1 661 150 BLOOD MIR-144-3P: A NOVEL DIAGNOSTIC AND THERAPEUTIC TOOL FOR DEPRESSION. MAJOR DEPRESSIVE DISORDER (MDD) IS THE LEADING CAUSE OF DISABILITY WORLDWIDE. THERE IS AN URGENT NEED FOR OBJECTIVE BIOMARKERS TO DIAGNOSE THIS HIGHLY HETEROGENEOUS SYNDROME, ASSIGN TREATMENT, AND EVALUATE TREATMENT RESPONSE AND PROGNOSIS. MICRORNAS (MIRNAS) ARE SHORT NON-CODING RNAS, WHICH ARE DETECTED IN BODY FLUIDS THAT HAVE EMERGED AS POTENTIAL BIOMARKERS OF MANY DISEASE CONDITIONS. THE PRESENT STUDY EXPLORED THE POTENTIAL USE OF MIRNAS AS BIOMARKERS FOR MDD AND ITS TREATMENT. WE PROFILED THE EXPRESSION LEVELS OF CIRCULATING BLOOD MIRNAS FROM MICE THAT WERE COLLECTED BEFORE AND AFTER EXPOSURE TO CHRONIC SOCIAL DEFEAT STRESS (CSDS), AN EXTENSIVELY VALIDATED MOUSE MODEL USED TO STUDY DEPRESSION, AS WELL AS AFTER EITHER REPEATED IMIPRAMINE OR SINGLE-DOSE KETAMINE TREATMENT. WE OBSERVED ROBUST DIFFERENCES IN BLOOD MIRNA SIGNATURES BETWEEN STRESS-RESILIENT AND STRESS-SUSCEPTIBLE MICE AFTER AN INCUBATION PERIOD, BUT NOT IMMEDIATELY AFTER EXPOSURE TO THE STRESS. FURTHERMORE, KETAMINE TREATMENT WAS MORE EFFECTIVE THAN IMIPRAMINE AT RE-ESTABLISHING BASELINE MIRNA EXPRESSION LEVELS, BUT ONLY IN MICE THAT RESPONDED BEHAVIORALLY TO THE DRUG. WE IDENTIFIED THE RED BLOOD CELL-SPECIFIC MIR-144-3P AS A CANDIDATE BIOMARKER TO AID DEPRESSION DIAGNOSIS AND PREDICT KETAMINE TREATMENT RESPONSE IN STRESS-SUSCEPTIBLE MICE AND MDD PATIENTS. LASTLY, WE DEMONSTRATE THAT SYSTEMIC KNOCKDOWN OF MIR-144-3P, VIA SUBCUTANEOUS ADMINISTRATION OF A SPECIFIC ANTAGOMIR, IS SUFFICIENT TO REDUCE THE DEPRESSION-RELATED PHENOTYPE IN STRESS-SUSCEPTIBLE MICE. RNA-SEQUENCING ANALYSIS OF BLOOD AFTER SUCH MIR-144-3P KNOCKDOWN REVEALED A BLUNTED TRANSCRIPTIONAL STRESS SIGNATURE AS WELL. THESE FINDINGS IDENTIFY MIR-144-3P AS A NOVEL TARGET FOR DIAGNOSIS OF MDD AS WELL AS FOR ANTIDEPRESSANT TREATMENT, AND ENHANCE OUR UNDERSTANDING OF EPIGENETIC PROCESSES ASSOCIATED WITH DEPRESSION. 2022 2 990 40 CHRONIC SOCIAL STRESS INDUCES DNA METHYLATION CHANGES AT AN EVOLUTIONARY CONSERVED INTERGENIC REGION IN CHROMOSOME X. CHRONIC STRESS RESULTING FROM PROLONGED EXPOSURE TO NEGATIVE LIFE EVENTS INCREASES THE RISK OF MOOD AND ANXIETY DISORDERS. ALTHOUGH CHRONIC STRESS CAN CHANGE GENE EXPRESSION RELEVANT FOR BEHAVIOR, MOLECULAR REGULATORS OF THIS CHANGE HAVE NOT BEEN FULLY DETERMINED. ONE PROCESS THAT COULD PLAY A ROLE IS DNA METHYLATION, AN EPIGENETIC PROCESS WHEREBY A METHYL GROUP IS ADDED ONTO NUCLEOTIDES, PREDOMINANTLY CYTOSINE IN THE CPG CONTEXT, AND WHICH CAN BE INDUCED BY CHRONIC STRESS. IT IS UNKNOWN TO WHAT EXTENT CHRONIC SOCIAL DEFEAT, A MODEL OF HUMAN SOCIAL STRESS, INFLUENCES DNA METHYLATION PATTERNS ACROSS THE GENOME. OUR STUDY ADDRESSED THIS QUESTION BY USING A TARGETED-CAPTURE APPROACH CALLED METHYL-SEQ TO INVESTIGATE DNA METHYLATION PATTERNS OF THE DENTATE GYRUS AT PUTATIVE REGULATORY REGIONS ACROSS THE MOUSE GENOME FROM MICE EXPOSED TO 14 DAYS OF SOCIAL DEFEAT. FINDINGS WERE REPLICATED IN INDEPENDENT COHORTS BY BISULFITE-PYROSEQUENCING. TWO DIFFERENTIALLY METHYLATED REGIONS (DMRS) WERE IDENTIFIED. ONE DMR WAS LOCATED AT INTRON 9 OF DROSHA, AND IT SHOWED REDUCED METHYLATION IN STRESSED MICE. THIS OBSERVATION REPLICATED IN ONE OF TWO INDEPENDENT COHORTS. A SECOND DMR WAS IDENTIFIED AT AN INTERGENIC REGION OF CHROMOSOME X, AND METHYLATION IN THIS REGION WAS INCREASED IN STRESSED MICE. THIS METHYLATION DIFFERENCE REPLICATED IN TWO INDEPENDENT COHORTS AND IN MAJOR DEPRESSIVE DISORDER (MDD) POSTMORTEM BRAINS. THESE RESULTS HIGHLIGHT A REGION NOT PREVIOUSLY KNOWN TO BE DIFFERENTIALLY METHYLATED BY CHRONIC SOCIAL DEFEAT STRESS AND WHICH MAY BE INVOLVED IN MDD. 2018 3 4093 35 MATERNAL SEPARATION FOLLOWED BY CHRONIC MILD STRESS IN ADULTHOOD IS ASSOCIATED WITH CONCERTED EPIGENETIC REGULATION OF AP-1 COMPLEX GENES. DEPRESSION IS ONE OF THE MOST PREVALENT MENTAL DISEASES WORLDWIDE. PATIENTS WITH PSYCHIATRIC DISEASES OFTEN HAVE A HISTORY OF