in 5-HTT TG mice. Expression of the gene encoding cocaine-and-amphetamine-related-peptide, which colocalizes with urocortin 1, was also increased in 5-HTT TG mutants. Real-time RT-PCR confirmed these data and immunoautoradiographic labeling showed that parallel changes in neuropeptide levels were confined to the non-preganglionic Edinger–Westphal nucleus. Thus, 5-HTT expression correlates with that of urocortin 1, suggesting that this peptide can be involved in the behavioral changes observed in 5-HTT mutant mice.
Keywords: Serotonin;; Serotonin transporter;; Urocortin1;; Gene expression;; Edinger–Westphal nucleus;; Anxiety;

Effect of chronic mild stress on hippocampal transcriptome in mice selected for high and low stress-induced analgesia and displaying different emotional behaviors by Pawel Lisowski; Grzegorz R. Juszczak; Joanna Goscik; Marek Wieczorek; Lech Zwierzchowski; Artur H. Swiergiel (45-62).
There is increasing evidence that mood disorders may derive from the impact of environmental pressure on genetically susceptible individuals. Stress-induced hippocampal plasticity has been implicated in depression. We studied hippocampal transcriptomes in strains of mice that display high (HA) and low (LA) swim stress-induced analgesia and that differ in emotional behaviors and responses to different classes of antidepressants. Chronic mild stress (CMS) affected expression of a number of genes common for both strains. CMS also produced strain specific changes in expression suggesting that hippocampal responses to stress depend on genotype. Considerably larger number of genes, biological processes, molecular functions, biochemical pathways, and gene networks were affected by CMS in LA than in HA mice. The results suggest that potential drug targets against detrimental effects of stress include glutamate transporters, and cholinergic, cholecystokinin (CCK), glucocorticoids, and thyroid hormones receptors. Furthermore, some biological processes evoked by stress and different between the strains, such as apoptosis, neurogenesis and chromatin modifications, may be responsible for the long-term, irreversible effects of stress and suggest a role for epigenetic regulation of mood related stress responses.
Keywords: Depression; Chronic stress; Hippocampus; Analgesia; Pain; Nociception; Gene expression; Microarrays; Mice;

Epistatic interaction of CREB1 and KCNJ6 on rumination and negative emotionality by Judit Lazary; Gabriella Juhasz; Ian M. Anderson; Christian P. Jacob; T. Trang Nguyen; Klaus-Peter Lesch; Andreas Reif; J.F. William Deakin; Gyorgy Bagdy (63-70).
G protein-activated K+ channel 2 (GIRK2) and cAMP-response element binding protein (CREB1) are involved in synaptic plasticity and their genes have been implicated depression and memory processing. Excessive rumination is a core cognitive feature of depression which is also present in remission. High scores on the Ruminative Response Scale (RRS) questionnaire are predictive of relapse and recurrence. Since rumination involves memory, we tested the hypothesis that variation in the genes encoding GIRK2 (KCNJ6) and CREB1 mechanisms would influence RRS scores. GIRK2 and CREB1 polymorphisms were studied in two independent samples (n = 651 and n = 1174) from the general population. Strongly significant interaction between the TT genotype of rs2070995 (located in KCNJ6) and the GG genotype of rs2253206 (located in CREB1) on RRS were found in both samples. These results were validated in an independent third sample (n = 565; individuals with personality disorders) showing significant main effect of the variants mentioned as well as significant interaction on a categorical diagnosis of Cluster C personality disorder (obsessional–compulsive, avoidant and dependent) in which rumination is a prominent feature. Our results suggest that genetic epistasis in post-receptor signaling pathways in memory systems may have relevance for depression and its treatment.
Keywords: Rumination;; GIRK2;; Genetic interaction;; Personality disorder;; Depression;

