Preclinical characterization and IND-enabling safety studies for PNT001, an antibody that recognizes cis-pT231 tau

BACKGROUND

The cis-conformer of tau phosphorylated at threonine-231 (cis-pT231 tau) is hypothesized to contribute to tauopathies. PNT001 is a humanized, monoclonal antibody that recognizes cis-pT231 tau. PNT001 was characterized to assess clinical development readiness.

METHODS

Affinity and selectivity were assessed by surface plasmon resonance and enzyme-linked immunosorbent assay. Immunohistochemistry (IHC) was performed with brain sections from human tauopathy patients and controls. Real-time quaking-induced conversion (RT-QuIC) was used to assess whether PNT001 reduced tau seeds from Tg4510 transgenic mouse brain. Murine PNT001 was evaluated in vivo in the Tg4510 mouse.

RESULTS

The affinity of PNT001 for a cis-pT231 peptide was 0.3 to 3 nM. IHC revealed neurofibrillary tangle-like structures in tauopathy patients with no detectable staining in controls. Incubation of Tg4510 brain homogenates with PNT001 lowered seeding in RT-QuIC. Multiple endpoints were improved in the Tg4510 mouse. No adverse findings attributable to PNT001 were detected in Good Laboratory Practice safety studies.

DISCUSSION

The data support clinical development of PNT001 in human tauopathies.

Neuronal Ndst1 depletion accelerates prion protein clearance and slows neurodegeneration in prion infection

Select prion diseases are characterized by widespread cerebral plaque-like deposits of amyloid fibrils enriched in heparan sulfate (HS), a abundant extracellular matrix component. HS facilitates fibril formation in vitro, yet how HS impacts fibrillar plaque growth within the brain is unclear. Here we found that prion-bound HS chains are highly sulfated, and that the sulfation is essential for accelerating prion conversion in vitro. Using conditional knockout mice to deplete the HS sulfation enzyme, Ndst1 (N-deacetylase / N-sulfotransferase) from neurons or astrocytes, we investigated how reducing HS sulfation impacts survival and prion aggregate distribution during a prion infection. Neuronal Ndst1-depleted mice survived longer and showed fewer and smaller parenchymal plaques, shorter fibrils, and increased vascular amyloid, consistent with enhanced aggregate transit toward perivascular drainage channels. The prolonged survival was strain-dependent, affecting mice infected with extracellular, plaque-forming, but not membrane bound, prions. Live PET imaging revealed rapid clearance of recombinant prion protein monomers into the CSF of neuronal Ndst1- deficient mice, neuronal, further suggesting that HS sulfate groups hinder transit of extracellular prion protein monomers. Our results directly show how a host cofactor slows the spread of prion protein through the extracellular space and identify an enzyme to target to facilitate aggregate clearance.

Tau seeds occur before earliest Alzheimer's changes and are prevalent across neurodegenerative diseases

Tau neurofibrillary tangles are a hallmark of Alzheimer's disease neuropathological change. However, it remains largely unclear how distinctive Alzheimer's disease tau seeds (i.e. 3R/4R) correlate with histological indicators of tau accumulation. Furthermore, AD tau co-pathology is thought to influence features and progression of other neurodegenerative diseases including Lewy body disease; yet measurements of different types of tau seeds in the setting of such diseases is an unmet need. Here, we use tau real-time quaking-induced conversion (RT-QuIC) assays to selectively quantitate 3R/4R tau seeds in the frontal lobe which accumulates histologically identifiable tau pathology at late disease stages of AD neuropathologic change. Seed quantitation across a spectrum of neurodegenerative disease cases and controls indicated tau seeding activity can be detected well before accompanying histopathological indication of tau deposits, and even prior to the earliest evidence of Alzheimer's-related tau accumulation anywhere in the brain. In later stages of AD, 3R/4R tau RT-QuIC measures correlated with immunohistochemical tau burden. In addition, Alzheimer's tau seeds occur in the vast majority of cases evaluated here inclusive of primary synucleinopathies, frontotemporal lobar degeneration and even controls albeit at multi-log lower levels than Alzheimer's cases. α-synuclein seeding activity confirmed synucleinopathy cases and further indicated the co-occurrence of α-synuclein seeds in some Alzheimer's disease and primary tauopathy cases. Our analysis indicates that 3R/4R tau seeds in the mid-frontal lobe correlate with the overall Braak stage and Alzheimer's disease neuropathologic change, supporting the quantitative predictive value of tau RT-QuIC assays. Our data also indicate 3R/4R tau seeds are elevated in females compared to males at high (≥ IV) Braak stages. This study suggests 3R/4R tau seeds are widespread even prior to the earliest stages of Alzheimer's disease changes, including in normal, and even young individuals, with prevalence across multiple neurodegenerative diseases to further define disease subtypes.

