Impaired Aversive Memory Formation in GPR37L1KO Mice

International journal of molecular sciences

2022 Nov 18

Veenit, V;Zhang, X;Paslawski, W;Mantas, I;Svenningsson, P;
PMID: 36430766 | DOI: 10.3390/ijms232214290

GPR37L1 is an orphan G-protein-coupled receptor, which is implicated in neurological disorders, but its normal physiological role is poorly understood. Its close homologue, GPR37, is implicated in Parkinson's disease and affective disorders. In this study, we set out to characterize adult and middle-aged global GPR37L1 knock-out (KO) mice regarding emotional behaviors. Our results showed that GPR37L1KO animals, except adult GPR37L1KO males, exhibited impaired retention of aversive memory formation as assessed by the shorter retention latency in a passive avoidance task. Interestingly, the viral-mediated deletion of GPR37L1 in conditional knockout mice in the hippocampus of middle-aged mice also showed impaired retention in passive avoidance tasks, similar to what was observed in global GPR37L1KO mice, suggesting that hippocampal GPR37L1 is involved in aversive learning processes. We also observed that middle-aged GPR37L1KO male and female mice exhibited a higher body weight than their wild-type counterparts. Adult and middle-aged GPR37L1KO female mice exhibited a reduced level of serum corticosterone and middle-aged GPR37L1KO females showed a reduced level of epinephrine in the dorsal hippocampus in the aftermath of passive avoidance task, with no such effects observed in GPR37L1KO male mice, suggesting that lack of GPR37L1 influences behavior and biochemical readouts in age- and sex-specific manners.

Pathological substrate of memory impairment in multiple system atrophy

Neuropathology and applied neurobiology

2022 Jul 29

Miki, Y;Tanji, K;Shinnai, K;Tanaka, MT;Altay, F;Foti, SC;Strand, C;Sasaki, T;Kon, T;Shimoyama, S;Furukawa, T;Nishijima, H;Yamazaki, H;Asi, YT;Bettencourt, C;Jaunmuktane, Z;Tada, M;Mori, F;Mizukami, H;Tomiyama, M;Lashuel, HA;Lashley, T;Kakita, A;Ling, H;Lees, AJ;Holton, JL;Warner, TT;Wakabayashi, K;
PMID: 35906771 | DOI: 10.1111/nan.12844

Synaptic dysfunction in Parkinson's disease is caused by propagation of pathogenic α-synuclein between neurons. Previously, in multiple system atrophy (MSA), pathologically characterised by ectopic deposition of abnormal α-synuclein predominantly in oligodendrocytes, we demonstrated that the occurrence of memory impairment was associated with the number of α-synuclein-positive neuronal cytoplasmic inclusions (NCIs) in the hippocampus. In the present study, we aimed to investigate how abnormal α-synuclein in the hippocampus can lead to memory impairment.We performed pathological and biochemical analyses using a mouse model of adult-onset MSA and human cases (MSA, N = 25; Parkinson's disease, N = 3; Alzheimer's disease, N = 2; normal controls, N = 11). In addition, the MSA model mice were examined behaviourally and physiologically.In the MSA model, inducible human α-synuclein was first expressed in oligodendrocytes and subsequently accumulated in the cytoplasm of excitatory hippocampal neurons (NCI-like structures) and their presynaptic nerve terminals with the development of memory impairment. α-Synuclein oligomers increased simultaneously in the hippocampus of the MSA model. Hippocampal dendritic spines also decreased in number, followed by suppression of long-term potentiation. Consistent with these findings obtained in the MSA model, post-mortem analysis of human MSA brain tissues showed that cases of MSA with memory impairment developed more NCIs in excitatory hippocampal neurons along with α-synuclein oligomers than those without.Our results provide new insights into the role of α-synuclein oligomers as a possible pathological cause of memory impairment in MSA.

