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Mun SH, Lee CS, Kim HJ, Kim J, Lee H, Yang J, Im SH, Kim JH, Seong JK, Hwang CS. Marchf6 E3 ubiquitin ligase critically regulates endoplasmic reticulum stress, ferroptosis, and metabolic homeostasis in POMC neurons. Cell Rep 2023; 42:112746. [PMID: 37421621 DOI: 10.1016/j.celrep.2023.112746] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 05/18/2023] [Accepted: 06/19/2023] [Indexed: 07/10/2023] Open
Abstract
The metabolic prohormone pro-opiomelanocortin (POMC) is generally translocated into the endoplasmic reticulum (ER) for entry into the secretory pathway. Patients with mutations within the signal peptide (SP) of POMC or its adjoining segment develop metabolic disorders. However, the existence, metabolic fate, and functional outcomes of cytosol-retained POMC remain unclear. Here, we show that SP-uncleaved POMC is produced in the cytosol of POMC neuronal cells, thus inducing ER stress and ferroptotic cell death. Mechanistically, the cytosol-retained POMC sequesters the chaperone Hspa5 and subsequently accelerates degradation of the glutathione peroxidase Gpx4, a core regulator of ferroptosis, via the chaperone-mediated autophagy. We also show that the Marchf6 E3 ubiquitin ligase mediates the degradation of cytosol-retained POMC, thereby preventing ER stress and ferroptosis. Furthermore, POMC-Cre-mediated Marchf6-deficient mice exhibit hyperphagia, reduced energy expenditure, and weight gain. These findings suggest that Marchf6 is a critical regulator of ER stress, ferroptosis, and metabolic homeostasis in POMC neurons.
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Affiliation(s)
- Sang-Hyeon Mun
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - Chang-Seok Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - Hyun Jin Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - Jiye Kim
- Korea Mouse Phenotyping Center, Seoul National University, Seoul 08826, South Korea; Laboratory of Developmental Biology and Genomics, Research Institute for Veterinary Science, and BK21 PLUS Program for Creative Veterinary Science Research, College of Veterinary Medicine, Seoul National University, Seoul 08826, South Korea; Interdisciplinary Program for Bioinformatics, Program for Cancer Biology and BIO-MAX/N-Bio Institute, Seoul National University, Seoul 08826, South Korea
| | - Haena Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - Jihye Yang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea
| | - Sin-Hyeog Im
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea; Institute of Convergence Science, Yonsei University, Seoul 03722, South Korea; ImmunoBiome, Inc, Pohang 37666, Republic of Korea
| | - Joung-Hun Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, South Korea; Institute of Convergence Science, Yonsei University, Seoul 03722, South Korea
| | - Je Kyung Seong
- Korea Mouse Phenotyping Center, Seoul National University, Seoul 08826, South Korea; Laboratory of Developmental Biology and Genomics, Research Institute for Veterinary Science, and BK21 PLUS Program for Creative Veterinary Science Research, College of Veterinary Medicine, Seoul National University, Seoul 08826, South Korea; Interdisciplinary Program for Bioinformatics, Program for Cancer Biology and BIO-MAX/N-Bio Institute, Seoul National University, Seoul 08826, South Korea
| | - Cheol-Sang Hwang
- Department of Life Sciences, Korea University, Seoul 02841, South Korea.
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Sun F, Shen H, Yang Q, Yuan Z, Chen Y, Guo W, Wang Y, Yang L, Bai Z, Liu Q, Jiang M, Lam JWY, Sun J, Ye R, Kwok RTK, Tang BZ. Dual Behavior Regulation: Tether-Free Deep-Brain Stimulation by Photothermal and Upconversion Hybrid Nanoparticles. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2210018. [PMID: 36864009 DOI: 10.1002/adma.202210018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 02/26/2023] [Indexed: 05/26/2023]
Abstract
Optogenetics has been plagued by invasive brain implants and thermal effects during photo-modulation. Here, two upconversion hybrid nanoparticles modified with photothermal agents, named PT-UCNP-B/G, which can modulate neuronal activities via photostimulation and thermo-stimulation under near-infrared laser irradiation at 980 nm and 808 nm, respectively, are demonstrated. PT-UCNP-B/G emits visible light (410-500 nm or 500-570 nm) through the upconversion process at 980 nm, while they exhibit efficient photothermal effect at 808 nm with no visible emission and tissue damage. Intriguingly, PT-UCNP-B significantly activates extracellular sodium currents in neuro2a cells expressing light-gated channelrhodopsin-2 (ChR2) ion channels under 980-nm irradiation, and inhibits potassium currents in human embryonic kidney 293 cells expressing the voltage-gated potassium channels (KCNQ1) under 808-nm irradiation in vitro. Furthermore, deep-brain bidirectional modulation of feeding behavior is achieved under tether-free 980 or 808-nm illumination (0.8 W cm-2 ) in mice stereotactically injected with PT-UCNP-B in the ChR2-expressing lateral hypothalamus region. Thus, PT-UCNP-B/G creates new possibility of utilizing both light and heat to modulate neural activities and provides a viable strategy to overcome the limits of optogenetics.