Cryo-EM of prion strains from the same genotype of host identifies conformational determinants

Prion strains in a given type of mammalian host are distinguished by differences in clinical presentation, neuropathological lesions, survival time, and characteristics of the infecting prion protein (PrP) assemblies. Near-atomic structures of prions from two host species with different PrP sequences have been determined but comparisons of distinct prion strains of the same amino acid sequence are needed to identify purely conformational determinants of prion strain characteristics. Here we report a 3.2 Å resolution cryogenic electron microscopy-based structure of the 22L prion strain purified from the brains of mice engineered to express only PrP lacking glycophosphatidylinositol anchors [anchorless (a) 22L]. Comparison of this near-atomic structure to our recently determined structure of the aRML strain propagated in the same inbred mouse reveals that these two mouse prion strains have distinct conformational templates for growth via incorporation of PrP molecules of the same sequence. Both a22L and aRML are assembled as stacks of PrP molecules forming parallel in-register intermolecular β-sheets and intervening loops, with single monomers spanning the ordered fibril core. Each monomer shares an N-terminal steric zipper, three major arches, and an overall V-shape, but the details of these and other conformational features differ markedly. Thus, variations in shared conformational motifs within a parallel in-register β-stack fibril architecture provide a structural basis for prion strain differentiation within a single host genotype.

Prions are protein-based pathogens that can spread within and between hosts without carrying a pathogen-specific nucleic acid genome. Given this protein-based propagation mechanism, a long-standing mystery in the prion disease field has been the molecular basis of distinct, faithfully propagating strains in a single type of mammalian host. Here we provide a direct, high-resolution cryo-EM-based comparison of the structures of two highly infectious prion strains isolated from the brains of mice of a single genotype. We show in detail how these two prion strains are protein filaments of mouse PrP molecules that display distinct conformational templates for growth on their tips. Our results identify purely conformational, rather than sequence-based, underpinnings of infectious and deadly prion strains.

Structural biology of ex vivo mammalian prions

The structures of prion protein (PrP)–based mammalian prions have long been elusive. However, cryo-EM has begun to reveal the near-atomic resolution structures of fully infectious ex vivo mammalian prion fibrils as well as relatively innocuous synthetic PrP amyloids. Comparisons of these various types of PrP fibrils are now providing initial clues to structural features that correlate with pathogenicity. As first indicated by electron paramagnetic resonance and solid-state NMR studies of synthetic amyloids, all sufficiently resolved PrP fibrils of any sort (n > 10) have parallel in-register intermolecular β-stack architectures. Cryo-EM has shown that infectious brain-derived prion fibrils of the rodent-adapted 263K and RML scrapie strains have much larger ordered cores than the synthetic fibrils. These bona fide prion strains share major structural motifs, but the conformational details and the overall shape of the fibril cross sections differ markedly. Such motif variations, as well as differences in sequence within the ordered polypeptide cores, likely contribute to strain-dependent templating. When present, N-linked glycans and glycophosphatidylinositol (GPI) anchors project outward from the fibril surface. For the mouse RML strain, these posttranslational modifications have little effect on the core structure. In the GPI-anchored prion structures, a linear array of GPI anchors along the twisting fibril axis appears likely to bind membranes in vivo, and as such, may account for pathognomonic membrane distortions seen in prion diseases. In this review, we focus on these infectious prion structures and their implications regarding prion replication mechanisms, strains, transmission barriers, and molecular pathogenesis.

Seed amplification and RT-QuIC assays to investigate protein seed structures and strains

The accumulation of misfolded proteins as amyloid fibrils in the brain is characteristic of most neurodegenerative disorders. These misfolded proteins are capable of self-amplifying through protein seeding mechanisms, leading to accumulation in the host. First shown for PrP prions and prion diseases, it is now recognized that self-propagating misfolded proteins occur broadly in neurodegenerative diseases and include amyloid-β (Aβ) and tau in Alzheimer's disease (AD), tau in chronic traumatic encephalopathy (CTE), Pick's disease (PiD), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP), and α-synuclein (α-syn) in Parkinson's disease (PD) and Lewy body dementias (LBD). Techniques able to directly measure these bioactive protein seeds include the real-time quaking-induced conversion (RT-QuIC) assays. Initially developed for the detection of PrP prions and subsequently for the detection of other misfolded protein seeds, these assays take advantage of the mechanism of protein-based self-propagation to result in exponential amplification of the initial protein seeds from biospecimens. Disease-specific "protein seeds" recruit and template the misfolding of native recombinant protein substrates to elongate amyloid fibrils. The amplification power of these assays allows for detection of minute amounts of disease-specific protein seeds to better support early and accurate diagnosis. In addition to the diagnostic capabilities, assay readouts have been shown to reveal biochemical, structural, and kinetic information of protein seed self-propagation. This review examines the various protein seed amplification assays currently available for distinct neurodegenerative diseases, with a focus on RT-QuIC assays, along with the insights their readouts provide into protein seed structures and strain differences.

