Disease Mouse Brain Research Articles

The interplay between microglial states and major risk factors in Alzheimer’s disease through the eyes of single-cell RNA-sequencing: beyond black and white

Microglia constitute ~10-20% of glial cells in the adult human brain. They are the resident phagocytic immune cells of the central nervous system and play an integral role as first responders during inflammation. Microglia are commonly classified as "HM" (homeostatic), "M1" (classically activated proinflammatory), or "M2" (alternatively activated). Multiple single-cell RNA-sequencing studies suggest that this discrete classification system does not accurately and fully capture the vast heterogeneity of microglial states in the brain. In fact, a recent single-cell RNA-sequencing study showed that microglia exist along a continuous spectrum of states. This spectrum spans heterogeneous populations of homeostatic and neuropathology-associated microglia in both healthy and Alzheimer's disease (AD) mouse brains. Major risk factors, such as sex, age, and genes, modulate microglial states, suggesting that shifts along the trajectory might play a causal role in AD pathogenesis. This study provides important insight into the cellular mechanisms of AD and underlines the potential of novel cell-based therapies for AD.

Pathological Alterations of Tau in Alzheimer's Disease and 3xTg-AD Mouse Brains.

Microtubule-associated protein tau in Alzheimer's disease (AD) brain is hyperphosphorylated, truncated, and aggregated into neurofibrillary tangles. Oligomeric and hyperphosphorylated tau (Oligo-tau) isolated from AD brain captures and templates normal tau into filaments both in vitro and in vivo; this prion-like activity is believed to be responsible for the progression of neurofibrillary pathology in AD. The 3xTg-AD mouse model develops both Aβ and tau pathologies and thus gains popularity in preclinical studies of AD. Despite the histopathological similarity of the 3xTg-AD model to AD, biochemical authenticity of tau alterations in this model remains elusive. To investigate the biochemical basis of tau pathology in 3xTg-AD brain, we here compared pathological alterations of tau in the aged 3xTg-AD brain to those in AD brain. We found that in contrast to substantial high molecular weight smear tau (HMW-tau) lacking the N-terminal portion and hyperphosphorylated at multiple sites in AD brain, tau in 3xTg-AD mouse brain showed no detectable HMW-tau or truncation but slightly increased phosphorylation when normalized with total tau. In addition, AT8 immunostaining exhibited filamentous tau inclusions in AD brain, but predominantly truffle-like morphology in aged 3xTg-AD mouse brain. Further, Oligo-tau isolated from 3xTg-AD mice showed minimal potency in capturing tau in vitro and seeding tau aggregation in cultured cells when compared to AD Oligo-tau. These findings suggest that the alterations of tau in 3xTg-AD mouse brain differ from those in AD brain. In 3xTg-AD mice, the lack of N-terminal truncation, scarce SDS/reducing reagent-resistant HMW-tau, and minimal hyperphosphorylation may collectively result in low potency in prion-like activityofthe Oligo-tau.

TRPC6 mRNA levels in peripheral leucocytes of patients with Alzheimer's disease and mild cognitive impairment: A case-control study

BackgroundTransient receptor potential canonical (TRPC) 6 inhibits Aβ in Alzheimer's disease (AD) mouse brain and improves the behavioral performance. AimsTo evaluate the association of TRPC6 expression in peripheral leucocytes from AD and mild cognitive impairment (MCI) patients and to explore its potential value in early diagnosis of AD. MethodsTRPC6 mRNA levels in peripheral leucocytes were detected by quantitative real-time PCR. The Spearman correlation test was used to ascertain the associations between TRPC6 and the scores of MMSE, ADL, CSDD, CDR. The Receiver Operating Characteristic (ROC) curve was drawn to evaluate the diagnostic potential of TRPC6 for AD and MCI. ResultsThere were 108 CE, 136 MCI, 164 Con and 60 PD in the study. The expression of TRPC6 mRNA level in peripheral leucocytes was significantly lower: 1) in patients with AD and MCI compared to Con; 2) in AD compared to MCI; 3) in hospitalized AD compared to AD from communities. There was a significantly positive correlation between TRPC6 mRNA and MMSE score (p = .001, R = 0.327). Significantly inverse correlations were found between TRPC6 and CDR score (p < 0.001, R = −0.303) as well as between TRPC6 and ADL score (p = .001, R = −0.342) for all AD. The area under curve of ROC was 0.881 for the classification of AD, and 0.706 for the classification of MCI, respectively. ConclusionTRPC6 expression is inversely correlated with cognitive performance of AD. TRPC6 in peripheral leucocytes may be a potential biomarker for the diagnosis of AD.

