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- All Subjects: Schizophrenia
- Creators: Gallitano, Amelia
Description
Environmental and genetic factors contribute to schizophrenia etiology, yet few studies have demonstrated how environmental stimuli impact genes associated with the disorder. Immediate early genes (IEGs) are of great interest to schizophrenia research because they are activated in response to physiological stress from the environment, and subsequently regulate the expression of downstream genes that are essential to neuropsychiatric function. An IEG, early growth response 3 (EGR3) has been identified as a main gene involved in a network of transcription factors implicated in schizophrenia susceptibility. The serotonin 2A receptor (5-HT2AR) seems to play an important role in schizophrenia and the dysfunction of the 5-HT2AR encoding gene, HTR2A, within the prefrontal cortex (PFC) contributes to multiple psychiatric illnesses including schizophrenia. EGR3's role as a transcription factor that is activated by environmental stimuli suggests it may regulate Htr2a transcription in response to physiological stress, thus affecting 5-HT2AR function in the prefrontal cortex (PFC). The aim of this study was to examine the relationship between Egr3 activation and Htr2a expression after an environmental stimulus. Sleep deprivation is an acute physiological stressor that activates Egr3. Therefore to examine the relationship between Egr3 and Htr2a expression after an acute stress, wild type and Egr3 knockout mice that express EGFP under the control of the Htr2a promoter were sleep deprived for 8 hours. We used immunohistochemistry to determine the location and density of Htr2a-EGFP expression after sleep deprivation and found that Htr2a-EGFP expression was not affected by sex or subregions of the PFC. Additionally, Htr2a-EGFP expression was not affected by the loss of Egr3 or sleep deprivation within the PFC. The LPFC subregions, layers V and VI showed significantly more Htr2a-EGFP expression than layers I-III in all animals for both sleep deprivation and control conditions. Possible explanations for the lack of significant effects in this study may be the limited sample size or possible biological abnormalities in the Htr2a-EGFP mice. Nonetheless, we did successfully visualize the anatomical distribution of Htr2a in the prefrontal cortex via immunohistochemical staining. This study and future studies will provide insight into how Egr3 activation affects Htr2a expression in the PFC and how physiological stress from the environment can alter candidate schizophrenia gene function.
ContributorsSabatino, Alissa Marie (Author) / Gallitano, Amelia (Thesis director) / Hruschka, Daniel (Thesis director) / Maple, Amanda (Committee member) / Barrett, The Honors College (Contributor)
Created2014-05
Description
Schizophrenia affects 1.1% of the population worldwide. Schizophrenia is a complex, multifactorial disorder. Stress can trigger psychotic episodes and exacerbate schizophrenic symptoms. For humans, one gene implicated in stress and schizophrenia in humans is the early growth response 3 (EGR3). Patients with genomic variations in EGR3 have reduced levels of EGR3 in the prefrontal brain region compared with healthy patients. Schizophrenic patients also have less serotonin 2A receptor (5HT2AR), which is coded by the gene Htr2a, in their prefrontal cortex. Mice that are Egr3-deficient also have decreased levels of 5HT2AR, suggesting that Egr3 may be involved in the regulation of 5HT2AR. The purpose of the experiment is to determine if EGR3 binds to the Htr2a gene promoter region by using a Chromatin immunoprecipitation (ChIP) assay. We will use ECS to increase EGR3 expression. Previously we have identified two upstream sites of interest where EGR3 potentially binds to the Htr2a gene, one which is distal and one proximal to the transcription start site. After ECS, increased binding is seen in the Htr2a distal region with EGR3 via the ChIP assay. Increased binding was not observed at either of the promoter sites; however, the t-test comparing the distal site of the ECS and the No ECS groups to have a p-value of 0.056, suggesting that increasing the number of animals (n=7) could possibly give a more accurate representation to test our hypothesis. However, the experiment still suggests increased expression and that EGR3 may bind to the distal site of Htr2a. Keywords: stress, environment, genetics, schizophrenia, EGR3, chromatin immunoprecipitation
ContributorsMishra, Abhinav (Author) / Buetow, Kenneth (Thesis director) / Gallitano, Amelia (Committee member) / Zhao, Xiuli (Committee member) / Barrett, The Honors College (Contributor) / School of Politics and Global Studies (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
Egr3 is an immediate early gene transcription factor that shows genetic association with schizophrenia, and is found in decreased levels in the brains of schizophrenia patients. Schizophrenia patients also exhibit cognitive and memory deficits, both of which Egr3 has been shown to play a crucial role in. Additionally, high levels of DNA damage are found in the brains of schizophrenia patients. A recent study has shown that DNA damage occurs as a result of normal physiological activity in neurons and is required for induction of gene expression of a subset of early response genes. Also, failure to repair this damage can lead to gene expression in a constitutive switched on state. Egr3 knockout (Egr3-/-) mice show deficits in hippocampal synaptic plasticity and memory. We were interested in characterizing downstream targets of EGR3 in the hippocampus. To determine these targets, electroconvulsive seizure (ECS) was carried out in Egr3 -/- versus wild type (WT) mice, and a microarray study was first done in our lab. ECS maximally stimulates Egr3 expression and we hypothesized that there would be gene targets that are differentially expressed between Egr3 -/- and WT mice that had been subjected to ECS. Two separate analyses of the microarray yielded 65 common genes that were determined as being differentially expressed between WT and Egr3 -/- mice after ECS. Further Ingenuity Pathway Analysis of these 65 genes indicated the Gadd45 signaling pathway to be the top canonical pathway, with the top four pathways all being associated with DNA damage or DNA repair. A literature survey was conducted for these 65 genes and their associated pathways, and 12 of the 65 genes were found to be involved in DNA damage response and/or DNA repair. Validation of differential expression was then conducted for each of the 12 genes, in both the original male cohort used for microarray studies and an additional female cohort of mice. 7 of these genes validated through quantitative real time PCR (qRT-PCR) in the original male cohort used for the microarray study, and 4 validated in both the original male cohort and an independent female cohort. Bioinformatics analysis yielded predicted EGR3 binding sites in promoters of these 12 genes, validating their role as potential transcription targets of EGR3. These data reveal EGR3 to be a novel regulator of DNA repair. Further studies will be needed to characterize the role of Egr3 in repairing DNA damage.