CHILDHOOD NEGLECT, INDICATING THAT EARLY-LIFE EXPERIENCES PREDISPOSE TO PSYCHIATRIC DISEASES IN ADULTHOOD. TWO STRONG MODELS WERE USED IN THE PRESENT STUDY: THE MATERNAL SEPARATION/EARLY DEPRIVATION MODEL (MS) AND THE CHRONIC MILD STRESS MODEL (CMS). IN BOTH MODELS, WE FOUND CHANGES IN THE EXPRESSION OF A NUMBER OF GENES SUCH AS CREB AND NPY. STRIKINGLY, THERE WAS A CLEAR REGULATION OF EXPRESSION OF FOUR GENES INVOLVED IN THE AP-1 COMPLEX: C-FOS, C-JUN, FOSB, AND JUN-B. INTERESTINGLY, DIFFERENT EXPRESSION LEVELS WERE OBSERVED DEPENDING ON THE MODEL, WHEREAS THE COMBINATION OF THE MODELS RESULTED IN A NORMAL LEVEL OF GENE EXPRESSION. THE EFFECTS OF MS AND CMS ON GENE EXPRESSION WERE ASSOCIATED WITH DISTINCT HISTONE METHYLATION/ACETYLATION PATTERNS OF ALL FOUR GENES. THE EPIGENETIC CHANGES, LIKE GENE EXPRESSION, WERE ALSO DEPENDENT ON THE SPECIFIC STRESSOR OR THEIR COMBINATION. THE OBTAINED RESULTS SUGGEST THAT SINGLE LIFE EVENTS LEAVE A MARK ON GENE EXPRESSION AND THE EPIGENETIC SIGNATURE OF GENE PROMOTERS, BUT A COMBINATION OF DIFFERENT STRESSORS AT DIFFERENT LIFE STAGES CAN FURTHER CHANGE GENE EXPRESSION THROUGH EPIGENETIC FACTORS, POSSIBLY CAUSING THE LONG-LASTING ADVERSE EFFECTS OF STRESS. 2021 4 3493 46 IDENTIFICATION OF KEY GENES, PATHWAYS, AND MIRNA/MRNA REGULATORY NETWORKS OF CUMS-INDUCED DEPRESSION IN NUCLEUS ACCUMBENS BY INTEGRATED BIOINFORMATICS ANALYSIS. INTRODUCTION: MAJOR DEPRESSIVE DISORDER (MDD) IS A RECURRENT, DEVASTATING MENTAL DISORDER, WHICH AFFECTS >350 MILLION PEOPLE WORLDWIDE, AND EXERTS SUBSTANTIAL PUBLIC HEALTH AND FINANCIAL COSTS TO SOCIETY. THUS, THERE IS A SIGNIFICANT NEED TO DISCOVER INNOVATIVE THERAPEUTICS TO TREAT DEPRESSION EFFICIENTLY. STRESS-INDUCED DYSFUNCTION IN THE SUBTYPE OF NEURONAL CELLS AND THE CHANGE OF SYNAPTIC PLASTICITY AND STRUCTURAL PLASTICITY OF NUCLEUS ACCUMBENS (NAC) ARE IMPLICATED IN DEPRESSION SYMPTOMOLOGY. HOWEVER, THE MOLECULAR AND EPIGENETIC MECHANISMS AND STRESSES TO THE NAC PATHOLOGICAL CHANGES IN DEPRESSION REMAIN ELUSIVE. MATERIALS AND METHODS: IN THIS STUDY, TREATMENT GROUP MICE WERE TREATED CONTINUALLY WITH THE CHRONIC UNPREDICTABLE MILD STRESS (CUMS) UNTIL EXPRESSION OF DEPRESSION-LIKE BEHAVIORS WERE FOUND. DEPRESSION WAS CONFIRMED WITH SUCROSE PREFERENCE, NOVELTY-SUPPRESSED FEEDING, FORCED SWIMMING, AND TAIL SUSPENSION TESTS. WE APPLIED HIGH-THROUGHPUT RNA SEQUENCING TO ASSESS MICRORNA EXPRESSION AND TRANSCRIPTIONAL PROFILES IN THE NAC TISSUE FROM DEPRESSION-LIKE BEHAVIORS MICE AND CONTROL MICE. THE REGULATORY NETWORK OF MIRNAS/MRNAS WAS CONSTRUCTED BASED ON THE HIGH-THROUGHPUT RNA SEQUENCE AND BIOINFORMATICS SOFTWARE PREDICTIONS. RESULTS: A TOTAL OF 17 MIRNAS AND 10 MRNAS WERE SIGNIFICANTLY UPREGULATED IN THE NAC OF CUMS-INDUCED MICE WITH DEPRESSION-LIKE BEHAVIORS, AND 12 MIRNAS AND 29 MRNAS WERE DOWNREGULATED. A SERIES OF BIOINFORMATICS ANALYSES SHOWED THAT THESE ALTERED MIRNAS PREDICTED TARGET MRNA AND DIFFERENTIALLY EXPRESSED MRNAS WERE SIGNIFICANTLY ENRICHED IN THE MAPK SIGNALING PATHWAY, GABAERGIC SYNAPSE, DOPAMINERGIC SYNAPSE, CYTOKINE-CYTOKINE RECEPTOR INTERACTION, AXON GUIDANCE, REGULATION OF AUTOPHAGY, AND SO ON. FURTHERMORE, DUAL LUCIFERASE REPORT ASSAY AND QRT-PCR RESULTS VALIDATED THE MIRNA/MRNA REGULATORY NETWORK. CONCLUSION: THE DETERIORATIONS OF GABAERGIC SYNAPSES, DOPAMINERGIC SYNAPSES, NEUROTRANSMITTER SYNTHESIS, AS WELL AS AUTOPHAGY-ASSOCIATED APOPTOTIC PATHWAY ARE ASSOCIATED WITH THE MOLECULAR PATHOLOGICAL MECHANISM OF CUMS-INDUCED DEPRESSION. 