Inhibition of EHMT1/2 rescues synaptic and cognitive functions for Alzheimer's disease
Ontology highlight
ABSTRACT: Epigenetic dysregulation, which leads to the alteration of gene expression in the brain, is suggested as one of the key pathophysiological bases of aging and neurodegeneration. Here we found that, in the late-stage familial Alzheimer’s disease (FAD) mouse model, repressive histone H3 dimethylation at lysine 9 (H3K9Me2) and euchromatic histone methyltransferases, EHMT1 and EHMT2 (H3K9Me2 catalyzer), were significantly elevated in the prefrontal cortex (PFC) region of post-mortem tissues from human patients with Alzheimer's disease. Concomitantly, H3K9Me2 at the promoter region of glutamate receptors was increased in PFC of aged FAD mice, which was linked to the diminished transcription, expression and function of AMPA and NMDA receptors. Treatment of FAD mice with specific EHMT1/2 inhibitors reversed histone hyper-methylation and led to the recovery of glutamate receptor expression and excitatory synaptic function in PFC and hippocampus. Chromatin immunoprecipitation-sequencing (ChIP-seq) data indicated that FAD mice exhibited genome-wide increase of H3K9Me2 enrichment at genes involved in neuronal signaling (including glutamate receptors), which was reversed by EHMT1/2 inhibition. Moreover, the impaired recognition memory, working memory, and spatial memory in aged FAD mice were rescued by the treatment with EHMT1/2 inhibitors. These results suggest that disrupted epigenetic regulation of glutamate receptor transcription underlies the synaptic and cognitive deficits in Alzheimer's disease, and targeting histone methylation enzymes may represent a novel therapeutic strategy for this prevalent neurodegenerative disorder.
Project description:EHMT1 haploinsufficiency causes Kleefstra syndrome (KS), a complex disorder of developmental delay and intellectual disability. EHMT1 encodes a lysine methyltransferase GLP and regulates histone H3 lysine 9 dimethylation (H3K9me2). Ehmt1 heterozygous mutant (Ehmt1∆/+) mice show KS-like abnormal behavioral phenotypes. Here, we examined the reversibility of decreased H3K9me2 by postnatal supply of GLP in post-mitotic neuron of Ehmt1∆/+ mice brain. For this purpose, we generated the mice harboring inducible Ehmt1 cDNA with CamKII-creER (Ehmt1 iTG-neuron mice) in Ehmt1∆/+ background. These mice expressed exogenous Ehmt1 in post-mitotic neuron upon Tamoxifen treatment. Using these mice, we sorted out NeuN+ cells from cortical region and performed Histone H3 K9-dimethyation ChIP analysis. Here we showed that Ehmt1 haploinsufficiency induces global reduction of euchromatic H3K9me2 especially in the euchromatic region of brain and that postnatal supply of GLP can reverse the diminished H3K9me2 phenotype, even in a postmitotic situation.
Project description:Oligodendrocyte progenitor cells (OPCs) represent a population of electrically active and dividing cells, which are capable of responding to neuronal activity, by proliferating and differentiating. Here we report that the repressive euchromatic H3K9me2 histone mark, deposited by the histone mehyltransferases EHMT1 and EHMT2 enzymes, increases in proliferating OPCs in mice following optogenetic stimulation of neuronal activity. Using primary cultured OPCs with genetic deletion of Ehmt1 and Ehmt2, and pharmacological inhibition of EHMT enzymatic activity, we reveal the importance of these enzymes in repressing the expression of genes regulating cell death and electrical properties in proliferating OPCs. Consistent with these findings, we detect higher levels of cholinergic muscarinic receptors, fewer numbers of oligodendrocyte lineage cells and lower levels of the myelin basic protein (MBP) in mice with lineage specific ablation of Ehmt1 and Ehmt2. Together these data suggest that the repressive H3K9me2 histone mark, whose levels increase in proliferating OPCs after neuronal stimulation, is an important modulator of cell death and proteins regulating the electrical properties of OPCs.
