Nontransgenic Mice Research Articles

A metabotropic glutamate receptor 3 (mGlu3R) isoform playing neurodegenerative roles in astrocytes is prematurely up-regulated in an Alzheimer's model.

Subtype 3 metabotropic glutamate receptor (mGlu3R) displays a broad range of neuroprotective effects. We previously demonstrated that mGlu3R activation in astrocytes protects hippocampal neurons from Aβ neurotoxicity through stimulation of both neurotrophin release and Aβ uptake. Alternative-spliced variants of mGlu3R were found in human brains. The most prevalent variant, mGlu3Δ4, lacks exon 4 encoding the transmembrane domain and can inhibit ligand binding to mGlu3R. To date, neither its role in neurodegenerative disorders nor its endogenous expression in CNS cells has been addressed. The present paper describes for the first time an association between altered hippocampal expression of mGlu3Δ4 and Alzheimer's disease (AD) in the preclinical murine model PDAPP-J20, as well as a deleterious effect of mGlu3Δ4 in astrocytes. As assessed by western blot, hippocampal mGlu3R levels progressively decreased with age in PDAPP-J20 mice. On the contrary, mGlu3Δ4 levels were drastically increased with aging in nontransgenic mice, but prematurely over-expressed in 5-month-old PDAPP-J20-derived hippocampi, prior to massive senile plaque deposition. Also, we found that mGlu3Δ4 co-precipitated with mGlu3R mainly in 5-month-old PDAPP-J20 mice. We further showed by western blot that primary cultured astrocytes and neurons expressed mGlu3Δ4, whose levels were reduced by Aβ, thereby discouraging a causal effect of Aβ on mGlu3Δ4 induction. However, heterologous expression of mGlu3Δ4 in astrocytes induced cell death, inhibited mGlu3R expression, and prevented mGlu3R-dependent Aβ glial uptake. Indeed, mGlu3Δ4 promoted neurodegeneration in neuron-glia co-cultures. These results provide evidence of an inhibitory role of mGlu3Δ4 in mGlu3R-mediated glial neuroprotective pathways, which may lie behind AD onset.

Simultaneous Alteration of the Circadian Variation of Memory, Hippocampal Synaptic Plasticity, and Metabolism in a Triple Transgenic Mouse Model of Alzheimer's Disease.

Alzheimer’s disease (AD) is characterized by progressive memory deficits accompanied by synaptic and metabolic deficits, namely of mitochondrial function. AD patients also display a disrupted circadian pattern. Thus, we now compared memory performance, synaptic plasticity, and mitochondria function in 24-week-old non-transgenic (non-Tg) and triple transgenic male mice modeling AD (3xTg-AD) at Zeitgeber 04 (ZT-4, inactive phase) and ZT-16 (active phase). Using the Morris water maze test to minimize the influence of circadian-associated locomotor activity, we observed a circadian variation in hippocampus-dependent learning performance in non-Tg mice, which was impaired in 3xTg-AD mice. 3xTg-AD mice also displayed a lack of circadian variation of their performance in the reversal spatial learning task. Additionally, the amplitude of hippocampal long-term potentiation also exhibited a circadian profile in non-Tg mice, which was not observed in 3xTg-AD mice. Moreover, cerebral cortical synaptosomes of non-Tg mice also displayed a circadian variation of FCCP-stimulated oxygen consumption as well as in mitochondrial calcium retention that were blunted in 3xTg-AD mice. In sum, this multidimensional study shows that the ability to maintain a circadian oscillation in brain behavior, synaptic plasticity, and synaptic mitochondria function are simultaneously impaired in 3xTg-AD mice, highlighting the effects of circadian misalignment in AD.

Modulation of myosin by cardiac myosin binding protein-C peptides improves cardiac contractility in ex-vivo experimental heart failure models

