Reconceptualising resilience within a translational framework is supported by unique and brain-region specific transcriptional signatures in mice
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ABSTRACT: Chronic social defeat (CSD) in mice has been increasingly employed in experimental resilience research. Particularly, the degree of CSD-induced social avoidance is used to classify animals into resilient (socially non-avoidant) versus susceptible (avoidant). Inspired by human data pointing to threat-safety discrimination and responsiveness to extinction training of aversive memories as characteristics of resilient individuals, we here describe a translationally informed stratification which identified three phenotypic subgroups of mice following CSD: the Discriminating-avoiders, characterised by successful social threat-safety discrimination and successful extinction of social avoidance; the Indiscriminate-avoiders, showing fear generalisation, and the Non-avoiders (absence of social avoidance) displaying impaired conditioned learning. Furthermore, and supporting the biological validity of our approach, we uncovered subgroup-specific transcriptional signatures in classical fear conditioning and anxiety-related brain regions. Our reconceptualisation of resilience in mice refines the currently used dichotomous classification and contributes to advancing future translational approaches.
Project description:Social anxiety disorder is characterized by a persistent and abnormal fear and avoidance of social situations, but available treatment options are rather unspecific. Using an established mouse social fear conditioning (SFC) paradigm, we profiled gene expression and chromatin alterations after acquisition and extinction of social fear within the septum, a brain region important for social fear and social behaviors. We validated coding and non-coding RNAs and found specific isoforms of the long non-coding RNA Meg3 to be regulated depending on the success of social fear extinction. In vivo knockdown of specific Meg3 isoforms in conditioned mice resulted in impaired social fear extinction, as revealed by lower social investigation levels at the end of the extinction training, accompanied with increased baseline activity of the PI3K/AKT signaling pathway. Using ATAC-Seq and CUT&RUN, we characterized alterations in chromatin level after social fear extinction and identified Auts2 and Dclk3 as potential targets of Meg3.
Project description:Social interactions are critical components for the survival of mammalian biology and evolution. Dysregulation of social behavior often leads to psychopathologies such as social anxiety disorder, which is characterized by an intense fear and avoidance of social situations. Using the social fear conditioning (SFC) paradigm, we analyzed expression levels of miR-132-3p and miR-124-3p within the septum, a brain region essential for social behavior and fear, after acquisition and extinction of social fear. Functional in vivo approaches using pharmacology, functional inhibition of miR-132-3p, viral miR-132 overexpression and shRNA-mediated knockdown of miR-132-3p within oxytocin receptor positive neurons confirmed septal miR-132-3p to be involved in social fear extinction and the oxytocin-mediated reversal of social fear. Moreover, Argonaute-RNA-co-immunoprecipitation-microarray analysis and further target mRNA quantification, depicted growth differentiation factor-5 (GDF-5) to be involved in miR-132-3p-mediated regulation of social fear extinction. Local application of GDF-5 resulted in impaired social fear extinction, an effect which seems to be mediated by miR-132-3p. In summary, we show that septal miR-132-3p is functionally involved in social fear extinction learning and oxytocin-mediated reversal of social fear.