Mass Spectrometry Imaging of Brain Cholesterol and Metabolites with Trifluoroacetic Acid-Enhanced Desorption Electrospray Ionization.

Imaging of cholesterol and other metabolites simultaneously by ambient mass spectrometry will greatly benefit biological studies, however, it still remains challenging. Herein, by adding acid into the desorption electrospray ionization (DESI) spray solvent, we achieved simultaneous mass spectrometry imaging of cholesterol and other metabolites directly from mouse brain sections. The introduction of acid increased the signal intensity of cholesterol in mouse brain tissues by approximately 21-fold. Additionally, the present strategy provided increased signal intensities for other metabolites up to 62-fold, as well as identification of seven more metabolites (23 vs 16 for acid-enhanced DESI vs DESI). Moreover, increased corelationships for alanine as well as putrescine and spermidine with cholesterol were discovered under acid-enhanced DESI. The potential of the present strategy in the fields of biological and medical research was demonstrated by investigating the level change for cholesterol, alanine, putrescine, and spermidine in Alzheimer's disease (AD) mouse brain.

Exploring Alzheimer's disease mouse brain through X-ray phase contrast tomography: From the cell to the organ

Alzheimer's disease (AD), the most common form of dementia, is a progressive neurodegenerative disorder associated with aberrant production of beta-amyloid (Aβ) peptide depositing in brain as amyloid plaques. While animal models allow investigation of disease progression and therapeutic efficacy, technology to fully dissect the pathological mechanisms of this complex disease at cellular and vascular levels is lacking.X-ray phase contrast tomography (XPCT) is an advanced non-destructive 3D multi-scale direct imaging from the cell through to the whole brain, with exceptional spatial and contrast resolution. We exploit XPCT to simultaneously analyse disease-relevant vascular and neuronal networks in AD mouse brain, without sectioning and staining. The findings clearly show the different typologies and internal structures of Aβ plaques, together with their interaction with patho/physiological cellular and neuro-vascular microenvironment. XPCT enables for the first time a detailed visualization of amyloid-angiopathy at capillary level, which is impossible to achieve with other approaches.XPCT emerges as added-value technology to explore AD mouse brain as a whole, preserving tissue chemistry and structure, enabling the comparison of physiological vs. pathological states at the level of crucial disease targets. In-vivo translation will permit to monitor emerging therapeutic approaches and possibly shed new light on pathological mechanisms of neurodegenerative diseases.

BACE1-cleavage of Sez6 and Sez6L is elevated in Niemann-Pick type C disease mouse brains

It is intriguing that a rare, inherited lysosomal storage disorder Niemann-Pick type C (NPC) shares similarities with Alzheimer’s disease (AD). We have previously reported an enhanced processing of β-amyloid precursor protein (APP) by β-secretase (BACE1), a key enzyme in the pathogenesis of AD, in NPC1-null cells. In this work, we characterized regional and temporal expression and processing of the recently identified BACE1 substrates seizure protein 6 (Sez6) and seizure 6-like protein (Sez6L), and APP, in NPC1-/- (NPC1) and NPC1+/+ (wt) mouse brains. We analysed 4-weeks old brains to detect the earliest changes associated with NPC, and 10-weeks of age to identify changes at terminal disease stage. Sez6 and Sez6L were selected due to their predominant cleavage by BACE1, and their potential role in synaptic function that may contribute to presentation of seizures and/or motor impairments in NPC patients. While an enhanced BACE1-cleavage of all three substrates was detected in NPC1 vs. wt-mouse brains at 4-weeks of age, at 10-weeks increased proteolysis by BACE1 was observed for Sez6L in the cortex, hippocampus and cerebellum of NPC1-mice. Interestingly, both APP and Sez6L were found to be expressed in Purkinje neurons and their immunostaining was lost upon Purkinje cell neurodegeneration in 10-weeks old NPC1 mice. Furthermore, in NPC1- vs. wt-mouse primary cortical neurons, both Sez6 and Sez6L showed increased punctuate staining within the endolysosomal pathway as well as increased Sez6L and BACE1-positive puncta. This indicates that a trafficking defect within the endolysosomal pathway may play a key role in enhanced BACE1-proteolysis in NPC disease. Overall, our findings suggest that enhanced proteolysis by BACE1 could be a part of NPC disease pathogenesis. Understanding the basic biology of BACE1 and the functional impact of cleavage of its substrates is important to better evaluate the therapeutic potential of BACE1 against AD and, possibly, NPC disease.