Cardiac myosin binding protein-C (cMyBP-C) is an important regulator of sarcomeric function. Reduced phosphorylation of cMyBP-C has been linked to compromised contractility in heart failure patients. Here, we used previously published cMyBP-C peptides 302A and 302S, surrogates of the regulatory phosphorylation site serine 302, as a tool to determine the effects of modulating the dephosphorylation state of cMyBP-C on cardiac contraction and relaxation in experimental heart failure (HF) models in vitro. Both peptides increased the contractility of papillary muscle fibers isolated from a mouse model expressing cMyBP-C phospho-ablation (cMyBP-CAAA) constitutively. Peptide 302A, in particular, could also improve the force redevelopment rate (ktr) in papillary muscle fibers from cMyBP-CAAA (nonphosphorylated alanines) mice. Consistent with the above findings, both peptides increased ATPase rates in myofibrils isolated from rats with myocardial infarction (MI), but not from sham rats. Furthermore, in the cMyBP-CAAA mouse model, both peptides improved ATPase hydrolysis rates. These changes were not observed in non-transgenic (NTG) mice or sham rats, indicating the specific effects of these peptides in regulating the dephosphorylation state of cMyBP-C under the pathological conditions of HF. Taken together, these studies demonstrate that modulation of cMyBP-C dephosphorylation state can be a therapeutic approach to improve myosin function, sarcomere contractility and relaxation after an adverse cardiac event. Therefore, targeting cMyBP-C could potentially improve overall cardiac performance as a complement to standard-care drugs in HF patients.

Differential location of NKT and MAIT cells within lymphoid tissue

Natural Killer T (NKT) cells and Mucosal-Associated Invariant T (MAIT) cells are innate-like T cells that express semi-invariant αβ T cell receptors (TCRs) through which they recognise CD1d and MR1 molecules, respectively, in complex with specific ligands. These cells play important roles in health and disease in many organs, but their precise intra-organ location is not well established. Here, using CD1d and MR1 tetramer staining techniques, we describe the precise location of NKT and MAIT cells in lymphoid and peripheral organs. Within the thymus, NKT cells were concentrated in the medullary side of the corticomedullary junction. In spleen and lymph nodes, NKT cells were mainly localised within T cell zones, although following in vivo activation with the potent NKT-cell ligand α-GalCer, they expanded throughout the spleen. MAIT cells were clearly detectable in Vα19 TCR transgenic mice and were rare but detectable in lymphoid tissue of non-transgenic mice. In contrast to NKT cells, MAIT cells were more closely associated with the B cell zone and red pulp of the spleen. Accordingly, we have provided an extensive analysis of the in situ localisation of NKT and MAIT cells and suggest differences between the intra-organ location of these two cell types.

Effects of Sarcomere Activators and Inhibitors Targeting Myosin Cross-Bridges on Ca2+-Activation of Mature and Immature Mouse Cardiac Myofilaments.

We tested the hypothesis that isoform shifts in sarcomeres of the immature heart modify the effect of cardiac myosin-directed sarcomere inhibitors and activators. Omecamtiv mecarbil (OM) activates tension and is in clinical trials for the treatment of adult acute and chronic heart failure. Mavacamten (Mava) inhibits tension and is in clinical trials to relieve hypercontractility and outflow obstruction in advanced genetic hypertrophic cardiomyopathy (HCM), which is often linked to mutations in sarcomeric proteins. To address the effect of these agents in developing sarcomeres, we isolated heart fiber bundles, extracted membranes with Triton X-100, and measured tension developed over a range of Ca2+ concentrations with and without OM or Mava treatment. We made measurements in fiber bundles from hearts of adult nontransgenic (NTG) controls expressing cardiac troponin I (cTnI), and from hearts of transgenic (TG-ssTnI) mice expressing the fetal/neonatal form, slow skeletal troponin I (ssTnI). We also compared fibers from 7- and 14-day-old NTG mice expressing ssTnI and cTnI. These studies were repeated with 7- and 14-day-old transgenic mice (TG-cTnT-R92Q) expressing a mutant form of cardiac troponin T (cTnT) linked to HCM. OM increased Ca2+-sensitivity and decreased cooperative activation in both ssTnI- and cTnI-regulated myofilaments with a similar effect: reducing submaximal tension in immature and mature myofilaments. Although Mava decreased tension similarly in cTnI- and ssTnI-regulated myofilaments controlled either by cTnT or cTnT-R92Q, its effect involved a depressed Ca2+-sensitivity in the mature cTnT-R92 myofilaments. Our data demonstrate an influence of myosin and thin-filament associated proteins on the actions of myosin-directed agents such as OM and Mava. SIGNIFICANCE STATEMENT: The effects of myosin-targeted activators and inhibitors on Ca2+-activated tension in developing cardiac sarcomeres presented here provide novel, ex vivo evidence as to their actions in early-stage cardiac disorders. These studies advance understanding of the molecular mechanisms of these agents, which are important in preclinical studies employing sarcomere Ca2+-response as a screening approach. The data also inform the use of commonly immature cardiac myocytes generated from human-inducible pluripotent stem cells in screening for sarcomere activators and inhibitors.

