Molecular Neurobiology

Cognitive processes require de novo gene transcription in neurons. Memory requires the rapid and robust transcription of a class of genes called immediate early genes (IEGs). IEG transcription is facilitated by the formation of a poised basal state, in which RNA polymerase II (RNAP2) initiates transcription, but remains paused downstream of the promoter. Upon neuronal depolarization, the paused RNAP2 is released to complete the synthesis of messenger RNA (mRNA) transcripts, a process stimulated by positive transcription elongation factor b (P-TEFb). In many cell types, P-TEFb is sequestered into a large inactive complex containing Hexamethylene bisacetamide inducible 1 (HEXIM1), but the impact of this interaction on neuronal gene transcription is not yet fully understood. In this study, we found that neuronal expression levels of HEXIM1 mRNA are highly correlated with impaired cognition in Alzheimers disease. It is also induced in the hippocampus during memory formation, and following depolarization in neurons. The role of HEXIM1 in neuronal gene transcription was then explored in murine neuronal cultures where we found that calcium frees P-TEFb from the HEXIM1 inhibitory complex. Modulation of P-TEFb by inhibiting the activity of the cyclin-dependent kinase 9 (CDK9) subunit of this complex significantly impacts IEG induction, particularly during repeated depolarization. Our findings indicate that HEXIM1 in complex with P-TEFb plays an important role in establishing and resetting the poised RNAP2 state, enabling efficient activation of genes necessary for synaptic plasticity.

The Alzheimers Amyloid Precursor Protein (APP) has determinant roles in neuronal development and function, both in its full-length conformation and as some of its proteolytic peptides, particularly secreted (s)APPa. Given that APP phosphorylation tightly regulates its trafficking, proteolysis, and protein-protein binding, it consequently affects several APP functions. The S655 residue, located in the basolateral sorting motif YTSI at APP C-terminus has been observed to be phosphorylated in mature full-length APP and its C-terminal fragments. Previously observed to modify APPs protein interactions, resulting in altered endolysosomal trafficking, andincreased half-life and sAPPa generation, phosphoS655 APP has potential to modulate APP-mediated neuronal differentiation. To study the phosphoS655 differential interactome relevant for neuronal differentiation, SH-SY5Y cells expressing Wt or S655 phosphomutants APP-GFP were differentiated at two time points. APP-GFP and their respective interacting partners were immunoprecipitated using GFP-trap, and interactors identified by mass spectrometry. Both dephospho and phosphoS655 interactomes were generally enriched in similar processes, primarily RNA processing and translation, as well as signal transduction, metabolism, and cytoskeleton remodeling. The smaller phosphoS655 interactome contributes for functional specialization via binding to e.g. FUBP3, ELAVL4, ATXN2, Tubulin, INA. Several of these specific binding partners are known to promote neurite outgrowth and likely underlie our experimental observation that phosphoS655 APP promotes neuritogenesis, particularly the formation of longer neuritic extensions. These results are not only important for the body of knowledge on this Alzheimers disease core protein, but may also aid in future therapies against this disease.

Glioma is a highly aggressive malignancy with a poor prognosis, particularly in grade IV glioblastoma. The monitoring of disease progression remains challenging due to high heterogeneity in the tumour and a lack of progressive markers to keep track of the tumour progression. This scarcity of good progressive biomarkers has led us to search for better options. SERPINA3 and SPP1 were investigated as potential dual biomarkers reflecting tumour microenvironment and enabling assessment of progression. In silico analysis was conducted, where correlation analysis was performed to evaluate the cell-type specificity of SERPINA3 in astrocytes and SPP1 in microglial cells, with comparisons across other neural populations in both low-grade glioma and glioblastoma. Pan-cancer expression analysis was conducted to determine whether these biomarkers remain significantly elevated in glioma relative to other malignancies, including hepatocellular carcinoma, given their hepatic origin. Alzheimers disease datasets were analysed to verify the relevance in neurodegenerative diseases. The in-silico analysis revealed that SERPINA3 and SPP1 show astrocytic and microglial specificity, respectively, and exhibit their highest expression levels in glioma across cancers. Co-expression analysis further identified enrichment of immunoregulatory pathways alongside upregulated oxidative stress-associated markers, highlighting the functional relevance of these biomarkers within the glioma microenvironment.

