Background: Dysregulation of the endocannabinoid system (eCBS) and the loss of CB1 receptors (CB1R) in the basal ganglia are well-established hallmarks of Huntington's disease (HD). As a result, significant research efforts have focused on targeting the eCBS to alleviate motor disturbances associated with the disease. Beyond its role in motor control, the eCBS is a complex signaling network critically involved in regulating learning and memory. Despite this, the potential involvement of eCBS dysfunction in the cognitive decline characteristic of HD, often manifested well before motor dysfunction, has remained largely unexplored. Methods: CB1R expression in the hippocampus was evaluated in both human HD samples and HD mouse models (R6/1 and Hdh models, including both sexes) using Western blotting, immunohistochemistry, and radioligand binding assays. To restore CB1R function, CB1R agonist WIN-55212-2 was systemically administered, or viral vectors encoding CB1R were locally infused into the hippocampus of HD mice. A multidisciplinary approach combining behavioral, biochemical, electrophysiological, and morphological analyses, was employed to investigate the molecular mechanisms underlying the effects of CB1R activation in the context of HD-related cognitive dysfunction. Results: In both human HD samples and HD mouse models, CB1R protein levels were reduced in the hippocampus, accompanied by structural synaptic alterations and impairment in spatial, recognition and working memory. Moreover, hippocampal depolarization-induced suppression of inhibition was significantly disrupted in R6/1 mice. Administration of WIN-55212-2 successfully restored these synaptic and cognitive deficits. Immunohistochemical analysis revealed that the CB1R decrease was specifically localized to GABAergic interneurons within the hippocampus. Notably, targeted restoration of CB1R expression in these interneurons via viral vector delivery was sufficient to rescue hippocampal-dependent memory deficits in HD mice. Conclusion: This study suggests that impaired CB1R function in hippocampal GABAergic interneurons contributes to memory dysfunction in HD., This work was supported by the Spanish Ministerio de Ciencia e Innovación (PID2021-123732OB-I00 to SG, PID2021-125118OB-I00 to MG, PID2019-106579RB-I00, and PID2022-142617NB-I00 to GP, and PID2022-141700OB-I00 to AB funded by MCIN/AEI/ https://doi.org/10.13039/501100011033). Fundació la Marató de TV3 (202013-30-31-32 to SG, MG and GP), AGAUR Generalitat de Catalunya (2021-SGR-01358 to AB and 2021-SGR 01086 to SG) and grants to R. R.-P. rom the Basque Government IT1454-22 to the "Neurochemistry and Neurodegeneration" consolidated research group; Instituto de Salud Carlos III through the project PI20/00153 (co-funded by European Regional Development Fund "A way to make Europe") and by BIOEF through the project BIO22/ALZ/010 funded by Eitb Maratoia. A P-V is the recipient of a PRE2022-101764 fellowship (PID2021-123732OB-I00). I.B.d.T. is the recipient of an Investigo fellowship funded by the European Union-Next Generation EU.

Brain pathophysiology in Down syndrome (DS), the most common genetic cause of intellectual disability, has traditionally been considered a consequence of neuronal dysfunction. However, although it is well documented that astrocytes play a critical role in brain homeostasis, synaptic regulation, and neuronal support, and their malfunction has been associated with the onset and progression of different neurological disorders, only a few studies have addressed whether astrocyte dysfunction can contribute to the DS pathophysiology. Astrocytes are increased in number and size, and show increased levels of expression of astroglial markers like S100ß and GFAP. In this study, we detected a region-specific increase in astrocyte population in CA1 and, to a lesser extent, in the dentate gyrus. Single-nucleus transcriptomic profiling identified markers associated with reactive astroglia, synaptic transmission, and neuroinflammation in trisomic astrocytes. Functional analysis revealed abnormal Ca2+ oscillations in trisomic astrocytes and impaired astrocyte-to-neuron communication in CA1, the most affected subregion, leading to astrocyte-mediated excitatory synaptic depression. Our findings demonstrate that astrocytes play an active and critical role in the pathophysiology of DS, not only as reactive responders to neuronal injury but as key contributors to the disease process itself. This astrocytic dysfunction presents a region-specific distribution within the hippocampus, suggesting localized vulnerability and complex glial involvement in DS-related neuropathology., The lab of MD is supported by the Secretaria d¿Universitats i Recerca del Departament d'Economia I Coneixement de la Generalitat de Catalunya (Grups consolidats 2017 SGR 926). We also acknowledge the support of the Agencia Estatal de Investigación (PID2022-141900OB-I00 INTO-DS funded by MICIU/AEI/10.13039/501100011033/FEDER, UE). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 848077). The publication is part of the grant PRE2018-084504, funded by MCIN/AEI/10.13039/501100011033 and by the FSE+ (AFB). Additionally, we have been supported by Fundació La Marató TV3 (201620-31 and 225619), and by PID2022-142617NB-I00 and PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/501100011033 to G.P.

