Phf8 loss confers resistance to depression-like and anxiety-like behaviors in mice.

PHF8 is a histone demethylase with specificity for repressive modifications. While mutations of PHF8 have been associated with cognitive defects and cleft lip/palate, its role in mammalian development and physiology remains unexplored. Here, we have generated a Phf8 knockout allele in mice to examine the consequences of Phf8 loss for development and behaviour. Phf8 deficient mice neither display obvious developmental defects nor signs of cognitive impairment. However, we report a striking resiliency to stress-induced anxiety- and depression-like behaviour on loss of Phf8. We further observe misregulation of serotonin signalling within the prefrontal cortex of Phf8 deficient mice and identify the serotonin receptors Htr1a and Htr2a as direct targets of PHF8. Our results clarify the functional role of Phf8 in mammalian development and behaviour and establish a direct link between Phf8 expression and serotonin signalling, identifying this histone demethylase as a potential target for the treatment of anxiety and depression.

Neuronal Deletion of Kmt2a/Mll1 Histone Methyltransferase in Ventral Striatum is Associated with Defective Spike-Timing-Dependent Striatal Synaptic Plasticity, Altered Response to Dopaminergic Drugs, and Increased Anxiety.

Lysine (K) methyltransferase 2a (Kmt2a) and other regulators of H3 lysine 4 methylation, a histone modification enriched at promoters and enhancers, are widely expressed throughout the brain, but molecular and cellular phenotypes in subcortical areas remain poorly explored. We report that Kmt2a conditional deletion in postnatal forebrain is associated with excessive nocturnal activity and with absent or blunted responses to stimulant and dopaminergic agonist drugs, in conjunction with near-complete loss of spike-timing-dependent long-term potentiation in medium spiny neurons (MSNs). Selective ablation of Kmt2a, but not the ortholog Kmt2b, in adult ventral striatum/nucleus accumbens neurons markedly increased anxiety scores in multiple behavioral paradigms. Striatal transcriptome sequencing in adult mutants identified 262 Kmt2a-sensitive genes, mostly downregulated in Kmt2a-deficient mice. Transcriptional repression includes the 5-Htr2a serotonin receptor, strongly associated with anxiety- and depression-related disorders in human and animal models. Consistent with the role of Kmt2a in promoting gene expression, the transcriptional regulators Bahcc1, Isl1, and Sp9 were downregulated and affected by H3K4 promoter hypomethylation. Therefore, Kmt2a regulates synaptic plasticity in striatal neurons and provides an epigenetic drug target for anxiety and dopamine-mediated behaviors.

Cognition and mood-related behaviors in L3mbtl1 null mutant mice.

Alterations in histone lysine methylation and epigenetic regulators of gene expression could play a role in the neurobiology and treatment of patients diagnosed with mood spectrum disorder, including depression and anxiety. Mutations and altered expression of various lysine methyltransferases (KMTs) and demethylases (KDMs) have been linked to changes in motivational and emotional behaviors in preclinical model systems. However, it is not known whether regulators operating downstream of histone lysine methylation could affect mood-related behavior. Malignant Brain Tumor (MBT) domain 'chromatin reader' proteins bind to methylated histone lysine residues and associate with chromatin remodeling complexes to facilitate or repress gene expression. MBT proteins, including the founding member, L3mbtl1, maintain high levels of expression in neurons of the mature brain. Here, we exposed L3mbtl1 null mutant mice to a wide range of tests exploring cognition and mood-relevant behaviors at baseline and in the context of social isolation, as a stressor to elicit depression-related behavior in susceptible mice. L3mbtl1 loss-of-function was associated with significant decreases in depression and and anxiety in some of the behavioral paradigms. This was not associated with a more generalized neurological dysfunction because cognition and memory remained unaltered in comparison to controls. These findings warrant further investigations on the role of MBT chromatin reader proteins in the context of emotional and affective behaviors.

Neuronal Kmt2a/Mll1 histone methyltransferase is essential for prefrontal synaptic plasticity and working memory.

Neuronal histone H3-lysine 4 methylation landscapes are defined by sharp peaks at gene promoters and other cis-regulatory sequences, but molecular and cellular phenotypes after neuron-specific deletion of H3K4 methyl-regulators remain largely unexplored. We report that neuronal ablation of the H3K4-specific methyltransferase, Kmt2a/Mixed-lineage leukemia 1 (Mll1), in mouse postnatal forebrain and adult prefrontal cortex (PFC) is associated with increased anxiety and robust cognitive deficits without locomotor dysfunction. In contrast, only mild behavioral phenotypes were observed after ablation of the Mll1 ortholog Kmt2b/Mll2 in PFC. Impaired working memory after Kmt2a/Mll1 ablation in PFC neurons was associated with loss of training-induced transient waves of Arc immediate early gene expression critical for synaptic plasticity. Medial prefrontal layer V pyramidal neurons, a major output relay of the cortex, demonstrated severely impaired synaptic facilitation and temporal summation, two forms of short-term plasticity essential for working memory. Chromatin immunoprecipitation followed by deep sequencing in Mll1-deficient cortical neurons revealed downregulated expression and loss of the transcriptional mark, trimethyl-H3K4, at <50 loci, including the homeodomain transcription factor Meis2. Small RNA-mediated Meis2 knockdown in PFC was associated with working memory defects similar to those elicited by Mll1 deletion. Therefore, mature prefrontal neurons critically depend on maintenance of Mll1-regulated H3K4 methylation at a subset of genes with an essential role in cognition and emotion.