Background and Hypothesis: Extracellular vesicles (EVs) are phospholipid bilayer vesicles released from cells containing proteins, lipids and nucleic acids derived from the parent cell. Alterations in miRNA expression within blood-derived EVs have been proposed as potential biomarkers of disease. Specifically, identification of differentially expressed miRNAs in patients with schizophrenia (SZ) compared to healthy individuals could be used as a "miRNA signature" to aid in diagnosis and treatment. We therefore aimed to identify differentially expressed miRNAs in plasma-derived EVs between people living with SZ and healthy controls and to correlate miRNA levels with SZ-relevant clinical measures. Study Design: Plasma-derived EVs were isolated from a cohort of 33 individuals with SZ and 34 controls. Expression of 84 miRNAs was examined using a RT-qPCR panel. Study Results: Three miRNAs (hsa-miR-30e-5p, hsa-miR-103a-3p, hsa-miR-200b-3p) were differentially expressed between controls and patients. Gene ontology analysis of putative target genes shared between these miRNAs revealed enrichment of biological process terms related to neurogenesis. Analysis of miRNA expression compared to clinical measures showed that hsa-miR-103a-3p expression was associated with working memory and negatively correlated with white matter integrity in the combined patient-control group. Conclusions: We have identified a miRNA signature for SZ in plasma-derived EVs and shown for the first time that hsa-miR-30e-5p expression is significantly increased in plasma-derived EVs in SZ. The genetic links between differentially expressed miRNAs and neurogenesis, along with the correlations of hsa-miR-103a-3p with working memory and white matter integrity may underlie the functional importance of altered expression of the identified miRNAs in SZ.

Alzheimers disease (AD) is a deadly neurodegenerative disorder with no cure. It is associated with several dysregulated pathways, including axonal transport. The latter supplies synapses with several essential components, including proteins and mRNAs. A proportion of RNAs in neurons is transported from the soma to neuronal extensions along microtubules in highly organized structures, known as Neuronal RNA Granules (NRGs). NRGs have a heterogeneous composition of coding and non-coding RNAs, RNA-binding proteins (RBPs), and components of translational machinery. In this study, we investigate the potential involvement of NRGs in AD pathogenesis, with a particular focus on the N6-methyladenosine (mA), a key RNA modification, and prion-like domain (PrLD) proteins. Our in-silico analysis revealed that a significant portion of mRNAs in NRGs are likely to be highly methylated. Using transcriptomic data from AD brain, we identify dysregulation of key genes in the mA-methylation pathway (METTL3, FTO, YTHDF2/3, eIF3m) as well as PrLD-containing proteins associated with NRGs (STAU2, YBX1). We further observe aberrant expression of mA-methylated mRNAs within both NRGs and synapses. Gene Ontology analysis highlights disruptions in pathways related to NRGs and synaptic function. Together, our findings suggest that impaired NRGs homeostasis may represent a critical and previously underappreciated contributor to AD pathogenesis. By outlining the potential roles of mA and PrLD proteins in regulating NRGs, this work offers a new conceptual framework to better understand AD and identify NRGs as a potential therapeutic target. Finally, we propose a working model illustrating how dysregulation of NRGs homeostasis may drive neurodegeneration in AD.

Traumatic brain injury (TBI) induces a series of neuropathological changes in the brain including neurogenesis, an important cellular response involved in brain repair and regeneration. TBI-enhanced neurogenesis in the dentate gyrus (DG) of the hippocampus is of particular importance due its contribution to learning and memory functions. In the neurogenic process, proliferation and differentiation of neural stem cells (NSCs) follow a well-characterized sequence controlled by many factors including Notch1, which plays essential roles in regulating NSC fate determination under physiological conditions in both developing and adult brains. Following TBI, the dynamic changes of NSCs and the involvement of Notch1 on their development at different stages post-injury are not fully characterized. In the current study, we examined the impact of TBI and Notch1 on NSCs proliferation, survival and neuronal differentiation. Utilizing transgenic mice with tamoxifen-induced GFP expression and Notch1 knock-out in nestin+ NSCs, we examined DG neurogenic response at acute, subacute and chronic stages following a moderate lateral fluid percussion injury. We found that TBI enhanced a proliferative response in the DG at the acute stage following injury; however, this injury response was abolished when Notch1 was conditionally deleted from nestin+ NSCs. We also found that injury and Notch1 deletion drove NSCs committing fate choice towards neuronal differentiation. The results of this study provides further knowledge regarding TBI-induced neurogenic response and Notch1 as the key regulating mechanism.