Enduring Controversial Story in the Human Brain

McGill Science Undergraduate Research Journal

2023 Mar 26

Niu, Z;Capolicchio, T;
| DOI: 10.26443/msurj.v18i1.194

Adult hippocampal neurogenesis (AHN) is a well-studied phenomenon that involves the derivation of new neurons from neural progenitor cells in the dentate gyrus region of the hippocampus, an area responsible for cognitive functions such as learning and memory storage. Moreover, the hippocampus is known to be implicated in neurological conditions such as Alzheimer's disease. Although AHN has been extensively observed in animal models for twenty years, its existence and persistence in humans have been widely debated in academia, heavily based on post-mortem immunohistochemical markers. Using the search engines PubMed and Google Scholar for “Adult Human Neurogenesis,” 143 articles that were most relevant to the history of AHN discovery, detection in rodents, immunohistochemical studies on post-mortem human sections, and therapeutic development targeting AHN were reviewed. This review article highlights the current understanding of AHN in rodents and humans, its implications in neurodegenerative diseases and therapeutics, and the inconsistencies and methodological variabilities encountered in studying AHN in humans. Furthermore, the correlation between AHN and diseases such as mood disorders and Alzheimer's disease is still not well established, with conflicting findings reported. Standardization of transcriptomic methodologies and increased availability of post-mortem human brain samples are crucial in advancing AHN research. This review article attempts to discover the fascinating and controversial world of adult human neurogenesis and its potential implications in treating neurological disorders. Apart from the discussion on AHN existence, tackling devastating diseases with this supplemental knowledge can lead to therapeutic advancements which greatly rely on understanding not only the presence of AHN but the mechanisms mediating its availability.

GHSR1a deficiency suppresses inhibitory drive on dCA1 pyramidal neurons and contributes to memory reinforcement

Cerebral cortex (New York, N.Y. : 1991)

2022 Jul 08

Li, N;Li, N;Yang, L;Gu, H;Ji, J;Zhou, H;Zhu, Q;Yu, M;Sun, Y;Zhou, Y;
PMID: 35797708 | DOI: 10.1093/cercor/bhac230

Growth hormone secretagogue receptor 1a (GHSR1a)-the receptor for orexigenic hormone ghrelin-is a G protein-coupled receptor that is widely distributed in the brain, including the hippocampus. Studies have demonstrated that genetic deletion of GHSR1a affects memory, suggesting the importance of ghrelin/GHSR1a signaling in cognitive control. However, current reports are controversial, and the mechanism underlying GHSR1a modulation of memory is uncertain. Here, we first report that global GHSR1a knockout enhances hippocampus-dependent memory, facilitates initial LTP in dorsal hippocampal Schaffer Collateral-CA1 synapses, and downregulates Akt activity in the hippocampus. Moreover, we show that the intrinsic excitability of GAD67+ interneurons-rather than neighboring pyramidal neurons in the dCA1-is suppressed by GHSR1a deletion, an effect that is antagonized by acute application of the Akt activator SC79. In addition, the inhibitory postsynaptic currents (IPSCs) on dCA1 pyramidal neurons are selectively reduced in mice with a GHSR1a deficiency. Finally, we demonstrate that selectively increasing the excitability of parvalbumin-expressing interneurons by hM3Dq-DREADDs increases IPSCs on dCA1 pyramidal neurons and normalizes memory in Ghsr1a KO mice. Our findings thus reveal a novel mechanism underlying memory enhancement of GHSR1a deficiency and herein support an adverse effect of GHSR1a signaling in hippocampus-dependent memory processes.

Single-cell RNA transcriptome analysis of CNS immune cells reveals CXCL16/CXCR6 as maintenance factors for tissue-resident T cells that drive synapse elimination

Genome medicine

2022 Sep 24

Rosen, SF;Soung, AL;Yang, W;Ai, S;Kanmogne, M;Davé, VA;Artyomov, M;Magee, JA;Klein, RS;
PMID: 36153630 | DOI: 10.1186/s13073-022-01111-0

Emerging RNA viruses that target the central nervous system (CNS) lead to cognitive sequelae in survivors. Studies in humans and mice infected with West Nile virus (WNV), a re-emerging RNA virus associated with learning and memory deficits, revealed microglial-mediated synapse elimination within the hippocampus. Moreover, CNS-resident memory T (TRM) cells activate microglia, limiting synapse recovery and inducing spatial learning defects in WNV-recovered mice. The signals involved in T cell-microglia interactions are unknown.Here, we examined immune cells within the murine WNV-recovered forebrain using single-cell RNA sequencing to identify putative ligand-receptor pairs involved in intercellular communication between T cells and microglia. Clustering and differential gene analyses were followed by protein validation and genetic and antibody-based approaches utilizing an established murine model of WNV recovery in which microglia and complement promote ongoing hippocampal synaptic loss.Profiling of host transcriptome immune cells at 25 days post-infection in mice revealed a shift in forebrain homeostatic microglia to activated subpopulations with transcriptional signatures that have previously been observed in studies of neurodegenerative diseases. Importantly, CXCL16/CXCR6, a chemokine signaling pathway involved in TRM cell biology, was identified as critically regulating CXCR6 expressing CD8+ TRM cell numbers within the WNV-recovered forebrain. We demonstrate that CXCL16 is highly expressed by all myeloid cells, and its unique receptor, CXCR6, is highly expressed on all CD8+ T cells. Using genetic and pharmacological approaches, we demonstrate that CXCL16/CXCR6 not only is required for the maintenance of WNV-specific CD8 TRM cells in the post-infectious CNS, but also contributes to their expression of TRM cell markers. Moreover, CXCR6+CD8+ T cells are required for glial activation and ongoing synapse elimination.We provide a comprehensive assessment of the role of CXCL16/CXCR6 as an interaction link between microglia and CD8+ T cells that maintains forebrain TRM cells, microglial and astrocyte activation, and ongoing synapse elimination in virally recovered animals. We also show that therapeutic targeting of CXCL16 in mice during recovery may reduce CNS CD8+ TRM cells.