Epigenetics and sex differences in the brain: A genome-wide comparison of histone-3 lysine-4 trimethylation (H3K4me3) in male and female mice.

Many neurological and psychiatric disorders exhibit gender disparities, and sex differences in the brain likely explain some of these effects. Recent work in rodents points to a role for epigenetics in the development or maintenance of neural sex differences, although genome-wide studies have so far been lacking. Here we review the existing literature on epigenetics and brain sexual differentiation and present preliminary analyses on the genome-wide distribution of histone-3 lysine-4 trimethylation in a sexually dimorphic brain region in male and female mice. H3K4me3 is a histone mark primarily organized as 'peaks' surrounding the transcription start site of active genes. We microdissected the bed nucleus of the stria terminalis and preoptic area (BNST/POA) in adult male and female mice and used ChIP-Seq to compare the distribution of H3K4me3 throughout the genome. We found 248 genes and loci with a significant sex difference in H3K4me3. Of these, the majority (71%) had larger H3K4me3 peaks in females. Comparisons with existing databases indicate that genes and loci with increased H3K4me3 in females are associated with synaptic function and with expression atlases from related brain areas. Based on RT-PCR, only a minority of genes with a sex difference in H3K4me3 has detectable sex differences in expression at baseline conditions. Together with previous findings, our data suggest that there may be sex biases in the use of epigenetic marks. Such biases could underlie sex differences in vulnerabilities to drugs or diseases that disrupt specific epigenetic processes.

Conserved higher-order chromatin regulates NMDA receptor gene expression and cognition.

Three-dimensional chromosomal conformations regulate transcription by moving enhancers and regulatory elements into spatial proximity with target genes. Here we describe activity-regulated long-range loopings bypassing up to 0.5 Mb of linear genome to modulate NMDA glutamate receptor GRIN2B expression in human and mouse prefrontal cortex. Distal intronic and 3' intergenic loop formations competed with repressor elements to access promoter-proximal sequences, and facilitated expression via a "cargo" of AP-1 and NRF-1 transcription factors and TALE-based transcriptional activators. Neuronal deletion or overexpression of Kmt2a/Mll1 H3K4- and Kmt1e/Setdb1 H3K9-methyltransferase was associated with higher-order chromatin changes at distal regulatory Grin2b sequences and impairments in working memory. Genetic polymorphisms and isogenic deletions of loop-bound sequences conferred liability for cognitive performance and decreased GRIN2B expression. Dynamic regulation of chromosomal conformations emerges as a novel layer for transcriptional mechanisms impacting neuronal signaling and cognition.

Chronic administration of THC prevents the behavioral effects of intermittent adolescent MDMA administration and attenuates MDMA-induced hyperthermia and neurotoxicity in rats.

Most recreational users of 3, 4-methylenedioxymethamphetamine (MDMA or "ecstasy") also take cannabis, in part because cannabis can reduce the dysphoric symptoms of the ecstasy come-down such as agitation and insomnia. Although previous animal studies have examined the acute effects of co-administering MDMA and Δ(9)-tetrahydrocannabinol (THC), which is the major psychoactive ingredient in cannabis, research on chronic exposure to this drug combination is lacking. Therefore, the present study was conducted to investigate the effects of chronic adolescent administration of both THC and MDMA on behavior and on regional serotonin transporter (SERT) binding and serotonin (5-HT) concentrations as indices of serotonergic system integrity. Male Sprague-Dawley rats were divided into four drug administration groups: (1) MDMA alone, (2) THC alone, (3) MDMA plus THC, and (4) vehicle controls. MDMA (2 × 10 mg/kg × 4 h) was administered every fifth day from postnatal day (PD) 35 to 60 to simulate intermittent recreational ecstasy use, whereas THC (5mg/kg) was given once daily over the same time period to simulate heavy cannabis use. THC unexpectedly produced a modest hyperthermic effect when administered alone, but in animals co-treated with both THC and MDMA, there was an attenuation of MDMA-induced hyperthermia on dosing days. Subsequent testing conducted after a drug washout period revealed that THC reduced MDMA-related behavioral changes in the emergence and social interaction tests of anxiety-like behavior and also blunted the MDMA-induced decrease in exploratory behavior in the hole-board test. THC additionally attenuated MDMA -induced decreases in 5-HT levels and in SERT binding in the frontal cortex, parietal cortex, and striatum, but not in the hippocampus. These results suggest that chronic co-administration of THC during adolescence can provide some protection against various adverse physiological, behavioral, and neurochemical effects produced by MDMA.