Project description:EHMT1 (also known as GLP) is a multifunctional protein, best known for its role as an H3K9me1 and H3K9me2 methyltransferase through its reportedly obligatory dimerization with EHMT2 (also known as G9A). Here, we investigated the role of EHMT1 in the oocyte in comparison to EHMT2 using oocyte-specific conditional knockout mouse models (Ehmt2 cKO, Ehmt1cKO, Ehmt1/2 cDKO), with ablation from the early phase of oocyte growth. Loss of EHMT1 in Ehmt1 cKO and Ehmt1/2 cDKO oocytes recapitulated meiotic defects observed in the Ehmt2 cKO; however, there was a significant impairment in oocyte maturation and developmental competence in Ehmt1 cKO and Ehmt1/2 cDKO oocytes beyond that observed in the Ehmt2cKO. Consequently, loss of EHMT1 in oogenesis results, upon fertilization, in mid-gestation embryonic lethality. To identify H3K9 methylation and other meaningful biological changes in each mutant to explore the molecular functions of EHMT1 and EHMT2, we performed immunofluorescence imaging, multi-omics sequencing, and mass spectrometry (MS)–based proteome analyses in cKO oocytes. Although H3K9me1 was depleted only upon loss of EHMT1, H3K9me2 was decreased, and H3K9me2-enriched domains were eliminated equally upon loss of EHMT1 or EHMT2. Furthermore, there were more significant changes in the transcriptome, DNA methylome, and proteome in Ehmt1/2 cDKO than Ehmt2 cKO oocytes, withtranscriptional derepression leading to increased protein abundance and local changes in genic DNA methylation in Ehmt1/2 cDKO oocytes. Together, our findings suggest that EHMT1 contributes to local transcriptional repression in the oocyte, partially independent of EHMT2, and is critical for oogenesis and oocyte developmental competence
Project description:Many of the genes disrupted in autism are identified as histone-modifying enzymes and chromatin remodelers, most prominently those that mediate histone methylation/demethylation. However, the role of histone methylation enzymes in the pathophysiology and treatment of autism remains unknown. To address this, we used mouse models of haploinsufficiency of the Shank3 gene (a highly penetrant monogenic autism risk factor), which exhibits prominent autism-like social deficits. We found that histone methyltransferases EHMT1 and EHMT2, as well as histone lysine 9 dimethylation (specifically catalyzed by EHMT1/2), were selectively increased in the prefrontal cortex (PFC) of Shank3-deficient mice and autistic human postmortem brains. Treatment with the EHMT1/2 inhibitor UNC0642 or knockdown of EHMT1/2 in PFC induced a robust rescue of autism-like social deficits in Shank3-deficient mice, and restored NMDAR-mediated synaptic function. Activityregulated cytoskeleton-associated protein (Arc) was identified as one of the causal factors underlying the rescuing effects of UNC0642 on NMDAR function and social behaviors in Shank3-deficient mice. UNC0642 treatment also restored a large set of genes involved in neural signaling in PFC of Shank3-deficient mice. These results suggest that targeting histone methylation enzymes to adjust gene expression and ameliorate synaptic defects could be a potential therapeutic strategy for autism.
Project description:Kleefstra syndrome, a disease with intellectual disability, autism spectrum disorders and other developmental defects is caused in humans by haploinsufficiency of EHMT1. Although EHMT1 and its paralog EHMT2 were shown to be histone methyltransferases responsible for deposition of the di-methylated H3K9 (H3K9me2), the exact nature of epigenetic dysfunctions in Kleefstra syndrome remains unknown. Here, we found that the epigenome of Ehmt1+/- adult mouse brain displays a marked increase of H3K9me2/3 which correlates with impaired expression of protocadherins, master regulators of neuronal diversity. Increased H3K9me3 was present already at birth, indicating that aberrant methylation patterns are established during embryogenesis. Interestingly, we found that Ehmt2+/- mice do not present neither the marked increase of H3K9me2/3 nor the cognitive deficits found in Ehmt1+/- mice, indicating an evolutionary diversification of functions. Our finding of increased H3K9me3 in Ehmt1+/- mice is the first one supporting the notion that EHMT1 can quench the deposition of tri-methylation by other Histone methyltransferases, ultimately leading to impaired neurocognitive functioning. Our insights into the epigenetic pathophysiology of Kleefstra syndrome may offer guidance for future developments of therapeutic strategies for this disease.