Reducing acetylated tau is neuroprotective in brain injury

Traumatic brain injury (TBI) is the largest non-genetic, non-aging related risk factor for Alzheimer's disease (AD). We report here that TBI induces tau acetylation (ac-tau) at sites acetylated also in human AD brain. This is mediated by S-nitrosylated-GAPDH, which simultaneously inactivates Sirtuin1 deacetylase and activates p300/CBP acetyltransferase, increasing neuronal ac-tau. Subsequent tau mislocalization causes neurodegeneration and neurobehavioral impairment, and ac-tau accumulates in the blood. Blocking GAPDH S-nitrosylation, inhibiting p300/CBP, or stimulating Sirtuin1 all protect mice from neurodegeneration, neurobehavioral impairment, and blood and brain accumulation of ac-tau after TBI. Ac-tau is thus a therapeutic target and potential blood biomarker of TBI that may represent pathologic convergence between TBI and AD. Increased ac-tau in human AD brain is further augmented in AD patients with history of TBI, and patients receiving the p300/CBP inhibitors salsalate or diflunisal exhibit decreased incidence of AD and clinically diagnosed TBI.

The Fabp5/calnexin complex is a prerequisite for sensitization of mice to experimental autoimmune encephalomyelitis

We previously showed that calnexin (Canx)-deficient mice are desensitized to experimental autoimmune encephalomyelitis (EAE) induction, a model that is frequently used to study inflammatory demyelinating diseases, due to increased resistance of the blood-brain barrier to immune cell transmigration. We also discovered that Fabp5, an abundant cytoplasmic lipid-binding protein found in brain endothelial cells, makes protein-protein contact with the cytoplasmic C-tail domain of Canx. Remarkably, both Canx-deficient and Fabp5-deficient mice commonly manifest resistance to EAE induction. Here, we evaluated the importance of Fabp5/Canx interactions on EAE pathogenesis and on the patency of a model blood-brain barrier to T-cell transcellular migration. The results demonstrate that formation of a complex comprised of Fabp5 and the C-tail domain of Canx dictates the permeability of the model blood-brain barrier to immune cells and is also a prerequisite for EAE pathogenesis.

Parameter estimation for discretely observed linear birth-and-death processes

Birth-and-death processes are widely used to model the development of biological populations. Although they are relatively simple models, their parameters can be challenging to estimate, as the likelihood can become numerically unstable when data arise from the most common sampling schemes, such as annual population censuses. A further difficulty arises when the discrete observations are not equi-spaced, for example, when census data are unavailable for some years. We present two approaches to estimating the birth, death, and growth rates of a discretely observed linear birth-and-death process: via an embedded Galton-Watson process and by maximizing a saddlepoint approximation to the likelihood. We study asymptotic properties of the estimators, compare them on numerical examples, and apply the methodology to data on monitored populations.

A single ultrasensitive assay for detection and discrimination of tau aggregates of Alzheimer and Pick diseases

Multiple neurodegenerative diseases are characterized by aggregation of tau molecules. Adult humans express six isoforms of tau that contain either 3 or 4 microtubule binding repeats (3R or 4R tau). Different diseases involve preferential aggregation of 3R (e.g Pick disease), 4R (e.g. progressive supranuclear palsy), or both 3R and 4R tau molecules [e.g. Alzheimer disease and chronic traumatic encephalopathy]. Three ultrasensitive cell-free seed amplification assays [called tau real-time quaking induced conversion (tau RT-QuIC) assays] have been developed that preferentially detect 3R, 4R, or 3R/4R tau aggregates in biospecimens. In these reactions, low-fg amounts of a given self-propagating protein aggregate (the seed) are incubated with a vast excess of recombinant tau monomers (the substrate) in multi-well plates. Over time, the seeds incorporate the substrate to grow into amyloids that can then be detected using thioflavin T fluorescence. Here we describe a tau RT-QuIC assay (K12 RT-QuIC) that, using a C-terminally extended recombinant 3R tau substrate (K12CFh), enables sensitive detection of Pick disease, Alzheimer disease, and chronic traumatic encephalopathy seeds in brain homogenates. The discrimination of Pick disease from Alzheimer disease and chronic traumatic encephalopathy cases is then achieved through the quantitative differences in K12 RT-QuIC assay thioflavin T responses, which correlate with structural properties of the reaction products. In particular, Fourier transform infrared spectroscopy analysis of the respective K12CFh amyloids showed distinct β-sheet conformations, suggesting at least partial propagation of the original seed conformations in vitro. Thus, K12 RT-QuIC provides a single assay for ultrasensitive detection and discrimination of tau aggregates comprised mainly of 3R, or both 3R and 4R, tau isoforms.