The Adiponectin Homolog Osmotin Enhances Neurite Outgrowth and Synaptic Complexity via AdipoR1/NgR1 Signaling in Alzheimer's Disease.

Alzheimer's disease is a major neurodegenerative disease characterized by memory loss and cognitive deficits. Recently, we reported that osmotin, which is a homolog of adiponectin, improved long-term potentiation and cognitive functions in Alzheimer's disease mice. Several lines of evidence have suggested that Nogo-A and the Nogo-66 receptor 1 (NgR1), which form a complex that inhibits long-term potentiation and cognitive function, might be associated with the adiponectin receptor 1 (AdipoR1), which is a receptor for osmotin. Here, we explore whether osmotin's effects on long-term potentiation and memory function are associated with NgR1 signaling via AdipoR1 in Alzheimer's disease. Osmotin reduced the expression of NgR1 without affecting Nogo-A expression. Furthermore, osmotin inhibited NgR1 signaling by prohibiting the formation of the Nogo-A and NgR1 ligand-receptor complex, resulting in enhanced neurite outgrowth; these effects disappeared in the presence of AdipoR1 interference. In addition, osmotin increased the expression of the pre- and postsynaptic markers synaptophysin and PSD-95, as well as the activation of the memory-associated markers AMPA receptor and CREB; these effects occurred in an AdipoR1- and NgR1-dependent manner. Osmotin was also found to enhance dendritic complexity and spine density in the hippocampal region of Alzheimer's disease mouse brains. These results suggest that osmotin can enhance neurite outgrowth and synaptic complexity through AdipoR1 and NgR1 signaling, implying that osmotin might be an effective therapeutic agent for Alzheimer's disease and that AdipoR1 might be a crucial therapeutic target for neurodegenerative diseases such as Alzheimer's.

Tissue Localization of Glycosphingolipid Accumulation in a Gaucher Disease Mouse Brain by LC-ESI-MS/MS and High-Resolution MALDI Imaging Mass Spectrometry

To better understand regional brain glycosphingolipid (GSL) accumulation in Gaucher disease (GD) and its relationship to neuropathology, a feasibility study using mass spectrometry and immunohistochemistry was conducted using brains derived from a GD mouse model (4L/PS/NA) homozygous for a mutant GCase (V394L [4L]) and expressing a prosaposin hypomorphic (PS-NA) transgene. Whole brains from GD and control animals were collected using one hemisphere for MALDI FTICR IMS analysis and the other for quantitation by LC-ESI-MS/MS. MALDI IMS detected several HexCers across the brains. Comparison with the brain hematoxylin and eosin (H&E) revealed differential signal distributions in the midbrain, brain stem, and CB of the GD brain versus the control. Quantitation of serial brain sections with LC-ESI-MS/MS supported the imaging results, finding the overall HexCer levels in the 4L/PS-NA brains to be four times higher than the control. LC-ESI-MS/MS also confirmed that the elevated hexosyl isomers were glucosylceramides rather than galactosylceramides. MALDI imaging also detected differential analyte distributions of lactosylceramide species and gangliosides in the 4L/PS-NA brain, which was validated by LC-ESI-MS/MS. Immunohistochemistry revealed regional inflammation, altered autophagy, and defective protein degradation correlating with regions of GSL accumulation, suggesting that specific GSLs may have distinct neuropathological effects.

Delineating Amyloid Plaque Associated Neuronal Sphingolipids in Transgenic Alzheimer's Disease Mice (tgArcSwe) Using MALDI Imaging Mass Spectrometry.