2019 5 6174 50 THE HIPPOCAMPUS, NEUROTROPHIC FACTORS AND DEPRESSION: POSSIBLE IMPLICATIONS FOR THE PHARMACOTHERAPY OF DEPRESSION. DEPRESSION IS A PREVALENT, HIGHLY DEBILITATING MENTAL DISORDER AFFECTING UP TO 15% OF THE POPULATION AT LEAST ONCE IN THEIR LIFETIME, WITH HUGE COSTS FOR SOCIETY. NEUROBIOLOGICAL MECHANISMS OF DEPRESSION ARE STILL NOT WELL KNOWN, ALTHOUGH THERE IS CONSENSUS ABOUT INTERPLAY BETWEEN GENETIC AND ENVIRONMENTAL FACTORS. ANTIDEPRESSANT MEDICATIONS ARE FREQUENTLY USED IN DEPRESSION, BUT AT LEAST 50% OF PATIENTS ARE POOR RESPONDERS, EVEN TO MORE RECENTLY DISCOVERED MEDICATIONS. FURTHERMORE, CLINICAL RESPONSE ONLY OCCURS FOLLOWING WEEKS TO MONTHS OF TREATMENT AND ONLY CHRONIC TREATMENT IS EFFECTIVE, SUGGESTING THAT ACTIONS BEYOND THE RAPIDLY OCCURRING EFFECT OF ENHANCING MONOAMINERGIC SYSTEMS, SUCH AS ADAPTATION OF THESE SYSTEMS, ARE RESPONSIBLE FOR THE EFFECTS OF ANTIDEPRESSANTS. RECENT STUDIES INDICATE THAT AN IMPAIRMENT OF SYNAPTIC PLASTICITY (NEUROGENESIS, AXON BRANCHING, DENDRITOGENESIS AND SYNAPTOGENESIS) IN SPECIFIC AREAS OF THE CNS, PARTICULARLY THE HIPPOCAMPUS, MAY BE A CORE FACTOR IN THE PATHOPHYSIOLOGY OF DEPRESSION. THE ABNORMAL NEURAL PLASTICITY MAY BE RELATED TO ALTERATIONS IN THE LEVELS OF NEUROTROPHIC FACTORS, NAMELY BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF), WHICH PLAY A CENTRAL ROLE IN PLASTICITY. AS BDNF IS REPRESSED BY STRESS, EPIGENETIC REGULATION OF THE BDNF GENE MAY PLAY AN IMPORTANT ROLE IN DEPRESSION. THE HIPPOCAMPUS IS SMALLER IN DEPRESSED PATIENTS, ALTHOUGH IT IS UNCLEAR WHETHER SMALLER SIZE IS A CONSEQUENCE OF DEPRESSION OR A PRE-EXISTING, VULNERABILITY MARKER FOR DEPRESSION. ENVIRONMENTAL STRESSORS TRIGGERING ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS CAUSE THE BRAIN TO BE EXPOSED TO CORTICOSTEROIDS, AFFECTING NEUROBEHAVIOURAL FUNCTIONS WITH A STRONG DOWNREGULATION OF HIPPOCAMPAL NEUROGENESIS, AND ARE A MAJOR RISK FACTOR FOR DEPRESSION. ANTIDEPRESSANT TREATMENT INCREASES BDNF LEVELS, STIMULATES NEUROGENESIS AND REVERSES THE INHIBITORY EFFECTS OF STRESS, BUT THIS EFFECT IS EVIDENT ONLY AFTER 3-4 WEEKS OF ADMINISTRATION, THE TIME COURSE FOR MATURATION OF NEW NEURONS. THE ABLATION OF HIPPOCAMPAL NEUROGENESIS BLOCKS THE BEHAVIOURAL EFFECTS OF ANTIDEPRESSANTS IN ANIMAL MODELS. THE ABOVE FINDINGS SUGGEST NEW POSSIBLE TARGETS FOR THE PHARMACOTHERAPY OF DEPRESSION SUCH AS NEUROTROPHIC FACTORS, THEIR RECEPTORS AND RELATED INTRACELLULAR SIGNALLING CASCADES; AGENTS COUNTERACTING THE EFFECTS OF STRESS ON HIPPOCAMPAL NEUROGENESIS (INCLUDING ANTAGONISTS OF CORTICOSTEROIDS, INFLAMMATORY CYTOKINES AND THEIR RECEPTORS); AND AGENTS FACILITATING THE ACTIVATION OF GENE EXPRESSION AND INCREASING THE TRANSCRIPTION OF NEUROTROPHINS IN THE BRAIN. 2011 6 1717 33 DYSREGULATED IMMUNE SYSTEM NETWORKS IN WAR VETERANS WITH PTSD IS AN OUTCOME OF ALTERED MIRNA EXPRESSION AND DNA METHYLATION. POST-TRAUMATIC STRESS DISORDER PATIENTS EXPERIENCE CHRONIC SYSTEMIC INFLAMMATION. HOWEVER, THE MOLECULAR PATHWAYS INVOLVED AND MECHANISMS REGULATING THE EXPRESSION OF GENES INVOLVED IN INFLAMMATORY PATHWAYS IN PTSD ARE REPORTED INADEQUATELY. THROUGH RNA SEQUENCING AND MIRNA MICROARRAY, WE IDENTIFIED 326 GENES AND 190 MIRNAS THAT WERE SIGNIFICANTLY DIFFERENT IN THEIR EXPRESSION LEVELS IN THE PBMCS OF PTSD PATIENTS. EXPRESSION PAIRING OF THE DIFFERENTIALLY EXPRESSED GENES AND MIRNAS INDICATED AN INVERSE RELATIONSHIP IN THEIR EXPRESSION. FUNCTIONAL ANALYSIS OF THE DIFFERENTIALLY EXPRESSED GENES INDICATED THEIR INVOLVEMENT IN THE CANONICAL PATHWAYS SPECIFIC TO IMMUNE SYSTEM BIOLOGY. DNA METHYLATION ANALYSIS OF DIFFERENTIALLY EXPRESSED GENES ALSO SHOWED A GRADUAL TREND TOWARDS DIFFERENCES BETWEEN CONTROL AND PTSD PATIENTS, AGAIN INDICATING A POSSIBLE ROLE OF THIS EPIGENETIC MECHANISM IN PTSD INFLAMMATION. OVERALL, COMBINING DATA FROM THE THREE TECHNIQUES PROVIDED A HOLISTIC VIEW OF SEVERAL PATHWAYS IN WHICH THE DIFFERENTIALLY EXPRESSED GENES WERE IMPACTED THROUGH EPIGENETIC MECHANISMS, IN PTSD. THUS, ANALYSIS COMBINING DATA FROM RNA-SEQ, MIRNA ARRAY AND DNA METHYLATION, CAN PROVIDE KEY EVIDENCE ABOUT DYSREGULATED PATHWAYS AND THE CONTROLLING MECHANISM IN PTSD. MOST IMPORTANTLY, THE PRESENT STUDY PROVIDES FURTHER EVIDENCE THAT INFLAMMATION IN PTSD COULD BE EPIGENETICALLY REGULATED. 2016 7 1790 33 EFFECT OF CHRONIC MILD STRESS ON HIPPOCAMPAL TRANSCRIPTOME IN MICE SELECTED FOR HIGH AND LOW STRESS-INDUCED ANALGESIA AND DISPLAYING DIFFERENT EMOTIONAL BEHAVIORS. 