Brutons tyrosine kinase (BTK) has been reported to be important in the inflammatory response in many diseases. However, its role and explicit mechanisms in intracerebral hemorrhage (ICH) remain unclear. Here, we used a mouse ICH model and transcriptomic datasets to explore the effect of BTK on neuroinflammation after ICH. Inhibiting BTK with ibrutinib alleviated ICH-induced neurological deficits and neuroinflammation in mice. After analyzing RNA-sequencing data of ICH and control mice by weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) analysis, we found that Btk was a hub gene in the green dynamic module. Also, 12 hub genes that closely interacted with BTK were identified in the key gene module, all having a critical role in the inflammatory process. Then, single cell RNA-sequencing data analysis showed that microglia were the immune cells that expressed the most BTK in the mouse brain. After dividing microglia in ICH mice into BTK_high and BTK_low groups, GO/KEGG enrichment analyses of differentially expressed genes (DEGs) between these two microglia groups revealed that most of the top 30 enriched pathways were immune-related. Then, gene set enrichment analysis (GSEA) of the BTK_high and BTK_low microglia showed that the expression levels of four anti-inflammatory and phagocytosis-related pathways were significantly lower in the BTK_high microglia than in the BTK_low microglia. Furthermore, gene set variation analysis (GSVA) demonstrated that multiple immune pathways were expressed differentially between the two microglia groups. Also, six microglia polarization scores were calculated, and the results showed that the BTK_high microglia tend to polarize towards M1 and M2b states, while the BTK_high microglia towards M2 (M2a, M2c) states. Finally, intercellular communication analysis was conducted, and BTK was revealed to promote communication between microglia and other immune cells both at the general level and in specific inflammatory pathways. In conclusion, our study showed that BTK is critical in promoting post-ICH neuroinflammation, at least partly by interacting with Btk-related hub genes and modulating microglias immune pathways, polarization, and intercellular communication.

Defective social behavior and cognitive functions are hallmarks of Autism spectrum disorders (ASD). The molecular mechanisms keeping social behavior in a physiological range are largely unknown. We recently found that conditional knockout (cKO) of tmiRNA cluster miR-379-410 in mouse hippocampal neurons leads to hypersocial behavior. Therefore, inhibiting miR-379-410 members might represent a strategy to promote sociability in ASD. As an ASD model, we chose knockdown (KD) of the ASD risk gene Tsc1, a key negative regulator of mTORC1. Acute Tsc1 knockdown (KD) in hippocampal neurons was sufficient to induce hyposociability and memory deficits in adult wild-type mice. In contrast, Tsc1 KD had no effect on sociability in miR-379-410 cKO mice, indicating a requirement of miR-379-410. Furthermore, Tsc1 KD led to upregulation of tmiR-495-3p, and inhibition of this miRNA by antisense oligonucleotides was sufficient to prevent hyposociability and memory impairments. Our findings suggest that miR-495-3p is a key downstream effector of the Tsc1/mTORC1 pathway in sociability, and that targeting miR-495-3p represents a therapeutic avenue for restoring social and cognitive impairments in ASD without affecting mTORC1 homeostasis.

Traumatic spinal cord injuries (SCIs) often result in permanent disabilities in humans. One major reason for the lack of recovery is the inability of adult mammalian descending neurons to regenerate their axons after injury. In contrast, several fish species, such as the sea lamprey, exhibit spontaneous axon regeneration and successful functional recovery following a complete SCI. Recent studies have shown that a SCI in rodents and humans induces gut microbiome dysbiosis, which can impair recovery. Therefore, our goal was to examine how the microbiome changes after SCI in a regenerating animal model (the larval sea lamprey) and whether these changes influence the spontaneous regeneration of descending neuropeptidergic (cholecystokinergic) axons. Our data show that a complete SCI triggers an initial shift (5 weeks post-injury) in gut microbial communities in larval lampreys, characterized by an expansion of Legionellaceae family members. However, a treatment with broad-spectrum antibiotic gentamicin during the first 5 weeks post-injury, which completely disrupted the gut microbiome (eliminating Legionellaceae and promoting Bradyrhizobiaceae expansion), did not affect the spontaneous regeneration of descending cholecystokinergic axons at 10 weeks post-injury. This finding indicates that changes in the intestinal microbial communities following a complete SCI probably do not influence the spontaneous regeneration of descending axons in lampreys.