Evidence of female-specific glial deficits in the hippocampus in a mouse model of prenatal stress by Áine T. Behan; Daniel L.A. van den Hove; Lynn Mueller; Marlon J.A. Jetten; Harry W.M. Steinbusch; David R. Cotter; Jos Prickaerts (71-79).
Prenatal stress (PS) has been associated with an increased incidence of numerous neuropsychiatric disorders, including depression, anxiety, schizophrenia, and autism. To determine the effects of PS on hippocampal-dependent behaviour hippocampal morphology, we examined behavioural responses and hippocampal cytoarchitecture of a maternal restraint stress paradigm of PS in C57BL6 mice. Female offspring only showed a reduction in hippocampal glial count in the pyramidal layer following PS. Additionally, only PS females showed increased depressive-like behaviour with cognitive deficits predominantly in female offspring when compared to males. This data provides evidence for functional female-specific glial deficits within the hippocampus as a consequence of PS.
Keywords: Prenatal stress; Mice; Hippocampus; Sexual dimorphism; Psychiatric disorders;

Enhanced hippocampal long-term potentiation following repeated MDMA treatment in Dark–Agouti rats by Raffaella Morini; Boris Mlinar; Gilda Baccini; Renato Corradetti (80-91).
In rats and primates, (±)3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) produces both long-lasting damage to serotonergic axons and memory impairment.Our objective was to determine effects of neurotoxic dose of MDMA on long-term potentiation (LTP) in hippocampal area CA1 in Dark–Agouti (DA) rats. One week after neurotoxic MDMA treatment in vivo (12.5 mg/kg i.p., once a week, per three weeks), serotonergic deficit was evident in hippocampal slices as 56.3% reduction in 5-HT content (p = 0.04) and as 68.4% reduction in the effect of endogenous 5-HT release on synaptic neurotransmission (p < 0.01). In hippocampal slices from the same animals, LTP was on average 46% greater than that observed in sham-treated controls (42.9 ± 3.5%; n = 12 vs. 29.2 ± 3.2%; n = 12; p < 0.01). Non-neurotoxic dose of MDMA (12.5 mg/kg, i.p., one time) did not change LTP one week after the treatment, suggesting correlation between serotonergic deficit and enhanced synaptic plasticity. We conclude that MDMA-induced impairment of learning and memory is not a consequence of hippocampal LTP inhibition.
Keywords: MDMA; Serotonin; Long-term potentiation; LTP; Hippocampus; Dark–Agouti rats;

Chronic social defeat stress, a depression model in rats, reduced struggling in the forced swimming test dependent on a hedonic trait-stressed rats with high sucrose intake struggled less. Social defeat reduced brain regional energy metabolism, and this effect was also more pronounced in rats with high sucrose intake. A number of changes in gene expression were identified after social defeat stress, most notably the down-regulation of Gsk3b and Map1b. The majority of differences were between stress-susceptible and resilient rats. Conclusively, correlates of inter-individual differences in stress resilience can be identified both at gene expression and oxidative metabolism levels.
Keywords: Chronic social defeat stress; Oxidative energy metabolism; Cytochrome oxidase histochemistry; Animal models of depression; Sucrose intake; Genome-wide expression profiling;

Opposing alterations in anxiety and species-typical behaviours in serotonin transporter overexpressor and knockout mice by Samantha J. Line; Christopher Barkus; Clare Coyle; Katie A. Jennings; Robert M. Deacon; Klaus P. Lesch; Trevor Sharp; David M. Bannerman (108-116).
Human gene association studies have produced conflicting findings regarding the relationship between the 5-HT transporter (5-HTT) and anxiety. In the present study genetically modified mice were utilised to examine the effects of changes in 5-HTT expression on anxiety. In addition, the influence of 5-HTT expression on two innate “species-typical” behaviours (burrowing and marble burying) and body weight was explored. Across a range of models, 5-HTT overexpressing mice displayed reduced anxiety-like behaviour whilst 5-HTT knockout mice showed increased anxiety-like behaviour, compared to wildtype controls. In tests of species-typical behaviour 5-HTT overexpressing mice showed some facilitation whilst 5-HTT knockout mice were impaired. Reciprocal effects were also seen on body weight, as 5-HTT overexpressors were lighter and 5-HTT knockouts were heavier than wildtype controls. These findings show that variation in 5-HTT gene expression produces robust changes in anxiety and species-typical behaviour. Furthermore, the data add further support to findings that variation of 5-HTT expression in the human population is linked to changes in anxiety-related personality traits.
Keywords: 5-HT;; 5-HT transporter;; Anxiety;; Transgenic mice;; Body weight;