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. 2011 8 2598 32 EPIGENETICS OF THE DEPRESSED BRAIN: ROLE OF HISTONE ACETYLATION AND METHYLATION. MAJOR DEPRESSIVE DISORDER IS A CHRONIC, REMITTING SYNDROME INVOLVING WIDELY DISTRIBUTED CIRCUITS IN THE BRAIN. STABLE ALTERATIONS IN GENE EXPRESSION THAT CONTRIBUTE TO STRUCTURAL AND FUNCTIONAL CHANGES IN MULTIPLE BRAIN REGIONS ARE IMPLICATED IN THE HETEROGENEITY AND PATHOGENESIS OF THE ILLNESS. EPIGENETIC EVENTS THAT ALTER CHROMATIN STRUCTURE TO REGULATE PROGRAMS OF GENE EXPRESSION HAVE BEEN ASSOCIATED WITH DEPRESSION-RELATED BEHAVIOR, ANTIDEPRESSANT ACTION, AND RESISTANCE TO DEPRESSION OR 'RESILIENCE' IN ANIMAL MODELS, WITH INCREASING EVIDENCE FOR SIMILAR MECHANISMS OCCURRING IN POSTMORTEM BRAINS OF DEPRESSED HUMANS. IN THIS REVIEW, WE DISCUSS RECENT ADVANCES IN OUR UNDERSTANDING OF EPIGENETIC CONTRIBUTIONS TO DEPRESSION, IN PARTICULAR THE ROLE OF HISTONE ACETYLATION AND METHYLATION, WHICH ARE REVEALING NOVEL MECHANISTIC INSIGHT INTO THE SYNDROME THAT MAY AID IN THE DEVELOPMENT OF NOVEL TARGETS FOR DEPRESSION TREATMENT. 2013 9 5645 30 SEX DEPENDENT ALTERATION OF EPIGENETIC MARKS AFTER CHRONIC MORPHINE TREATMENT IN MICE ORGANS. EPIGENETIC MARKS MAY BE ALSO AFFECTED BY SEVERAL FACTORS, SUCH AS AGE, LIFESTYLE, EARLY LIFE EXPERIENCES AND EXPOSURE TO CHEMICALS OR DRUGS, SUCH AS OPIOIDS. PREVIOUS STUDIES HAVE FOCUSED ON HOW MORPHINE EPIGENETICALLY REGULATES DIFFERENT REGIONS OF THE BRAIN THAT ARE IMPLICATED IN TOLERANCE, DEPENDENCE AND OTHER PSYCHIATRIC DISORDERS MORE RELATED TO THE PHYSIO-PATHOLOGICAL EFFECTS OF OPIOIDS. NEVERTHELESS, A SIGNIFICANT KNOWLEDGE GAP REMAINS REGARDING THE EFFECT OF CHRONIC TREATMENT ON OTHER ORGANS AND BIOLOGICAL SYSTEMS. THEREFORE, THE AIM OF THIS WORK IS TO INCREASE OUR KNOWLEDGE ABOUT THE IMPACT OF CHRONIC MORPHINE EXPOSURE ON DNA METHYLATION AND HISTONE MODIFICATION LEVELS IN EACH OF THE ORGANS OF MALE AND FEMALE MODEL MICE IN VIVO. OUR RESULTS REVEAL, FOR THE FIRST TIME, THAT CHRONIC MORPHINE TREATMENT INDUCED CHANGES IN DNA METHYLATION/HYDROXYMETHYLATION AND HISTONE MODIFICATION IN-VIVO AT THE SYSTEMIC LEVEL, REVEALING A POTENTIAL PHYSIOLOGICAL EFFECT ON THE REGULATION OF GENE EXPRESSION. NOTABLY, MORPHINE-INDUCED EPIGENETIC MODIFICATION OCCURS IN A SEX-DEPENDENT MANNER, REVEALING THE EXISTENCE OF DIFFERENT UNDERLYING MECHANISMS OF EPIGENETIC MODIFICATION IN MALE AND FEMALE MICE. 2021 10 110 29 A ROLE FOR ACTIVITY-DEPENDENT EPIGENETICS IN THE DEVELOPMENT AND TREATMENT OF MAJOR DEPRESSIVE DISORDER. CHRONIC STRESSORS, DURING DEVELOPMENTAL SENSITIVE PERIODS AND BEYOND, CONTRIBUTE TO THE RISK OF DEVELOPING PSYCHIATRIC CONDITIONS, INCLUDING MAJOR DEPRESSIVE DISORDER (MDD). EPIGENETIC MECHANISMS INCLUDING DNA METHYLATION AND HISTONE MODIFICATIONS, AT KEY STRESS RESPONSE AND NEUROTROPHIN GENES, ARE INCREASINGLY IMPLICATED IN MEDIATING THIS RISK. ALTHOUGH THE EXACT MECHANISMS THROUGH WHICH STRESSFUL ENVIRONMENTAL STIMULI ALTER THE EPIGENOME ARE STILL UNCLEAR, RESEARCH FROM THE LEARNING AND MEMORY FIELDS INDICATES THAT EPIGENOMIC MARKS CAN BE ALTERED, AT LEAST IN PART, THROUGH CALCIUM-DEPENDENT SIGNALING CASCADES IN DIRECT RESPONSE TO NEURONAL ACTIVITY. IN THIS REVIEW, WE HIGHLIGHT KEY FINDINGS FROM THE STRESS, MDD, AND LEARNING AND MEMORY FIELDS TO PROPOSE A MODEL WHERE STRESS REGULATES DOWNSTREAM CELLULAR FUNCTIONING THROUGH ACTIVITY-DEPENDENT EPIGENETIC CHANGES. FURTHERMORE, WE SUGGEST THAT BOTH TYPICAL AND NOVEL ANTIDEPRESSANT TREATMENTS MAY EXERT POSITIVE INFLUENCE THROUGH SIMILAR, ACTIVITY-DEPENDENT PATHWAYS. 