Brain slice preparations are widely used for research in neuroscience. However, a high-quality preparation is essential and there is no consensus regarding stable parameters that can be used to define the status of the brain slice preparation after its collection at different time points. Thus, it is critical to fully characterize the experimental conditions for ex vivo studies using brain slices for electrophysiological recording. In this study, we used a multiplatform (LC-MS and GC-MS) untargeted metabolomics-based approach to shed light on the metabolome and lipidome changes taking place at different time intervals during the brain slice preparation process. We have found significant modifications in the levels of 300 compounds, including several lipid classes and their derivatives, as well as metabolites involved in the GABAergic pathway and the TCA cycle. All these preparation-dependent changes in the brain biochemistry related to the time interval should be taken into consideration for future studies to facilitate non-biased interpretations of the experimental results., This work was supported by grants from the following entities: FEDER Program 2014-2020 of the Community of Madrid (Ref.S2017/ BMD3684), Centro de Investigación en Red sobre Enfermedades Neurodegenerativas (CIBERNED, CB06/05/0066, Spain) and the Spanish “Ministerio de Ciencia, Innovación y Universidades” (grant PGC2018-094307-B-I00 to J.D and RTI2018-095166-B-I00 to C.B; the Cajal Blue Brain Project [the Spanish partner of the Blue Brain Project initiative from EPFL, Switzerland to J.D]; the PhD fellowship program from MINECO (Spain) (BES-2017-080303) to CG-A; and MINECO grant (BFU2016-75107-P,PID2019-106579RB-I00) and CSICPIE grant (2019AEP152) to G.P.).

GABA interneurons play a critical role in higher brain functions. Astrocytic glial cells interact with synapses throughout the whole brain and are recognized as regulatory elements of excitatory synaptic transmission. However, it is largely unknown how GABAergic interneurons and astrocytes interact and contribute to stable performance of complex behaviors. Here, we found that genetic ablation of GABA receptors in medial prefrontal cortex astrocytes altered low-gamma oscillations and firing properties of cortical neurons, which affected goal-directed behaviors. Remarkably, working memory deficits were restored by optogenetic stimulation of astrocytes with melanopsin. Furthermore, melanopsin-activated astrocytes in wild-type mice enhanced the firing rate of cortical neurons and gamma oscillations, as well as improved cognition. Therefore, our work identifies astrocytes as a hub for controlling inhibition in cortical circuits, providing a novel pathway for the behaviorally relevant midrange time-scale regulation of cortical information processing and consistent goal-directed behaviors., We thank the T. Korotkova Lab, C. González-Arias and C. Heikenfeld for technical support; the Molecular and Cellular Biology Unit from the Cajal Institute for technical assistance; B. Bettler, A. Araque, M. Navarrete, E. D. Martín and A. Fernández-Ruiz for critical review of the manuscript; and Buzsáki Lab members for valuable suggestions. This work was supported by the MCIU/AEI/FEDER, UE (BES-2014-067594) to S.M.; a European Molecular Biology Organization (EMBO) postdoctoral fellowship (EMBO ALTF 1161-2017) and a Human Frontiers Science Program (HFSP) postdoctoral fellowship (LT0000717/2018) to M.V.; the Deutsche Forschungsgemeinschaft (DFG: SPP1665, 1799/1-2 and Heisenberg Program 1799/2-1 and 1799/3-1) to A.P.; the MCIU/AEI/FEDER, UE (BFU2016-75107-P), and MCIU/AEI/FEDER, UE (PID2019- 106579RB-I00), 202020E073 from the CSIC, and the Cajal Blue Brain Project (C080020-
09; the Spanish partner of the Blue Brain Project initiat.

Here, we present a protocol to selectively downregulate GABA receptor (GABAR) expression in astrocytes of mouse medial prefrontal cortex (mPFC). We first describe the procedure of surgeries and viral injections. We then detail genetic, histological, and functional characterizations of astrocytic GABAR ablation using RT-PCR, imaging, and behavioral assays. The use of GABA flox mice can be easily adapted to generate astrocyte-selective GABAR ablation in different brain areas and postnatal stages, leading to local downregulation of GABAergic-astrocyte signaling without developmental issues. For complete details on the use and execution of this protocol, please refer to Mederos et al. (2021)., This research was supported by grants from the MICINN/AEI/FEDER, UE-Spain (PRE2020-092999) to A.S.-R.; EMBO ALTF 327-2021 to S.M.; PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/501100011033; ASTROTECH 956325 H2020-MSCA-ITN-2020, and Fundacio ́ La Marato ́TV3 #225619 to G.P.

