Severe neurodegeneration in brains of transgenic rats producing human tau prions.

Both wild-type and mutant tau proteins can misfold into prions and self-propagate in the central nervous system of animals and people. To extend the work of others, we investigated the molecular basis of tau prion-mediated neurodegeneration in transgenic (Tg) rats expressing mutant human tau (P301S); this line of Tg rats is denoted Tg12099. We used the rat Prnp promoter to drive the overexpression of mutant tau (P301S) in the human 0N4R isoform.

Therapeutic Trial of anle138b in Mouse Models of Genetic Prion Disease.

Phenotypic screening has yielded small-molecule inhibitors of prion replication that are effective against certain prion strains but not others. Here, we sought to test the small molecule anle138b in multiple mouse models of prion disease. In mice inoculated with the RML strain of prions, anle138b doubled survival and durably suppressed astrogliosis measured by live-animal bioluminescence imaging.

Fibril treatment changes protein interactions of tau and α-synuclein in human neurons.

In several neurodegenerative disorders, the neuronal proteins tau and α-synuclein adopt aggregation-prone conformations capable of replicating within and between cells. To better understand how these conformational changes drive neuropathology, we compared the interactomes of tau and α-synuclein in the presence or the absence of recombinant fibril seeds. Human embryonic stem cells with an inducible neurogenin-2 transgene were differentiated into glutamatergic neurons expressing (1) WT 0N4R tau, (2) mutant (P301L) 0N4R tau, (3) WT α-synuclein, or (4) mutant (A53T) α-synuclein, each genetically fused to a promiscuous biotin ligase (BioID2).

How an Infection of Sheep Revealed Prion Mechanisms in Alzheimer's Disease and Other Neurodegenerative Disorders.

Although it is not yet universally accepted that all neurodegenerative diseases (NDs) are prion disorders, there is little disagreement that Alzheimer's disease (AD), Parkinson's disease, frontotemporal dementia (FTD), and other NDs are a consequence of protein misfolding, aggregation, and spread. This widely accepted perspective arose from the prion hypothesis, which resulted from investigations on scrapie, a common transmissible disease of sheep and goats. The prion hypothesis argued that the causative infectious agent of scrapie was a novel proteinaceous pathogen devoid of functional nucleic acids and distinct from viruses, viroids, and bacteria.

Tau aggregates are RNA-protein assemblies that mislocalize multiple nuclear speckle components.

Tau aggregates contribute to neurodegenerative diseases, including frontotemporal dementia and Alzheimer's disease (AD). Although RNA promotes tau aggregation in vitro, whether tau aggregates in cells contain RNA is unknown. We demonstrate, in cell culture and mouse brains, that cytosolic and nuclear tau aggregates contain RNA with enrichment for small nuclear RNAs (snRNAs) and small nucleolar RNAs (snoRNAs).

Prion protein lowering is a disease-modifying therapy across prion disease stages, strains and endpoints.

Lowering of prion protein (PrP) expression in the brain is a genetically validated therapeutic hypothesis in prion disease. We recently showed that antisense oligonucleotide (ASO)-mediated PrP suppression extends survival and delays disease onset in intracerebrally prion-infected mice in both prophylactic and delayed dosing paradigms. Here, we examine the efficacy of this therapeutic approach across diverse paradigms, varying the dose and dosing regimen, prion strain, treatment timepoint, and examining symptomatic, survival, and biomarker readouts.

Core transcriptional regulatory circuits in prion diseases.

Complex diseases involve dynamic perturbations of pathophysiological processes during disease progression. Transcriptional programs underlying such perturbations are unknown in many diseases. Here, we present core transcriptional regulatory circuits underlying early and late perturbations in prion disease.

Replication of multiple system atrophy prions in primary astrocyte cultures from transgenic mice expressing human α-synuclein.

Glial cytoplasmic inclusions (GCIs) containing aggregated and hyperphosphorylated α-synuclein are the signature neuropathological hallmark of multiple system atrophy (MSA). Native α-synuclein can adopt a prion conformation that self-propagates and spreads throughout the brain ultimately resulting in neurodegeneration. A growing body of evidence argues that, in addition to oligodendrocytes, astrocytes contain α-synuclein inclusions in MSA and other α-synucleinopathies at advanced stages of disease.

Tau impairs neural circuits, dominating amyloid-β effects, in Alzheimer models in vivo.