Alzheimer's disease amyloid-β pathology in the lens of the eye

Neuropathological hallmarks of Alzheimer's disease (AD) include pathogenic accumulation of amyloid-β (Aβ) peptides and age-dependent formation of amyloid plaques in the brain. AD-associated Aβ neuropathology begins decades before onset of cognitive symptoms and slowly progresses over the course of the disease. We previously reported discovery of Aβ deposition, β-amyloidopathy, and co-localizing supranuclear cataracts (SNC) in lenses from people with AD, but not other neurodegenerative disorders or normal aging. We confirmed AD-associated Aβ molecular pathology in the lens by immunohistopathology, amyloid histochemistry, immunoblot analysis, epitope mapping, immunogold electron microscopy, quantitative immunoassays, and tryptic digest mass spectrometry peptide sequencing. Ultrastructural analysis revealed that AD-associated Aβ deposits in AD lenses localize as electron-dense microaggregates in the cytoplasm of supranuclear (deep cortex) fiber cells. These Aβ microaggregates also contain αB-crystallin and scatter light, thus linking Aβ pathology and SNC phenotype expression in the lenses of people with AD. Subsequent research identified Aβ lens pathology as the molecular origin of the distinctive cataracts associated with Down syndrome (DS, trisomy 21), a chromosomal disorder invariantly associated with early-onset Aβ accumulation and Aβ amyloidopathy in the brain. Investigation of 1249 participants in the Framingham Eye Study found that AD-associated quantitative traits in brain and lens are co-heritable. Moreover, AD-associated lens traits preceded MRI brain traits and cognitive deficits by a decade or more and predicted future AD. A genome-wide association study of bivariate outcomes in the same subjects identified a new AD risk factor locus in the CTNND2 gene encoding δ-catenin, a protein that modulates Aβ production in brain and lens. Here we report identification of AD-related human Aβ (hAβ) lens pathology and age-dependent SNC phenotype expression in the Tg2576 transgenic mouse model of AD. Tg2576 mice express Swedish mutant human amyloid precursor protein (APP-Swe), accumulate hAβ peptides and amyloid pathology in the brain, and exhibit cognitive deficits that slowly progress with increasing age. We found that Tg2576 trangenic (Tg+) mice, but not non-transgenic (Tg–) control mice, also express human APP, accumulate hAβ peptides, and develop hAβ molecular and ultrastructural pathologies in the lens. Tg2576 Tg+ mice exhibit age-dependent Aβ supranuclear lens opacification that recapitulates lens pathology and SNC phenotype expression in human AD. In addition, we detected hAβ in conditioned medium from lens explant cultures prepared from Tg+ mice, but not Tg– control mice, a finding consistent with constitutive hAβ generation in the lens. In vitro studies showed that hAβ promoted mouse lens protein aggregation detected by quasi-elastic light scattering (QLS) spectroscopy. These results support mechanistic (genotype-phenotype) linkage between Aβ pathology and AD-related phenotypes in lens and brain. Collectively, our findings identify Aβ pathology as the shared molecular etiology of two age-dependent AD-related cataracts associated with two human diseases (AD, DS) and homologous murine cataracts in the Tg2576 transgenic mouse model of AD. These results represent the first evidence of AD-related Aβ pathology outside the brain and point to lens Aβ as an optically-accessible AD biomarker for early detection and longitudinal monitoring of this devastating neurodegenerative disease.

Prostacyclin Promotes Degenerative Pathology in a Model of Alzheimer's Disease.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is the most common form of dementia in aged populations. A substantial amount of data demonstrates that chronic neuroinflammation can accelerate neurodegenerative pathologies. In AD, chronic neuroinflammation results in the upregulation of cyclooxygenase and increased production of prostaglandin H2, a precursor for many vasoactive prostanoids. While it is well-established that many prostaglandins can modulate the progression of neurodegenerative disorders, the role of prostacyclin (PGI2) in the brain is poorly understood. We have conducted studies to assess the effect of elevated prostacyclin biosynthesis in a mouse model of AD. Upregulated prostacyclin expression significantly worsened multiple measures associated with amyloid-β (Aβ) disease pathologies. Mice overexpressing both Aβ and PGI2 exhibited impaired learning and memory and increased anxiety-like behavior compared with non-transgenic and PGI2 control mice. PGI2 overexpression accelerated the development of Aβ accumulation in the brain and selectively increased the production of soluble Aβ42. PGI2 damaged the microvasculature through alterations in vascular length and branching; Aβ expression exacerbated these effects. Our findings demonstrate that chronic prostacyclin expression plays a novel and unexpected role that hastens the development of the AD phenotype.