Insulin-like growth factor-I (IGF-I) exerts multiple actions, yet the role of IGF-I from different sources is poorly understood. Here, we explored the functional and behavioral consequences of the conditional deletion of Igf-I in the nervous system (Igf-I Δ/Δ), and demonstrated that long-term potentiation was impaired in hippocampal slices. Moreover, Igf-I Δ/Δ mice showed spatial memory deficits in the Morris water maze, and the significant sex-dependent differences displayed by Igf-I Ctrl/Ctrl mice disappeared in Igf-I Δ/Δ mice in the open field and rota-rod tests. Brain Igf-I deletion disorganized the granule cell layer of the dentate gyrus (DG), and it modified the relative expressions of GAD and VGLUT1, which are preferentially localized to inhibitory and excitatory presynaptic terminals. Furthermore, Igf-I deletion altered protein modules involved in receptor trafficking, synaptic proteins, and proteins that functionally interact with estrogen and androgen metabolism. Our findings indicate that brain IGF-I is crucial for long-term potentiation, and that it is involved in the regulation of spatial memory and sexual dimorphic behaviors, possibly by maintaining the granule cell layer structure and the stability of synaptic-related protein modules., We thank Lucía Vicario (Instituto Cajal-CSIC, Madrid, Spain) for helping with the composition of the figures, and Dr. M Sefton (BiomedRed SL, Madrid, Spain) for English editing. This work was funded by grants from the Spanish “Ministerio Ciencia, Innovación y Universidades, and the Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación” (MICIU and MICINN/AEI SAF2016-80419-R, PID2019-109059RB-100, and CIBERNED CB06/05/0065 to C Vicario; PID2019-110356RB-I00/AEI/10.13039/501100011033 to J Fernández-Irigoyen and E Santamaría; PID2019-104376RB-I00 to I Torres-Alemán; and PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe to G Perea, and BES-2017-080303 to C González-Arias).

Astrocytes play crucial roles in brain homeostasis and are regulatory elements of neuronal and synaptic physiology. Astrocytic alterations have been found in Major Depressive Disorder (MDD) patients; however, the consequences of astrocyte Ca signaling in MDD are poorly understood. Here, we found that corticosterone-treated juvenile mice (Cort-mice) showed altered astrocytic Ca dynamics in mPFC both in resting conditions and during social interactions, in line with altered mice behavior. Additionally, Cort-mice displayed reduced serotonin (5-HT)-mediated Ca signaling in mPFC astrocytes, and aberrant 5-HT-driven synaptic plasticity in layer 2/3 mPFC neurons. Downregulation of astrocyte Ca signaling in naïve animals mimicked the synaptic deficits found in Cort-mice. Remarkably, boosting astrocyte Ca signaling with Gq-DREADDS restored to the control levels mood and cognitive abilities in Cort-mice. This study highlights the important role of astrocyte Ca signaling for homeostatic control of brain circuits and behavior, but also reveals its potential therapeutic value for depressive-like states., This work was supported by PID2019-106579RB-I00 and PID2022-142617NB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe” to G.P, by PLEC2022-009385 funded by MCIN/AEI/10.13039/501100011033 and by “NextGeneration EU/PRTR” to GP; La Marató TV3 Foundation #225619 to GP. BES-2017-080303 to CG-A and PRE2020-092999 to AS-R by MCIN/AEI/FEDER,UE. PEJ-2020-AI/BMD-18675 to LA. Deutsche Forschungsgemeinschaft (DFG) SFB 894, SFB 1158 and SPP 1757 to FK.

