1
|
Bartesaghi R. Brain circuit pathology in Down syndrome: from neurons to neural networks. Rev Neurosci 2022; 34:365-423. [PMID: 36170842 DOI: 10.1515/revneuro-2022-0067] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 08/28/2022] [Indexed: 11/15/2022]
Abstract
Down syndrome (DS), a genetic pathology caused by triplication of chromosome 21, is characterized by brain hypotrophy and impairment of cognition starting from infancy. While studies in mouse models of DS have elucidated the major neuroanatomical and neurochemical defects of DS, comparatively fewer investigations have focused on the electrophysiology of the DS brain. Electrical activity is at the basis of brain functioning. Therefore, knowledge of the way in which brain circuits operate in DS is fundamental to understand the causes of behavioral impairment and devise targeted interventions. This review summarizes the state of the art regarding the electrical properties of the DS brain, starting from individual neurons and culminating in signal processing in whole neuronal networks. The reported evidence derives from mouse models of DS and from brain tissues and neurons derived from individuals with DS. EEG data recorded in individuals with DS are also provided as a key tool to understand the impact of brain circuit alterations on global brain activity.
Collapse
Affiliation(s)
- Renata Bartesaghi
- Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, Italy
| |
Collapse
|
2
|
Kleschevnikov AM. Enhanced GIRK2 channel signaling in Down syndrome: A feasible role in the development of abnormal nascent neural circuits. Front Genet 2022; 13:1006068. [PMID: 36171878 PMCID: PMC9510977 DOI: 10.3389/fgene.2022.1006068] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 08/24/2022] [Indexed: 11/24/2022] Open
Abstract
The most distinctive feature of Down syndrome (DS) is moderate to severe cognitive impairment. Genetic, molecular, and neuronal mechanisms of this complex DS phenotype are currently under intensive investigation. It is becoming increasingly clear that the abnormalities arise from a combination of initial changes caused by triplication of genes on human chromosome 21 (HSA21) and later compensatory adaptations affecting multiple brain systems. Consequently, relatively mild initial cognitive deficits become pronounced with age. This pattern of changes suggests that one approach to improving cognitive function in DS is to target the earliest critical changes, the prevention of which can change the ‘trajectory’ of the brain development and reduce the destructive effects of the secondary alterations. Here, we review the experimental data on the role of KCNJ6 in DS-specific brain abnormalities, focusing on a putative role of this gene in the development of abnormal neural circuits in the hippocampus of genetic mouse models of DS. It is suggested that the prevention of these early abnormalities with pharmacological or genetic means can ameliorate cognitive impairment in DS.
Collapse
|
3
|
Di Franco N, Drutel G, Roullot-Lacarrière V, Julio-Kalajzic F, Lalanne V, Grel A, Leste-Lasserre T, Matias I, Cannich A, Gonzales D, Simon V, Cota D, Marsicano G, Piazza PV, Vallée M, Revest JM. Differential expression of the neuronal CB1 cannabinoid receptor in the hippocampus of male Ts65Dn Down syndrome mouse model. Mol Cell Neurosci 2022; 119:103705. [PMID: 35158060 DOI: 10.1016/j.mcn.2022.103705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/27/2022] [Accepted: 02/08/2022] [Indexed: 10/19/2022] Open
Abstract
Down syndrome (DS) or Trisomy 21 is the most common genetic cause of mental retardation with severe learning and memory deficits. DS is due to the complete or partial triplication of human chromosome 21 (HSA21) triggering gene overexpression and protein synthesis alterations responsible for a plethora of mental and physical phenotypes. Among the diverse brain target systems that affect hippocampal-dependent learning and memory deficit impairments in DS, the upregulation of the endocannabinoid system (ECS), and notably the overexpression of the cannabinoid type-1 receptor (CB1), seems to play a major role. Combining various protein and gene expression targeted approaches using western blot, qRT-PCR and FISH techniques, we investigated the expression pattern of ECS components in the hippocampus (HPC) of male Ts65Dn mice. Among all the molecules that constitute the ECS, we found that the expression of the CB1 is altered in the HPC of Ts65Dn mice. CB1 distribution is differentially segregated between the dorsal and ventral part of the HPC and within the different cell populations that compose the HPC. CB1 expression is upregulated in GABAergic neurons of Ts65Dn mice whereas it is downregulated in glutamatergic neurons. These results highlight a complex regulation of the CB1 encoding gene (Cnr1) in Ts65Dn mice that could open new therapeutic solutions for this syndrome.