Short-term effects of simulated microgravity on morphology and gene expression in human breast cancer cells

Introduction

Microgravity has been shown to impose various effects on breast cancer cells. We exposed human breast cancer cells to simulated microgravity and studied morphology and alterations in gene expression.

Materials and methods

Human breast cancer cells were exposed to simulated microgravity in a random positioning machine (RPM) for 24 h. Morphology was observed under light microscopy, and gene alteration was studied by qPCR.

Results

After 24 h, formation of three-dimensional structures (spheroids) occurred. BRCA1 expression was significantly increased (1.9×, p < 0.05) in the adherent cells under simulated microgravity compared to the control. Expression of KRAS was significantly decreased (0.6×, p < 0.05) in the adherent cells compared to the control. VCAM1 was significantly upregulated (6.6×, 2.0×, p < 0.05 each) in the adherent cells under simulated microgravity and in the spheroids. VIM expression was significantly downregulated (0.45×, 0.44×, p < 0.05 each) in the adherent cells under simulated microgravity and in the spheroids. There was no significant alteration in the expression of MAPK1, MMP13, PTEN, and TP53.

Conclusions

Simulated microgravity induces spheroid formation in human breast cancer cells within 24 h and alters gene expression toward modified adhesion properties, enhanced cell repair, and phenotype preservation. Further insights into the underlying mechanisms could open up the way toward new therapies.

Correction to: 4-Repeat tau seeds and templating subtypes as brain and CSF biomarkers of frontotemporal lobar degeneration

The original version of this article unfortunately contained a mistake. The Panel A in the published figure 5 is incorrect. The corrected Figure 5 is placed in the following page.

4-Repeat tau seeds and templating subtypes as brain and CSF biomarkers of frontotemporal lobar degeneration

To address the need for more meaningful biomarkers of tauopathies, we have developed an ultrasensitive tau seed amplification assay (4R RT-QuIC) for the 4-repeat (4R) tau aggregates of progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and other diseases with 4R tauopathy. The assay detected seeds in 106-109-fold dilutions of 4R tauopathy brain tissue but was orders of magnitude less responsive to brain with other types of tauopathy, such as from Alzheimer's disease cases. The analytical sensitivity for synthetic 4R tau fibrils was ~ 50 fM or 2 fg/sample. A novel dimension of this tau RT-QuIC testing was the identification of three disease-associated classes of 4R tau seeds; these classes were revealed by conformational variations in the in vitro amplified tau fibrils as detected by thioflavin T fluorescence amplitudes and FTIR spectroscopy. Tau seeds were detected in postmortem cerebrospinal fluid (CSF) from all neuropathologically confirmed PSP and CBD cases but not in controls. CSF from living subjects had weaker seeding activities; however, mean assay responses for cases clinically diagnosed as PSP and CBD/corticobasal syndrome were significantly higher than those from control cases. Altogether, 4R RT-QuIC provides a practical cell-free method of detecting and subtyping pathologic 4R tau aggregates as biomarkers.

Short-term effects of simulated microgravity on morphology and gene expression in human breast cancer cells

INTRODUCTION

Microgravity has been shown to impose various effects on breast cancer cells. We exposed human breast cancer cells to simulated microgravity and studied morphology and alterations in gene expression.

MATERIALS AND METHODS

Human breast cancer cells were exposed to simulated microgravity in a random positioning machine (RPM) for 24 h. Morphology was observed under light microscopy, and gene alteration was studied by qPCR.

RESULTS

After 24 h, formation of three-dimensional structures (spheroids) occurred. BRCA1 expression was significantly increased (1.9×, p < 0.05) in the adherent cells under simulated microgravity compared to the control. Expression of KRAS was significantly decreased (0.6×, p < 0.05) in the adherent cells compared to the control. VCAM1 was significantly upregulated (6.6×, 2.0×, p < 0.05 each) in the adherent cells under simulated microgravity and in the spheroids. VIM expression was significantly downregulated (0.45×, 0.44×, p < 0.05 each) in the adherent cells under simulated microgravity and in the spheroids. There was no significant alteration in the expression of MAPK1, MMP13, PTEN, and TP53.