The coexistence of amyloid-β (Aβ) plaques and tau neurofibrillary tangles in the neocortex is linked to neural system failure and cognitive decline in Alzheimer's disease. However, the underlying neuronal mechanisms are unknown. By employing in vivo two-photon Ca imaging of layer 2/3 cortical neurons in mice expressing human Aβ and tau, we reveal a dramatic tau-dependent suppression of activity and silencing of many neurons, which dominates over Aβ-dependent neuronal hyperactivity.

Tau reduction in the presence of amyloid-β prevents tau pathology and neuronal death in vivo.

Several studies have now supported the use of a tau lowering agent as a possible therapy in the treatment of tauopathy disorders, including Alzheimer's disease. In human Alzheimer's disease, however, concurrent amyloid-β deposition appears to synergize and accelerate tau pathological changes. Thus far, tau reduction strategies that have been tested in vivo have been examined in the setting of tau pathology without confounding amyloid-β deposition.

Evidence for sortilin modulating regional accumulation of human tau prions in transgenic mice.

Misfolding of tau proteins into prions and their propagation along neural circuits are thought to result in neurodegeneration causing Alzheimer's disease, progressive supranuclear palsy, chronic traumatic encephalopathy, and other tauopathies. Little is known about the molecular processes mediating tau prion replication and spreading in different brain regions. Using transgenic (Tg) mice with a neuronal promoter driving expression of human mutant (P301S) tau, we found that tau prion formation and histopathologic deposition is largely restricted to the hindbrain.

A novel vector for transgenesis in the rat CNS.

The larger brain of the rat enables a much greater repertoire of complex behaviors than mice, likely making rats preferential for investigating neurodegeneration. Because molecular tools for specific expression of transgenes in the rat brain are sparse, we chose Prnp encoding the prion protein (PrP) to develop a novel vector to drive transgene expression in the rat brain. We compared the rat Prnp sequence with mouse and Syrian hamster Prnp sequences, identifying conserved genetic elements and hypothesizing that these elements would be able to drive neuronal transgene expression.

Prion Protein and Genetic Susceptibility to Diseases Caused by Its Misfolding.

Early genetic studies on scrapie, an infectious neurodegenerative disease of sheep that was adapted to mice, provided evidence in support of the hypothesis that the agent was a slow virus with a nucleic acid genome independent of the host. Particularly compelling support for an independent genome came from the existence of strains of scrapie agent, some of which were true breeding, while others appeared to mutate under selective pressure. Kuru, a neurodegenerative disease in the remote highlands of Papua New Guinea, had pathological changes similar to those in scrapie and also proved to be transmissible.

Brain Perivascular Macrophages Initiate the Neurovascular Dysfunction of Alzheimer Aβ Peptides.

Rationale: Increasing evidence indicates that alterations of the cerebral microcirculation may play a role in Alzheimer disease, the leading cause of late-life dementia. The amyloid-β peptide (Aβ), a key pathogenic factor in Alzheimer disease, induces profound alterations in neurovascular regulation through the innate immunity receptor CD36 (cluster of differentiation 36), which, in turn, activates a Nox2-containing NADPH oxidase, leading to cerebrovascular oxidative stress. Brain perivascular macrophages (PVM) located in the perivascular space, a major site of brain Aβ collection and clearance, are juxtaposed to the wall of intracerebral resistance vessels and are a powerful source of reactive oxygen species.

Enhanced Tau Aggregation in the Presence of Amyloid β.

Amyloid plaques and neurofibrillary tangles co-occur in Alzheimer disease, but with different topological and temporal patterns. Whether these two lesions are independent or pathobiologically related is uncertain. For example, amyloid deposition in the neocortex precedes the spread of tau neurofibrillary tangles from the limbic areas to the cortex.

Tau Antibody Targeting Pathological Species Blocks Neuronal Uptake and Interneuron Propagation of Tau in Vitro.

The clinical progression of Alzheimer disease (AD) is associated with the accumulation of tau neurofibrillary tangles, which may spread throughout the cortex by interneuronal tau transfer. If so, targeting extracellular tau species may slow the spreading of tau pathology and possibly cognitive decline. To identify suitable target epitopes, we tested the effects of a panel of tau antibodies on neuronal uptake and aggregation in vitro.

Spread of tau down neural circuits precedes synapse and neuronal loss in the rTgTauEC mouse model of early Alzheimer's disease.

