title: G9a/GLP histone lysine dimethyltransferase complex activity in the hippocampus and the entorhinal cortex is required for gene activation and silencing during memory consolidation.
abstract: Learning triggers alterations in gene transcription in brain regions such as the hippocampus and the entorhinal cortex (EC) that are necessary for long-term memory (LTM) formation. Here, we identify an essential role for the G9a/G9a-like protein (GLP) lysine dimethyltransferase complex and the histone H3 lysine 9 dimethylation (H3K9me2) marks it catalyzes, in the transcriptional regulation of genes in area CA1 of the rat hippocampus and the EC during memory consolidation. Contextual fear learning increased global levels of H3K9me2 in area CA1 and the EC, with observable changes at the Zif268, DNMT3a, BDNF exon IV, and cFOS gene promoters, which occurred in concert with mRNA expression. Inhibition of G9a/GLP in the EC, but not in the hippocampus, enhanced contextual fear conditioning relative to control animals. The inhibition of G9a/GLP in the EC induced several histone modifications that include not only methylation but also acetylation. Surprisingly, we found that downregulation of G9a/GLP activity in the EC enhanced H3K9me2 in area CA1, resulting in transcriptional silencing of the non-memory permissive gene COMT in the hippocampus. In addition, synaptic plasticity studies at two distinct EC-CA1 cellular pathways revealed that G9a/GLP activity is critical for hippocampus-dependent long-term potentiation initiated in the EC via the perforant pathway, but not the temporoammonic pathway. Together, these data demonstrate that G9a/GLP differentially regulates gene transcription in the hippocampus and the EC during memory consolidation. Furthermore, these findings support the possibility of a role for G9a/GLP in the regulation of cellular and molecular cross talk between these two brain regions during LTM formation.
authors.affiliation: The Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: Swati
authors.initials: S
authors.lastname: Gupta-Agarwal
authors.forename: Aimee V
authors.initials: AV
authors.lastname: Franklin
authors.forename: Thomas
authors.initials: T
authors.lastname: Deramus
authors.forename: Muriah
authors.initials: M
authors.lastname: Wheelock
authors.forename: Robin L
authors.initials: RL
authors.lastname: Davis
authors.forename: Lori L
authors.initials: LL
authors.lastname: McMahon
authors.forename: Farah D
authors.initials: FD
authors.lastname: Lubin
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D003213:Conditioning, Psychological / Q000502:physiology; D003463:Cues; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D004558:Electric Stimulation; D018728:Entorhinal Cortex / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005239:Fear; D020868:Gene Silencing / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000201:enzymology* / Q000502:physiology; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008745:Methylation; D018408:Patch-Clamp Techniques; D011108:Polymers; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology*
chemical_list: D001381:Azepines; C518299:BIX 01294; D019208:Brain-Derived Neurotrophic Factor; D004791:Enzyme Inhibitors; C407025:HTR bioplant; D006657:Histones; D011108:Polymers; D011799:Quinazolines; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D011495:Histone-Lysine N-Methyltransferase; D051076:Proto-Oncogene Proteins c-fyn