2018 11 4321 33 MICRORNAS IN MAJOR DEPRESSIVE DISORDER. MAJOR DEPRESSIVE DISORDER (MDD) IS A SEVERE AND CHRONIC PSYCHIATRIC DISORDER WITH A HIGH PREVALENCE IN THE POPULATION. ALTHOUGH OUR UNDERSTANDING OF ITS PATHOPHYSIOLOGICAL MECHANISMS HAS SIGNIFICANTLY INCREASED OVER THE YEARS, AVAILABLE TREATMENTS STILL PRESENT SEVERAL LIMITATIONS AND ARE NOT EFFECTIVE TO ALL MDD PATIENTS. EPIGENETIC MECHANISMS HAVE RECENTLY BEEN SUGGESTED TO PLAY KEY ROLES IN MDD PATHOGENESIS AND TREATMENT, INCLUDING THE EFFECTS OF SMALL NONCODING RNAS KNOWN AS MICRORNAS (MIRNAS). MIRNAS CAN MODULATE GENE EXPRESSION POSTTRANSCRIPTIONALLY BY INTERFERING WITH THE STABILITY AND TRANSLATION OF MESSENGER RNA MOLECULES AND ARE ALSO KNOWN TO CROSS-TALK WITH OTHER EPIGENETIC MECHANISMS. IN THIS REVIEW, WE WILL SUMMARIZE AND DISCUSS RECENT FINDINGS OF ALTERATIONS IN MIRNAS IN TISSUES OF PATIENTS WITH MDD AND EVIDENCE OF TREATMENT-INDUCED EFFECTS IN THESE MOLECULES. 2019 12 1967 43 EPIGENETIC ALTERATION OF THE DOPAMINE TRANSPORTER GENE IN ALCOHOL-DEPENDENT PATIENTS IS ASSOCIATED WITH AGE. CHRONIC ALCOHOL ABUSE AND DEPENDENCE ARE ASSOCIATED WITH DYSFUNCTIONAL DOPAMINERGIC NEUROTRANSMISSION IN MESOCORTICOLIMBIC CIRCUITS. GENETIC AND ENVIRONMENTAL FACTORS HAVE BEEN SHOWN TO MODULATE SUSCEPTIBILITY TO ALCOHOL DEPENDENCE, AND BOTH MAY ACT THROUGH EPIGENETIC MECHANISMS THAT CAN MODULATE GENE EXPRESSION, E.G. DNA METHYLATION AT CPG SITES. RECENT STUDIES HAVE SUGGESTED THAT DNA METHYLATION PATTERNS MAY CHANGE OVER TIME. HOWEVER, FEW DATA ARE AVAILABLE CONCERNING THE RATE OF THESE CHANGES IN SPECIFIC GENES. A RECENT STUDY FOUND THAT HYPERMETHYLATION OF THE PROMOTER OF THE DOPAMINE TRANSPORTER (DAT) GENE WAS POSITIVELY CORRELATED WITH ALCOHOL DEPENDENCE AND NEGATIVELY CORRELATED WITH ALCOHOL CRAVING. THE AIM OF THE PRESENT STUDY WAS TO REPLICATE THESE FINDINGS IN A LARGER SAMPLE OF ALCOHOL-DEPENDENT PATIENTS AND POPULATION-BASED CONTROLS MATCHED FOR AGE AND SEX. NO DIFFERENCE IN METHYLATION LEVEL WAS OBSERVED BETWEEN PATIENTS AND CONTROLS, AND NO DIFFERENCE IN METHYLATION LEVEL WAS OBSERVED BEFORE AND AFTER ALCOHOL WITHDRAWAL IN PATIENTS. HOWEVER, PATIENTS WITH MORE SEVERE CRAVING SHOWED A TREND TOWARDS LOWER DAT METHYLATION LEVELS (P = 0.07), WHICH IS CONSISTENT WITH PREVIOUS FINDINGS. FURTHERMORE, IN OUR OVERALL SAMPLE, DAT METHYLATION LEVELS INCREASED WITH AGE. INTERESTINGLY, A SEPARATE ANALYSIS OF PATIENTS SUGGESTED THAT THIS FINDING WAS MAINLY DRIVEN BY THE PATIENT GROUP. ALTHOUGH THE PRESENT DATA DO NOT CLARIFY WHETHER CHRONIC ALCOHOL ABUSE IS RESPONSIBLE FOR THIS PHENOMENON OR MERELY ENHANCES AN AGEING-SPECIFIC PROCESS, OUR FINDINGS SUGGEST THAT HYPERMETHYLATION IN ALCOHOL-DEPENDENT PATIENTS IS A CONSEQUENCE, RATHER THAN A CAUSE, OF THE DISORDER. 2014 13 5467 44 RESILIENT PHENOTYPE IN CHRONIC MILD STRESS PARADIGM IS ASSOCIATED WITH ALTERED EXPRESSION LEVELS OF MIR-18A-5P AND SEROTONIN 5-HT(1A) RECEPTOR IN DORSAL PART OF THE HIPPOCAMPUS. DISTURBED SEROTONERGIC SIGNALING IN THE HIPPOCAMPUS OBSERVED IN MANY INDIVIDUALS VULNERABLE TO STRESS HAS BEEN SUGGESTED AS ONE OF THE PRIMARY FACTORS CONTRIBUTING TO THE DEVELOPMENT OF DEPRESSION. HOWEVER, LITTLE IS KNOWN ABOUT THE PHYSIOLOGY OF THE BRAIN IN THE RESILIENT PHENOTYPE. RESILIENT SUBJECTS MAINTAIN A POSITIVE MOOD AND PSYCHOLOGICAL BALANCE DESPITE BEING UNDER THE STRESS INFLUENCE. IN OUR STUDY, WE GENERATED STRESS-VULNERABLE AND RESILIENT RATS BY USING A CHRONIC MILD STRESS (CMS) PARADIGM. USING DIFFERENT MOLECULAR APPROACHES, WE REVEALED THAT RESILIENT ANIMALS EXHIBITED A SIGNIFICANTLY DECREASED EXPRESSION LEVEL OF MIR-18A-5P AND, IN THE SAME TIME, AN ELEVATED LEVEL OF 5-HT1AR IN DORSAL, BUT NOT VENTRAL, PART OF THE HIPPOCAMPUS. DESCRIBED BIOCHEMICAL CHANGES WERE NOT OBSERVED IN ANIMALS BEHAVIORALLY VULNERABLE TO STRESS. FURTHER, IN VITRO ANALYSIS SHOWED THAT MIR-18A-5P MAY BE A NEGATIVE EPIGENETIC REGULATOR OF 5-HT1AR SINCE THE TREATMENT OF ADULT HIPPOCAMPAL NEURONS WITH MIR-18A-5P MIMIC SIGNIFICANTLY LOWERED THE EXPRESSION LEVEL OF MRNA ENCODING 5-HT1AR. MOREOVER, BIOINFORMATIC ANALYSIS OF POTENTIAL TARGET GENES EXPRESSED IN THE HIPPOCAMPUS AND BEING REGULATED BY MIR-18A-5P SHOWED THAT THIS MICRORNA MAY REGULATE BIOLOGICAL PROCESSES, SUCH AS AXONOGENESIS, WHICH ARE IMPORTANT IN THE FUNCTIONING OF THE HIPPOCAMPUS IN BOTH RATS AND HUMANS. ALL THESE MOLECULAR FEATURES MAY CONTRIBUTE TO SEROTONERGIC HOMEOSTATIC BALANCE AT THE LEVEL OF SEROTONIN TURNOVER OBSERVED IN HIPPOCAMPI OF RESILIENT BUT NOT STRESS-VULNERABLE RATS. DELINEATION OF FURTHER MOLECULAR AND BIOCHEMICAL MARKERS UNDERLYING RESILIENCE TO STRESS MAY CONTRIBUTE TO THE DEVELOPMENT OF NEW ANTIDEPRESSANT STRATEGIES WHICH WILL RESTORE RESILIENT PHENOTYPE IN DEPRESSED PATIENTS. 