Project description:Trauma-related disorders arise from inefficient fear extinction and have immeasurable social and economic costs. Here, we characterized mouse phenotypes that spontaneously show individual differences in adaptive or maladaptive fear extinction and, before the traumatic experience, we found that specific morphological, electrophysiological and transcriptomic patterns of fear matrix pyramidal neurons predispose to trauma-related disorders. Finally, by using an optogenetic approach we showed the possibility to rescue the inefficient fear extinction activating fear matrix infralimbic pyramidal neurons
Project description:Extinction learning refers to the phenomenon that a previously learned response to an environmental stimulus, for example the expression of an aversive behavior upon exposure to a specific context, is reduced when the stimulus is repeatedly presented in the absence of a previously paired aversive event. Extinction of fear memories has been implicated with the treatment of anxiety disease but the molecular processes that underlie fear extinctionare only beginning to emerge. Here we show that fear extinction initiates up-regulation of hippocampal insulin-growth factor 2 (Igf2) and down-regulation of insulin-growth factor binding protein 7 (Igfbp7). In line with this observation we demonstrate that IGF2 facilitates fear extinction, while IGFBP7 impairs fear extinction in an IGF2-dependent manner. Furthermore, we identify one cellular substrate of altered IGF2-signaling during fear extinction. To this end we show that fear extinction-induced IGF2/IGFBP7-signaling promotes the survival of 17-19 day-old newborn hippocampal neurons. In conclusion, our data suggests that therapeutic strategies that enhance IGF2-signaling and adult neurogenesis might be suitable to treat disease linked to excessive fear memory. We employed mice to investigate fear extinction in the hippocampus-dependent contextual fear conditioning paradigm. To this end, male C57BL/6J mice were exposed to the fear conditioning box (context) followed by an electric foot-shock which elicits the acquisition of conditioned contextual fear. For extinction training animals were repeatedly reexposed to the conditioned context on consecutive days (24h interval) without receiving the footshockagain (extinction trial, E). This procedure eventually results in the decline of the aversive freezing behavior. Mice that were exposed to the conditioning context without receiving fear conditioning training served as control groups. To gain a better understanding of the molecular processes underlying fear extinction we performed a genome-wide analysis of the hippocampal transcriptome during fear extinction. In the employed paradigm fear extinction is a gradual process. To capture the longitudinal course of fear extinction we decided to perform hippocampal microarray analysis at two time points: (1) After the first extinction trial (E1) when animals display high levels of aversive freezing behavior and (2) at the extinction trial on which the freezing behavior was significantly reduced when compared to E1. This extinction trial, in the case of this experiment E5, we termed “extinction trial low freezing” (ELF). Mice that were exposed to the conditioning context without receiving fear conditioning training served as control groups (3). For all three groups we hybridized 5 samples (biological replicates).
Project description:Chronic social isolation (CSIS) generates two stress-related phenotypes, resilience and susceptibility. Although brain energy metabolism is important in regulating social behaviors, the molecular mechanisms underlying CSIS resilience remain unclear. To identify protein changes and altered biochemical pathways and processes for resilience to CSIS, prefrontal cortical cytosolic proteomic profiling was performed comparing CSIS-resilient with CSIS-susceptible and control rats. Potential predictive proteins discriminating between the CSIS-resilient and CSIS-susceptible groups were identified by support vector machine-based sequential feature selection and random forest-based feature importance scores. Predominantly decreased levels of glycolytic enzymes, G protein-coupled receptor proteins, Ras subfamily of GTPase proteins, and antioxidant proteins were found in CSIS-resilient vs. CSIS-susceptible groups. Altered levels of Gapdh and proteins involved in microtubule and cytoskeletal organization, and calcium-binding proteins were identified between the two phenotypes. These dynamic changes were accompanied by increased levels of proteins involved in GABA synthesis, the proteasome system, nitrogen metabolism, and chaperone-mediated protein folding. The overall ratio of significantly up- and down-regulated cytosolic proteins suggests adaptive cellular alterations as part of the stress-coping process specific for the CSIS-resilient phenotype.
Project description:An animal’s ability to cope with or succumb to deleterious effects of chronic psychological stress may be rooted in the brain’s immune responses manifested in microglial activity. Mice subjected to chronic social defeat (CSD) were categorized as susceptible (CSD-S) or resilient (CSD-R) based on behavioral phenotyping, and their microglial RNAs were isolated and analyzed by global gene expression microarrays. Microglia transcriptome from CSD-S mice was enriched for pathways that describe phases of CNS healing to sterile injury including, inflammation, oxidative stress, debris clearance, and wound resolution. Histochemical experiments confirmed the array predictions: CSD-S microglia showed elevated phagocytosis and oxidative stress, and the brains of CSD-S but not CSD-R or HC mice showed vascular leakage of intravenously injected fluorescent tracers. The results suggest that the inflammatory profile of CSD-S microglia may be precipitated by leakage of blood-born substances into brain parenchyma. We hypothesize that these CNS-centric responses contribute to the stress-susceptible behavioral phenotype.