The HCM I79N pathogenic variant in cardiac TNT induces thick filament malfunction and myofilament lattice rearrangement

Missense variant Ile79Asn in human cardiac troponin T (HcTnT-I79N) has been associated with familial hypertrophic cardiomyopathy (HCM), arrhythmia and sudden cardiac death. Little is known about effects of this pathogenic variant on cardiac myofilament function and structure. To fill this gap, cardiac tissues were harvested from non-transgenic (NTg) control mice and transgenic mice bearing HcTnT-I79N. Left ventricular papillary muscle bundles were permeabilized and mounted for mechanical measurements.

Small Heat Shock Protein 22 Improves Cognition and Learning in the Tauopathic Brain.

The microtubule-associated protein tau pathologically accumulates and aggregates in Alzheimer’s disease (AD) and other tauopathies, leading to cognitive dysfunction and neuronal loss. Molecular chaperones, like small heat-shock proteins (sHsps), can help deter the accumulation of misfolded proteins, such as tau. Here, we tested the hypothesis that the overexpression of wild-type Hsp22 (wtHsp22) and its phosphomimetic (S24,57D) Hsp22 mutant (mtHsp22) could slow tau accumulation and preserve memory in a murine model of tauopathy, rTg4510. Our results show that Hsp22 protected against deficits in synaptic plasticity and cognition in the tauopathic brain. However, we did not detect a significant change in tau phosphorylation or levels in these mice. This led us to hypothesize that the functional benefit was realized through the restoration of dysfunctional pathways in hippocampi of tau transgenic mice since no significant benefit was measured in non-transgenic mice expressing wtHsp22 or mtHsp22. To identify these pathways, we performed mass spectrometry of tissue lysates from the injection site. Overall, our data reveal that Hsp22 overexpression in neurons promotes synaptic plasticity by regulating canonical pathways and upstream regulators that have been characterized as potential AD markers and synaptogenesis regulators, like EIF4E and NFKBIA.

Tau Knockout and α-Synuclein A53T Synergy Modulated Parvalbumin-Positive Neurons Degeneration Staging in Substantia Nigra Pars Reticulata of Parkinson's Disease-Liked Model.

The loss of parvalbumin-positive (PV+) neurons in the substantia nigra pars reticulata (SNR) was observed in patients with end-stage Parkinson’s disease (PD) and our previously constructed old-aged Pitx3-A53Tα-Syn × Tau–/– triple transgenic mice model of PD. The aim of this study was to examine the progress of PV+ neurons loss. We demonstrated that, as compared with non-transgenic (nTg) mice, the accumulation of α-synuclein in the SNR of aged Pitx3-A53Tα-Syn × Tau–/– mice was increased obviously, which was accompanied by the considerable degeneration of PV+ neurons and the massive generation of apoptotic NeuN+TUNEL+ co-staining neurons. Interestingly, PV was not costained with TUNEL, a marker of apoptosis. PV+ neurons in the SNR may undergo a transitional stage from decreased expression of PV to increased expression of NeuN and then to TUNEL expression. In addition, the degeneration of PV+ neurons and the expression of NeuN were rarely observed in the SNR of nTg and the other triple transgenic mice. Hence, we propose that Tau knockout and α-syn A53T synergy modulate PV+ neurons degeneration staging in the SNR of aged PD-liked mice model, and NeuN may be suited for an indicator that suggests degeneration of SNR PV+ neurons. However, the molecular mechanism needs to be further investigated.

The Effects of Physical Running on Dendritic Spines and Amyloid-beta Pathology in 3xTg-AD Male Mice.

Memory loss is the key symptom of Alzheimer's disease (AD). As successful drug treatments have not yet been identified, non-pharmaceutical interventions such as physical exercise and training have been employed to improve the memory function of people with dementia. We investigated the effect of prolonged physical running on hippocampal-dependent spatial memory and its underlying mechanisms using a well-established rodent model of AD. 3xTg-AD transgenic mice and non-transgenic mice were subjected to voluntary wheel running for 5 months (1 hour per day, 5 days per week), followed by spatial memory testing. After the behavioral testing, dendritic spines, synapses, and synaptic proteins as well as amyloid-beta (Aβ) pathology were analyzed in the dorsal hippocampi. Running improved hippocampal-dependent spatial memory in 3xTg-AD mice. This running strategy prevented both thin and mushroom-type spines on CA1 pyramidal cells in 3xTg-AD mice, whereas the effects of running in non-transgenic mice were limited to thin spines. The enormous effects of running on spines were accompanied by an increased number of synapses and upregulated expression of synaptic proteins. Notably, running downregulated the processing of amyloid precursor protein, decreasing intracellular APP expression and extracellular Aβ accumulation, and spatial memory performance correlated with levels of Aβ peptides Aβ1-40 and Aβ1-42. These data suggest that prolonged running may improve memory in preclinical AD via slowing down the amyloid pathology and preventing the loss of synaptic contacts.

