Examining the effects of the histone methyltransferase inhibitor BIX-01294 on histone modifications and gene expression in both a clinical population and mouse models

Abstract

Schizophrenia has been consistently characterized by abnormal patterns of gene down-regulation, increased restrictive chromatin assemblies, and reduced transcriptional activity. Histone methyltransferase (HMT) mRNA and H3K9me2 levels are elevated in postmortem brain and peripheral blood cells of persons with schizophrenia. Moreover, this epigenomic state likely contributes to the disease, as HMT levels correlate with clinical symptomatology. This manuscript sought to establish the potential therapeutic value of the HMT inhibitor BIX-01294 (BIX). Human peripheral mononuclear cells (PBMC) from 24 individuals with schizophrenia and 24 healthy individuals were cultured in the presence of BIX (5uM or 10uM). Mice were given once daily intraperitoneal injections of BIX (0.5 or 1mg/kg) for one week. Cultured cells, mouse cortex, or striatum was harvested, RNA extracted and RT-PCR conducted for several schizophrenia candidate genes: IL-6, Gad1, Nanog, KLF4, Reln, and Bdnf9a. Total H3K9me2 levels were measured using western blot while H3K9me2 binding to selected genes of interest was conducted using chromatin immunoprecipitation (ChIP). Neuronal subtype-specific BDNF conditional knockdown was conducted using the cre/lox system of mutant animals. Treatment with BIX decreased H3K9me2 and increased selected mRNA levels in cultured PBMCs from both normal controls and participants with schizophrenia. In mice, peripheral administration of BIX decreased cortical H3K9me2 levels and increased schizophrenia candidate gene expression. In BDNF conditional knockdown animals, BIX administration was able to significantly rescue Bdnf9a mRNA levels in ChAT and D1 Bdnf conditional knockdown mice. The results presented in this manuscript demonstrate a potential for further research into the clinical effectiveness of histone modifying pharmacology in the treatment of schizophrenia.

Histone Methyltransferases SUV39H1 and G9a and DNA Methyltransferase DNMT1 in Penumbra Neurons and Astrocytes after Photothrombotic Stroke

“…The study investigated the putative neuroprotective effect of the following inhibitors of epigenetic proteins were used: DNMT1 (5-azacytidine or decitabine (0.2 mg/kg, 1 per day, 7 days) [31][32][33], histone methyltransferases SUV39H1 and G9a (BIX01294 (0.5 mg/kg, once a day, 7 days) [34], and A-366 (2 mg/kg, once a day, 7 days) [35]. They were dissolved in dimethyl sulfoxide (DMSO) and then diluted in sterile saline.…”

Differential H3K9me2 heterochromatin levels and concordant mRNA expression in postmortem brain tissue of individuals with schizophrenia, bipolar, and controls

“…Therefore, our non-significant mRNA expression results may be a result of the variable antipsychotic dosing present in our sample. We have also shown that antipsychotic treatment in vitro can decrease heterochromatin levels and increase promoter phosphorylation and mRNA expression of genes that are tolerized (heterochromatinized) via an endotoxin tolerance paradigm, while other promoters do not respond in this way ( 36 , 60 ). This targeted response to antipsychotic treatment could be an explanation for the LIPJ and NRGN genes that did not show coordination with their H3K9me2 promoter occupation levels.…”

Epigenetic Regulation of Optic Nerve Development, Protection, and Repair

“…The dimethylation of histone 3 at lysine 9 (H3K9Me2) has been recognized as a chromatin silencer, and it is specifically catalyzed by G9a, a histone methyltransferase [ 80 ]. Increased H3K9Me2 has been demonstrated to limit the binding of transcription factors to the promoters of their downstream genes and thus diminishes their further expression [ 81 ]. Moreover, G9a has also been found to be significantly expressed in adult mouse retinas and throughout the development.…”