Collapse
Affiliation(s)
- Nadia Di Franco
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Guillaume Drutel
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | | | | | - Valérie Lalanne
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Agnès Grel
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | | | - Isabelle Matias
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Astrid Cannich
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Delphine Gonzales
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Vincent Simon
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Daniela Cota
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Giovanni Marsicano
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | | | - Monique Vallée
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France
| | - Jean-Michel Revest
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, F-33000 Bordeaux, France.
| |
Collapse
|
4
|
Kleschevnikov A. GIRK2 Channels in Down Syndrome and Alzheimer's Disease. Curr Alzheimer Res 2022; 19:819-829. [PMID: 36567290 DOI: 10.2174/1567205020666221223122110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 11/26/2022] [Accepted: 11/29/2022] [Indexed: 12/27/2022]
Abstract
Cognitive impairment in Down syndrome (DS) results from the abnormal expression of hundreds of genes. However, the impact of KCNJ6, a gene located in the middle of the 'Down syndrome critical region' of chromosome 21, seems to stand out. KCNJ6 encodes GIRK2 (KIR3.2) subunits of G protein-gated inwardly rectifying potassium channels, which serve as effectors for GABAB, m2, 5HT1A, A1, and many other postsynaptic metabotropic receptors. GIRK2 subunits are heavily expressed in neocortex, cerebellum, and hippocampus. By controlling resting membrane potential and neuronal excitability, GIRK2 channels may thus affect both synaptic plasticity and stability of neural circuits in the brain regions important for learning and memory. Here, we discuss recent experimental data regarding the role of KCNJ6/GIRK2 in neuronal abnormalities and cognitive impairment in models of DS and Alzheimer's disease (AD). The results compellingly show that signaling through GIRK2 channels is abnormally enhanced in mouse genetic models of Down syndrome and that partial suppression of GIRK2 channels with pharmacological or genetic means can restore synaptic plasticity and improve impaired cognitive functions. On the other hand, signaling through GIRK2 channels is downregulated in AD models, such as models of early amyloidopathy. In these models, reduced GIRK2 channel signaling promotes neuronal hyperactivity, causing excitatory-inhibitory imbalance and neuronal death. Accordingly, activation of GABAB/GIRK2 signaling by GIRK channel activators or GABAB receptor agonists may reduce Aβ-induced hyperactivity and subsequent neuronal death, thereby exerting a neuroprotective effect in models of AD.
Collapse
|
5
|
Signalling pathways contributing to learning and memory deficits in the Ts65Dn mouse model of Down syndrome. Neuronal Signal 2021; 5:NS20200011. [PMID: 33763235 PMCID: PMC7955101 DOI: 10.1042/ns20200011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 01/30/2023] Open
Abstract
Down syndrome (DS) is a genetic trisomic disorder that produces life-long changes in physiology and cognition. Many of the changes in learning and memory seen in DS are reminiscent of disorders involving the hippocampal/entorhinal circuit. Mouse models of DS typically involve trisomy of murine chromosome 16 is homologous for many of the genes triplicated in human trisomy 21, and provide us with good models of changes in, and potential pharmacotherapy for, human DS. Recent careful dissection of the Ts65Dn mouse model of DS has revealed differences in key signalling pathways from the basal forebrain to the hippocampus and associated rhinal cortices, as well as changes in the microstructure of the hippocampus itself. In vivo behavioural and electrophysiological studies have shown that Ts65Dn animals have difficulties in spatial memory that mirror hippocampal deficits, and have changes in hippocampal electrophysiological phenomenology that may explain these differences, and align with expectations generated from in vitro exploration of this model. Finally, given the existing data, we will examine the possibility for pharmacotherapy for DS, and outline the work that remains to be done to fully understand this system.