Loss of neuronal Tet2 enhances hippocampal-dependent cognitive function

Cell reports

2022 Nov 08

Pratt, KJB;Shea, JM;Remesal-Gomez, L;Bieri, G;Smith, LK;Couthouis, J;Chen, CP;Roy, IJ;Gontier, G;Villeda, SA;
PMID: 36351399 | DOI: 10.1016/j.celrep.2022.111612

DNA methylation has emerged as a critical modulator of neuronal plasticity and cognitive function. Notwithstanding, the role of enzymes that demethylate DNA remain to be fully explored. Here, we report that loss of ten-eleven translocation methylcytosine dioxygenase 2 (Tet2), which catalyzes oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), in adult neurons enhances cognitive function. In the adult mouse hippocampus, we detected an enrichment of Tet2 in neurons. Viral-mediated neuronal overexpression and RNA interference of Tet2 altered dendritic complexity and synaptic-plasticity-related gene expression in vitro. Overexpression of neuronal Tet2 in adult hippocampus, and loss of Tet2 in adult glutamatergic neurons, resulted in differential hydroxymethylation associated with genes involved in synaptic transmission. Functionally, overexpression of neuronal Tet2 impaired hippocampal-dependent memory, while loss of neuronal Tet2 enhanced memory. Ultimately, these data identify neuronal Tet2 as a molecular target to boost cognitive function.

A02 Altered epigenetic and transcriptional regulation during striatum-dependent memory in HD mice

A: Pathogenic mechanisms

2022 Sep 01

Alcalá-Vida, R;Lotz, C;Seguin, J;Decraene, C;Brulé, B;Awada, A;Bombardier, A;Cosquer, B;Pereira de Vasconcelos, A;Brouillet, E;Cassel, J;Boutillier, A;Merienne, K;
| DOI: 10.1136/jnnp-2022-ehdn.2

Epigenetic mechanisms are altered in the striatum of HD patients and mouse models, but how they might contribute to pathogenesis, including cognitive deficits, is unclear. Epigenetic regulation is critical to learning and memory processes, through transcriptional control of gene program promoting neural plasticity. We asked whether memory-associated epigenetic and transcriptional responses were impaired in HD R6/1 mice. To this end, we trained R6/1 mice (and control mice) in an aquatic navigation task, the double H maze, which allows assessing striatum-dependent memory (e.g. egocentric spatial memory). We then generated ChIP-seq, 4C-seq and RNA-seq datasets on striatal tissue of HD and control mice during egocentric memory processing, including memory acquisition and consolidation/recall. Egocentric memory was altered since early symptomatic stage in R6/1 mice, which correlated with dramatic reduction of striatal epigenetic and transcriptional changes induced by memory process. More specifically, multi-omic analysis showed that, during memory acquisition, 3D chromatin re-organization and transcriptional induction at BDNF-related genes were diminished in R6/1 striatum. Moreover, we found that changes in H3K9 acetylation (H3K9ac), which accompanied memory process in normal striatum, were attenuated in R6/1 striatum. Functional enrichment analyses further indicated that altered H3K9ac regulation during late phase of egocentric memory process (e.g. consolidation/recall) contributed to impaired TGFβ-dependent cellular plasticity. Together, this study provides support to the hypothesis that epigenetic dysregulation in HD contributes to cognitive deficits, and shed light on new targets of striatal plasticity, particularly H3K9ac and TFGβ signaling.