ContributorsBarkatullah, Arhem Fatima (Author) / Newbern, Jason (Thesis director) / Gallitano, Amelia (Committee member) / Marballi, Ketan (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Schizophrenia risk is influenced by both genetic and environmental factors. The immediate early gene early growth response 3 (Egr3), is regulated downstream of several schizophrenia risk genes and encodes a zinc-finger transcription factor protein. Previous studies from our lab indicate that Egr3 deficient (Egr3 -/-) mice exhibit schizophrenia-like phenotypes. We also discovered decreased serotonin 2a receptors (5-HT2AR) in the Egr3 -/- mice, similar to studies that reported decreased 5-HT2ARs in schizophrenia patients. We previously reported that sleep deprivation, a mild stress, causes the over expression of Egr3 and the serotonin 2a gene (Htr2a) in the cortex. To determine whether EGR3, a transcription factor, regulates Htr2a in the prefrontal cortex after sleep deprivation, Egr3 -/-and Egr3 +/+ mice were sleep deprived for eight hours. Transgenic mice were used that expressed enhanced green fluorescent protein (EGFP) under control of the Htr2a promoter via a bacterial artificial chromosome (BAC). Immunohistochemistry was performed to identify EGFP containing cells. Data analysis revealed no significant interaction between genotype and sleep deprivation in 5-HT2AR/EGFP containing cells within the prefrontal cortex. Based on the findings of this study, more data is needed to better determine the relationship between sleep deprivation and its effect on the regulation of Htr2a through in an EGR3 dependent manner.
ContributorsReznik, Derek Lee (Author) / Wilson-Rawls, Jeanne (Thesis director) / Gallitano, Amelia (Committee member) / Anderson, Karen (Committee member) / School of Sustainability (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
About 1% of the United States adult population currently suffers from schizophrenia. The symptoms of schizophrenia can be broken down into three main categories including: positive symptoms such as psychoses, negative symptoms such as anhedonia, and cognitive symptoms such as memory difficulties. The early growth response 3 (Egr3) is part of a family of genes known as the immediate early genes (IEGs), which are zinc-finger transcription factors. IEGs are not protein synthesis dependent, which means that they can be activated quickly, within 30-45 minutes, in response to certain environmental stimuli such as sleep deprivation. Egr3, an activity dependent gene, may be up-regulated by both genetic and environmental cues. Egr3 is thought to play an integral role in a biochemical pathway that may explain the onset of schizophrenia. However, the exact causes of schizophrenia remain unknown. Egr3 is not only activated in response to environmental factors, but has also been linked to many genes that are associated with schizophrenia in humans (Huentelman et al., 2015). Post-mortem brain tissue studies of patients with schizophrenia have decreased levels of EGR3 in their prefrontal cortex (PFC) and mice lacking Egr3 (Egr3 -/-) exhibit schizophrenia-like phenotypes such as locomotor hyperactivity. Egr 3 -/- mice also exhibit a diminished head twitch response to 2,5-Dimethoxy-4-iodoamphetamine (DOI), a 5-HT2A agonist (Yamada, et al., 2007; Gallitano-Mendel, et al., 2008). A link was established between schizophrenia patients and the serotonin 2A receptor (5-HT2AR) upon recognizing that 5-HT2AR agonists like lysergic acid diethylamide (LSD) create hallucinations similar to those in schizophrenic patients and 5-HT2AR antagonists such as the second-generation antipsychotic clozapine can reverse those hallucinations (Sommer, 2012). Paradoxically, however, post-mortem studies of schizophrenia patients have actually shown a decrease in PFC 5-HT2ARs as well as a 70% decrease found in the PFC of Egr3 -/- mice (Rasmussen, et al., 2010; Williams, et al., 2012). Therefore, we hypothesize that EGR3 directly regulates expression of 5-HT2ARs. To test this we will use virus-mediated overexpression of 5-HT2ARs in the PFCs of mice to see if we can rescue the schizophrenia-like phenotypes of the Egr3 -/- mice. After bilateral PFC stereotaxic injection of herpes simplex virus (HSV) with enhanced green fluorescent protein (EGFP) or HSV-Htr2a-EGFP in both wild type (WT) and Egr3 -/- mice, the mice were behaviorally tested using locomotor activity and DOI-induced head twitch response. We found that Egr3-/- mice, compared to WT mice, demonstrated locomotor hyperactivity and a decreased DOI-induced head twitch response, confirming prior findings, but no significant main effect of virus. A significant effect of the HSV-Htr2a-EGFP was seen when comparing DOI-induced head twitch response in WT mice to Egr3 -/- mice. WT mice showed a higher number of head twitches in comparison to the knockout mice. These findings suggest further research must be conducted in order to investigate whether a functional 5-HT2AR is being translated and correctly transported to the membrane. These findings may also point to an unknown factor mediating the regulation between Egr3 and 5-HT2ARs.