During cerebral cortex development, excitatory pyramidal neurons (PNs) establish specific projection patterns while receiving inputs from GABAergic inhibitory interneurons (INs). Whether these inhibitory inputs can shape PNs' projection patterns is, however, unknown. While layer 4 (L4) PNs of the primary somatosensory (S1) cortex are all born as long-range callosal projection neurons (CPNs), most of them acquire local connectivity upon activity-dependent elimination of their interhemispheric axons during postnatal development. Here, we demonstrate that precise developmental regulation of inhibition is key for the retraction of S1L4 PNs' callosal projections. Ablation of somatostatin INs leads to premature inhibition from parvalbumin INs onto S1L4 PNs and prevents them from acquiring their barrel-restricted local connectivity pattern. As a result, adult S1L4 PNs retain interhemispheric projections responding to tactile stimuli, and the mice lose whisker-based texture discrimination. Overall, we show that temporally ordered IN activity during development is key to shaping local ipsilateral S1L4 PNs' projection pattern, which is required for fine somatosensory processing., L.B.-G. and A.A. hold fellowships from the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie (grant agreement no. 713673) and the “La Caixa” Foundation [ID 100010434; the fellowship codes are LCF/BQ/IN17/11620044 (L.B.-G.) and LCF/BQ/DI21/11860049 (A.A.)]. C.G.-A. holds a fellowship funded by MCIU/AEI/10.13039/501100011033 and by ESF “Investing in your future” (BES-2017-080303), and P.C. and A.S.-C. were funded by fellowships from MICIU (PRE2021-099425 and FJC2021-047621-I, respectively). G.P. acknowledges funding from La Marató TV3 Foundation (nos. 225619) and PID2019-106579RB-I00 from MCIU/AEI/10.13039/501100011033. M.N. acknowledges funding from SAF2017-83117-R funded by MCIU/AEI/10.13039/501100011033; “ERDF A way of making Europe” funded by the “European Union”; PID2020-112831GB-I00 funded by MCIU/AEI/10.13039/501100011033; and PEJ-2021-TL/BMD-22114 funded by “la Consejería de Educación, Universidades, Ciencia y Portavocía,” de la Comunidad de Madrid. F.L. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement number 949652) also supporting N.S.D.L.R, the Valencian Community (CIDEGENT), and the “Severo Ochoa Centers of Excellence” from the MICIU., Peer reviewed

Cereblon/CRBN is a substrate-recognition component of the
Cullin4A-DDB1-Roc1 E3 ubiquitin ligase complex. Destabilizing
mutations in the human CRBN gene cause a form of autosomal
recessive non-syndromic intellectual disability (ARNSID) that is
modelled by knocking-out the mouse Crbn gene. A reduction in
excitatory neurotransmission has been proposed as an underlying
mechanism of the disease. However, the precise factors eliciting
this impairment remain mostly unknown. Here we report that CRBN
molecules selectively located on glutamatergic neurons are
necessary for proper memory function. Combining various in vivo
approaches, we show that the cannabinoid CB 1 receptor (CB 1 R), a
key suppressor of synaptic transmission, is overactivated in CRBN
deficiency-linked ARNSID mouse models, and that the memory
deficits observed in these animals can be rescued by acute
CB 1 R-selective pharmacological antagonism. Molecular studies
demonstrated that CRBN interacts physically with CB 1 R and impairs
the CB 1 R-G i/o -cAMP-PKA pathway in a ubiquitin ligase-
independent manner. Taken together, these findings unveil that
CB 1 R overactivation is a driving mechanism of CRBN deficiency-
linked ARNSID and anticipate that the antagonism of CB 1 R could
constitute a new therapy for this orphan disease., This work was supported by the Spanish Ministerio de Ciencia e Innovación
(MICINN/FEDER; grants PID2021-125118OB-I00 to MG, PID2020-113938RB-
I00 to EM and VC, PID2019-106579RB-I00 and PID2022-142617NB-I00 to GP,
and PID2019-106404RB-I00 to LU), as well as by the Generalitat de Catalunya
(grant 2021-SGR-00230 to EM and VC). LB was supported by INSERM. CC-I
and IBM were supported by contracts from the Spanish Ministerio de Universidades (Formación de Profesorado Universitario Program, references
FPU16/02593 and FPU15/01833, respectively). CC-I was also supported by an
EMBO short-term fellowship (reference STF-8930). We are indebted to Dr.
Benjamin L. Ebert for the kind donation of HEK-293T-CRBN-KO and parental
HEK-293T-CRBN-WT cells. We also thank David Martín-Gutiérrez, Lucía
Rivera-Endrinal, Dr. Daniel García-Ovejero, Dr. Eduardo Molina-Holgado, and
the personnel of the core microscopy centre, the genomics unit, and the animal
facilities of Universidad Complutense de Madrid for their expert technical
assistance., Peer reviewed