Central FGF21 production regulates memory but not peripheral metabolism

Cell reports

2022 Aug 23

Zhou, B;Claflin, KE;Flippo, KH;Sullivan, AI;Asghari, A;Tadinada, SM;Jensen-Cody, SO;Abel, T;Potthoff, MJ;
PMID: 36001982 | DOI: 10.1016/j.celrep.2022.111239

Fibroblast growth factor 21 (FGF21) is a liver-derived endocrine hormone that functions to regulate energy homeostasis and macronutrient intake. Recently, FGF21 was reported to be produced and secreted from hypothalamic tanycytes, to regulate peripheral lipid metabolism; however, rigorous investigation of FGF21 expression in the brain has yet to be accomplished. Using a mouse model that drives CRE recombinase in FGF21-expressing cells, we demonstrate that FGF21 is not expressed in the hypothalamus, but instead is produced from the retrosplenial cortex (RSC), an essential brain region for spatial learning and memory. Furthermore, we find that central FGF21 produced in the RSC enhances spatial memory but does not regulate energy homeostasis or sugar intake. Finally, our data demonstrate that administration of FGF21 prolongs the duration of long-term potentiation in the hippocampus and enhances activation of hippocampal neurons. Thus, endogenous and pharmacological FGF21 appear to function in the hippocampus to enhance spatial memory.

PD-L1/PD-1 checkpoint pathway regulates hippocampal neuronal excitability and learning and memory behavior

Neuron

2023 Jun 15

Zhao, J;Bang, S;Furutani, K;McGinnis, A;Jiang, C;Roberts, A;Donnelly, CR;He, Q;James, ML;Berger, M;Ko, MC;Wang, H;Palmiter, RD;Ji, RR;
PMID: 37348508 | DOI: 10.1016/j.neuron.2023.05.022

Programmed death protein 1 (PD-1) and its ligand PD-L1 constitute an immune checkpoint pathway. We report that neuronal PD-1 signaling regulates learning/memory in health and disease. Mice lacking PD-1 (encoded by Pdcd1) exhibit enhanced long-term potentiation (LTP) and memory. Intraventricular administration of anti-mouse PD-1 monoclonal antibody (RMP1-14) potentiated learning and memory. Selective deletion of PD-1 in excitatory neurons (but not microglia) also enhances LTP and memory. Traumatic brain injury (TBI) impairs learning and memory, which is rescued by Pdcd1 deletion or intraventricular PD-1 blockade. Conversely, re-expression of Pdcd1 in PD-1-deficient hippocampal neurons suppresses memory and LTP. Exogenous PD-L1 suppresses learning/memory in mice and the excitability of mouse and NHP hippocampal neurons through PD-1. Notably, neuronal activation suppresses PD-L1 secretion, and PD-L1/PD-1 signaling is distinctly regulated by learning and TBI. Thus, conditions that reduce PD-L1 levels or PD-1 signaling could promote memory in both physiological and pathological conditions.

MiR-181a-5p promotes neural stem cell proliferation and enhances the learning and memory of aged mice

Aging cell

2023 Feb 16

Sun, Q;Ma, L;Qiao, J;Wang, X;Li, J;Wang, Y;Tan, A;Ye, Z;Wu, Y;Xi, J;Kang, J;
PMID: 36797653 | DOI: 10.1111/acel.13794

Hippocampal neural stem cell (NSC) proliferation is known to decline with age, which is closely linked to learning and memory impairments. In the current study, we found that the expression level of miR-181a-5p was decreased in the hippocampal NSCs of aged mice and that exogenous overexpression of miR-181a-5p promoted NSC proliferation without affecting NSC differentiation into neurons and astrocytes. The mechanistic study revealed that phosphatase and tensin homolog (PTEN), a negative regulator of the AKT signaling pathway, was the target of miR-181a-5p and knockdown of PTEN could rescue the impairment of NSC proliferation caused by low miR-181a-5p levels. Moreover, overexpression of miR-181a-5p in the dentate gyrus enhanced the proliferation of NSCs and ameliorated learning and memory impairments in aged mice. Taken together, our findings indicated that miR-181a-5p played a functional role in NSC proliferation and aging-related, hippocampus-dependent learning and memory impairments.