ContributorsHoebee, Shelby Marie (Author) / Van Horn, Wade (Thesis director) / Gallitano, Amelia (Committee member) / Department of Psychology (Contributor) / School of Molecular Sciences (Contributor) / School of Criminology and Criminal Justice (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Immediate early genes (IEGs) are rapidly activated in response to an environmental stimulus, and most code for transcription factors that mediate processes of synaptic plasticity, learning, and memory. EGR3, an immediate early gene transcription factor, is a mediator of biological processes that are disrupted in patients with schizophrenia (SCZ). A microarray experiment conducted by our lab revealed that Egr3 also regulates genes involved in DNA damage response. A recent study revealed that physiological neuronal activity results in the formation of DNA double-stranded breaks (DSBs) in the promoters of IEGs. Additionally, they showed that these DSBs are essential for inducing the expression of IEGs, and failure to repair these DSBs results in the persistent expression of IEGs. We hypothesize that Egr3 plays a role in repairing activity- induced DNA DSBs, and mice lacking Egr3 should have an abnormal accumulation of these DSBs. Before proceeding with that experiment, we conducted a preliminary investigation to determine if electroconvulsive stimulation (ECS) is a reliable method of inducing activity- dependent DNA damage, and to measure this DNA damage in three subregions of the hippocampus: CA1, CA3, and dentate gyrus (DG). We asked the question, are levels of DNA DSBs different between these hippocampal subregions in animals at baseline and following electroconvulsive stimulation (ECS)? To answer this question, we quantified γ-H2AX, a biomarker of DNA DSBs, in the hippocampal subregions of wildtype mice. Due to technical errors and small sample size, we were unable to substantiate our preliminary findings. Despite these shortcomings, our experimental design can be modified in future studies that investigate the role of Egr3 in activity-induced DNA damage repair.
ContributorsKhoshaba, Rami Samuel (Author) / Newbern, Jason (Thesis director) / Gallitano, Amelia (Committee member) / Marballi, Ketan (Committee member) / School of Molecular Sciences (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Damage to DNA can affect the genes it encodes; if this damage is not repaired, abnormal proteins may be produced and cellular functions may be disturbed. DNA damage has been implicated in the initiation and progression of a variety of diseases. Conversely, DNA damage has also been discovered to contribute to beneficial biological processes. Madabhushi and colleagues (2015) determined that activity-dependent DNA double strand breaks (DSBs) in the promoter region of immediate early genes (IEGs) induced their expression. EGR3 is an IEG transcription factor which regulates the expression of growth factors and synaptic plasticity-associated genes. In a previously conducted microarray experiment, it was revealed that EGR3 regulates the expression of genes associated with DNA repair such as Cenpa and Nr4a2. These findings inspired us to investigate if EGR3 affects DNA repair in vivo. Before conducting this experiment, we sought to standardize and optimize a method of inducing DNA damage in the hippocampus. Electroconvulsive stimulation (ECS) is utilized to induce neuronal activity. Since neuronal activity leads to the formation of DNA DSBs, we theorized that ECS could be used to induce DNA DSBs in the hippocampus. We predicted that mice that receive ECS would have more DNA DSBs than those that receive the sham treatment. Gamma H2AX, a biomarker for DNA damage, was utilized to quantify DNA DSBs. Gamma H2AX expression in the dentate gyrus, CA1 and CA3 regions of the hippocampus was compared between mice that received the sham treatment and mice that received ECS. Mice that received ECS were sacrificed either 1 or 2 hours post-administration, constituting treatment conditions of 1 hr post-ECS and 2 hrs post-ECS. Our results suggest that ECS has a statistically significant effect exclusively in the CA1 region of the hippocampus. However, our analyses may have been limited due to sample size. A power analysis was conducted, and the results suggest that a sample size of n=4 mice will be sufficient to detect significant differences across treatments in all three regions of the hippocampus. Ultimately, future studies with an increased sample size will need to be conducted to conclusively assess the use of ECS to induce DNA damage within the hippocampus.
ContributorsAden, Aisha Abubakar (Author) / Newbern, Jason (Thesis director) / Gallitano, Amelia (Thesis director) / Marballi, Ketan (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05