Collapse
|
6
|
Neuroanatomical alterations in higher-order thalamic nuclei of fetuses with Down syndrome. Clin Neurol Neurosurg 2020; 194:105870. [PMID: 32480293 DOI: 10.1016/j.clineuro.2020.105870] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 04/20/2020] [Accepted: 04/22/2020] [Indexed: 11/23/2022]
Abstract
OBJECTIVES Down syndrome (DS) is a genetic condition characterized by cognitive disability starting from infancy. Children with DS exhibit deficits in several cognitive domains, including executive function, i.e., a set of cognitive processes that heavily depend on higher-order thalamic nuclei. The goal of this study was to establish whether executive function-related thalamic nuclei of fetuses with DS exhibit neuroanatomical alterations that may contribute to the defects in higher-order control processes seen in children with DS. PATIENTS AND METHODS In brain sections from fetuses with DS and control fetuses (gestational week 17-22), we evaluated the cellularity in the mediodorsal nucleus (MD), the centromedian nucleus (CM), and the parafascicular nucleus (PF) of the thalamus and the density of proliferating cells in the third ventricle. RESULTS We found that all three nuclei had a notably reduced cell density. This defect was associated with a reduced density of proliferating cells in the third ventricle, suggesting that the reduced cellularity in the MD, CM, and PF of fetuses with DS was due to neurogenesis impairment. The separate evaluation of projection neurons and interneurons in the MD, CM, and PF showed that in fetuses with DS the density of projection neurons was reduced, with no changes in interneuron density. CONCLUSION This study provides novel evidence for DS-linked cellularity alterations in the MD, CM, and PF and suggests that altered signal processing in these nuclei may be involved in the impairment in higher-order control processes observed in individuals with DS starting from infancy.
Collapse
|
7
|
Lee SE, Duran-Martinez M, Khantsis S, Bianchi DW, Guedj F. Challenges and Opportunities for Translation of Therapies to Improve Cognition in Down Syndrome. Trends Mol Med 2019; 26:150-169. [PMID: 31706840 DOI: 10.1016/j.molmed.2019.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 10/02/2019] [Accepted: 10/03/2019] [Indexed: 02/07/2023]
Abstract
While preclinical studies have reported improvement of behavioral deficits in the Ts65Dn mouse model of Down syndrome (DS), translation to human clinical trials to improve cognition in individuals with DS has had a poor success record. Timing of the intervention, choice of animal models, strategy for drug selection, and lack of translational endpoints between animals and humans contributed to prior failures of human clinical trials. Here, we focus on in vitro cell models from humans with DS to identify the molecular mechanisms underlying the brain phenotype associated with DS. We emphasize the importance of using these cell models to screen for therapeutic molecules, followed by validating them in the most suitable animal models prior to initiating human clinical trials.
Collapse
Affiliation(s)
- Sarah E Lee
- Medical Genetics Branch (Prenatal Genomic and Therapy Section), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Monica Duran-Martinez
- Medical Genetics Branch (Prenatal Genomic and Therapy Section), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sabina Khantsis
- Medical Genetics Branch (Prenatal Genomic and Therapy Section), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Diana W Bianchi
- Medical Genetics Branch (Prenatal Genomic and Therapy Section), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA; Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda 20892, MD, USA
| | - Faycal Guedj
- Medical Genetics Branch (Prenatal Genomic and Therapy Section), National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
8
|
Rueda N, Flórez J, Dierssen M, Martínez-Cué C. Translational validity and implications of pharmacotherapies in preclinical models of Down syndrome. PROGRESS IN BRAIN RESEARCH 2019; 251:245-268. [PMID: 32057309 DOI: 10.1016/bs.pbr.2019.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Neurodevelopmental disorders are challenging to study in the laboratory, and despite a large investment, few novel treatments have been developed in the last decade. While animal models have been valuable in elucidating disease mechanisms and in providing insights into the function of specific genes, the predictive validity of preclinical models to test potential therapies has been questioned. In the last two decades, diverse new murine models of Down syndrome (DS) have been developed and numerous studies have demonstrated neurobiological alterations that could be responsible for the cognitive and behavioral phenotypes found in this syndrome. In many cases, similar alterations were found in murine models and in individuals with DS, although several phenotypes shown in animals have yet not been confirmed in the human condition. Some of the neurobiological alterations observed in mice have been proposed to account for their changes in cognition and behavior, and have received special attention because of being putative therapeutic targets. Those include increased oxidative stress, altered neurogenesis, overexpression of the Dyrk1A gene, GABA-mediated overinhibition and Alzheimer's disease-related neurodegeneration. Subsequently, different laboratories have tested the efficacy of pharmacotherapies targeting these alterations. Unfortunately, animal models are limited in their ability to mimic the extremely complex process of human neurodevelopment and neuropathology. Therefore, the safety and efficacy identified in animal studies are not always translated to humans, and most of the drugs tested have not demonstrated any positive effect or very limited efficacy in clinical trials. Despite their limitations, though, animal trials give us extremely valuable information for developing and testing drugs for human use that cannot be obtained from molecular or cellular experiments alone. This chapter reviews some of these therapeutic approaches and discusses some reasons that could account for the discrepancy between the findings in mouse models of DS and in humans, including: (i) the incomplete resemble of the genetic alterations of available mouse models of DS and human trisomy 21, (ii) the lack of evidence that some of the phenotypic alterations found in mice (e.g., GABA-mediated overinhibition, and alterations in adult neurogenesis) are also present in DS individuals, and (iii) the inaccuracy and/or inadequacy of the methods used in clinical trials to detect changes in the cognitive and behavioral functions of people with DS. Despite the shortcomings of animal models, animal experimentation remains an invaluable tool in developing drugs. Thus, we will also discuss how to increase predictive validity of mouse models.