CONCLUSIONS

Simulated microgravity induces spheroid formation in human breast cancer cells within 24 h and alters gene expression toward modified adhesion properties, enhanced cell repair, and phenotype preservation. Further insights into the underlying mechanisms could open up the way toward new therapies.

Million-fold sensitivity enhancement in proteopathic seed amplification assays for biospecimens by Hofmeister ion comparisons

Recent work with prion diseases and synucleinopathies indicates that accurate diagnostic methods for protein-folding diseases can be based on the ultrasensitive, amplified measurement of pathological aggregates in biospecimens. A better understanding of the physicochemical factors that control the seeded polymerization of such aggregates, and their amplification in vitro, should allow improvements in existing assay platforms, as well as the development of new assays for other proteopathic aggregates. Here, we systematically investigated the effects of the ionic environment on the polymerization of tau, α-synuclein, and the prion protein (PrP) induced by aggregates in biospecimens. We screened salts of the Hofmeister series, a relative ordering of strongly and weakly hydrated salts that tend to precipitate or solubilize proteins. We found that sensitivities of tau-based assays for Alzheimer's seeds and PrP-based assays for prions were best in weakly hydrated anions. In contrast, we saw an inverse trend with different tau-based assays, improving detection sensitivity for progressive supranuclear palsy seeds by ≈106 Hofmeister analysis also improved detection of sporadic Creutzfeldt-Jakob disease prions in human nasal brushings and chronic wasting disease prions in deer-ear homogenates. Our results demonstrate strong and divergent influences of ionic environments on the amplification and detection of proteopathic seeds as biomarkers for protein-folding diseases.

Transmissibility versus Pathogenicity of Self-Propagating Protein Aggregates

The prion-like spreading and accumulation of specific protein aggregates appear to be central to the pathogenesis of many human diseases, including Alzheimer's and Parkinson's. Accumulating evidence indicates that inoculation of tissue extracts from diseased individuals into suitable experimental animals can in many cases induce the aggregation of the disease-associated protein, as well as related pathological lesions. These findings, together with the history of the prion field, have raised the questions about whether such disease-associated protein aggregates are transmissible between humans by casual or iatrogenic routes, and, if so, do they propagate enough in the new host to cause disease? These practical considerations are important because real, and perhaps even only imagined, risks of human-to-human transmission of diseases such as Alzheimer's and Parkinson's may force costly changes in clinical practice that, in turn, are likely to have unintended consequences. The prion field has taught us that a single protein, PrP, can aggregate into forms that can propagate exponentially in vitro, but range from being innocuous to deadly when injected into experimental animals in ways that depend strongly on factors such as conformational subtleties, routes of inoculation, and host responses. In assessing the hazards posed by various disease-associated, self-propagating protein aggregates, it is imperative to consider both their actual transmissibilities and the pathological consequences of their propagation, if any, in recipient hosts.

Antisense oligonucleotides extend survival of prion-infected mice

Prion disease is a fatal, incurable neurodegenerative disease of humans and other mammals caused by conversion of cellular prion protein (PrP^C) into a self-propagating neurotoxic conformer (prions; PrP^Sc). Strong genetic proofs of concept support lowering PrP expression as a therapeutic strategy. Antisense oligonucleotides (ASOs) can provide a practical route to lowering 1 target mRNA in the brain, but their development for prion disease has been hindered by 3 unresolved issues from prior work: uncertainty about mechanism of action, unclear potential for efficacy against established prion infection, and poor tolerability of drug delivery by osmotic pumps. Here, we test ASOs delivered by bolus intracerebroventricular injection to intracerebrally prion-infected WT mice. Prophylactic treatments given every 2–3 months extended survival times 61%–98%, and a single injection at 120 days after infection, near the onset of clinical signs, extended survival 55% (87 days). In contrast, a nontargeting control ASO was ineffective. Thus, PrP lowering is the mechanism of action of ASOs effective against prion disease in vivo, and infrequent — or even single — bolus injections of ASOs can slow prion neuropathogenesis and markedly extend survival, even when initiated near clinical signs. These findings should empower development of PrP-lowering therapy for prion disease.

ASO-mediated prion protein suppression delays disease and extends survival, even in mice with established prion infection.