The major pathological hallmarks of Alzheimer’s disease (AD) are the progressive aggregation and accumulation of beta-amyloid (Aβ) and hyperphosphorylated tau protein into neurotoxic deposits. Aβ aggregation has been suggested as the critical early inducer, driving the disease progression. However, the factors that promote neurotoxic Aβ aggregation remain elusive. Imaging mass spectrometry (IMS) is a powerful technique to comprehensively elucidate the spatial distribution patterns of lipids, peptides, and proteins in biological tissue sections. In the present study, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS)-based imaging was used on transgenic Alzheimer’s disease mouse (tgArcSwe) brain tissue to investigate the sphingolipid microenvironment of individual Aβ plaques and elucidate plaque-associated sphingolipid alterations. Multivariate data analysis was used to interrogate the IMS data for identifying pathologically relevant, anatomical features based on their lipid chemical profile. This approach revealed sphingolipid species that distinctly located to cortical and hippocampal deposits, whose Aβ identity was further verified using fluorescent amyloid staining and immunohistochemistry. Subsequent multivariate statistical analysis of the spectral data revealed significant localization of gangliosides and ceramides species to Aβ positive plaques, which was accompanied by distinct local reduction of sulfatides. These plaque-associated changes in sphingolipid levels implicate a functional role of sphingolipid metabolism in Aβ plaque pathology and AD pathogenesis. Taken together, the presented data highlight the potential of imaging mass spectrometry as a powerful approach for probing Aβ plaque-associated lipid changes underlying AD pathology.

Oxygen consumption deficit in Huntington disease mouse brain under metabolic stress

In vivo evidence for brain mitochondrial dysfunction in animal models of Huntington disease (HD) is scarce. We applied the novel 17O magnetic resonance spectroscopy (MRS) technique on R6/2 mice to directly determine rates of oxygen consumption (CMRO2) and assess mitochondrial function in vivo Basal respiration and maximal CMRO2 in the presence of the mitochondrial uncoupler dinitrophenol (DNP) were compared using 16.4 T in isoflurane anesthetized wild type (WT) and HD mice at 9 weeks. At rest, striatal CMRO2 of R6/2 mice was equivalent to that of WT, indicating comparable mitochondrial output despite onset of motor symptoms in R6/2. After DNP injection, the maximal CMRO2 in both striatum and cortex of R6/2 mice was significantly lower than that of WT, indicating less spare energy generating capacity. In a separate set of mice, oligomycin injection to block ATP generation decreased CMRO2 equally in brains of R6/2 and WT mice, suggesting oxidative phosphorylation capacity and respiratory coupling were equivalent at rest. Expression levels of representative mitochondrial proteins were compared from harvested tissue samples. Significant differences between R6/2 and WT included: in striatum, lower VDAC and the mitochondrially encoded cytochrome oxidase subunit I relative to actin; in cortex, lower tricarboxylic acid cycle enzyme aconitase and higher protein carbonyls; in both, lower glycolytic enzyme enolase. Therefore in R6/2 striatum, lowered CMRO2 may be attributed to a decrease in mitochondria while the cortical CMRO2 decrease may result from constraints upstream in energetic pathways, suggesting regionally specific changes and possibly rates of metabolic impairment.

Increased Electron Paramagnetic Resonance Signal Correlates with Mitochondrial Dysfunction and Oxidative Stress in an Alzheimer's disease Mouse Brain.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized clinically by cognitive decline and memory loss. The pathological features are amyloid-β peptide (Aβ) plaques and intracellular neurofibrillary tangles. Many studies have suggested that oxidative damage induced by reactive oxygen species (ROS) is an important mechanism for AD progression. Our recent study demonstrated that oxidative stress could further impair mitochondrial function. In the present study, we adopted a transgenic mouse model of AD (mAPP, overexpressing AβPP/Aβ in neurons) and performed redox measurements using in vivo electron paramagnetic resonance (EPR) imaging with methoxycarbamyl-proxyl (MCP) as a redox-sensitive probe for studying oxidative stress in an early stage of pathology in a transgenic AD mouse model. Through assessing oxidative stress, mitochondrial function and cognitive behaviors of mAPP mice at the age of 8-9 months, we found that oxidative stress and mitochondrial dysfunction appeared in the early onset of AD. Increased ROS levels were associated with defects of mitochondrial and cognitive dysfunction. Notably, the in vivo EPR method offers a unique way of assessing tissue oxidative stress in living animals under noninvasive conditions, and thus holds a potential for early diagnosis and monitoring the progression of AD.