Collapse
Affiliation(s)
- Noemí Rueda
- Department of Physiology and Pharmacology, University of Cantabria, Santander, Spain
| | - Jesús Flórez
- Department of Physiology and Pharmacology, University of Cantabria, Santander, Spain
| | - Mara Dierssen
- Cellular and Systems Neurobiology, Systems Biology Program, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Carmen Martínez-Cué
- Department of Physiology and Pharmacology, School of Medicine, University of Cantabria, Santander, Spain.
| |
Collapse
|
9
|
Unbalanced dendritic inhibition of CA1 neurons drives spatial-memory deficits in the Ts2Cje Down syndrome model. Nat Commun 2019; 10:4991. [PMID: 31676751 PMCID: PMC6825203 DOI: 10.1038/s41467-019-13004-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 10/15/2019] [Indexed: 12/21/2022] Open
Abstract
Overinhibition is assumed one of the main causes of cognitive deficits (e.g. memory impairment) in mouse models of Down syndrome (DS). Yet the mechanisms that drive such exaggerated synaptic inhibition and their behavioral effects remain unclear. Here we report the existence of bidirectional alterations to the synaptic inhibition on CA1 pyramidal cells in the Ts2Cje mouse model of DS which are associated to impaired spatial memory. Furthermore, we identify triplication of the kainate receptor (KAR) encoding gene Grik1 as the cause of these phenotypes. Normalization of Grik1 dosage in Ts2Cje mice specifically restored spatial memory and reversed the bidirectional alterations to CA1 inhibition, but not the changes in synaptic plasticity or the other behavioral modifications observed. We propose that modified information gating caused by disturbed inhibitory tone rather than generalized overinhibition underlies some of the characteristic cognitive deficits in DS. Exaggerated synaptic inhibition is hypothesised to be a main cause of cognitive deficits in Down syndrome models. The authors identify triplication of the kainate receptor encoding gene Grik1 as the cause of memory deficits due to a reorganization of synaptic inhibition along the CA1 dendritic tree.
Collapse
|
10
|
Day SM, Yang W, Wang X, Stern JE, Zhou X, Macauley SL, Ma T. Glucagon-Like Peptide-1 Cleavage Product Improves Cognitive Function in a Mouse Model of Down Syndrome. eNeuro 2019; 6:ENEURO.0031-19.2019. [PMID: 31040160 PMCID: PMC6520642 DOI: 10.1523/eneuro.0031-19.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/01/2019] [Accepted: 04/02/2019] [Indexed: 12/13/2022] Open
Abstract
Currently there is no effective therapy available for cognitive impairments in Down syndrome (DS), one of the most prevalent forms of intellectual disability in humans associated with the chromosomes 21 trisomy. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that maintains glucose homeostasis by stimulating insulin secretion. Its natural cleavage product GLP-1 (9-36) lacks insulinotropic effects and has a low binding affinity for GLP-1 receptors; thus, GLP-1 (9-36) has historically been identified as an inactive metabolite. Conversely, recent work has demonstrated interesting physiological properties of GLP-1 (9-36) such as cardioprotection and neuroprotection. We have previously shown that GLP-1 (9-36) administration enhances neuronal plasticity in young WT mice and ameliorates cognitive deficits in a mouse model of Alzheimer's disease. Here, we report that systemic administration of GLP-1 (9-36) in Ts65Dn DS model mice of either sex resulted in decreased mitochondrial oxidative stress in hippocampus and improved dendritic spine morphology, increase of mature spines and reduction of immature spines. Importantly, these molecular alterations translated into functional changes in that long-term potentiation failure and cognitive impairments in TsDn65 DS model mice were rescued with GLP-1 (9-36) treatment. We also show that chronic GLP-1 (9-36) treatment did not alter glucose tolerance in either WT or DS model mice. Our findings suggest that GLP-1 (9-36) treatment may have therapeutic potential for DS and other neurodegenerative diseases associated with increased neuronal oxidative stress.