Anorexia nervosa is characterized by maladaptive eating behavior and cognitive dysfunction, which could be explained by a neuroinflammation. A gut dysbiosis could link gastrointestinal alterations to central dysfunctions, particularly via the toll-like receptor 4 (TLR4), which has been shown to play a key role in the activity-based anorexia (ABA) model. We aimed to evaluate the neuroinflammation and its behavioral consequences in the ABA model, and to decipher the role of the microbiota-gut-brain axis, and more specifically of TLR4, in these alterations of the central nervous system. We show that chronic restriction is more strongly associated with gut inflammation, cecal microbiota alteration and neuroinflammatory processes in the hippocampus than acute restriction. The hippocampal glial response is characterized by a loss of astrocyte density, and an increased number of deramified microglia. We further demonstrate that these alterations are independent of TLR4 expressed by intestinal epithelial cells. In conclusion, our results highlight that the chronicity of ABA-associated undernutrition alters the response of glial cells in the hippocampus that is linked with changes in microbiota composition, highlighting the importance of faster diagnosis and treatment of AN.

BackgroundExtracellular vesicles (EV), secreted membrane particles involved in cell-to-cell communication, carry important information on immunity and its dysregulation. Recent studies have demonstrated the crucial role of peripheral and central inflammation in causing Parkinsons disease (PD), as well as the involvement of EV in mediating neuron-glial interactions during neurodegeneration. However, the underlying mechanism of plasmatic EV in PD pathogenesis remains unknown. MethodsEV were isolated from pool of plasma of PD patients and age- and sex-matched healthy controls (HC) using size-exclusion chromatography and characterized by nanoparticle tracking analysis, western blot, and transmission electron microscopy. SH-SY5Y neurons and HMC3 microglia cells were treated with EV, and their impact was evaluated using flow cytometry and immunofluorescence. Conditioned medium (CM) from EV-treated HMC3 cells was applied to SH-SY5Y neurons to determine indirect neurotoxic effects. Cytokine profiling and senescence-like features of EV-treated HMC3 cells were assessed. Unbiased proteomic analysis of PD-EV and HC-EV were further performed. ResultsPD-EV induced axonal degeneration and cell death in SH-SY5Y neurons and increased levels of TNF-, IL-1{beta}, IFN-{gamma}, IL-8, and CCL11, accompanied by the expression of p16INK4a in HMC3 cells, suggesting a proinflammatory, senescence-associated secretory phenotype (SASP). Enrichment pathway analysis revealed that these changes were mainly related to inflammatory and immune responses. Moreover, CM from PD-EV-HMC3 cells increased apoptotic cell death in SH-SY5Y neurons more than direct PD-EV. Notably, proteomic analysis of PD-EV showed higher expression of proteins involved in complement cascades, immune response, phagocytosis, and post translational protein translation, further supporting the potential of EV to induce inflammatory changes in PD. ConclusionsThis study demonstrates that plasmatic PD-EV contributes to neuronal degeneration by reducing neuronal integrity and indirectly by activating microglia through the secretion of pro-inflammatory, senescence-associated mediators. Circulating EV exerts a role in bridging peripheral inflammation with microglia, modulating neuroinflammatory events.

Amyloid Precursor Protein (APP) has been reported to partially localize to mitochondria, and mitochondrial dysfunction is a key feature of Alzheimers disease; however, the mechanisms linking APP to mitochondrial functions remain incompletely defined. In this study, we identified an interaction between APP and phosphoglycerate mutase family member 5 (PGAM5), a mitochondrial protein phosphatase. We confirmed their endogenous interaction in mouse brain tissue and determined that APP and PGAM5 are both present at mitochondria-ER contact sites (MERCS) and. Using in vitro binding assays, we demonstrate a direct interaction between the linker region of APP and a region of PGAM5 that includes the Kelch-like ECH-associated protein 1 (Keap-1) binding domain. PGAM5 is known to anchor a portion of Nuclear factor erythroid 2 p45-related factor 2 (Nrf2) through Keap1 at the outer mitochondrial membrane and regulates mitochondrial respiration and stress responses. We found that the Nrf2-regulated genes Hmox1 (Heme oxygenase-1) and Nqo1 (NADH:quinone oxidoreductase 1), which are involved in mitochondrial respiration, are downregulated in APP KO astrocytes. Accordingly, mitochondria isolated from the brains of APP knockout (KO) mice have impaired substrate-specific respiration and electron transport chain (ETC) function. Together, these findings suggest that APP supports mitochondrial respiration by binding to PGAM5 and modulating Keap1-Nrf2 signaling.