Selective expression of neurodegenerative diseases-related mutant p150Glued in midbrain dopaminergic neurons causes progressive degeneration of nigrostriatal pathway

Aim: Missense mutations of dynactin subunit p150Glued have been associated with multiple neurodegenerative diseases, including Perry syndrome, characterized by inherited parkinsonism, depression, weight loss, and hypoventilation. The current study investigated how the pathogenic mutant p150Glued affects the integrity and function of the nigrostriatal dopaminergic (DA) pathway in vivo. Methods: Using a tetracycline-controlled transcriptional regulation system, transgenic mouse models were generated with selective overexpression of wild-type, motor neuron disease-related G59S mutant, or Perry syndrome-related G71R mutant human p150Glued in midbrain DA neurons. A series of behavioral, neuropathological, neurochemical, electrochemical, and biochemical studies were performed on the mice to examine and compare the pathogenic impact of the two mutant p150Glued on the survival and function of midbrain DA neurons. Results: Compared with non-transgenic control mice, transgenic mice overexpressing wild-type human p150Glued showed neither motor phenotypes nor pathological, functional, or biochemical abnormalities of the nigrostriatal DA pathway. Transgenic mice overexpressing G59S mutant p150Glued displayed weight loss, motor deficits, early-onset defects in dopamine transmission, and early-onset loss of DA neurons and axons. Transgenic mice overexpressing G71R p150Glued mutant exhibited hyperactivities, impaired motor coordination, early-onset dysfunction of dopamine uptake, and late-onset loss of DA neurons and axons. In addition, overexpression of either G59S or G71R mutant p150Glued in midbrain DA neurons preferentially downregulated the expression of dopamine transporter at dopaminergic axon terminals. Furthermore, G59S mutant p150Glued rather than G71R mutant p150Glued formed aggregates in midbrain DA neurons in vivo, and the aggregates trapped dynein/dynactin, co-localized with lysosomes, and upregulated ubiquitination. Conclusion: These findings demonstrate that selective expression of either G59S or G71R mutant p150Glued in mouse midbrain DA neurons leads to progressive degeneration of the nigrostriatal DA pathway and indicate that G59S and G71R mutant p150Glued exhibit differential pathogenic impact on the survival and function of midbrain DA neurons in vivo.

Correlation of 18F-Fluorodeoxyglucose Glucose Uptake by Liver Cancer and Transcriptional Regulation of the Warburg Effects in ATT-MYC Mouse Model of Liver Cancer

Background It was previously reported that diethylnitrosamine (DEN) enhanced liver cancer progression in ATT-MYC mouse model of liver cancer. Radiogenomics is a new tool in advanced science technology that gives information on tumor biology, non-tumor surrounding tissue, the degree of tumor size and presence of necrosis of cells especially with joined micro computed tomography – positron emission tomographys (CT/PETs). Aim To evaluate the correlation of gene expression and non-invasive microPET information of the liver tumors at different points of the stage of growth. Methods Exon array expression of the liver of ATT-MYC mice treated with DEN or butylated hydroxytoluene (BHT) compared to control non-transgenic mice were analyzed by array track and the current data were also compared to microarray expression of liver tumor of ATT-MYC mice. Results The expression of genes responsible for glucose transport such as glut1, 3, 4, hk1, slc1a5, slc1a1, slc1a4, slc1a2, gp6c and gpc-1-3-4 were up-regulated significantly in DEN-treated transgenic mice immediately after end of treatment (p≤0.05), while glut2 (fold change 0.9503, p-value 0.4385) and hk2 (fold change 3.0589, p-value 0.0565) genes were increased not significantly immediately after end of treatment. Additionally, at 4.5-months of observation after the end of treatment slc1a5, slc38a2, glut1, glut4 and gpc3-4 genes had a significant fold change in liver tumor tissue in DEN treated mice when compared to BHT or control transgenic or non-transgenic one. While hk1, 2, slc5a1, slc1a4, glut2, glut3, g6pc and gpc-1 genes were increased non-significantly in the liver of treated mice when compared to control group at 4.5-months of observation after the end of treatment. Notably, c-myc, hif-1 and aldoa glycolytic genes were expressed significantly both time points of 4 and 8.5-months while ldhb, hk-2 and PKM2 were increased non-significantly in DEN treatment when compared to BHT/control non-transgenic animals. Conclusion There is a definitive correlation between genes responsible for glucose transport and 18F-Fluorodeoxyglucose (FDG) uptake in the early and advanced degree of liver carcinogenesis. This study of glucose pathway in Hepatocellular carcinoma (HCC) at different stages of early and advanced one is the potential for therapeutic anticancer therapy.