Collapse
Affiliation(s)
- Stephen M Day
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
- Department of Integrative Physiology & Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Wenzhong Yang
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Xin Wang
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Jennifer E Stern
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Xueyan Zhou
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Shannon L Macauley
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| | - Tao Ma
- Departments of Internal Medicine and Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
- Department of Integrative Physiology & Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157
| |
Collapse
|
11
|
Developmental excitatory-to-inhibitory GABA polarity switch is delayed in Ts65Dn mice, a genetic model of Down syndrome. Neurobiol Dis 2018; 115:1-8. [PMID: 29550538 DOI: 10.1016/j.nbd.2018.03.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 03/01/2018] [Accepted: 03/07/2018] [Indexed: 11/23/2022] Open
Abstract
Down syndrome (DS) is the most frequent genetic cause of developmental abnormalities leading to intellectual disability. One notable phenomenon affecting the formation of nascent neural circuits during late developmental periods is developmental switch of GABA action from depolarizing to hyperpolarizing mode. We examined properties of this switch in DS using primary cultures and acute hippocampal slices from Ts65Dn mice, a genetic model of DS. Cultures of DIV3-DIV13 Ts65Dn and control normosomic (2 N) neurons were loaded with FURA-2 AM, and GABA action was assessed using local applications. In 2 N cultures, the number of GABA-activated cells dropped from ~100% to 20% between postnatal days 3-13 (P3-P13) reflecting the switch in GABA action polarity. In Ts65Dn cultures, the timing of this switch was delayed by 2-3 days. Next, microelectrode recordings of multi-unit activity (MUA) were performed in CA3 slices during bath application of the GABAA agonist isoguvacine. MUA frequency was increased in P8-P12 and reduced in P14-P22 slices reflecting the switch of GABA action from excitatory to inhibitory mode. The timing of this switch was delayed in Ts65Dn by approximately 2 days. Finally, frequency of giant depolarizing potentials (GDPs), a form of primordial neural activity, was significantly increased in slices from Ts65Dn pups at P12 and P14. These experimental evidences show that GABA action polarity switch is delayed in Ts65Dn model of DS, and that these changes lead to a delay in maturation of nascent neural circuits. These alterations may affect properties of neural circuits in adult animals and, therefore, represent a prospective target for pharmacotherapy of cognitive impairment in DS.
Collapse
|
12
|
Caraci F, Iulita MF, Pentz R, Flores Aguilar L, Orciani C, Barone C, Romano C, Drago F, Cuello AC. Searching for new pharmacological targets for the treatment of Alzheimer's disease in Down syndrome. Eur J Pharmacol 2017; 817:7-19. [DOI: 10.1016/j.ejphar.2017.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 09/26/2017] [Accepted: 10/04/2017] [Indexed: 11/26/2022]
|
13
|
Vidal V, García-Cerro S, Martínez P, Corrales A, Lantigua S, Vidal R, Rueda N, Ozmen L, Hernández MC, Martínez-Cué C. Decreasing the Expression of GABA A α5 Subunit-Containing Receptors Partially Improves Cognitive, Electrophysiological, and Morphological Hippocampal Defects in the Ts65Dn Model of Down Syndrome. Mol Neurobiol 2017; 55:4745-4762. [PMID: 28717969 DOI: 10.1007/s12035-017-0675-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 06/27/2017] [Indexed: 12/31/2022]
Abstract
Trisomy 21 or Down syndrome (DS) is the most common cause of intellectual disability of a genetic origin. The Ts65Dn (TS) mouse, which is the most commonly used and best-characterized mouse model of DS, displays many of the cognitive, neuromorphological, and biochemical anomalies that are found in the human condition. One of the mechanisms that have been proposed to be responsible for the cognitive deficits in this mouse model is impaired GABA-mediated inhibition. Because of the well-known modulatory role of GABAA α5 subunit-containing receptors in cognitive processes, these receptors are considered to be potential targets for improving the intellectual disability in DS. The chronic administration of GABAA α5-negative allosteric modulators has been shown to be procognitive without anxiogenic or proconvulsant side effects. In the present study, we use a genetic approach to evaluate the contribution of GABAA α5 subunit-containing receptors to the cognitive, electrophysiological, and neuromorphological deficits in TS mice. We show that reducing the expression of GABAA α5 receptors by deleting one or two copies of the Gabra5 gene in TS mice partially ameliorated the cognitive impairments, improved long-term potentiation, enhanced neural differentiation and maturation, and normalized the density of the GABAergic synapse markers. Reducing the gene dosage of Gabra5 in TS mice did not induce motor alterations and anxiety or affect the viability of the mice. Our results provide further evidence of the role of GABAA α5 receptor-mediated inhibition in cognitive impairment in the TS mouse model of DS.