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Affiliation(s)
- Feiyi Sun
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
| | - Hanchen Shen
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
| | - Qinghu Yang
- College of Life Science & Research Center for Natural Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yanan University, Yanan, 716000, P. R. China
| | - Zhaoyue Yuan
- College of Life Science & Research Center for Natural Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yanan University, Yanan, 716000, P. R. China
| | - Yuyang Chen
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
| | - Weihua Guo
- Department of Chemistry, State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Yu Wang
- College of Life Science & Research Center for Natural Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yanan University, Yanan, 716000, P. R. China
| | - Liang Yang
- College of Life Science & Research Center for Natural Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yanan University, Yanan, 716000, P. R. China
| | - Zhantao Bai
- College of Life Science & Research Center for Natural Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yanan University, Yanan, 716000, P. R. China
| | - Qingqing Liu
- School of Chinese Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, 999077, P. R. China
| | - Ming Jiang
- College of Life Science & Research Center for Natural Peptide Drugs, Shaanxi Engineering & Technological Research Center for Conversation & Utilization of Regional Biological Resources, Yanan University, Yanan, 716000, P. R. China
| | - Jacky W Y Lam
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
| | - Jianwei Sun
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
| | - Ruquan Ye
- Department of Chemistry, State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong, 999077, P. R. China
| | - Ryan T K Kwok
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
| | - Ben Zhong Tang
- Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science & Technology, Kowloon, Hong Kong, 999077, P. R. China
- School of Science and Engineering, Shenzhen Institute of Aggregate Science and Technology, The Chinese University of Hong Kong, Shenzhen, 518172, P. R. China
- Center of Aggregation-Induced Emission, South China University of Technology, Guangzhou, 510640, P. R. China
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Avramescu RG, Flores C. We're not in Kansas anymore: ectopic dopaminergic terminals as an explanation for the positive symptoms in psychiatric pathology. J Psychiatry Neurosci 2023; 48:E74-E77. [PMID: 36810305 PMCID: PMC9949873 DOI: 10.1503/jpn.230015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Affiliation(s)
- Radu Gabriel Avramescu
- From the Douglas Mental Health University Institute, Montréal, Que., Canada (Avramescu, Flores); and the Department of Psychiatry and Department of Neurology and Neurosurgery, McGill University, Montréal, Que., Canada (Flores)
| | - Cecilia Flores
- From the Douglas Mental Health University Institute, Montréal, Que., Canada (Avramescu, Flores); and the Department of Psychiatry and Department of Neurology and Neurosurgery, McGill University, Montréal, Que., Canada (Flores)
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Pré D, Wooten AT, Biesmans S, Hinckley S, Zhou H, Sherman SP, Kakad P, Gearhart J, Bang AG. Development of a platform to investigate long-term potentiation in human iPSC-derived neuronal networks. Stem Cell Reports 2022; 17:2141-2155. [PMID: 35985330 PMCID: PMC9481914 DOI: 10.1016/j.stemcr.2022.07.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 01/25/2023] Open
Abstract
Impairment of long-term potentiation (LTP) is a common feature of many pre-clinical models of neurological disorders; however, studies in humans are limited by the inaccessibility of the brain. Human induced pluripotent stem cells (hiPSCs) provide a unique opportunity to study LTP in disease-specific genetic backgrounds. Here we describe a multi-electrode array (MEA)-based assay to investigate chemically induced LTP (cLTP) across entire networks of hiPSC-derived midbrain dopaminergic (DA) and cortical neuronal populations that lasts for days, allowing studies of the late phases of LTP and enabling detection of associated molecular changes. We show that cLTP on midbrain DA neuronal networks is largely independent of the N-methyl-D-aspartate receptor (NMDAR) and partially dependent on brain-derived neurotrophic factor (BDNF). Finally, we describe activity-regulated gene expression induced by cLTP. This cLTP-MEA assay platform will enable phenotype discovery and higher-throughput analyses of synaptic plasticity on hiPSC-derived neurons.