This work introduces NeoMag, a system designed to enhance cell mechanics assays in substrate deformation studies. NeoMag uses multidomain magneto-active materials to mechanically actuate the substrate, transmitting reversible mechanical cues to cells. The system boasts full flexibility in alternating loading substrate deformation modes, seamlessly adapting to both upright and inverted microscopes. The multidomain substrates facilitate mechanobiology assays on 2D and 3D cultures. The integration of the system with nanoindenters allows for precise evaluation of cellular mechanical properties under varying substrate deformation modes. The system is used to study the impact of substrate deformation on astrocytes, simulating mechanical conditions akin to traumatic brain injury and ischemic stroke. The results reveal local heterogeneous changes in astrocyte stiffness, influenced by the orientation of subcellular regions relative to substrate strain. These stiffness variations, exceeding 50% in stiffening and softening, and local deformations significantly alter calcium dynamics. Furthermore, sustained deformations induce actin network reorganization and activate Piezo1 channels, leading to an initial increase followed by a long-term inhibition of calcium events. Conversely, fast and dynamic deformations transiently activate Piezo1 channels and disrupt the actin network, causing long-term cell softening. These findings unveil mechanical and functional alterations in astrocytes during substrate deformation, illustrating the multiple opportunities this technology offers., 947723/H2020 European Research Council
101081713/HORIZON EUROPE European Research Council
FPU20/01459/Ministerio de Universidades
PID2019-109820RB-I00/Ministerio de Ciencia, Innovación y Universidades
PID2019-106579RB-I00/Ministerio de Ciencia, Innovación y Universidades, Peer reviewed

Cereblon/CRBN is a substrate-recognition component of the Cullin4A-DDB1-Roc1 E3 ubiquitin ligase complex. Destabilizing mutations in the human CRBN gene cause a form of autosomal recessive non-syndromic intellectual disability (ARNSID) that is modelled by knocking-out the mouse Crbn gene. A reduction in excitatory neurotransmission has been proposed as an underlying mechanism of the disease. However, the precise factors eliciting this impairment remain mostly unknown. Here we report that CRBN molecules selectively located on glutamatergic neurons are necessary for proper memory function. Combining various in vivo approaches, we show that the cannabinoid CB1 receptor (CB1R), a key suppressor of synaptic transmission, is overactivated in CRBN deficiency-linked ARNSID mouse models, and that the memory deficits observed in these animals can be rescued by acute CB1R-selective pharmacological antagonism. Molecular studies demonstrated that CRBN interacts physically with CB1R and impairs the CB1R-Gi/o-cAMP-PKA pathway in a ubiquitin ligase-independent manner. Taken together, these findings unveil that CB1R overactivation is a driving mechanism of CRBN deficiency-linked ARNSID and anticipate that the antagonism of CB1R could constitute a new therapy for this orphan disease., This work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN/FEDER; grants PID2021-125118OB-I00 to MG, PID2020-113938RB-I00 to EM and VC, PID2019-106579RB-I00 and PID2022-142617NB-I00 to GP, and PID2019-106404RB-I00 to LU), as well as by the Generalitat de Catalunya (grant 2021-SGR-00230 to EM and VC). LB was supported by INSERM. CC-Iand IBM were supported by contracts from the Spanish Ministerio de Universidades (Formación de Profesorado Universitario Program, referencesFPU16/02593 and FPU15/01833, respectively). CC-I was also supported by an EMBO short-term fellowship (reference STF-8930). We are indebted to Dr.Benjamin L. Ebert for the kind donation of HEK-293T-CRBN-KO and parental HEK-293T-CRBN-WT cells. We also thank David Martín-Gutiérrez, Lucía Rivera-Endrinal, Dr. Daniel García-Ovejero, Dr. Eduardo Molina-Holgado, and the personnel of the core microscopy centre, the genomics unit, and the animal facilities of Universidad Complutense de Madrid for their expert technical assistance.

This work introduces NeoMag, a system designed to enhance cell mechanics assays in substrate deformation studies. NeoMag uses multidomain magneto-active materials to mechanically actuate the substrate, transmitting reversible mechanical cues to cells. The system boasts full flexibility in alternating loading substrate deformation modes, seamlessly adapting to both upright and inverted microscopes. The multidomain substrates facilitate mechanobiology assays on 2D and 3D cultures. The integration of the system with nanoindenters allows for precise evaluation of cellular mechanical properties under varying substrate deformation modes. The system is used to study the impact of substrate deformation on astrocytes, simulating mechanical conditions akin to traumatic brain injury and ischemic stroke. The results reveal local heterogeneous changes in astrocyte stiffness, influenced by the orientation of subcellular regions relative to substrate strain. These stiffness variations, exceeding 50% in stiffening and softening, and local deformations significantly alter calcium dynamics. Furthermore, sustained deformations induce actin network reorganization and activate Piezo1 channels, leading to an initial increase followed by a long-term inhibition of calcium events. Conversely, fast and dynamic deformations transiently activate Piezo1 channels and disrupt the actin network, causing long-term cell softening. These findings unveil mechanical and functional alterations in astrocytes during substrate deformation, illustrating the multiple opportunities this technology offers., C. G.-C. and M. F.-d.l.T. authors contributed equally to this work. The authors thank Lotte van Dasler for the relevant discussion. The authors acknowledged support from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Program (Grant agreement no. 947723, project: 4D-BIOMAP and Grant agreement no. 101081713, project: ISBIOMECH). G.P. acknowledged support from PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/5011 00011033 and by “ERDF A way of making Europe”, and La Marató TV3 Foundation #225619. AMB acknowledged support from Ministerio de Ciencia, Innovación y Universidades, Agencia Estatal de Investigación Grant PID2019-109820RB-I00, MCIN/AEI/10.13039/501100011033/, co-financed by the European Regional Development Fund (ERDF), ‘A way of making Europe’. C.G.-C. acknowledged support from the Ministerio de Universidades, Spain (FPU20/01459) and A.M.B. from Universidad Carlos III de Madrid ('Ayudas para la recualificación del profesorado funcionario o contratado')., Peer reviewed

