Egr3 is a novel regulator of DNA damage response genes in the mouse hippocampus
Ketan K. Marballi1, Samuel Brunwasser2, Arhem Barkatullah1, Kimberly Meyers1, Janet Campbell1, Amelia L. Gallitano1* 1University of Arizona College of Medicine - Phoenix 2Washington University in St. Louis
Early growth response (Egr) immediate early gene (IEG) transcription factors are crucial regulators of synaptic plasticity and are critical for memory formation. Egr family members EGR1 and EGR3 are associated with risk for psychiatric illnesses, including schizophrenia, and are reduced in the brains of these patients. Psychiatric disorders are accompanied by cognitive and memory deficits. In addition, brain tissue from psychiatric disorder patients show high levels of DNA damage. Recent studies have found that DNA damage induced by normal physiologic activity induces expression of IEGs such as Egr1 in neurons. These studies suggest that DNA double strand breaks, a form of DNA damage may serve as an “on” switch for activation of IEGs which, in turn, regulate synaptic plasticity and memory formation. However, for IEGs to be ready to respond to a subsequent stimulus, this damage must be repaired. Here we report that Egr3 regulates genes involved in DNA repair in response to neuronal activity. In order to identify novel gene targets of EGR3 in the hippocampus, we carried out global gene expression studies using a microarray in both wild type (WT) and Egr3-/- male mice using a model of Egr3 induction namely electroconvulsive seizure (ECS). Briefly male mice received no ECS/ ECS (n = 4 per group) followed by hippocampal RNA extraction and global gene expression analyses carried out using Illumina WG-6 microarray. Gene pattern and Genome studio programs were used for identifying differentially expressed genes (DEGs). Validation of candidate genes was carried out using quantitative real time PCR in both the original male cohort and an independent female cohort (n = 4-5 per group). 64 common genes identified in both programs were used for biological and functional analysis using Ingenuity pathway analysis (IPA). GADD45B (growth arrest and DNA-damage-inducible 45 beta) signaling (p = 2.04 E-05) was revealed as the top pathway in WT mice vs. Egr3-/- 1hour post-ECS. A literature survey revealed at least 13 genes from the differentially expressed gene list to be involved in DNA damage response. We successfully validated 7 of these genes in the original male cohort and 3 genes in both the original male and an independent female cohort. Based on these results we hypothesize that Egr3 regulates genes that repair or “turn off” the DNA damage “switch” that activates IEGs. Dysfunction in Egr3 may thereby result in an accumulation of DNA damage contributing to cognitive and neurobehavioral deficits.
Funding: NIH R01 MH097803, R21MH113154
Credits: None available.
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