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Affiliation(s)
- Deborah Pré
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Alexander T Wooten
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Steven Biesmans
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Sandy Hinckley
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Haowen Zhou
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Sean P Sherman
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Priyanka Kakad
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Jeffrey Gearhart
- Henry M. Jackson Foundation for the Advancement of Military Medicine on Contract to USAF School of Aerospace Medicine, Wright-Patterson AFB, Dayton, OH 45433, USA
| | - Anne G Bang
- Conrad Prebys Center for Chemical Genomics, Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
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Bian WJ, Brewer CL, Kauer JA, de Lecea L. Adolescent sleep shapes social novelty preference in mice. Nat Neurosci 2022; 25:912-923. [PMID: 35618950 PMCID: PMC9283223 DOI: 10.1038/s41593-022-01076-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 04/14/2022] [Indexed: 12/17/2022]
Abstract
Sleep disturbances frequently occur in neurodevelopmental disorders such as autism, but the developmental role of sleep is largely unexplored, and a causal relationship between developmental sleep defects and behavioral consequences in adulthood remains elusive. Here, we show that in mice, sleep disruption (SD) in adolescence, but not in adulthood, causes long-lasting impairment in social novelty preference. Furthermore, adolescent SD alters the activation and release patterns of dopaminergic neurons in the ventral tegmental area (VTA) in response to social novelty. This developmental sleep function is mediated by balanced VTA activity during adolescence; chemogenetic excitation mimics, whereas silencing rescues, the social deficits of adolescent SD. Finally, we show that in Shank3-mutant mice, improving sleep or rectifying VTA activity during adolescence ameliorates adult social deficits. Together, our results identify a critical role of sleep and dopaminergic activity in the development of social interaction behavior.
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Affiliation(s)
- Wen-Jie Bian
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA.
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, USA.
| | - Chelsie L Brewer
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, USA
| | - Julie A Kauer
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, USA
| | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA.
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, USA.
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Zhang J, Navarrete M, Wu Y, Zhou Y. 14-3-3 Dysfunction in Dorsal Hippocampus CA1 (dCA1) Induces Psychomotor Behavior via a dCA1-Lateral Septum-Ventral Tegmental Area Pathway. Front Mol Neurosci 2022; 15:817227. [PMID: 35237127 PMCID: PMC8882652 DOI: 10.3389/fnmol.2022.817227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 01/14/2022] [Indexed: 11/22/2022] Open
Abstract
While hippocampal hyperactivity is implicated in psychosis by both human and animal studies, whether it induces a hyperdopaminergic state and the underlying neural circuitry remains elusive. Previous studies established that region-specific inhibition of 14-3-3 proteins in the dorsal hippocampus CA1 (dCA1) induces schizophrenia-like behaviors in mice, including a novelty-induced locomotor hyperactivity. In this study, we showed that 14-3-3 dysfunction in the dCA1 over-activates ventral tegmental area (VTA) dopaminergic neurons, and such over-activation is necessary for eliciting psychomotor behavior in mice. We demonstrated that such hippocampal dysregulation of the VTA during psychomotor behavior is dependent on an over-activation of the lateral septum (LS), given that inhibition of the LS attenuates over-activation of dopaminergic neurons and psychomotor behavior induced by 14-3-3 inhibition in the dCA1. Moreover, 14-3-3 inhibition-induced neuronal activations within the dCA1-LS-VTA pathway and psychomotor behavior can be reproduced by direct chemogenetic activation of LS-projecting dCA1 neurons. Collectively, these results suggest that 14-3-3 dysfunction in the dCA1 results in hippocampal hyperactivation which leads to psychomotor behavior via a dCA1-LS-VTA pathway.