Project description:Homeostatic plasticity, a form of synaptic plasticity, maintains the fine balance between overall excitation and inhibition in developing and mature neuronal networks. Although the synaptic mechanisms of homeostatic plasticity are well characterized, the associated transcriptional program remains poorly understood. We show that the Kleefstra syndrome-associated protein, EHMT1, plays a critical and cell-autonomous role in synaptic scaling by responding to attenuated neuronal firing or sensory drive. Chronic activity deprivation increased the amount of neuronal dimethylated H3 at lysine 9 (H3K9me2), the catalytic product of EHMT1 and an epigenetic marker for gene repression. Genetic knockdown and pharmacological blockade of EHMT1 or EHMT2 prevented the increase of H3K9me2 and synaptic scaling up. Furthermore, BDNF repression was preceded by EHMT1/2-mediated H3K9me2 deposition at the Bdnf promoter during synaptic scaling up, both in vivo or in vivo. These findings suggest that changes in chromatin state through H3K9me2 governs a repressive program to achieve synaptic scaling. 12 samples (4 conditions in biological triplicate), 3 wt, 3 wt tetradotoxin treated, 3 k.d., 3 k.d. tetradotoxin treated
Project description:G9a (EHMT2) and the G9a-like protein GLP (EHMT1) form a stable G9a/GLP heterodimer in embryonic stem cells and function cooperatively to establish and maintain the abundant repressive H3K9me2 modification, in addition to modifying several non-histone proteins. The G9a-dependent H3K9me2 is implicated in lineage-specific gene silencing and covers large chromosomal domains. While the mechanism of H3K9me2maintenance by G9a/GLP is known, how new patterns of this modification are established is not well understood. With this in mind, we used FLAG affinity purification of G9a under two different stringency conditions (150 and 300 mM NaCl) coupled with mass spectrometry to identify proteins stably associated with G9a/GLP, which could serve as potential recruiters of the complex to unmodified chromatin.
Project description:Transition from a partially reprogrammed pre-iPSC state to iPSC state can be achieved by modulating levels of histone modifying enzymes or proteins that can bind to histone modifications We used microarrays to determine the gene expression profile of pre-iPSCs depleted for either 3 histone methyltransferases together or the HP1gamma protein pre-iPSCs were subjected to simultaneous siRNA mediated knockdown of Ehmt1, Ehmt2 and Setdb1- which is the 3XHMT sample that mediate H3k9me2/me3 or Cbx3( HP1gamma) or control siRNA to luciferase
Project description:Kleefstra syndrome (KS, also known as 9q.34.3 deletion syndrome) is a rare genetic disorder characterized by a developmental delay, abnormal behaviors and autism-like features. This syndrome is caused by haplo-insufficiency of the euchromatin histone methyltransferase 1 gene (EHMT1/GLP/KDM1D). This gene product, GLP is a methyltransferase responsible for mono- and di-methylation of lysine 9 on histone H3 N-terminal tail, which modulates epigenetic information. Ehmt1 heterozygous mutant (Ehmt1∆/+) mice show KS-like abnormal behavioral phenotypes and utilized as KS model mice. Here, we isolated nuclei from adult Ehmt1∆/+ mice cortex and analysed gene expression precisely by single nucleus RNA-seq analysis. It showed that many genes were up or down regulated in different cell types of Ehmt1∆/+ mice brain. Among them, inflammation associating genes are up-regulated in Ehmt1∆/+ mice neuronal cells. And this up-regulation was reversed by postnatal supply of GLP in post-mitotic neuron of Ehmt1∆/+ mice brain.
Project description:Homeostatic plasticity, a form of synaptic plasticity, maintains the fine balance between overall excitation and inhibition in developing and mature neuronal networks. Although the synaptic mechanisms of homeostatic plasticity are well characterized, the associated transcriptional program remains poorly understood. We show that the Kleefstra syndrome-associated protein, EHMT1, plays a critical and cell-autonomous role in synaptic scaling by responding to attenuated neuronal firing or sensory drive. Chronic activity deprivation increased the amount of neuronal dimethylated H3 at lysine 9 (H3K9me2), the catalytic product of EHMT1 and an epigenetic marker for gene repression. Genetic knockdown and pharmacological blockade of EHMT1 or EHMT2 prevented the increase of H3K9me2 and synaptic scaling up. Furthermore, BDNF repression was preceded by EHMT1/2-mediated H3K9me2 deposition at the Bdnf promoter during synaptic scaling up, both in vivo or in vivo. These findings suggest that changes in chromatin state through H3K9me2 governs a repressive program to achieve synaptic scaling.