Project description:Susceptibility or resilience to posttraumatic stress disorder (PTSD) depends on one’s ability to appropriately adjust synaptic plasticity for coping with the traumatic experience. Activity-regulated mRNA translation synthesizes plasticity-related proteins to support long-term synaptic changes and memory. Hence, cytoplasmic polyadenylation element-binding protein 3-knockout (CPEB3-KO) mice, showing dysregulated translation-associated synaptic rigidity, may be susceptible to PTSD-like behavior. Here, using a context-dependent auditory fear conditioning and extinction paradigm, we found that CPEB3-KO mice exhibited traumatic intensity-dependent PTSD-like fear memory. A genome-wide screen of CPEB3-bound transcripts revealed that Nr3c1, encoding glucocorticoid receptor (GR), was translationally suppressed by CPEB3. Thus, CPEB3-KO neurons with elevated GR expression exhibited increased corticosterone-induced calcium influx and decreased mRNA and protein levels of brain-derived neurotrophic factor (Bdnf). Moreover, the reduced expression of BDNF was associated with increased GR level during fear extinction in CPEB3-KO hippocampi. Intracerebroventricular delivery of BDNF before extinction training mitigated spontaneous fear intrusion in CPEB3-KO mice during extinction recall. Analysis of two GEO datasets revealed decreased transcriptomic expression of CPEB3 but not NR3C1 in peripheral blood mononuclear cells of humans with PTSD. Collectively, this study reveals that CPEB3, as a potential PTSD-risk gene, downregulates Nr3c1 translation to maintain proper GR-BDNF signaling for fear extinction.
Project description:ATP-dependent chromatin remodeling proteins are being implicated increasingly in the regulation of complex behaviors, including models of several psychiatric disorders. Here, we demonstrate that Baz1b, an accessory subunit of the ISWI family of chromatin remodeling complexes, is upregulated in the nucleus accumbens (NAc), a key brain reward region, in both chronic cocaine-treated mice and mice that are resilient to chronic social defeat stress. In contrast, no regulation is seen in mice that are susceptible to this chronic stress. Viral-mediated overexpression of Baz1b, along with its associated subunit Smarca5, in mouse NAc is sufficient to potentiate both rewarding responses to cocaine, including cocaine self-administration, and resilience to chronic social defeat stress. However, despite these similar, proreward behavioral effects, genome-wide mapping of BAZ1B in NAc revealed mostly distinct subsets of genes regulated by these chromatin remodeling proteins after chronic exposure to either cocaine or social stress. Together, these findings suggest important roles for BAZ1B and its associated chromatin remodeling complexes in NAc in the regulation of reward behaviors to distinct emotional stimuli and highlight the stimulus-specific nature of the actions of these regulatory proteins. BAZ1B (WSTF) ChIP-seq of mouse. Cocaine vs Saline, 3 biological replicates. In social defeat model: Normal control vs Susceptible vs Resilient, 3 biological replicates.
Project description:Extinction learning refers to the phenomenon that a previously learned response to an environmental stimulus, for example the expression of an aversive behavior upon exposure to a specific context, is reduced when the stimulus is repeatedly presented in the absence of a previously paired aversive event. Extinction of fear memories has been implicated with the treatment of anxiety disease but the molecular processes that underlie fear extinctionare only beginning to emerge. Here we show that fear extinction initiates up-regulation of hippocampal insulin-growth factor 2 (Igf2) and down-regulation of insulin-growth factor binding protein 7 (Igfbp7). In line with this observation we demonstrate that IGF2 facilitates fear extinction, while IGFBP7 impairs fear extinction in an IGF2-dependent manner. Furthermore, we identify one cellular substrate of altered IGF2-signaling during fear extinction. To this end we show that fear extinction-induced IGF2/IGFBP7-signaling promotes the survival of 17-19 day-old newborn hippocampal neurons. In conclusion, our data suggests that therapeutic strategies that enhance IGF2-signaling and adult neurogenesis might be suitable to treat disease linked to excessive fear memory.
Project description:To identify R-SDS-induced changes in gene expression profiles in the mPFC, we performed transcriptome analysis in the mPFC without or with R-SDS. We separately analyzed the data from susceptible mice, which showed social avoidance after R-SDS, and resilient mice, which did not, in addition to those from naïve mice.