Collapse
Affiliation(s)
- Verónica Vidal
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Susana García-Cerro
- Departamento de Fundamentos Clínicos, Unidad de Farmacología, Universitat de Barcelona, Barcelona, Spain
| | - Paula Martínez
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Andrea Corrales
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Sara Lantigua
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Rebeca Vidal
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain.,Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC (Universidad de Cantabria, CSIC, SODERCAN), Santander, Spain.,Centro de Investigacion Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
| | - Noemí Rueda
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain
| | - Laurence Ozmen
- Pharma Research and Early Development, Hoffman-La Roche Ltd., Basel, Switzerland
| | | | - Carmen Martínez-Cué
- Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad deCantabria, Santander, Spain.
| |
Collapse
|
14
|
Helm S, Blayney M, Whited T, Noroozi M, Lin S, Kern S, Green D, Salehi A. Deleterious Effects of Chronic Folate Deficiency in the Ts65Dn Mouse Model of Down Syndrome. Front Cell Neurosci 2017. [PMID: 28649192 PMCID: PMC5465284 DOI: 10.3389/fncel.2017.00161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Folate is an important B vitamin naturally found in the human diet and plays a critical role in methylation of nucleic acids. Indeed, abnormalities in this major epigenetic mechanism play a pivotal role in the pathogenesis of cognitive deficit and intellectual disability in humans. The most common cause of cognitive dysfunction in children is Down syndrome (DS). Since folate deficiency is very common among the pediatric population, we questioned whether chronic folate deficiency (CFD) exacerbates cognitive dysfunction in a mouse model of DS. To test this, adult Ts65Dn mice and their disomic littermates were chronically fed a diet free of folic acid while preventing endogenous production of folate in the digestive tract for a period of 8 weeks. Our results show that the Ts65Dn mouse model of DS was significantly more vulnerable to CFD in terms of plasma homocysteine and N5-methyltetrahydrofolate (5-MTHF) levels. Importantly, these changes were linked to degenerative alterations in hippocampal dendritic morphology and impaired nest building behavior in Ts65Dn mice. Based on our results, a rigorous examination of folate intake and its metabolism in individuals with DS is warranted.
Collapse
Affiliation(s)
- Susan Helm
- Natural Science Division, Pepperdine UniversityMalibu, CA, United States
| | - Morgan Blayney
- Natural Science Division, Pepperdine UniversityMalibu, CA, United States
| | - Taylor Whited
- Natural Science Division, Pepperdine UniversityMalibu, CA, United States
| | - Mahjabin Noroozi
- VA Palo Alto Health Care System (VAPAHCS)Palo Alto, CA, United States.,Department of Psychiatry and Behavioral Sciences, Stanford University School of MedicinePalo Alto, CA, United States
| | - Sen Lin
- Natural Science Division, Pepperdine UniversityMalibu, CA, United States
| | - Semira Kern
- Natural Science Division, Pepperdine UniversityMalibu, CA, United States
| | - David Green
- Natural Science Division, Pepperdine UniversityMalibu, CA, United States
| | - Ahmad Salehi
- VA Palo Alto Health Care System (VAPAHCS)Palo Alto, CA, United States.,Department of Psychiatry and Behavioral Sciences, Stanford University School of MedicinePalo Alto, CA, United States
| |
Collapse
|
15
|
Kleschevnikov AM, Yu J, Kim J, Lysenko LV, Zeng Z, Yu YE, Mobley WC. Evidence that increased Kcnj6 gene dose is necessary for deficits in behavior and dentate gyrus synaptic plasticity in the Ts65Dn mouse model of Down syndrome. Neurobiol Dis 2017; 103:1-10. [PMID: 28342823 DOI: 10.1016/j.nbd.2017.03.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/09/2017] [Accepted: 03/21/2017] [Indexed: 11/15/2022] Open
Abstract