Relationship between ubiquilin-1 and BACE1 in human Alzheimer's disease and APdE9 transgenic mouse brain and cell-based models

Accumulation of β-amyloid (Aβ) and phosphorylated tau in the brain are central events underlying Alzheimer's disease (AD) pathogenesis. Aβ is generated from amyloid precursor protein (APP) by β-site APP-cleaving enzyme 1 (BACE1) and γ-secretase-mediated cleavages. Ubiquilin-1, a ubiquitin-like protein, genetically associates with AD and affects APP trafficking, processing and degradation. Here, we have investigated ubiquilin-1 expression in human brain in relation to AD-related neurofibrillary pathology and the effects of ubiquilin-1 overexpression on BACE1, tau, neuroinflammation, and neuronal viability in vitro in co-cultures of mouse embryonic primary cortical neurons and microglial cells under acute neuroinflammation as well as neuronal cell lines, and in vivo in the brain of APdE9 transgenic mice at the early phase of the development of Aβ pathology. Ubiquilin-1 expression was decreased in human temporal cortex in relation to the early stages of AD-related neurofibrillary pathology (Braak stages 0–II vs. III–IV). There was a trend towards a positive correlation between ubiquilin-1 and BACE1 protein levels. Consistent with this, ubiquilin-1 overexpression in the neuron-microglia co-cultures with or without the induction of neuroinflammation resulted in a significant increase in endogenously expressed BACE1 levels. Sustained ubiquilin-1 overexpression in the brain of APdE9 mice resulted in a moderate, but insignificant increase in endogenous BACE1 levels and activity, coinciding with increased levels of soluble Aβ40 and Aβ42. BACE1 levels were also significantly increased in neuronal cells co-overexpressing ubiquilin-1 and BACE1. Ubiquilin-1 overexpression led to the stabilization of BACE1 protein levels, potentially through a mechanism involving decreased degradation in the lysosomal compartment. Ubiquilin-1 overexpression did not significantly affect the neuroinflammation response, but decreased neuronal viability in the neuron-microglia co-cultures under neuroinflammation. Taken together, these results suggest that ubiquilin-1 may mechanistically participate in AD molecular pathogenesis by affecting BACE1 and thereby APP processing and Aβ accumulation.

Adult neural progenitor cells from Huntington's disease mouse brain exhibit increased proliferation and migration due to enhanced calcium and ROS signals.

Huntington's disease (HD) is an inherited human neurodegenerative disorder characterized by uncontrollable movement, psychiatric disturbance and cognitive decline. Impaired proliferative/differentiational potentials of adult neural progenitor cells (ANPCs) have been thought to be a pathogenic mechanism involved in it. In this study, we aimed to elucidate intrinsic properties of ANPCs subjected to neurodegenerative condition in YAC128 HD mice. ANPCs were isolated from the SVZ regions of 4-month-old WT and YAC128 mice. Cell proliferation, migration and neuronal differentiation invitro were compared between these two genotypes with/without Ca(2+) inhibitors or ROS scavenger treatments. Differences in ANPC proliferation and differentiation capabilities invivo between the two genotypes were evaluated using Ki-67 and Doublecortin (DCX) immunofluorescence respectively. Compared to WT ANPCs, YAC128 ANPCs had significantly enhanced cell proliferation, migration and neuronal differentiation invitro, accompanied by increased Ca(2+) and ROS signals. Raised proliferation and migration in YAC128 ANPCs were abolished by Ca(2+) signalling antagonists and ROS scavenging. However, invivo, HD ANPCs failed to show any elevated proliferation or differentiation. Increased Ca(2+) signalling and higher level of ROS conferred HD ANPC enhancement of proliferation and migration potentials. However, the invivo micro-environment did not support endogenous ANPCs to respond appropriately to neuronal loss in these YAC128 mouse brains.