Parkinsons disease (PD) is characterized by progressive dopaminergic neurodegeneration driven by complex interactions among oxidative stress, impaired survival signaling, and protein homeostasis disruption. Emerging evidence suggests that endogenous retroelements, including human endogenous retrovirus K (HERV-K), may contribute to neurodegenerative processes; however, their role in PD remains poorly defined. Here, we investigated whether dopaminergic neurotoxic stress induces HERV-K activation and whether modulation of pro-survival signaling pathways influences this response in PD-relevant cellular models. Using undifferentiated SHSY5Y cells and neuron-like retinoic acid-differentiated SHSY5Y cells, we show that exposure to the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) induces a rapid and robust transcriptional de-repression of HERV-K Env gene. HERV-K activation occurs early after toxin exposure, scales with the intensity of the insult, and is associated with alterations in oxidative stress defenses, survival signaling pathways, and protein homeostasis. Notably, 6-OHDA treatment promotes the accumulation and cytoplasmic mislocalization of phosphorylated TAR DNA-binding protein 43 (pTDP-43), a pathological feature linked to neurodegenerative proteinopathies. Pharmacological modulation of the Wnt/{beta}-catenin pathway by the natriuretic peptide atrial natriuretic peptide (ANP) significantly attenuates neurotoxin-induced HERV-K activation, restores oxidative stress-related and survival signaling markers, and limits pTDP-43 accumulation and mislocalization. These findings indicate that reinforcement of Wnt/{beta}-catenin dependent protective pathways constrains stress-driven HERV-K de-repression and associated molecular alterations. Overall, this study identifies HERV-K activation as an early stress-responsive feature in PD-like cellular models and supports the existence of a functional interplay between retroelement regulation, survival signaling, and protein homeostasis. Modulation of Wnt/{beta}-catenin signaling may represent a strategy to limit retroelement-associated pathological responses in PD.

Mucopolysaccharidosis III (MPS III or Sanfilippo disease) is a spectrum of 4 genetic disorders (MPS IIIA-D), caused by defects in the genes SGSH, NAGLU, HGSNAT and GNS encoding enzymes involved in degradation of heparan sulfate (HS). HS accumulates in brain tissues and causes neuronal dysfunction and neurodegeneration leading to neuropsychiatric problems, developmental delays, childhood dementia, blindness and death during the second decade of life. Previously, we demonstrated that pathophysiological mechanisms, underlying MPS IIIC in mouse models, involves functional pathological changes, affecting synaptogenesis and synaptic transmission and leading to learning and memory deficits. These results suggested that a treatment for MPS III could be developed by using compounds inducing synaptogenesis. In the current study, we tested the efficacy of a synthetic peptide ACTH(4-7)PGP, an analog of adrenocorticotropic hormone fragment, previously used as a neuroprotective and anti-inflammatory medication for treatment of acute neurological conditions, including stroke. We show that intranasal administration of ACTH(4-7)PGP restores defective synaptic transmission in CA1 pyramidal neurons of MPS IIIA and MPS IIIC mouse models and rescues the decrease in synaptic proteins in cultured MPS IIIC mouse hippocampal neurons and iPSC-derived neurons of human MPS IIIA, MPS IIIB and MPS IIIC patients. Furthermore, daily intranasal administration of ACTH(4-7)PGP to MPS IIIC and MPS IIIA mice reduces hyperactivity and rescues defects in working and spatial memory, delays progression of CNS pathology including neuroinflammation and axonal demyelination, and increases the lifespan. Together with the absence of any adverse reactions to ACTH(4-7)PGP in the MPS III and WT mice, our results justify testing the drugs efficacy in clinical settings.