Down syndrome (DS), trisomy 21, is caused by increased dose of genes present on human chromosome 21 (HSA21). The gene-dose hypothesis argues that a change in the dose of individual genes or regulatory sequences on HSA21 is necessary for creating DS-related phenotypes, including cognitive impairment. We focused on a possible role for Kcnj6, the gene encoding Kir3.2 (Girk2) subunits of a G-protein-coupled inwardly-rectifying potassium channel. This gene resides on a segment of mouse Chromosome 16 that is present in one extra copy in the genome of the Ts65Dn mouse, a well-studied genetic model of DS. Kir3.2 subunit-containing potassium channels serve as effectors for a number of postsynaptic metabotropic receptors including GABAB receptors. Several studies raise the possibility that increased Kcnj6 dose contributes to synaptic and cognitive abnormalities in DS. To assess directly a role for Kcnj6 gene dose in cognitive deficits in DS, we produced Ts65Dn mice that harbor only 2 copies of Kcnj6 (Ts65Dn:Kcnj6++- mice). The reduction in Kcnj6 gene dose restored to normal the hippocampal level of Kir3.2. Long-term memory, examined in the novel object recognition test with the retention period of 24h, was improved to the level observed in the normosomic littermate control mice (2N:Kcnj6++). Significantly, both short-term and long-term potentiation (STP and LTP) was improved to control levels in the dentate gyrus (DG) of the Ts65Dn:Kcnj6++- mouse. In view of the ability of fluoxetine to suppress Kir3.2 channels, we asked if fluoxetine-treated DG slices of Ts65Dn:Kcnj6+++ mice would rescue synaptic plasticity. Fluoxetine increased STP and LTP to control levels. These results are evidence that increased Kcnj6 gene dose is necessary for synaptic and cognitive dysfunction in the Ts65Dn mouse model of DS. Strategies aimed at pharmacologically reducing channel function should be explored for enhancing cognition in DS.
Collapse
Affiliation(s)
- Alexander M Kleschevnikov
- Department of Neurosciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
| | - Jessica Yu
- Department of Neurosciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Jeesun Kim
- Department of Neurosciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Larisa V Lysenko
- Department of Neurosciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA; Academy of Biology and Biotechnology of Southern Federal University, 194/1 Stachki Str, Rostov-na-Donu 344090, Russian Federation
| | - Zheng Zeng
- Department of Neurosciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Y Eugene Yu
- The Children's Guild Foundation Down Syndrome Research Program, Genetics Program and Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
| | - William C Mobley
- Department of Neurosciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| |
Collapse
|
16
|
Contestabile A, Magara S, Cancedda L. The GABAergic Hypothesis for Cognitive Disabilities in Down Syndrome. Front Cell Neurosci 2017; 11:54. [PMID: 28326014 PMCID: PMC5339239 DOI: 10.3389/fncel.2017.00054] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 02/14/2017] [Indexed: 12/04/2022] Open
Abstract
Down syndrome (DS) is a genetic disorder caused by the presence of a third copy of chromosome 21. DS affects multiple organs, but it invariably results in altered brain development and diverse degrees of intellectual disability. A large body of evidence has shown that synaptic deficits and memory impairment are largely determined by altered GABAergic signaling in trisomic mouse models of DS. These alterations arise during brain development while extending into adulthood, and include genesis of GABAergic neurons, variation of the inhibitory drive and modifications in the control of neural-network excitability. Accordingly, different pharmacological interventions targeting GABAergic signaling have proven promising preclinical approaches to rescue cognitive impairment in DS mouse models. In this review, we will discuss recent data regarding the complex scenario of GABAergic dysfunctions in the trisomic brain of DS mice and patients, and we will evaluate the state of current clinical research targeting GABAergic signaling in individuals with DS.
Collapse
Affiliation(s)
- Andrea Contestabile
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia (IIT) Genova, Italy
| | - Salvatore Magara
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia (IIT) Genova, Italy
| | - Laura Cancedda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia (IIT)Genova, Italy; Dulbecco Telethon InstituteGenova, Italy
| |
Collapse
|