Synaptic dysfunction and loss is the strongest pathological correlate of cognitive decline in Alzheimer's disease (AD) with increasing evidence implicating neuropathological tau protein in this process. Despite the knowledge that tau spreads through defined synaptic circuits, it is currently unknown whether synapse loss occurs before the accumulation of tau or as a consequence. To address this, we have used array tomography to examine an rTgTauEC mouse model expressing a P301L human tau transgene and a transgene labeling cytoplasm red (tdTomato) and presynaptic terminals green (Synaptophysin-EGFP).

Neurodegenerative Disease Transmission and Transgenesis in Mice.

Although the discovery of the prion protein (PrP) resulted from its co-purification with scrapie infectivity in Syrian hamsters, work with genetically defined and genetically modified mice proved crucial for understanding the fundamental processes involved not only in prion diseases caused by PrP misfolding, aggregation, and spread but also in other, much more common, neurodegenerative brain diseases. In this review, we focus on methodological and conceptual approaches used to study scrapie and related PrP misfolding diseases in mice and how these approaches have advanced our understanding of related disorders including Alzheimer's and Parkinson's disease.

The familial dysautonomia disease gene is required in the developing and adult mouse central nervous system.

Hereditary sensory and autonomic neuropathies (HSANs) are a genetically and clinically diverse group of disorders defined by peripheral nervous system (PNS) dysfunction. HSAN type III, known as familial dysautonomia (FD), results from a single base mutation in the gene that encodes a scaffolding unit (ELP1) for a multi-subunit complex known as Elongator. Since mutations in other Elongator subunits (ELP2 to ELP4) are associated with central nervous system (CNS) disorders, the goal of this study was to investigate a potential requirement for in the CNS of mice The sensory and autonomic pathophysiology of FD is fatal, with the majority of patients dying by age 40.

Postnatal Hyperplasic Effects of ActRIIB Blockade in a Severely Dystrophic Muscle.

The efficacy of two ActRIIB ligand-trapping agents (RAP-031 and RAP-435) in treating muscular dystrophy was examined by determining their morphological effects on the severely dystrophic triangularis sterni (TS) muscle of the mdx mouse, a model for Duchenne muscular dystrophy. These agents trap all endogenous ligands to the ActRIIB receptor and thereby block myostatin signaling in a highly selective manner. Short-term (1 month) and long-term (3 months) in vivo treatment of 1-month-old mdx mice increased myonuclei and fiber cross section (FCS) density but did not alter individual fiber size.

Reduction of ciliary length through pharmacologic or genetic inhibition of CDK5 attenuates polycystic kidney disease in a model of nephronophthisis.

Polycystic kidney diseases (PKDs) comprise a subgroup of ciliopathies characterized by the formation of fluid-filled kidney cysts and progression to end-stage renal disease. A mechanistic understanding of cystogenesis is crucial for the development of viable therapeutic options. Here, we identify CDK5, a kinase active in post mitotic cells, as a new and important mediator of PKD progression.

Human tau increases amyloid β plaque size but not amyloid β-mediated synapse loss in a novel mouse model of Alzheimer's disease.

Alzheimer's disease is characterized by the presence of aggregates of amyloid beta (Aβ) in senile plaques and tau in neurofibrillary tangles, as well as marked neuron and synapse loss. Of these pathological changes, synapse loss correlates most strongly with cognitive decline. Synapse loss occurs prominently around plaques due to accumulations of oligomeric Aβ.

Stabilizing the Hsp70-Tau Complex Promotes Turnover in Models of Tauopathy.

Heat shock protein 70 (Hsp70) is a chaperone that normally scans the proteome and initiates the turnover of some proteins (termed clients) by linking them to the degradation pathways. This activity is critical to normal protein homeostasis, yet it appears to fail in diseases associated with abnormal protein accumulation. It is not clear why Hsp70 promotes client degradation under some conditions, while sparing that protein under others.

Improvement of ENU Mutagenesis Efficiency Using Serial Injection and Mismatch Repair Deficiency Mice.

ENU mutagenesis is a powerful method for generating novel lines of mice that are informative with respect to both fundamental biological processes and human disease. Rapid developments in genomic technology have made the task of identifying causal mutations by positional cloning remarkably efficient. One limitation of this approach remains the mutation frequency achievable using standard treatment protocols, which currently generate approximately 1-2 sequence changes per megabase when optimized.