Variation in the human serotonin transporter gene (hSERT; 5-HTT) resulting in a life-long alteration in SERT function influences anxiety and the risk of developing affective disorders. The mechanisms underlying the influence of the hSERT gene on these phenotypes remain unclear but may involve altered 5-HT receptor function. Here we characterise the cerebral metabolic response to 5-HT2A/C receptor activation in two transgenic mouse models of altered SERT function, SERT knock-out (SERT KO) and hSERT over-expressing (hSERT OE) mice, to test the hypothesis that genetically mediated variability in SERT expression alters 5-HT2A/C function. We found that a constitutive increase in SERT expression (hSERT OE) enhanced, whereas a constitutive decrease in SERT expression (SERT KO) attenuated, 5-HT2A/C function. Therefore, altered 5-HT2A/C receptor functioning in response to hSERT gene variation may contribute to its influence on affective phenotypes.
Keywords: Serotonin; Serotonin transporter; Transgenic mice; 5-HT2A/C receptor; 2-Deoxyglucose imaging; Brain function;

The HTR1A and HTR1B receptor genes influence stress-related information processing by Krisztina Mekli; Antony Payton; Fabio Miyajima; Hazel Platt; Emma Thomas; Darragh Downey; Kathryn Lloyd-Williams; Diana Chase; Zoltan G. Toth; Rebecca Elliott; William E. Ollier; Ian M. Anderson; J.F. William Deakin; Gyorgy Bagdy; Gabriella Juhasz (129-139).
The serotonergic system has been widely implicated in stress related psychiatric disorders such as depression and anxiety. We investigated the possible association between depression and anxiety scores and SNPs within the HTR1A and HTR1B genes in a population sample (n = 1387). There was no direct SNP-phenotype association, but in interaction with recent stressful life events rs6295 G, rs878567 T alleles and rs6296 C alleles were associated with significantly higher symptom scores. A subset of control subjects (n = 101) took part in a computerised face emotion processing task. Healthy rs6295 GG carriers did not show an affective bias to perceive more negative emotions but reacted more quickly to fearful faces. Thus we conclude that the serotonin-1A receptor conveys vulnerability to these psychiatric disorders by modulating threat-related information processing. Our results extend previous findings of an interaction between stressful life events and the serotonin transporter gene to two other genes in the serotonergic pathway and emphasise the possible role of increased threat-related information processing as an intermediate phenotype.
Keywords: Stress; HTR1A; HTR1B; Depression; Anxiety;

The effect of acute citalopram on face emotion processing in remitted depression: A pharmacoMRI study by Ian M. Anderson; Gabriella Juhasz; Emma Thomas; Darragh Downey; Shane McKie; J.F. William Deakin; Rebecca Elliott (140-148).
Both reduced serotonergic (5-HT) function and negative emotional biases have been associated with vulnerability to depression. In order to investigate whether these might be related we examined 5-HT modulation of affective processing in 14 remitted depressed subjects compared with 12 never depressed controls matched for age and sex. Participants underwent function magnetic resonance imaging (fMRI) during a covert face emotion task with and without intravenous citalopram (7.5 mg) pretreatment. Compared with viewing neutral faces, and irrespective of group, citalopram enhanced left anterior cingulate blood oxygen level dependent (BOLD) response to happy faces, right posterior insula and right lateral orbitofrontal responses to sad faces, and reduced amygdala responses bilaterally to fearful faces. In controls, relative to remitted depressed subjects, citalopram increased bilateral hippocampal responses to happy faces and increased right anterior insula response to sad faces. These findings were not accounted for by changes in BOLD responses to viewing neutral faces. These results are consistent with previous findings showing 5-HT modulation of affective processing; differences found in previously depressed participants compared with controls may contribute to emotional processing biases underlying vulnerability to depressive relapse.
Keywords: Remitted depression; fMRI; PharmacoMRI; Face emotion processing; Citalopram;

Contents (149-150).