Acetylation of Tau Induces Alzheimer's Disease-Associated Tau in Transgenic Mice

Alzheimer’s disease (AD) is a neurodegenerative disorder that is characterized by neurofibrillary tangles (NFTs) and amyloid beta plaques. These NFTs are made up of aggregated tau proteins. Tau is involved in stabilizing microtubules and does not usually display aggregation. Acetylation of tau protein causes an increase in tau aggregation but its role in AD progression is still not well understood. I hypothesized that enhanced acetylated tau results in an increase in AD-like tau pathology. To test this, a murine prion promoter-tauKQ transgene was injected into the mouse fertilized oocyte. The tauKQ mutation alters lysine to glutamine to mimic acetylation of tau. Nontransgenic mice were used as controls. AT8 and GT-38 antibodies were used in immunohistochemistry (IHC) to target phosphorylated tau and AD-associated tau, respectively. GT-38 is conformation-dependent and requires 3R and 4R tau isoforms which makes it specific to AD. Through immunofluorescence, increased phosphorylated tau was observed in the hippocampus of the tauKQ mice compared to the nontransgenic mice. I focused on the dentate gyrus, CA1 region, and the mossy fibers of the CA3 region since they are involved in many memory processes. Through chromogenic IHC, the tauKQ mice exhibited more 3R+4R tau isoform pathology in the mossy fibers than the nontransgenic mice. This data suggests that an acetylation mimic is sufficient to stimulate an abundance of AD-related tau pathology in transgenic mice which is consistent with my hypothesis. The tauKQ mouse model can assist in understanding the role of tau acetylation and tau progression for AD.

Differentially targeted seeding reveals unique pathological alpha-synuclein propagation patterns.

Parkinson’s disease is a progressive neurodegenerative disorder characterized by the intracellular accumulation of insoluble alpha-synuclein aggregates into Lewy bodies and neurites. Increasing evidence indicates that Parkinson’s disease progression results from the spread of pathologic alpha-synuclein through neuronal networks. However, the exact mechanisms underlying the propagation of abnormal proteins in the brain are only partially understood. The objective of this study was first to describe the long-term spatiotemporal distributions of Lewy-related pathology in mice injected with alpha-synuclein preformed fibrils and then to recreate these patterns using a computational model that simulates in silico the spread of pathologic alpha-synuclein.In this study, 87 2–3-month-old non-transgenic mice were injected with alpha-synuclein preformed fibrils to generate a comprehensive post-mortem dataset representing the long-term spatiotemporal distributions of hyperphosphorylated alpha-synuclein, an established marker of Lewy pathology, across the 426 regions of the Allen Mouse Brain Atlas. The mice were injected into either the caudoputamen, nucleus accumbens or hippocampus, and followed over 24 months with pathologic alpha-synuclein quantified at seven intermediate time points. The pathologic patterns observed at each time point in this high-resolution dataset were then compared to those generated using a Susceptible-Infected-Removed (SIR) computational model, an agent-based model that simulates the spread of pathologic alpha-synuclein for every brain region taking simultaneously into account the effect of regional brain connectivity and Snca gene expression.Our histopathological findings showed that differentially targeted seeding of pathological alpha-synuclein resulted in unique propagation patterns over 24 months and that most brain regions were permissive to pathology. We found that the SIR model recreated the observed distributions of pathology over 24 months for each injection site. Null models showed that both Snca gene expression and connectivity had a significant influence on model fit.In sum, our study demonstrates that the combination of normal alpha-synuclein concentration and brain connectomics contributes to making brain regions more vulnerable to the pathological process, providing support for a prion-like spread of pathologic alpha-synuclein. We propose that this rich dataset and the related computational model will help test new hypotheses regarding mechanisms that may alter the spread of pathologic alpha-synuclein in the brain.

