EZH2-Mediated H3K27me3 Targets Transcriptional Circuits of Neuronal Differentiation

Abstract

The Polycomb Repressive Complex 2 (PRC2) plays important roles in the epigenetic regulation of cellular development and differentiation through H3K27me3-dependent transcriptional repression. Aberrant PRC2 activity has been associated with cancer and neurodevelopmental disorders, particularly with respect to the malfunction of sits catalytic subunit EZH2. Here, we investigated the role of the EZH2-mediated H3K27me3 apposition in neuronal differentiation. We made use of a transgenic mouse model harboring Ezh2 conditional KO alleles to derive embryonic stem cells and differentiate them into glutamatergic neurons. Time course transcriptomics and epigenomic analyses of H3K27me3 in absence of EZH2 revealed a significant dysregulation of molecular networks affecting the glutamatergic differentiation trajectory that resulted in: (i) the deregulation of transcriptional circuitries related to neuronal differentiation and synaptic plasticity, in particular LTD, as a direct effect of EZH2 loss and (ii) the appearance of a GABAergic gene expression signature during glutamatergic neuron differentiation. These results expand the knowledge about the molecular pathways targeted by Polycomb during glutamatergic neuron differentiation.

Gonadal Sex and Sex-Chromosome Complement Interact to Affect Ethanol Consumption in Adolescent Four Core Genotypes Mice

“…Moreover, co-immunoprecipitation of AR and KDM6A has been reported in prostate cancer cells (expressing the oncogenic TMPRSS2:ERG gene fusion) [209] and AR has been demonstrated to decrease expression of KDM6B [210]. Additionally, the Polycomb repressor complex 2 (PRC2) adds H3K27me3 repressive marks [211] and its catalytic subunit (EZH2 [212]) and required subunit for H3K27me3 binding (EED [213]) directly regulate AR binding to hormone response elements [214]. Lastly, querying the protein interaction network between AR, KDM6A, EZH2 and EED as predicted via STRING (a database of known and predicted protein-protein interactions) returns statistically significant protein-protein interaction enrichment in both humans (p = 0.0001) and mice (p = 0.005) [215].…”

Shaking up the silence: consequences of HMGN1 antagonizing PRC2 in the Down syndrome brain

“…EED ablation also resulted in functional deficits manifested in the altered electrophysiological properties of the neurons, abnormal production of cell-specific metabolites, and pathological behavioral phenotypes in mice [ 153 ]. In agreement with this, conditional EZH2 inactivation via Cre -inducible deletion of the SET domain in glutamatergic neurons in vitro led to their altered differentiation trajectory and the switch towards a transcriptomic signature associated with GABAergic neurons [ 132 ]. The enhancement in GABAergic signature and the overproduction of interneurons following EZH2 ablation was also shown in mouse cerebellum [ 155 ], further implicating PRC2 in the establishment and maintenance of neuronal identity, as well as the balance between the different neuronal populations.…”

“…PRC2 is involved in transcriptional silencing through its methyltransferase (HMT) activity, catalyzing the mono-, di-, and tri-methylation of H3K27 [ 130 , 131 ]. It has many roles specifically within the central nervous system, including effects on maturation [ 132 ], proliferation [ 133 ], and the identity of neural stem cells [ 134 ], migration and maturation of neurons [ 135 ], and gliogenesis [ 136 , 137 ]. The proper function of PRC2 is required for the silencing of specific genes to allow the transcription of other genes that mediate alternative cellular processes.…”

“…EZH2-KO results in the reduction of neural progenitor proliferation Liu et al [ 166 ] Appropriate neuronal orientation and cortical radial migration EZH2 inhibition results in abnormal neuronal orientation reduced neuronal numbers at the cortical plate and ectopic expression of Reelin Zhao et al [ 135 ] EZH2-mediated repression of Netrin1 is necessary for the appropriate migration of pontine neurons in the cortico-ponto-cerebellar pathway in mice. EZH2-KO results in ectopic Netrin1 induction and aberrant neuronal migration Di Meglio et al [ 156 ] Maintenance of neuronal identity Deletion of EED disrupts the acquisition and maintenance of neuronal identity and functionality in differentiated dopaminergic and serotonergic neurons Toskas et al [ 153 ] Conditional knock-out of EZH2 results in reduced proliferation of granule precursor cells, decrease in the Purkinje cell population and increase in GABAergic interneurons in the mouse cerebellum Feng et al [ 155 ] Conditional KO of EZH2 results in loss of H3K27me3 marks in differentiating neurons and causes changes to molecular networks that govern glutamatergic neuron differentiation, leading to a disruption in the balance of inhibitory/excitatory neurons during the development Buontempo et al [ 132 ] Combined EZH1 and EZH2 KO leads to a loss of H3K27me3 marks in MSNs in the striatum, down-regulation of lineage-specific and function-specific MSN genes, and upregulation of the death-promoting genes Von Schimmelmann et al [ 154 ] Glial cell development and fate determination Pharmacological inhibition of EZH2 leads to increased expression of Olig1 and Olig2. Increased depositions of H3K27me3 marks are detected in the genomic loci of Olig1 and Olig2 in HMGN-KO ESCs Deng et al [ 124 ] KO of EZH2 or EED do not affect the generation of OPC but inhibit their differentiation into mature, myelinating oligodendrocytes.…”

“…The underproduction of GABAergic neurons and their abnormal migration was also demonstrated in an in vitro model derived from DS iPSCs and attributed to the increased levels of p21-activated kinase 1 (PAK1) [ 242 ], a binding target for SUZ12 [ 68 ]. Moreover, the commitment and lineage development of inhibitory neurons are PRC2-dependent [ 132 , 243 ] and while OLIG2 is triplicated in DS, it is also known to be highly regulated by HMGN1 [ 121 ], suggesting that despite the above discrepancy between the studies, there is a consistency in reported deficits in the interneuron motility and the disbalance between the excitatory and inhibitory neurons that can be potentially caused by the gene dosage of HMGN1 and subsequent dysregulation of PRC2 targets.…”