Mass Spectrometry Analysis of Wild-Type and Knock-in Q140/Q140 Huntington's Disease Mouse Brains Reveals Changes in Glycerophospholipids Including Alterations in Phosphatidic Acid and Lyso-Phosphatidic Acid.

Huntington's disease (HD) is a neurodegenerative disease caused by a CAG expansion in the HD gene, which encodes the protein Huntingtin. Huntingtin associates with membranes and can interact directly with glycerophospholipids in membranes. We analyzed glycerophospholipid profiles from brains of 11 month old wild-type (WT) and Q140/Q140 HD knock-in mice to assess potential changes in glycerophospholipid metabolism. Polar lipids from cerebellum, cortex, and striatum were extracted and analyzed by liquid chromatography and negative ion electrospray tandem mass spectrometry analysis (LC-MS/MS). Gene products involved in polar lipid metabolism were studied using western blotting, immuno-electron microscopy and qPCR. Significant changes in numerous species of glycerophosphate (phosphatidic acid, PA) were found in striatum, cerebellum and cortex from Q140/Q140 HD mice compared to WT mice at 11 months. Changes in specific species could also be detected for other glycerophospholipids. Increases in species of lyso-PA (LPA) were measured in striatum of Q140/Q140 HD mice compared to WT. Protein levels for c-terminal binding protein 1 (CtBP1), a regulator of PA biosynthesis, were reduced in striatal synaptosomes from HD mice compared to wild-type at 6 and 12 months. Immunoreactivity for CtBP1 was detected on membranes of synaptic vesicles in striatal axon terminals in the globus pallidus. These novel results identify a potential site of molecular pathology caused by mutant Huntingtin that may impart early changes in HD.

Monoclonal Antibodies against Aβ42 Fibrils Distinguish Multiple Aggregation State Polymorphisms in Vitro and in Alzheimer Disease Brain

Amyloidogenic proteins generally form intermolecularly hydrogen-bonded β-sheet aggregates, including parallel, in-register β-sheets (recognized by antiserum OC) or antiparallel β-sheets, β-solenoids, β-barrels, and β-cylindrins (recognized by antiserum A11). Although these groups share many common properties, some amyloid sequences have been reported to form polymorphic structural variants or strains. We investigated the humoral immune response to Aβ42 fibrils and produced 23 OC-type monoclonal antibodies recognizing distinct epitopes differentially associated with polymorphic structural variants. These mOC antibodies define at least 18 different immunological profiles represented in aggregates of amyloid-β (Aβ). All of the antibodies strongly prefer amyloid aggregates over monomer, indicating that they recognize conformational epitopes. Most of the antibodies react with N-terminal linear segments of Aβ, although many recognize a discontinuous epitope consisting of an N-terminal domain and a central domain. Several of the antibodies that recognize linear Aβ segments also react with fibrils formed from unrelated amyloid sequences, indicating that reactivity with linear segments of Aβ does not mean the antibody is sequence-specific. The antibodies display strikingly different patterns of immunoreactivity in Alzheimer disease and transgenic mouse brain and identify spatially and temporally unique amyloid deposits. Our results indicate that the immune response to Aβ42 fibrils is diverse and reflects the structural polymorphisms in fibrillar amyloid structures. These polymorphisms may contribute to differences in toxicity and consequent effects on pathological processes. Thus, a single therapeutic monoclonal antibody may not be able to target all of the pathological aggregates necessary to make an impact on the overall disease process.

Voxel-based morphometry with templates and validation in a mouse model of Huntington’s disease

Despite widespread application to human imaging, voxel-based morphometry (VBM), where images are compared following grey matter (GM) segmentation, is seldom used in mice. Here VBM is performed for the R6/2 model of Huntington’s disease, a progressive neurological disorder. This article discusses issues in translating the methods to mice and shows that its statistical basis is sound in mice as it is in human studies. Whole brain images from live transgenic and control mice are segmented into GM maps after processing and compared to produce statistical parametric maps of likely differences. To assess whether false positives were likely to occur, a large cohort of ex vivo magnetic resonance brain images were sampled with permutation testing. Differences were seen particularly in the striatum and cortex, in line with studies performed ex vivo and as seen in human patients. In validation, the rate of false positives is as expected and these have no discernible distribution through the brain. The study shows that VBM successfully detects differences in the Huntington’s disease mouse brain. The method is rapid compared to manual delineation and reliable. The templates created here for the mouse brain are freely released for other users in addition to an open-source software toolbox for performing mouse VBM.