Combinatorial model of amyloid β and tau reveals synergy between amyloid deposits and tangle formation.

To illuminate the pathological synergy between Aβ and tau leading to emergence of neurofibrillary tangles (NFT) in Alzheimer's disease (AD), here, we have performed a comparative neuropathological study utilising three distinctive variants of human tau (WT tau, P301L mutant tau and S320F mutant tau). Previously, in non-transgenic mice, we showed that WT tau or P301L tau does not form NFT while S320F tau can spontaneously aggregate into NFT, allowing us to test the selective vulnerability of these different tau conformations to the presence of Aβ plaques. We injected recombinant AAV-tau constructs into neonatal APP transgenic TgCRND8 mice or into 3-month-old TgCRND8 mice; both cohorts were aged 3months post injection. This allowed us to test how different tau variants synergise with soluble forms of Aβ (pre-deposit cohort) or with frank Aβ deposits (post-deposit cohort). Expression of WT tau did not produce NFT or altered Aβ in either cohort. In the pre-deposit cohort, S320F tau induced Aβ plaque deposition, neuroinflammation and synaptic abnormalities, suggesting that early tau tangles affect the amyloid cascade. In the post-deposit cohort, contemporaneous expression of S320F tau did not exacerbate amyloid pathology, showing a dichotomy in Aβ-tau synergy based on the nature of Aβ. P301L tau produced NFT-type inclusions in the post-deposit cohort, but not in the pre-deposit cohort, indicating pathological synergy with pre-existing Aβ deposits. Our data show that different tau mutations representing specific folding variants of tau synergise with Aβ to different extents, depending on the presence of cerebral deposits.

Lats2 promotes heart failure by stimulating p53-mediated apoptosis during pressure overload

The Hippo pathway plays a wide variety of roles in response to stress in the heart. Lats2, a component of the Hippo pathway, is phosphorylated by Mst1/2 and, in turn, phosphorylates YAP, causing inactivation of YAP. Lats2 stimulates apoptosis and negatively affects hypertrophy in cardiomyocytes. However, the role of Lats2 during cardiac stress is poorly understood in vivo. Lats2 is activated in the mouse heart in response to transverse aortic constriction (TAC). We used systemic Lats2 +/- mice to elucidate the role of endogenous Lats2. Cardiac hypertrophy and dysfunction induced by 4 weeks of TAC were attenuated in Lats2 +/- mice, and interstitial fibrosis and apoptosis were suppressed. Although TAC upregulated the Bcl-2 family proapoptotic (Bax and Bak) and anti-apoptotic (Bcl-2 and Bcl-xL) molecules in non-transgenic mice, TAC-induced upregulation of Bax and Bak was alleviated and that of Bcl-2 was enhanced in Lats2 +/- mice. TAC upregulated p53, but this upregulation was abolished in Lats2 +/- mice. Lats2-induced increases in apoptosis and decreases in survival in cardiomyocytes were inhibited by Pifithrin-α, a p53 inhibitor, suggesting that Lats2 stimulates apoptosis via a p53-dependent mechanism. In summary, Lats2 is activated by pressure overload, thereby promoting heart failure by stimulating p53-dependent mechanisms of cell death.

A time-restricted feeding intervention reduces alterations in circadian behaviors and pathology in a mouse model of Alzheimer's disease.

Circadian rhythm disruptions impact nearly all Alzheimer's disease (AD) patients, with daytime sleepiness, sundowning, sleep fragmentation, and night-time insomnia being common disturbances. These early and progressive declines support the role of circadian dysfunction as a driver of AD pathology, hence the therapeutic potential of circadian-modulating interventions needs to be investigated. One of the most powerful regulators of the circadian system is the daily feed/fast cycle. We have recently shown that early, presymptomatic time-restricted feeding (TRF) can ameliorate a range of symptoms related to neurodegenerative conditions, including improving sleep/wake timing and circadian rhythmicity. At 12 months of age, the APP23 mouse model of AD (expressing the human APP gene containing the Swedish mutation) exhibits disrupted behavior resembling sundowning. We hypothesized that imposing early-age TRF in APP23 mice would improve circadian rhythmicity and deter the disruptions observed to emerge and progress with advancing neuropathology. Adult male and female APP23 transgenic (AD) and littermate non-transgenic (control) mice were housed individually and subjected to ab libitum (ALF) feeding or a TRF protocol consisting of 6-hours feeding in the middle of the active phase followed by 18-hours fasting for 3 months. Behavioral sleep (48 hours) and ongoing cage locomotor activity were recorded from an early age. Our analysis shows that AD mice exhibit disruptions in total sleep (P < 0.001) and the emergence of excessive wakefulness (P < 0.001). AD mice also show significant active-phase agitation (P < 0.05) accompanied by excessive sleep-phase fragmentation (P < 0.05). TRF induced nutritional ketosis (β-Hydroxybutyrate > 0.5 mM) accompanied by reduced blood glucose when compared to ALF mice, although mice consumed equivalent volumes of food in both experimental groups. Importantly, TRF improved total and sleep-phase sleep in AD mice (P < 0.05) and significantly reduced agitation and fragmentation (P < 0.05). Early application of TRF can forestall circadian disruptions in AD mice. TRF has been reported to modulate expression of clock and clock-controlled genes, transcriptional regulators, metabolism related genes, BDNF, and other neurotrophic factors. Our results suggest that these changes may also impact sleep, circadian behaviors, and agitation associated with AD.