2019 14 883 40 CHRONIC COCAINE-REGULATED EPIGENOMIC CHANGES IN MOUSE NUCLEUS ACCUMBENS. BACKGROUND: INCREASING EVIDENCE SUPPORTS A ROLE FOR ALTERED GENE EXPRESSION IN MEDIATING THE LASTING EFFECTS OF COCAINE ON THE BRAIN, AND RECENT WORK HAS DEMONSTRATED THE INVOLVEMENT OF CHROMATIN MODIFICATIONS IN THESE ALTERATIONS. HOWEVER, ALL SUCH STUDIES TO DATE HAVE BEEN RESTRICTED BY THEIR RELIANCE ON MICROARRAY TECHNOLOGIES THAT HAVE INTRINSIC LIMITATIONS. RESULTS: WE USE NEXT GENERATION SEQUENCING METHODS, RNA-SEQ AND CHIP-SEQ FOR RNA POLYMERASE II AND SEVERAL HISTONE METHYLATION MARKS, TO OBTAIN A MORE COMPLETE VIEW OF COCAINE-INDUCED CHANGES IN GENE EXPRESSION AND ASSOCIATED ADAPTATIONS IN NUMEROUS MODES OF CHROMATIN REGULATION IN THE MOUSE NUCLEUS ACCUMBENS, A KEY BRAIN REWARD REGION. WE DEMONSTRATE AN UNEXPECTEDLY LARGE NUMBER OF PRE-MRNA SPLICING ALTERATIONS IN RESPONSE TO REPEATED COCAINE TREATMENT. IN ADDITION, WE IDENTIFY COMBINATIONS OF CHROMATIN CHANGES, OR SIGNATURES, THAT CORRELATE WITH COCAINE-DEPENDENT REGULATION OF GENE EXPRESSION, INCLUDING THOSE INVOLVING PRE-MRNA ALTERNATIVE SPLICING. THROUGH BIOINFORMATIC PREDICTION AND BIOLOGICAL VALIDATION, WE IDENTIFY ONE PARTICULAR SPLICING FACTOR, A2BP1(RBFOX1/FOX-1), WHICH IS ENRICHED AT GENES THAT DISPLAY CERTAIN CHROMATIN SIGNATURES AND CONTRIBUTES TO DRUG-INDUCED BEHAVIORAL ABNORMALITIES. TOGETHER, THIS DELINEATION OF THE COCAINE-INDUCED EPIGENOME IN THE NUCLEUS ACCUMBENS REVEALS SEVERAL NOVEL MODES OF REGULATION BY WHICH COCAINE ALTERS THE BRAIN. CONCLUSIONS: WE ESTABLISH COMBINATORIAL CHROMATIN AND TRANSCRIPTIONAL PROFILES IN MOUSE NUCLEUS ACCUMBENS AFTER REPEATED COCAINE TREATMENT. THESE RESULTS SERVE AS AN IMPORTANT RESOURCE FOR THE FIELD AND PROVIDE A TEMPLATE FOR THE ANALYSIS OF OTHER SYSTEMS TO REVEAL NEW TRANSCRIPTIONAL AND EPIGENETIC MECHANISMS OF NEURONAL REGULATION. 2014 15 6775 27 [ALCOHOL DEPENDENCE MEDIATED BY MONOAMINE NEUROTRANSMITTERS IN THE CENTRAL NERVOUS SYSTEM]. ALCOHOL DEPENDENCE, A CHRONIC RELAPSING BRAIN DISEASE WITH THE CHARACTERISTICS OF DRINKING ALCOHOL OUT OF CONTROL, HAS BECOME A SERIOUS SOCIAL PROBLEM. MONOAMINE NEUROTRANSMITTERS, MAINLY INCLUDING DOPAMINE AND 5-HYDROXYTRYP NOTTAMINE, PLAY IMPORTANT ROLES IN THE OCCURRENCE, DEVELOPMENT AND NEURAL DYSFUNCTION OF ALCOHOL DEPENDENCE SYNDROME. IN THIS REVIEW, THE ROLES OF KEY FACTORS OF THE MONOAMINE SYSTEM (DOPAMINE RECEPTOR GENES, 5-HYDROXYTRYPTAMINE RECEPTOR GENES, TRANSPORTER GENES, TYROSINE HYDROXYLASE GENE, TRYPTOPHANHYDROXYLASE GENE AND MONOAMINE OXIDASE GENE) IN ALCOHOL DEPENDENCE WERE DISCUSSED, AND STRATEGIES FOR FURTHER STUDIES OF MOLECULAR MECHANISMS WERE PROPOSED BASED ON GENE KNOCKOUT MICE MODELS GENERATED IN OUR LABORATORY. THEN, COMBINING WITH STUDIES ON TYROSINE HYDROXYLASE ACTIVATOR CAMKII IN OUR LAB, THERAPEUTIC TARGETS WERE DISCUSSED. BESIDES, EPIGENETIC STRATEGIES FOR PREVENTION AND TREATMENT OF ALCOHOL DEPENDENCE SYNDROME WERE PROPOSED. FURTHERMORE, MANIPULATING METHYLATION LEVELS IN GENE REGULATORY REGIONS AND ALTERNATIVE SPLICING OF PRE-MRNAS MIGHT ALSO HAVE CLINICAL IMPLICATIONS. FINALLY, BASED ON NEW FINDINGS ON GENETIC POLYMORPHISM, IT IS OF GREAT POTENTIAL TO CARRY OUT INDIVIDUAL PREVENTION AND TREATMENT FOR PATIENTS SUFFERING FROM ALCOHOL DEPENDENCE. 