Cereblon/CRBN is a substrate-recognition component of the Cullin4A-DDB1-Roc1 E3 ubiquitin ligase complex. Destabilizing mutations in the human CRBN gene cause a form of autosomal recessive non-syndromic intellectual disability (ARNSID) that is modelled by knocking-out the mouse Crbn gene. A reduction in excitatory neurotransmission has been proposed as an underlying mechanism of the disease. However, the precise factors eliciting this impairment remain mostly unknown. Here we report that CRBN molecules selectively located on glutamatergic neurons are necessary for proper memory function. Combining various in vivo approaches, we show that the cannabinoid CB1 receptor (CB1R), a key suppressor of synaptic transmission, is overactivated in CRBN deficiency-linked ARNSID mouse models, and that the memory deficits observed in these animals can be rescued by acute CB1R-selective pharmacological antagonism. Molecular studies demonstrated that CRBN interacts physically with CB1R and impairs the CB1R-Gi/o-cAMP-PKA pathway in a ubiquitin ligase-independent manner. Taken together, these findings unveil that CB1R overactivation is a driving mechanism of CRBN deficiency-linked ARNSID and anticipate that the antagonism of CB1R could constitute a new therapy for this orphan disease., This work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN/FEDER; grants PID2021-125118OB-I00 to MG, PID2020-113938RB-I00 to EM and VC, PID2019-106579RB-I00 and PID2022-142617NB-I00 to GP, and PID2019-106404RB-I00 to LU), as well as by the Generalitat de Catalunya (grant 2021-SGR-00230 to EM and VC). LB was supported by INSERM. CC-I and IBM were supported by contracts from the Spanish Ministerio de Universidades (Formación de Profesorado Universitario Program, references FPU16/02593 and FPU15/01833, respectively). CC-I was also supported by an EMBO short-term fellowship (reference STF-8930). We are indebted to Dr. Benjamin L. Ebert for the kind donation of HEK-293T-CRBN-KO and parental HEK-293T-CRBN-WT cells. We also thank David Martín-Gutiérrez, Lucía Rivera-Endrinal, Dr. Daniel García-Ovejero, Dr. Eduardo Molina-Holgado, and the personnel of the core microscopy centre, the genomics unit, and the animal facilities of Universidad Complutense de Madrid for their expert technical assistance., Peer reviewed

This article belongs to the Special Issue Cellular and Molecular Alterations in the Down Syndrome Brain: A Starting Point for the Design of Therapeutic Approaches., Brain pathophysiology in Down syndrome (DS), the most common genetic cause of intellectual disability, has traditionally been considered a consequence of neuronal dysfunction. However, although it is well documented that astrocytes play a critical role in brain homeostasis, synaptic regulation, and neuronal support, and their malfunction has been associated with the onset and progression of different neurological disorders, only a few studies have addressed whether astrocyte dysfunction can contribute to the DS pathophysiology. Astrocytes are increased in number and size, and show increased levels of expression of astroglial markers like S100β and GFAP. In this study, we detected a region-specific increase in astrocyte population in CA1 and, to a lesser extent, in the dentate gyrus. Single-nucleus transcriptomic profiling identified markers associated with reactive astroglia, synaptic transmission, and neuroinflammation in trisomic astrocytes. Functional analysis revealed abnormal Ca2+ oscillations in trisomic astrocytes and impaired astrocyte-to-neuron communication in CA1, the most affected subregion, leading to astrocyte-mediated excitatory synaptic depression. Our findings demonstrate that astrocytes play an active and critical role in the pathophysiology of DS, not only as reactive responders to neuronal injury but as key contributors to the disease process itself. This astrocytic dysfunction presents a region-specific distribution within the hippocampus, suggesting localized vulnerability and complex glial involvement in DS-related neuropathology., The lab of MD is supported by the Secretaria d’Universitats i Recerca del Departament d’Economia I Coneixement de la Generalitat de Catalunya (Grups consolidats 2017 SGR 926). We also acknowledge the support of the Agencia Estatal de Investigación (PID2022-141900OB-I00 INTO-DS funded by MICIU/AEI/10.13039/501100011033/FEDER, UE). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 848077). The publication is part of the grant PRE2018-084504, funded by MCIN/AEI/10.13039/501100011033 and by the FSE+ (AFB). Additionally, we have been supported by Fundació La Marató TV3 (201620-31 and 225619), and by PID2022-142617NB-I00 and PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/501100011033 to G.P., Peer reviewed