Positive and Negative Selective Allosteric Modulators of α5 GABAA Receptors: Effects on Emotionality, Motivation, and Motor Function in the 5xFAD Model of Alzheimer's Disease.

Positive and negative allosteric modulators of α5 GABAA receptors (PAM and NAM, respectively) are worthy of investigation as putative treatments of Alzheimer's disease (AD). However, their potential to modify a dynamic range of behaviors in AD models needs to be systematically examined. The study aimed to assess effects of MP-III-022 as PAM and PWZ-029 as NAM on emotional reactivity, motivation, and motor function, as well as on gene expression of GABRA2, GABRA3 and GABRA5 subunit of GABAA receptors in prefrontal cortex (PFC) and hippocampus (HC) in 5xFAD mice, as an early-onset transgenic AD model. The 6-month-old 5xFAD transgenic and non-transgenic mice of both genders underwent a battery of reflexes and behavioral tests (sensorimotor tests, elevated plus maze, and open field) after 10-day intraperitoneal treatment with MP-III-022, PWZ-029, or solvent. The behavioral battery was followed by qPCR analysis of gene expression. MP-III-022 induced a decline in motor function, while PWZ-029 further decreased emotionality of transgenic males, as compared to the transgenic control. No interfering effects on non-cognitive behavior were observed in female mice. In HC, both treatments reversed reciprocal GABRA2 and GABRA3 changes in transgenic females. In PFC, MP-III-022 decreased GABRA5 in both genders, while PWZ-029 increased GABRA2 in male transgenic animals. Gender-dependent protracted effects of PAMs and NAMs in AD model, with detrimental impact on motor capabilities of PAM, and attenuation of emotionality elicited by NAM in transgenic males, were revealed. This favors future research of α5 GABAA receptor modulation in females as more promising.

Mitochondrial Fusion Suppresses Tau Pathology-Induced Neurodegeneration and Cognitive Decline.

Abnormalities of mitochondrial fission and fusion, dynamic processes known to be essential for various aspects of mitochondrial function, have repeatedly been reported to be altered in Alzheimer's disease (AD). Neurofibrillary tangles are known as a hallmark feature of AD and are commonly considered a likely cause of neurodegeneration in this devastating disease. To understand the pathological role of mitochondrial dynamics in the context of tauopathy. The widely used P301S transgenic mice of tauopathy (P301S mice) were crossed with transgenic TMFN mice with the forced expression of Mfn2 specifically in neurons to obtain double transgenic P301S/TMFN mice. Brain tissues from 11-month-old non-transgenic (NTG), TMFN, P301S, and P301S/TMFN mice were analyzed by electron microscopy, confocal microscopy, immunoblot, histological staining, and immunostaining for mitochondria, tau pathology, and tau pathology-induced neurodegeneration and gliosis. The cognitive function was assessed by the Barnes maze. P301S mice exhibited mitochondrial fragmentation and a consistent decrease in Mfn2 compared to age-matched NTG mice. When P301S mice were crossed with TMFN mice (P301S/TMFN mice), neuronal loss, as well as mitochondria fragmentation were significantly attenuated. Greatly alleviated tau hyperphosphorylation, filamentous aggregates, and thioflavin-S positive tangles were also noted in P301S/TMFN mice. Furthermore, P301S/TMFN mice showed marked suppression of neuroinflammation and improved cognitive performance in contrast to P301S mice. These in vivo findings suggest that promoted mitochondrial fusion suppresses toxic tau accumulation and associated neurodegeneration, which may protect against the progression of AD and related tauopathies.