Multiple lines of evidence indicate that alterations in glial cells and the blood-brain barrier (BBB) contribute to anxiety- and depression-like behaviors in murine models of depression and chronic stress. Although behavioral and psychological symptoms of dementia (BPSD) represent a major feature of Alzheimers disease (AD), this relationship has received limited attention in this pathology. Using the 3xTg-AD mouse model of AD at an early pathological stage, this study explored the relationship between BPSD and variations of BBB and glial cell markers in specific brain regions (hippocampus, basolateral amygdala [BLA], and prefrontal cortex). Memory and emotional behaviors were assessed using a battery of behavioral tests. Endothelial tight junction (TJ) proteins, along with astrocyte and microglial markers, were quantified by western blotting or/and immunohistochemistry in the hippocampus, BLA, and prefrontal cortex. While spatial and recognition memory remained intact, 3xTg-AD mice exhibited an anxio-depressive-like phenotype, impaired coping strategies, and reduced cognitive flexibility. Compared with control mice, 3xTg-AD mice displayed an increased expression of TJ proteins in the hippocampus and BLA, increased microglial cell density in the BLA and the dentate gyrus, and fewer and shorter microglial cell branches in the BLA. A principal component analysis revealed a positive correlation between anxio-depressive-like behaviors and altered microglial morphology in the BLA, whereas impaired cognitive flexibility positively correlates with ZO-1 expression and microglial cell density in the hippocampus. These findings demonstrate an early association between the BBB, glial cells and AD-related BPSD symptoms in 3-month-old 3xTg-AD mice.

Mitochondrial pyruvate carrier (MPC) inhibition was found protective in models of neurodegenerative diseases, such as Alzheimers and Parkinsons. However, little is known about MPC as a potential therapeutic target in Huntingtons disease (HD), a neurodegenerative disorder with dysregulation of the pro-survival pathway integrated stress response (ISR). Here, we investigate if MPC inhibition modulates the ISR and mitigates mutant huntingtin (mut-Htt) proteotoxicity in a cellular HD model. We treated cells expressing N-terminal fragments of wild-type- (wt-) or mut-Htt with two MPC inhibitors (mitoglitazone and UK5099) or solvent control. Metabolism was assessed analysing resazurin reduction, oxygen consumption, extracellular acidification, and ATP levels. ISR activation and huntingtin proteostasis were assessed using western-blot and filter-trap assays. Mut-Htt-expressing cells showed decreased resazurin reduction and ATP levels, and increased eIF2 phosphorylation, indicating metabolic stress and ISR activation. MPC inhibitors (100 {micro}M) increased resazurin reduction and decreased respiration. The latter was rescued by the membrane-permeant methyl pyruvate, which bypasses MPC inhibition. In wt-Htt-expressing cells, MPC inhibitors increased levels of ATP and ISR markers, suggesting metabolic adaptation and ISR activation. In mut-Htt-expressing cells, MPC inhibitors preserved ATP levels and attenuated mut-Htt-induced eIF2 phosphorylation but without changing soluble or aggregated mut-Htt levels. This work showed that MPC inhibition differentially modulates the ISR: it activates ISR in control cells and attenuates overactive ISR in mut-Htt-expressing cells. However, MPC inhibition did not impact the proteostasis of N-terminal fragment mut-Htt. Further studies are essential to explore MPC inhibition in less severe full-length mut-Htt-expressing models to better understand its therapeutic potential in HD.

GD3 synthase (GD3S) is a key enzyme in the production of gangliosides, sialylated membrane glycosphingolipids with essential physiological roles in mammalian brains. To elucidate the molecular bases of neuropathological findings associated with GD3S deficiency, we performed a multilayered analysis focused on the functionality of ion transporters Na +/K+-ATPase (NKA) and plasma membrane Ca2+-ATPase (PMCA) in the cortex and cerebellum of GD3S-deficient mice (GD3S-/-). We examined global transcriptomes, NKA and PMCA gene and protein expression, the influence of membrane lipid composition on lipid raft integrity, and the activity of both ATPases, pairing them with an exploratory principal component analysis. Transcriptomic data reveal that sets of genes involved in ion transport and membrane dynamics are differentially expressed in the absence of GD3S, whereas qRT-PCR data confirm changes in gene expression of specific NKA and PMCA subunits or isoforms. Altered protein expression and significantly lower activity of both NKA and PMCA were found in the cerebral cortex of GD3S-/- mice. Detailed lipidomic analysis revealed segregation of cholesterol into lipid rafts, which may lead to disordered membrane lipid architecture in GD3S deficiency. Additionally, altered ganglioside composition was found to affect the activities of NKA and PMCA in the brain tissue of GD3S-/- mice. Our results confirm that an imbalance in membrane ganglioside composition leads to significant alterations in ion transporter function. Experimental restoration of ATPase activity in cortical homogenates by administering exogenous b-series gangliosides may aid in developing therapeutic strategies targeting deficits in GD3S and other enzymes of ganglioside biosynthesis.