2014 16 3375 30 HISTONE POSTTRANSLATIONAL MODIFICATIONS PREDICT SPECIFIC ALTERNATIVE EXON SUBTYPES IN MAMMALIAN BRAIN. A COMPELLING BODY OF LITERATURE, BASED ON NEXT GENERATION CHROMATIN IMMUNOPRECIPITATION AND RNA SEQUENCING OF REWARD BRAIN REGIONS INDICATES THAT THE REGULATION OF THE EPIGENETIC LANDSCAPE LIKELY UNDERLIES CHRONIC DRUG ABUSE AND ADDICTION. IT IS NOW CRITICAL TO DEVELOP HIGHLY INNOVATIVE COMPUTATIONAL STRATEGIES TO REVEAL THE RELEVANT REGULATORY TRANSCRIPTIONAL MECHANISMS THAT MAY UNDERLIE NEUROPSYCHIATRIC DISEASE. WE HAVE ANALYZED CHROMATIN REGULATION OF ALTERNATIVE SPLICING, WHICH IS IMPLICATED IN COCAINE EXPOSURE IN MICE. RECENT LITERATURE HAS DESCRIBED CHROMATIN-REGULATED ALTERNATIVE SPLICING, SUGGESTING A NOVEL FUNCTION FOR DRUG-INDUCED NEUROEPIGENETIC REMODELING. HOWEVER, THE EXTENT OF THE GENOME-WIDE ASSOCIATION BETWEEN PARTICULAR HISTONE MODIFICATIONS AND ALTERNATIVE SPLICING REMAINS UNEXPLORED. TO ADDRESS THIS, WE HAVE DEVELOPED NOVEL COMPUTATIONAL APPROACHES TO MODEL THE ASSOCIATION BETWEEN ALTERNATIVE SPLICING AND HISTONE POSTTRANSLATIONAL MODIFICATIONS IN THE NUCLEUS ACCUMBENS (NAC), A BRAIN REWARD REGION. USING CLASSICAL STATISTICAL METHODS AND MACHINE LEARNING TO COMBINE CHIP-SEQ AND RNA-SEQ DATA, WE FOUND THAT SPECIFIC HISTONE MODIFICATIONS ARE STRONGLY ASSOCIATED WITH VARIOUS ASPECTS OF DIFFERENTIAL SPLICING. H3K36ME3 AND H3K4ME1 HAVE THE STRONGEST ASSOCIATION WITH SPLICING INDICATING THEY PLAY A SIGNIFICANT ROLE IN ALTERNATIVE SPLICING IN BRAIN REWARD TISSUE. 2017 17 4642 41 NEURONAL PLASTICITY: A LINK BETWEEN STRESS AND MOOD DISORDERS. ALTHOUGH STRESS REPRESENTS THE MAJOR ENVIRONMENTAL ELEMENT OF SUSCEPTIBILITY FOR MOOD DISORDERS, THE RELATIONSHIP BETWEEN STRESS AND DISEASE REMAINS TO BE FULLY ESTABLISHED. IN THE PRESENT ARTICLE WE REVIEW THE EVIDENCE IN SUPPORT FOR A ROLE OF NEURONAL PLASTICITY, AND IN PARTICULAR OF NEUROTROPHIC FACTORS. EVEN THOUGH DECREASED LEVELS OF NOREPINEPHRINE AND SEROTONIN MAY UNDERLIE DEPRESSIVE SYMPTOMS, COMPELLING EVIDENCE NOW SUGGESTS THAT MOOD DISORDERS ARE CHARACTERIZED BY REDUCED NEURONAL PLASTICITY, WHICH CAN BE BROUGHT ABOUT BY EXPOSURE TO STRESS AT DIFFERENT STAGES OF LIFE. INDEED THE EXPRESSION OF NEUROTROPHIC MOLECULES, SUCH AS THE NEUROTROPHIN BDNF, IS REDUCED IN DEPRESSED SUBJECTS AS WELL AS IN EXPERIMENTAL ANIMALS EXPOSED TO ADVERSE EXPERIENCE AT EARLY STAGES OF LIFE OR AT ADULTHOOD. THESE CHANGES SHOW AN ANATOMICAL SPECIFICITY AND MIGHT BE SUSTAINED BY EPIGENETIC MECHANISMS. PHARMACOLOGICAL INTERVENTION MAY NORMALIZE SUCH DEFECTS AND IMPROVE NEURONAL FUNCTION THROUGH THE MODULATION OF THE SAME FACTORS THAT ARE DEFECTIVE IN DEPRESSION. SEVERAL STUDIES HAVE DEMONSTRATED THAT CHRONIC, BUT NOT ACUTE, ANTIDEPRESSANT TREATMENT INCREASES THE EXPRESSION OF BDNF AND MAY ENHANCE ITS LOCALIZATION AT SYNAPTIC LEVEL. ANTIDEPRESSANT TREATMENT CAN NORMALIZE DEFICITS IN NEUROTROPHIN EXPRESSION PRODUCED BY CHRONIC STRESS PARADIGMS, BUT MAY ALSO ALTER THE MODULATION OF BDNF UNDER ACUTE STRESSFUL CONDITIONS. IN SUMMARY, THERE IS GOOD AGREEMENT IN CONSIDERING NEURONAL PLASTICITY, AND THE EXPRESSION OF KEY PROTEINS SUCH AS THE NEUROTROPHIN BDNF, AS A CENTRAL PLAYER FOR THE EFFECTS OF STRESS ON BRAIN FUNCTION AND ITS IMPLICATION FOR PSYCHOPATHOLOGY. ACCORDINGLY, EFFECTIVE TREATMENTS SHOULD NOT LIMIT THEIR EFFECTS TO THE CONTROL OF NEUROTRANSMITTER AND HORMONAL DYSFUNCTIONS, BUT SHOULD BE ABLE TO NORMALIZE DEFECTIVE MECHANISMS THAT SUSTAIN THE IMPAIRMENT OF NEURONAL PLASTICITY. 2009 18 4604 29 NEGATIVE EVIDENCE FOR A FUNCTIONAL ROLE OF NEURONAL DNMT3A IN PERSISTENT PAIN. TRADITIONALLY, NEUROSCIENCE HAS HAD TO RELY ON MIXED TISSUE ANALYSIS TO EXAMINE TRANSCRIPTIONAL AND EPIGENETIC CHANGES IN THE CONTEXT OF NERVOUS SYSTEM FUNCTION OR PATHOLOGY. HOWEVER, PARTICULARLY WHEN STUDYING CHRONIC PAIN CONDITIONS, THIS APPROACH CAN BE FLAWED, SINCE IT NEGLECTS TO TAKE INTO ACCOUNT THE SHIFTING CONTRIBUTION OF DIFFERENT CELL TYPES ACROSS EXPERIMENTAL CONDITIONS. HERE, WE DEMONSTRATE THIS USING THE EXAMPLE OF DNA METHYLTRANSFERASES (DNMTS) - A GROUP OF EPIGENETIC MODIFIERS CONSISTING OF DNMT1, DNMT3A, AND DNMT3B IN MAMMALIAN CELLS. WE USED SENSORY NEURON-SPECIFIC KNOCKOUT MICE FOR DNMT3A/3B AS WELL AS PHARMACOLOGICAL BLOCKADE OF DNMT1 TO STUDY THEIR ROLE IN NOCICEPTION. IN CONTRAST TO PREVIOUS ANALYSES ON WHOLE TISSUE, WE FIND THAT DNMT3A AND 3B PROTEIN IS NOT EXPRESSED IN ADULT DRG NEURONS, THAT NONE OF THE DNA METHYLTRANSFERASES ARE REGULATED WITH INJURY AND THAT INTERFERING WITH THEIR FUNCTION HAS NO EFFECT ON NOCICEPTION. OUR RESULTS THEREFORE CURRENTLY DO NOT SUPPORT A ROLE FOR NEURONAL DNA METHYLTRANSFERASES IN PAIN PROCESSING IN ADULT ANIMALS. 