Seeding selectivity and ultrasensitive detection of tau aggregate conformers of Alzheimer disease

Alzheimer disease (AD) and chronic traumatic encephalopathy (CTE) involve the abnormal accumulation in the brain of filaments composed of both three-repeat (3R) and four-repeat (4R) (3R/4R) tau isoforms. To probe the molecular basis for AD's tau filament propagation and to improve detection of tau aggregates as potential biomarkers, we have exploited the seeded polymerization growth mechanism of tau filaments to develop a highly selective and ultrasensitive cell-free tau seed amplification assay optimized for AD (AD real-time quaking-induced conversion or AD RT-QuIC). The reaction is based on the ability of AD tau aggregates to seed the formation of amyloid fibrils made of certain recombinant tau fragments. AD RT-QuIC detected seeding activity in AD (n = 16) brains at dilutions as extreme as 10⁷-10¹⁰-fold, but was 10²-10⁶-fold less responsive when seeded with brain from most cases of other types of tauopathy with comparable loads of predominant 3R or 4R tau aggregates. For example, AD brains had average seeding activities that were orders of magnitude higher than Pick disease brains with predominant 3R tau deposits, but the opposite was true using our previously described Pick-optimized tau RT-QuIC assay. CTE brains (n = 2) had seed concentrations comparable to the weakest of the AD specimens, and higher than 3 of 4 specimens with 3R/4R primary age-related tauopathy. AD seeds shared properties with the tau filaments found in AD brains, as AD seeds were sarkosyl-insoluble, protease resistant, and reactive with tau antibodies. Moreover, AD RT-QuIC detected as little as 16 fg of pure synthetic tau fibrils. The distinctive seeding activity exhibited by AD and CTE tau filaments compared to other types of tauopathies in these seeded polymerization reactions provides a mechanistic basis for their consistent propagation as specific conformers in patients with 3R/4R tau diseases. Importantly, AD RT-QuIC also provides rapid ultrasensitive quantitation of 3R/4R tau-seeding activity as a biomarker.

Ultrasensitive RT-QuIC Seed Amplification Assays for Disease-Associated Tau, α-Synuclein, and Prion Aggregates

The abnormal assembly of tau, α-synuclein (αSyn), or prion protein into oligomers and multimers underpins the molecular pathogenesis of multiple neurodegenerative diseases. Such pathological aggregates can often grow by seeded polymerization mechanisms. We and others have taken advantage of these mechanisms to amplify seeding activities in vitro and devise ultrasensitive, specific and quantitative assays for these etiological biomarkers. Real-time quaking-induced conversion (RT-QuIC) assays are performed in multiwell plates with fluorescent readouts, facilitating efficient throughput. Prion RT-QuIC assays on cerebrospinal fluid (CSF) samples are being widely used for antemortem diagnosis of human prion diseases. Recently, we have also described a tau RT-QuIC prototype that has been optimized for Pick disease (with predominant 3R tau pathology) that detects 3R tau seeds in postmortem CSF, and brain tissue dilutions as extreme as a billion-fold. αSyn RT-QuIC prototypes have also been developed, providing ~92% diagnostic sensitivity and 100% specificity for Parkinson's disease and dementia with Lewy bodies using antemortem CSF. Here we provide detailed protocols for our 3R tau and αSyn RT-QuIC assays and refer the reader to published up-to-date protocols for prion RT-QuIC assays (Orru et al. Methods Mol Biol 1658:185-203, 2017; Schmitz et al. Nat Protoc 11:2233-2242, 2016).

Calnexin is necessary for T cell transmigration into the central nervous system

In multiple sclerosis (MS), a demyelinating inflammatory disease of the CNS, and its animal model (experimental autoimmune encephalomyelitis; EAE), circulating immune cells gain access to the CNS across the blood-brain barrier to cause inflammation, myelin destruction, and neuronal damage. Here, we discovered that calnexin, an ER chaperone, is highly abundant in human brain endothelial cells of MS patients. Conversely, mice lacking calnexin exhibited resistance to EAE induction, no evidence of immune cell infiltration into the CNS, and no induction of inflammation markers within the CNS. Furthermore, calnexin deficiency in mice did not alter the development or function of the immune system. Instead, the loss of calnexin led to a defect in brain endothelial cell function that resulted in reduced T cell trafficking across the blood-brain barrier. These findings identify calnexin in brain endothelial cells as a potentially novel target for developing strategies aimed at managing or preventing the pathogenic cascade that drives neuroinflammation and destruction of the myelin sheath in MS.

