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Yelhekar TD, Meng M, Doupe J, Lin Y. All IEGs Are Not Created Equal-Molecular Sorting Within the Memory Engram. ADVANCES IN NEUROBIOLOGY 2024; 38:81-109. [PMID: 39008012 DOI: 10.1007/978-3-031-62983-9_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
When neurons are recruited to form the memory engram, they are driven to activate the expression of a series of immediate-early genes (IEGs). While these IEGs have been used relatively indiscriminately to identify the so-called engram neurons, recent research has demonstrated that different IEG ensembles can be physically and functionally distinct within the memory engram. This inherent heterogeneity of the memory engram is driven by the diversity in the functions and distributions of different IEGs. This process, which we call molecular sorting, is analogous to sorting the entire population of engram neurons into different sub-engrams molecularly defined by different IEGs. In this chapter, we will describe the molecular sorting process by systematically reviewing published work on engram ensemble cells defined by the following four major IEGs: Fos, Npas4, Arc, and Egr1. By comparing and contrasting these likely different components of the memory engram, we hope to gain a better understanding of the logic and significance behind the molecular sorting process for memory functions.
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Affiliation(s)
- Tushar D Yelhekar
- Department of Psychiatry, O'Donnell Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Meizhen Meng
- Department of Psychiatry, O'Donnell Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Neuroscience Graduate Program, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Joslyn Doupe
- Neuroscience Graduate Program, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Yingxi Lin
- Department of Psychiatry, O'Donnell Brain Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Davidson CJ, Mascarin AT, Yahya MA, Rubio FJ, Gheidi A. Approaches and considerations of studying neuronal ensembles: a brief review. Front Cell Neurosci 2023; 17:1310724. [PMID: 38155864 PMCID: PMC10752959 DOI: 10.3389/fncel.2023.1310724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 11/27/2023] [Indexed: 12/30/2023] Open
Abstract
First theorized by Hebb, neuronal ensembles have provided a framework for understanding how the mammalian brain operates, especially regarding learning and memory. Neuronal ensembles are discrete, sparsely distributed groups of neurons that become activated in response to a specific stimulus and are thought to provide an internal representation of the world. Beyond the study of region-wide or projection-wide activation, the study of ensembles offers increased specificity and resolution to identify and target specific memories or associations. Neuroscientists interested in the neurobiology of learning, memory, and motivated behavior have used electrophysiological-, calcium-, and protein-based proxies of neuronal activity in preclinical models to better understand the neurobiology of learned and motivated behaviors. Although these three approaches may be used to pursue the same general goal of studying neuronal ensembles, technical differences lead to inconsistencies in the output and interpretation of data. This mini-review highlights some of the methodologies used in electrophysiological-, calcium-, and protein-based studies of neuronal ensembles and discusses their strengths and weaknesses.
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Affiliation(s)
- Cameron J. Davidson
- William Beaumont School of Medicine, Oakland University, Rochester, MI, United States
| | - Alixandria T. Mascarin
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, MI, United States
| | - Majd A. Yahya
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, MI, United States
| | - F. Javier Rubio
- Neuronal Ensembles in Addiction Section, Behavioral Neuroscience Research Branch, Intramural Research Program/National Institute on Drug Abuse/National Institutes of Health, Bethesda, MD, United States
| | - Ali Gheidi
- Department of Biomedical Sciences, Mercer University, Macon, GA, United States
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Mahringer D, Zmarz P, Okuno H, Bito H, Keller GB. Functional correlates of immediate early gene expression in mouse visual cortex. PEER COMMUNITY JOURNAL 2022; 2:e45. [PMID: 37091727 PMCID: PMC7614465 DOI: 10.24072/pcjournal.156] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
During visual development, response properties of layer 2/3 neurons in visual cortex are shaped by experience. Both visual and visuomotor experience are necessary to co-ordinate the integration of bottom-up visual input and top-down motor-related input. Whether visual and visuomotor experience engage different plasticity mechanisms, possibly associated with the two separate input pathways, is still unclear. To begin addressing this, we measured the expression level of three different immediate early genes (IEG) (c-fos, egr1 or Arc) and neuronal activity in layer 2/3 neurons of visual cortex before and after a mouse's first visual exposure in life, and subsequent visuomotor learning. We found that expression levels of all three IEGs correlated positively with neuronal activity, but that first visual and first visuomotor exposure resulted in differential changes in IEG expression patterns. In addition, IEG expression levels differed depending on whether neurons exhibited primarily visually driven or motor-related activity. Neurons with strong motor-related activity preferentially expressed EGR1, while neurons that developed strong visually driven activity preferentially expressed Arc. Our findings are consistent with the interpretation that bottom-up visual input and top-down motor-related input are associated with different IEG expression patterns and hence possibly also with different plasticity pathways.
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Affiliation(s)
- David Mahringer
- Faculty of Natural Sciences, University of Basel, Basel, Switzerland
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Pawel Zmarz
- Faculty of Natural Sciences, University of Basel, Basel, Switzerland
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Hiroyuki Okuno
- Department of Biochemistry and Molecular Biology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Kagoshima 890-8544, Japan
| | - Haruhiko Bito
- Department of Neurochemistry, Graduate School of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Georg B Keller
- Faculty of Natural Sciences, University of Basel, Basel, Switzerland
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
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Chen QN, Ding XL, Guo XX, Zhou G, Guan JS. Suv39h1 regulates memory stability by inhibiting the expression of Shank1 in hippocampal newborn neurons. Eur J Neurosci 2022; 55:1424-1441. [PMID: 35181969 DOI: 10.1111/ejn.15626] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/11/2022] [Accepted: 02/15/2022] [Indexed: 11/28/2022]
Abstract
Adult newborn neurons are involved in memory encoding and extinction, but the neural mechanism is unclear. We found the adult newborn neurons at 4 weeks are recruited by learning and subjected to epigenetic regulations, consequently reducing their ability to be re-recruited later. After removal of the epigenetic blockage, Suv39h1 KO mice showed an increased recruiting number of aged newborn neurons and enhanced flexibility in learning tasks. Besides NRXN1, we found SHANK1, the synaptic scaffold protein, is one of the major targets of Suv39h1, regulating memory stability. Expression of Shank1 is transiently engaged to enhance synaptogenesis during learning and is strongly suppressed by Suv39h1 from 5 hours after learning. Exogenously overexpression of Shank1 in dentate gyrus increased the density of mushroom spines and decreased the persistency of old memories. Our study indicated the activity-regulated epigenetic modification in newly matured newborn neurons in hippocampus insulates temporally distinct experiences and stabilizes old memories.
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Affiliation(s)
- Qi-Nan Chen
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China.,Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xin-Lu Ding
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xiu-Xian Guo
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Gang Zhou
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Ji-Song Guan
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China.,CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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