2018 19 6427 34 THE TRANSITION FROM ACUTE TO CHRONIC PAIN: DYNAMIC EPIGENETIC REPROGRAMMING OF THE MOUSE PREFRONTAL CORTEX UP TO 1 YEAR AFTER NERVE INJURY. CHRONIC PAIN IS ASSOCIATED WITH PERSISTENT STRUCTURAL AND FUNCTIONAL CHANGES THROUGHOUT THE NEUROAXIS, INCLUDING IN THE PREFRONTAL CORTEX (PFC). THE PFC IS IMPORTANT IN THE INTEGRATION OF SENSORY, COGNITIVE, AND EMOTIONAL INFORMATION AND IN CONDITIONED PAIN MODULATION. WE PREVIOUSLY REPORTED WIDESPREAD EPIGENETIC REPROGRAMMING IN THE PFC MANY MONTHS AFTER NERVE INJURY IN RODENTS. EPIGENETIC MODIFICATIONS, INCLUDING DNA METHYLATION, CAN DRIVE CHANGES IN GENE EXPRESSION WITHOUT MODIFYING DNA SEQUENCES. TO DATE, LITTLE IS KNOWN ABOUT EPIGENETIC DYSREGULATION AT THE ONSET OF ACUTE PAIN OR HOW IT PROGRESSES AS PAIN TRANSITIONS FROM ACUTE TO CHRONIC. WE HYPOTHESIZE THAT ACUTE PAIN AFTER INJURY RESULTS IN RAPID AND PERSISTENT EPIGENETIC REMODELLING IN THE PFC THAT EVOLVES AS PAIN BECOMES CHRONIC. WE FURTHER PROPOSE THAT UNDERSTANDING EPIGENETIC REMODELLING WILL PROVIDE INSIGHTS INTO THE MECHANISMS DRIVING PAIN-RELATED CHANGES IN THE BRAIN. EPIGENOME-WIDE ANALYSIS WAS PERFORMED IN THE MOUSE PFC 1 DAY, 2 WEEKS, 6 MONTHS, AND 1 YEAR AFTER PERIPHERAL INJURY USING THE SPARED NERVE INJURY IN MICE. SPARED NERVE INJURY RESULTED IN RAPID AND PERSISTENT CHANGES IN DNA METHYLATION, WITH ROBUST DIFFERENTIAL METHYLATION OBSERVED BETWEEN SPARED NERVE INJURY AND SHAM-OPERATED CONTROL MICE AT ALL TIME POINTS. HUNDREDS OF DIFFERENTIALLY METHYLATED GENES WERE IDENTIFIED, INCLUDING MANY WITH KNOWN FUNCTION IN PAIN. PATHWAY ANALYSIS REVEALED ENRICHMENT IN GENES RELATED TO STIMULUS RESPONSE AT EARLY TIME POINTS, IMMUNE FUNCTION AT LATER TIME POINTS, AND ACTIN AND CYTOSKELETAL REGULATION THROUGHOUT THE TIME COURSE. THESE RESULTS EMPHASIZE THE IMPORTANCE OF CONSIDERING PAIN CHRONICITY IN BOTH PAIN RESEARCH AND IN TREATMENT OPTIMIZATION. 2020 20 6414 42 THE STRESSED SYNAPSE 2.0: PATHOPHYSIOLOGICAL MECHANISMS IN STRESS-RELATED NEUROPSYCHIATRIC DISORDERS. STRESS IS A PRIMARY RISK FACTOR FOR SEVERAL NEUROPSYCHIATRIC DISORDERS. EVIDENCE FROM PRECLINICAL MODELS AND CLINICAL STUDIES OF DEPRESSION HAVE REVEALED AN ARRAY OF STRUCTURAL AND FUNCTIONAL MALADAPTIVE CHANGES, WHEREBY ADVERSE ENVIRONMENTAL FACTORS SHAPE THE BRAIN. THESE CHANGES, OBSERVED FROM THE MOLECULAR AND TRANSCRIPTIONAL LEVELS THROUGH TO LARGE-SCALE BRAIN NETWORKS, TO THE BEHAVIOURS REVEAL A COMPLEX MATRIX OF INTERRELATED PATHOPHYSIOLOGICAL PROCESSES THAT DIFFER BETWEEN SEXES, PROVIDING INSIGHT INTO THE POTENTIAL UNDERPINNINGS OF THE SEX BIAS OF NEUROPSYCHIATRIC DISORDERS. ALTHOUGH MANY PRECLINICAL STUDIES USE CHRONIC STRESS PROTOCOLS, LONG-TERM CHANGES ARE ALSO INDUCED BY ACUTE EXPOSURE TO TRAUMATIC STRESS, OPENING A PATH TO IDENTIFY DETERMINANTS OF RESILIENT VERSUS SUSCEPTIBLE RESPONSES TO BOTH ACUTE AND CHRONIC STRESS. EPIGENETIC REGULATION OF GENE EXPRESSION HAS EMERGED AS A KEY PLAYER UNDERLYING THE PERSISTENT IMPACT OF STRESS ON THE BRAIN. INDEED, HISTONE MODIFICATION, DNA METHYLATION AND MICRORNAS ARE CLOSELY INVOLVED IN MANY ASPECTS OF THE STRESS RESPONSE AND REVEAL THE GLUTAMATE SYSTEM AS A KEY PLAYER. THE SUCCESS OF KETAMINE HAS STIMULATED A WHOLE LINE OF RESEARCH AND DEVELOPMENT ON DRUGS DIRECTLY OR INDIRECTLY TARGETING GLUTAMATE FUNCTION. HOWEVER, THE CHALLENGE OF TRANSLATING THE EMERGING UNDERSTANDING OF STRESS PATHOPHYSIOLOGY INTO EFFECTIVE CLINICAL TREATMENTS REMAINS A MAJOR CHALLENGE. 2022