Likely Transiting Exocomets Detected By Kepler

We present the first good evidence for exocomet transits of a host star in continuum light in data from the Kepler mission. The Kepler star in question, KIC 3542116, is of spectral type F2V and is quite bright at Kp = 10. The transits have a distinct asymmetric shape with a steeper ingress and slower egress that can be ascribed to objects with a trailing dust tail passing over the stellar disk. There are three deeper transits with depths of ≃ 0.1% that last for about a day, and three that are several times more shallow and of shorter duration. The transits were found via an exhaustive visual search of the entire Kepler photometric data set, which we describe in some detail. We review the methods we use to validate the Kepler data showing the comet transits, and rule out instrumental artefacts as sources of the signals. We fit the transits with a simple dust-tail model, and find that a transverse comet speed of ∼35-50 km s-1 and a minimum amount of dust present in the tail of ∼ 1016 g are required to explain the larger transits. For a dust replenishment time of ∼10 days, and a comet lifetime of only ∼300 days, this implies a total cometary mass of ≳ 3 × 1017 g, or about the mass of Halley's comet. We also discuss the number of comets and orbital geometry that would be necessary to explain the six transits detected over the four years of Kepler prime-field observations. Finally, we also report the discovery of a single comet-shaped transit in KIC 11084727 with very similar transit and host-star properties.

Phosphorylated human tau associates with mouse prion protein amyloid in scrapie-infected mice but does not increase progression of clinical disease

Tauopathies are a family of neurodegenerative diseases in which fibrils of human hyperphosphorylated tau (P-tau) are believed to cause neuropathology. In Alzheimer disease, P-tau associates with A-beta amyloid and contributes to disease pathogenesis. In familial human prion diseases and variant CJD, P-tau often co-associates with prion protein amyloid, and might also accelerate disease progression. To test this latter possibility, here we compared progression of amyloid prion disease in vivo after scrapie infection of mice with and without expression of human tau. The mice used expressed both anchorless prion protein (PrP) and membrane-anchored PrP, that generate disease associated amyloid and non-amyloid PrP (PrPSc) after scrapie infection. Human P-tau induced by scrapie infection was only rarely associated with non-amyloid PrPSc, but abundant human P-tau was detected at extracellular, perivascular and axonal deposits associated with amyloid PrPSc. This pathology was quite similar to that seen in familial prion diseases. However, association of human and mouse P-tau with amyloid PrPSc did not diminish survival time following prion infection in these mice. By analogy, human P-tau may not affect prion disease progression in humans. Alternatively, these results might be due to other factors, including rapidity of disease, blocking effects by mouse tau, or low toxicity of human P-tau in this model.

Amplified Detection of Prions and Other Amyloids by RT-QuIC in Diagnostics and the Evaluation of Therapeutics and Disinfectants

Among the most sensitive, specific and practical of methods for detecting prions are the real-time quaking-induced conversion (RT-QuIC) assays. These assays exploit the fundamental self-propagating activity of prions to amplify the presence of prion seeds by as much as a trillion-fold. The reactions can detect most of the known mammalian prion diseases, often with sensitivities greater than those of animal bioassays. RT-QuIC assays are performed in multiwell plates with fluorescence detection and have now reached the sensitivity and practicality required for routine prion disease diagnostics. Some key strains of prions within particular host species, e.g., humans, cattle, and sheep, can be discriminated by comparison of RT-QuIC responses with different recombinant prion protein substrates. The most thoroughly validated diagnostic application of RT-QuIC is in the diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) using cerebrospinal fluid. Diagnostic sensitivities as high as 96% can be achieved in less than 24h with specificities of 98%-100%. The ability, if needed, to also test nasal swab samples can increase the RT-QuIC sensitivity for sCJD to virtually 100%. In addition to diagnostic applications, RT-QuIC has also been used in the testing of prion disinfectants and potential therapeutics. Mechanistically related assays are also now being developed for other protein misfolding diseases.

Proline and lysine residues provide modulatory switches in amyloid formation: Insights from prion protein

Amyloidogenic proteins have an increased propensity to reorganize into the highly structured, β sheet rich structures that characterize amyloid. The probability of attaining these highly structured assemblies is influenced by multiple factors, including amino acid composition and environmental conditions. Evolutionary selection for amino acid sequences that prevent amyloid formation could further modulate amyloid-forming propensity. Indeed, we have recently identified specific proline and lysine residues, contained within a highly conserved central region of prion protein (PrP), that impede PrP amyloid formation in vitro. These prolines are mutated in certain forms of the human familial genetic disease, Gerstmann-Straüssler-Schneiker (GSS) syndrome. Here, I discuss the influence of these proline and lysine residues on PrP amyloid formation and how such anti-amyloidogenic primary amino acid sequences might be modulated to influence protein amyloidogenicity.