Traumatic brain injuries (TBIs) result from impact to or rapid displacement of the brain and can lead to various neurological deficits involving working memory, decision-making, and anxiety. While large-scale effects of brain damage are well-described for more severe TBIs, less is known about the extent and duration of cognitive deficits at the mild level. Interval timing can provide a helpful window into cognition in mice and humans. Interval-timing behavior is impaired in a wide range of neuropsychiatric disease states, such as Parkinsons disease. Furthermore, novel object recognition (NOR) and the Barnes maze (BM) tests are valuable assays for evaluating spatial learning, working memory, and anxiety-like behavior in mice. Here, we employed a weight-drop model of mild TBI (mTBI) to investigate changes in internal cognitive states resulting from mTBI treatment. mTBI mice were not significantly impaired in either interval timing or NOR, but they demonstrated impaired spatial memory in the Barnes Maze. Interestingly, within-sex comparisons revealed impairments in male mTBI mice in the interval-timing task and the NOR, suggesting that male and female mice may be differently affected by mTBIs.

Contactin-associated protein-like 2 (CNTNAP2) is a transmembrane protein that mediates neuron-glia interactions and regulates dendritic spine growth and neuronal migration. Mutations in the CNTNAP2 gene are linked to autism and epilepsy. Younger Cntnap2 KO mice mimic autism phenotypes, while older mice are a model for epilepsy. Thus, comparing behavioral phenotypes across different ages is needed to better understand the age dependent development of disordered brain networks in Cntnap2 mutants. Male and female Cntnap2 KO and WT controls were tested across different age groups (4, 5, 7, 9, and [~]11 months) using digging, stimulus (reactivity), and nesting assays. Older Cntnap2 KO mice (7, 9, and [~]11 months) showed a significant increase in home cage reactivity (stimulus) assay compared to younger mice at 4 and 5 months of age. Similar trends were observed in male and female Cntnap2 KO mice. No significant differences were observed in WT controls. A significant difference in digging assay was observed in KO female mice between younger (4 month) and older mice post nest removal. An age-dependent significant reduction in nesting behavior was observed in female KO mice; however, no difference was observed in the WT controls. Immunohistochemical analysis showed age dependent change interneuron and microglial network in Cntnap2 KO mice. Our findings suggest disruption in home cage behavior and reactivity in older pre-epileptic Cntnap2 KO mice indicating an age-dependent network alteration and behavior deficits. Significance StatementThis study investigates the age-dependent behavioral changes in Cntnap2 KO mice due to underlying changes in the neuronal network. It has been shown that younger Cntnap2 KO mice display autistic behaviors and that older Cntnap2 KO mice have epilepsy, but it is unknown how behavior is affected during the intervening period of epileptogenesis. We find that female Cntnap2 KO mice at 11 months of age have increased reactivity and decreased motor activity compared to younger age groups, whereas WT mice show no relationship between age and behavior. Overall, the loss of Cntnap2 alters behavior in an age-dependent and sex-specific manner, indicating progressive dysregulation of the neuronal network.

Tau protein, the primary component in neurofibrillary tangles characteristic of Alzheimers Disease and related dementia disorders, normally regulates microtubule growth and stability. While tau dysfunction contributes to the progression of tauopathies, the role of microtubules in disease has remained unclear. Through forward genetic screening in Caenorhabditis elegans tauopathy models, we found multiple tubulin gene mutations that rescue tau-mediated neurodegeneration. Whole animal behavioral and in vitro biochemical assays were employed to characterize mutation-driven effects on neuron function, neurodegeneration, and effects on tubulin and tau proteins as well as microtubule function. Mutant tubulin genes were found to confer different levels of suppression correlating with the level of mutant gene expression. Mutant tubulins did not drastically alter total tau protein levels, tau phosphorylation or aggregation, however tau-induced neurodegeneration was rescued. The suppression of tau toxicity by tubulin gene mutations cannot be explained by changes in tau or tubulin expression, tau phosphorylation, or tau aggregation state. Rather the tubulin mutations appear to act by influencing global microtubule properties. In vitro experiments using C. elegans tubulin in semi-isolated and isolated contexts have indicated changes to microtubule properties without observable changes to tau-tubulin affinity. This work suggests that manipulation of microtubules can rescue tauopathy even when pathological tau species persist, supporting the importance of understanding microtubule contributions to disease progression and investigation into microtubule targeted gene therapy or small molecule approaches for tauopathy intervention.