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Affiliation(s)
| | | | | | - Yi Zhou
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, United States
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Guo Z, Li S, Wu J, Zhu X, Zhang Y. Maternal Deprivation Increased Vulnerability to Depression in Adult Rats Through DRD2 Promoter Methylation in the Ventral Tegmental Area. Front Psychiatry 2022; 13:827667. [PMID: 35308874 PMCID: PMC8924051 DOI: 10.3389/fpsyt.2022.827667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 01/21/2022] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVE Early life adversity is a risk factor for depression in adulthood; however, the underlying mechanisms are not well understood. This study aims to investigate the effect of DNA methylation of DRD2 gene on early life stress-induced depression in adult rats. METHODS Newborn Sprague-Dawley rats were randomly assigned to four groups: maternal deprivation group (MD), chronic unpredictable stress (CUS) group, maternal deprivation plus chronic unpredictable stress (MD/CUS) group, and normal control group (NOR). Behaviors were measured by open field test (OFT), sucrose preference test (SPT), and Original Research Article forced swimming test (FST). Fecal CORT level was detected by ELISA. Bisulfite amplicon sequencing PCR was used to assess methylation levels of DRD2 promoter. RESULTS CUS and MD/CUS rats had a significantly shorter total distance, longer immobility time, and higher CORT level, while MD and MD/CUS rats had a significantly lower percentage of central distance, more feces, lower rate of sucrose preference, and lower levels of DRD2 protein and mRNA in the VTA than NOR rats. CUS rats showed a significantly higher DRD2 mRNA and protein levels in the VTA than NOR rats. CUS, MD, and MD/CUS rats showed a significantly higher level of DRD2 promoter methylation than NOR rats. CORT level was significantly correlated with the sucrose preference rate in SPT, the immobility time in FST, the total distance, and the number of fecal pellets in OFT. DRD2 protein level was significantly correlated with the sucrose preference rate and the number of fecal pellets. DRD2 mRNA level was significantly correlated with the percentage of central distance and the number of fecal pellets in OFT. The level of DRD2 promoter methylation was significantly correlated with the sucrose preference rate, immobility time, total distance, the percentage of central distance, and the number of fecal pellets. CONCLUSIONS Early life MD increased vulnerability to stress-induced depressive-like behavior in adult rats. Enhanced DRD2 promoter methylation in the VTA may increase the susceptibility to depression.
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Affiliation(s)
- Zhenli Guo
- Medical Psychological Center, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Shansi Li
- Medical Psychological Center, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Jialing Wu
- Medical Psychological Center, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Xiongzhao Zhu
- Medical Psychological Center, The Second Xiangya Hospital, Central South University, Changsha, China.,Medical Psychological Institute of Central South University, Central South University, Changsha, China.,National Clinical Research Center for Mental Disorders, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Yi Zhang
- Medical Psychological Center, The Second Xiangya Hospital, Central South University, Changsha, China.,Medical Psychological Institute of Central South University, Central South University, Changsha, China.,National Clinical Research Center for Mental Disorders, The Second Xiangya Hospital, Central South University, Changsha, China
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Mesman S, Smidt MP. Acquisition of the Midbrain Dopaminergic Neuronal Identity. Int J Mol Sci 2020; 21:ijms21134638. [PMID: 32629812 PMCID: PMC7369932 DOI: 10.3390/ijms21134638] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/22/2020] [Accepted: 06/26/2020] [Indexed: 02/06/2023] Open
Abstract
The mesodiencephalic dopaminergic (mdDA) group of neurons comprises molecularly distinct subgroups, of which the substantia nigra (SN) and ventral tegmental area (VTA) are the best known, due to the selective degeneration of the SN during Parkinson’s disease. However, although significant research has been conducted on the molecular build-up of these subsets, much is still unknown about how these subsets develop and which factors are involved in this process. In this review, we aim to describe the life of an mdDA neuron, from specification in the floor plate to differentiation into the different subsets. All mdDA neurons are born in the mesodiencephalic floor plate under the influence of both SHH-signaling, important for floor plate patterning, and WNT-signaling, involved in establishing the progenitor pool and the start of the specification of mdDA neurons. Furthermore, transcription factors, like Ngn2, Ascl1, Lmx1a, and En1, and epigenetic factors, like Ezh2, are important in the correct specification of dopamine (DA) progenitors. Later during development, mdDA neurons are further subdivided into different molecular subsets by, amongst others, Otx2, involved in the specification of subsets in the VTA, and En1, Pitx3, Lmx1a, and WNT-signaling, involved in the specification of subsets in the SN. Interestingly, factors involved in early specification in the floor plate can serve a dual function and can also be involved in subset specification. Besides the mdDA group of neurons, other systems in the embryo contain different subsets, like the immune system. Interestingly, many factors involved in the development of mdDA neurons are similarly involved in immune system development and vice versa. This indicates that similar mechanisms are used in the development of these systems, and that knowledge about the development of the immune system may hold clues for the factors involved in the development of mdDA neurons, which may be used in culture protocols for cell replacement therapies.
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