Dysregulation of the endocannabinoid system (eCBS) and the loss of CB1 receptors (CB1R) in the basal ganglia are well-established hallmarks of Huntington's disease (HD). As a result, significant research efforts have focused on targeting the eCBS to alleviate motor disturbances associated with the disease. Beyond its role in motor control, the eCBS is a complex signaling network critically involved in regulating learning and memory. Despite this, the potential involvement of eCBS dysfunction in the cognitive decline characteristic of HD, often manifested well before motor dysfunction, has remained largely unexplored., This work was supported by the Spanish Ministerio de Ciencia e Innovación (PID2021-123732OB-I00 to SG, PID2021-125118OB-I00 to MG, PID2019-106579RB-I00, and PID2022-142617NB-I00 to GP, and PID2022-141700OB-I00 to AB funded by MCIN/AEI/ https://doi.org/10.13039/501100011033). Fundació la Marató de TV3 (202013-30-31–32 to SG, MG and GP), AGAUR Generalitat de Catalunya (2021-SGR-01358 to AB and 2021-SGR 01086 to SG) and grants to R. R.-P. from the Basque Government IT1454-22 to the “Neurochemistry and Neurodegeneration” consolidated research group; Instituto de Salud Carlos III through the project PI20/00153 (co-funded by European Regional Development Fund “A way to make Europe”) and by BIOEF through the project BIO22/ALZ/010 funded by Eitb Maratoia. A P-V is the recipient of a PRE2022-101764 fellowship (PID2021-123732OB-I00). I.B.d.T. is the recipient of an Investigo fellowship funded by the European Union-Next Generation EU., Peer reviewed

Brain pathophysiology in Down syndrome (DS), the most common genetic cause of intellectual disability, has traditionally been considered a consequence of neuronal dysfunction. However, although it is well documented that astrocytes play a critical role in brain homeostasis, synaptic regulation, and neuronal support, and their malfunction has been associated with the onset and progression of different neurological disorders, only a few studies have addressed whether astrocyte dysfunction can contribute to the DS pathophysiology. Astrocytes are increased in number and size, and show increased levels of expression of astroglial markers like S100ß and GFAP. In this study, we detected a region-specific increase in astrocyte population in CA1 and, to a lesser extent, in the dentate gyrus. Single-nucleus transcriptomic profiling identified markers associated with reactive astroglia, synaptic transmission, and neuroinflammation in trisomic astrocytes. Functional analysis revealed abnormal Ca2+ oscillations in trisomic astrocytes and impaired astrocyte-to-neuron communication in CA1, the most affected subregion, leading to astrocyte-mediated excitatory synaptic depression. Our findings demonstrate that astrocytes play an active and critical role in the pathophysiology of DS, not only as reactive responders to neuronal injury but as key contributors to the disease process itself. This astrocytic dysfunction presents a region-specific distribution within the hippocampus, suggesting localized vulnerability and complex glial involvement in DS-related neuropathology., The lab of MD is supported by the Secretaria d¿Universitats i Recerca del Departament d'Economia I Coneixement de la Generalitat de Catalunya (Grups consolidats 2017 SGR 926). We also acknowledge the support of the Agencia Estatal de Investigación (PID2022-141900OB-I00 INTO-DS funded by MICIU/AEI/10.13039/501100011033/FEDER, UE). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 848077). The publication is part of the grant PRE2018-084504, funded by MCIN/AEI/10.13039/501100011033 and by the FSE+ (AFB). Additionally, we have been supported by Fundació La Marató TV3 (201620-31 and 225619), and by PID2022-142617NB-I00 and PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/501100011033 to G.P.