Anti-Amyloid-β-Mediated Positron Emission Tomography Imaging in Alzheimer's Disease Mouse Brains

Antibody-mediated imaging of amyloid β (Aβ) in Alzheimer's disease (AD) offers a promising strategy to detect and monitor specific Aβ species, such as oligomers, that have important pathological and therapeutic relevance. The major current limitation of antibodies as a diagnostic and imaging device is poor blood-brain-barrier permeability. A classical anti-Aβ antibody, 6E10, is modified with 10 kDa polyethylene glycol (PEG) and a positron emitting isotope, Copper-64 (t½ = 12.7 h), and intravenously delivered to the TgCRND8 mouse model of Alzheimer's disease. Modification of 6E10 with PEG (6E10-PEG) increases accumulation of 6E10 in brain tissue in both TgCRND8 and wild type control animals. 6E10-PEG differentiates TgCRND8 animals from wild type controls using positron emission tomography (PET) and provides a framework for using antibodies to detect pathology using non-invasive medical imaging techniques.

Network Organization of the Huntingtin Proteomic Interactome in Mammalian Brain

We used affinity-purification mass spectrometry to identify 747 candidate proteins that are complexed with Huntingtin (Htt) in distinct brain regions and ages in Huntington's disease (HD) and wild-type mouse brains. To gain a systems-level view of the Htt interactome, we applied Weighted Correlation Network Analysis to the entire proteomic data set to unveil a verifiable rank of Htt-correlated proteins and a network of Htt-interacting protein modules, with each module highlighting distinct aspects of Htt biology. Importantly, the Htt-containing module is highly enriched with proteins involved in 14-3-3 signaling, microtubule-based transport, and proteostasis. Top-ranked proteins in this module were validated as Htt interactors and genetic modifiers in an HD Drosophila model. Our study provides a compendium of spatiotemporal Htt-interacting proteins in the mammalian brain and presents an approach for analyzing proteomic interactome data sets to build in vivo protein networks in complex tissues, such as the brain.

Overexpression of the kynurenine pathway enzyme tryptophan 2,3-dioxygenase in triple-transgenic (3xTg) Alzheimer's disease mouse brain

Overexpression of the kynurenine pathway enzyme tryptophan 2,3-dioxygenase in triple-transgenic (3xTg) Alzheimer's disease mouse brain

Polyglutamine expansion in huntingtin alters its interaction with phospholipids

Huntingtin has an expanded polyglutamine tract in patients with Huntington's disease. Huntingtin localizes to intracellular and plasma membranes but the function of huntingtin at membranes is unknown. Previously we reported that exogenously expressed huntingtin bound pure phospholipids using protein-lipid overlays. Here we show that endogenous huntingtin from normal (Hdh(7Q/7Q)) mouse brain and mutant huntingtin from Huntington's disease (Hdh(140Q/140Q)) mouse brain bound to large unilamellar vesicles containing phosphoinositol (PI) PI 3,4-bisphosphate, PI 3,5-bisphosphate, and PI 3,4,5-triphosphate [PI(3,4,5)P3]. Huntingtin interactions with multivalent phospholipids were similar to those of dynamin. Mutant huntingtin associated more with phosphatidylethanolamine and PI(3,4,5)P3 than did wild-type huntingtin, and associated with other phospholipids not recognized by wild-type huntingtin. Wild-type and mutant huntingtin also bound to large unilamellar vesicles containing cardiolipin, a phospholipid specific to mitochondrial membranes. Maximal huntingtin-phospholipid association required inclusion of huntingtin amino acids 171-287. Endogenous huntingtin recruited to the plasma membrane in cells that incorporated exogenous PI 3,4-bisphosphate and PI(3,4,5)P3 or were stimulated by platelet-derived growth factor or insulin growth factor 1, which both activate PI 3-kinase. These data suggest that huntingtin interacts with membranes through specific phospholipid associations and that mutant huntingtin may disrupt membrane trafficking and signaling at membranes.