Anti-Cholestatic Therapy with Obeticholic Acid Improves Short-Term Memory in Bile Duct Ligated Mice

The American journal of pathology

2022 Oct 13

Gee, LMV;Barron-Millar, B;Leslie, J;Richardson, C;Zaki, MYW;Luli, S;Burgoyne, RA;Cameron, RIT;Smith, GR;Brain, JG;Innes, B;Jopson, L;Dyson, JK;McKay, KRC;Pechlivanis, A;Holmes, E;Berlinguer-Palmini, R;Victorelli, S;Mells, GF;Sandford, RN;Palmer, J;Kirby, JA;Kiourtis, C;Mokochinski, J;Hall, Z;Bird, TG;Borthwick, LA;Morris, CM;Hanson, PS;Jurk, D;Stoll, EA;LeBeau, FEN;Jones, DEJ;Oakley, F;
PMID: 36243043 | DOI: 10.1016/j.ajpath.2022.09.005

Patients with cholestatic liver disease, including those with primary biliary cholangitis, can experience symptoms of impaired cognition or brain fog. This phenomenon remains unexplained and is currently untreatable. Bile duct ligation (BDL) is an established rodent model of cholestasis. In addition to liver changes, BDL animals develop cognitive symptoms early in the disease process (before development of cirrhosis and/or liver failure). The cellular mechanisms underpinning these cognitive symptoms are poorly understood. Herein, we explored the neurocognitive symptom manifestations, and tested potential therapies, in BDL mice, and used human neuronal cell cultures to explore translatability to humans. BDL animals exhibited short-term memory loss and showed reduced astrocyte coverage of the blood-brain barrier, destabilized hippocampal network activity, and neuronal senescence. Ursodeoxycholic acid (first-line therapy for most human cholestatic diseases) did not reverse symptomatic or mechanistic aspects. In contrast, obeticholic acid (OCA), a farnesoid X receptor agonist and second-line anti-cholestatic agent, normalized memory function, suppressed blood-brain barrier changes, prevented hippocampal network deficits, and reversed neuronal senescence. Co-culture of human neuronal cells with either BDL or human cholestatic patient serum induced cellular senescence and increased mitochondrial respiration, changes that were limited again by OCA. Our findings provide new insights into the mechanism of cognitive symptoms in BDL animals, suggesting that OCA therapy or farnesoid X receptor agonism could be used to limit cholestasis-induced neuronal senescence.

Inhibitory top-down projections from zona incerta mediate neocortical memory

Neuron

2023 Jan 04

Schroeder, A;Pardi, MB;Keijser, J;Dalmay, T;Groisman, AI;Schuman, EM;Sprekeler, H;Letzkus, JJ;
PMID: 36610397 | DOI: 10.1016/j.neuron.2022.12.010

Top-down projections convey a family of signals encoding previous experiences and current aims to the sensory neocortex, where they converge with external bottom-up information to enable perception and memory. Whereas top-down control has been attributed to excitatory pathways, the existence, connectivity, and information content of inhibitory top-down projections remain elusive. Here, we combine synaptic two-photon calcium imaging, circuit mapping, cortex-dependent learning, and chemogenetics in mice to identify GABAergic afferents from the subthalamic zona incerta as a major source of top-down input to the neocortex. Incertocortical transmission undergoes robust plasticity during learning that improves information transfer and mediates behavioral memory. Unlike excitatory pathways, incertocortical afferents form a disinhibitory circuit that encodes learned top-down relevance in a bidirectional manner where the rapid appearance of negative responses serves as the main driver of changes in stimulus representation. Our results therefore reveal the distinctive contribution of long-range (dis)inhibitory afferents to the computational flexibility of neocortical circuits.

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	Description
sense Example: Hs-LAG3-sense	Standard probes for RNA detection are in antisense. Sense probe is reverse complent to the corresponding antisense probe.
Intron# Example: Mm-Htt-intron2	Probe targets the indicated intron in the target gene, commonly used for pre-mRNA detection
Pool/Pan Example: Hs-CD3-pool (Hs-CD3D, Hs-CD3E, Hs-CD3G)	A mixture of multiple probe sets targeting multiple genes or transcripts
No-XSp Example: Hs-PDGFB-No-XMm	Does not cross detect with the species (Sp)
XSp Example: Rn-Pde9a-XMm	designed to cross detect with the species (Sp)
O# Example: Mm-Islr-O1	Alternative design targeting different regions of the same transcript or isoforms
CDS Example: Hs-SLC31A-CDS	Probe targets the protein-coding sequence only
EnEm	Probe targets exons n and m
En-Em	Probe targets region from exon n to exon m
Retired Nomenclature
tvn Example: Hs-LEPR-tv1	Designed to target transcript variant n
ORF Example: Hs-ACVRL1-ORF	Probe targets open reading frame
UTR Example: Hs-HTT-UTR-C3	Probe targets the untranslated region (non-protein-coding region) only
5UTR Example: Hs-GNRHR-5UTR	Probe targets the 5' untranslated region only
3UTR Example: Rn-Npy1r-3UTR	Probe targets the 3' untranslated region only
Pan Example: Pool	A mixture of multiple probe sets targeting multiple genes or transcripts

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