Background: Dysregulation of the endocannabinoid system (eCBS) and the loss of CB1 receptors (CB1R) in the basal ganglia are well-established hallmarks of Huntington's disease (HD). As a result, significant research efforts have focused on targeting the eCBS to alleviate motor disturbances associated with the disease. Beyond its role in motor control, the eCBS is a complex signaling network critically involved in regulating learning and memory. Despite this, the potential involvement of eCBS dysfunction in the cognitive decline characteristic of HD, often manifested well before motor dysfunction, has remained largely unexplored. Methods: CB1R expression in the hippocampus was evaluated in both human HD samples and HD mouse models (R6/1 and Hdh models, including both sexes) using Western blotting, immunohistochemistry, and radioligand binding assays. To restore CB1R function, CB1R agonist WIN-55212-2 was systemically administered, or viral vectors encoding CB1R were locally infused into the hippocampus of HD mice. A multidisciplinary approach combining behavioral, biochemical, electrophysiological, and morphological analyses, was employed to investigate the molecular mechanisms underlying the effects of CB1R activation in the context of HD-related cognitive dysfunction. Results: In both human HD samples and HD mouse models, CB1R protein levels were reduced in the hippocampus, accompanied by structural synaptic alterations and impairment in spatial, recognition and working memory. Moreover, hippocampal depolarization-induced suppression of inhibition was significantly disrupted in R6/1 mice. Administration of WIN-55212-2 successfully restored these synaptic and cognitive deficits. Immunohistochemical analysis revealed that the CB1R decrease was specifically localized to GABAergic interneurons within the hippocampus. Notably, targeted restoration of CB1R expression in these interneurons via viral vector delivery was sufficient to rescue hippocampal-dependent memory deficits in HD mice. Conclusion: This study suggests that impaired CB1R function in hippocampal GABAergic interneurons contributes to memory dysfunction in HD., This work was supported by the Spanish Ministerio de Ciencia e Innovación (PID2021-123732OB-I00 to SG, PID2021-125118OB-I00 to MG, PID2019-106579RB-I00, and PID2022-142617NB-I00 to GP, and PID2022-141700OB-I00 to AB funded by MCIN/AEI/ https://doi.org/10.13039/501100011033). Fundació la Marató de TV3 (202013-30-31-32 to SG, MG and GP), AGAUR Generalitat de Catalunya (2021-SGR-01358 to AB and 2021-SGR 01086 to SG) and grants to R. R.-P. rom the Basque Government IT1454-22 to the "Neurochemistry and Neurodegeneration" consolidated research group; Instituto de Salud Carlos III through the project PI20/00153 (co-funded by European Regional Development Fund "A way to make Europe") and by BIOEF through the project BIO22/ALZ/010 funded by Eitb Maratoia. A P-V is the recipient of a PRE2022-101764 fellowship (PID2021-123732OB-I00). I.B.d.T. is the recipient of an Investigo fellowship funded by the European Union-Next Generation EU.

Insulin-like growth factor-I (IGF-I) exerts multiple actions, yet the role of IGF-I from different sources is poorly understood. Here, we explored the functional and behavioral consequences of the conditional deletion of Igf-I in the nervous system (Igf-I¿/¿), and demonstrated that long-term potentiation was impaired in hippocampal slices. Moreover, Igf-I¿/¿ mice showed spatial memory deficits in the Morris water maze, and the significant sex-dependent differences displayed by Igf-ICtrl/Ctrl mice disappeared in Igf-I¿/¿ mice in the open field and rota-rod tests. Brain Igf-I deletion disorganized the granule cell layer of the dentate gyrus (DG), and it modified the relative expressions of GAD and VGLUT1, which are preferentially localized to inhibitory and excitatory presynaptic terminals. Furthermore, Igf-I deletion altered protein modules involved in receptor trafficking, synaptic proteins, and proteins that functionally interact with estrogen and androgen metabolism. Our findings indicate that brain IGF-I is crucial for long-term potentiation, and that it is involved in the regulation of spatial memory and sexual dimorphic behaviors, possibly by maintaining the granule cell layer structure and the stability of synaptic-related protein modules., This work was funded by grants from the Spanish “Ministerio Ciencia, Innovación y Universidades, and the Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación” (MICIU and MICINN/AEI SAF2016-80419-R, PID2019-109059RB-100, and CIBERNED CB06/05/0065 to C Vicario; PID2019-110356RB-I00/AEI/10.13039/501100011033 to J Fernández-Irigoyen and E Santamaría; PID2019-104376RB-I00 to I Torres-Alemán; and PID2019-106579RB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe to G Perea, and BES-2017-080303 to C González-Arias.