Endocrine Control of Exaggerated Trait Growth in Rhinoceros Beetles

Juvenile hormone (JH) is a key insect growth regulator frequently involved in modulating phenotypically plastic traits such as caste determination in eusocial species, wing polymorphisms in aphids, and mandible size in stag beetles. The jaw morphology of stag beetles is sexually-dimorphic and condition-dependent; males have larger jaws than females and those developing under optimum conditions are larger in overall body size and have disproportionately larger jaws than males raised under poor conditions. We have previously shown that large males have higher JH titers than small males during development, and ectopic application of fenoxycarb (JH analog) to small males can induce mandibular growth similar to that of larger males. What remains unknown is whether JH regulates condition-dependent trait growth in other insects with extreme sexually selected structures. In this study, we tested the hypothesis that JH mediates the condition-dependent expression of the elaborate horns of the Asian rhinoceros beetle, Trypoxylus dichotomus. The sexually dimorphic head horn of this beetle is sensitive to nutritional state during larval development. Like stag beetles, male rhinoceros beetles receiving copious food produce disproportionately large horns for their body size compared with males under restricted diets. We show that JH titers are correlated with body size during the late feeding and early prepupal periods, but this correlation disappears by the late prepupal period, the period of maximum horn growth. While ectopic application of fenoxycarb during the third larval instar significantly delayed pupation, it had no effect on adult horn size relative to body size. Fenoxycarb application to late prepupae also had at most a marginal effect on relative horn size. We discuss our results in context of other endocrine signals of condition-dependent trait exaggeration and suggest that different beetle lineages may have co-opted different physiological signaling mechanisms to achieve heightened nutrient-sensitive weapon growth.

Factors That Improve RT-QuIC Detection of Prion Seeding Activity

Rapid and sensitive detection of prions is important in managing prion diseases. The real-time quaking-induced conversion (RT-QuIC) assay for prion seeding activity has been applied to many prion diseases and provides for specific antemortem diagnostic testing. We evaluated RT-QuIC’s long-term consistency and varied multiple reaction parameters. Repeated assays of a single scrapie sample using multiple plate readers and recombinant prion protein (rPrP^Sen) substrates gave comparable results. N-terminal truncated hamster rPrP^Sen (residues 90–231) hastened both prion-seeded and prion-independent reactions but maintained a clear kinetic distinction between the two. Raising temperatures or shaking speeds accelerated RT-QuIC reactions without compromising specificity. When applied to nasal brushings from Creutzfeldt-Jakob disease patients, higher temperatures accelerated RT-QuIC kinetics, and the use of hamster rPrP^Sen (90–231) strengthened RT-QuIC responses. Elongation of shaking periods reduced scrapie-seeded reaction times, but continuous shaking promoted false-positive reactions. Furthermore, pH 7.4 provided for more rapid RT-QuIC reactions than more acidic pHs. Additionally, we show that small variations in the amount of sodium dodecyl sulfate (SDS) significantly impacted the assay. Finally, RT-QuIC performed in multiplate thermoshakers followed by fluorescence readings in separate plate readers enhanced assay throughput economically. Collectively, these results demonstrate improved speed, efficacy and practicality of RT-QuIC assays and highlight variables to be optimized for future applications.

Anoctamin 6 is localized in the primary cilium of renal tubular cells and is involved in apoptosis-dependent cyst lumen formation

Primary cilia are antenna-like structures projected from the apical surface of various mammalian cells including renal tubular cells. Functional or structural defects of the cilium lead to systemic disorders comprising polycystic kidneys as a key feature. Here we show that anoctamin 6 (ANO6), a member of the anoctamin chloride channel family, is localized in the primary cilium of renal epithelial cells in vitro and in vivo. ANO6 was not essential for cilia formation and had no effect on in vitro cyst expansion. However, knockdown of ANO6 impaired cyst lumen formation of MDCK cells in three-dimensional culture. In the absence of ANO6, apoptosis was reduced and epithelial cells were incompletely removed from the center of cell aggregates, which form in the early phase of cystogenesis. In line with these data, we show that ANO6 is highly expressed in apoptotic cyst epithelial cells of human polycystic kidneys. These data identify ANO6 as a cilium-associated protein and suggest its functional relevance in cyst formation.

Endoplasmic reticulum quality control and dysmyelination

Dysmyelination contributes to several human diseases including multiple sclerosis, Charcot-Marie-Tooth, leukodystrophies, and schizophrenia and can result in serious neurological disability. Properly formed, compacted myelin sheaths are required for appropriate nerve conduction velocities and the health and survival of neurons. Many different molecular mechanisms contribute to dysmyelination and many of these mechanisms originate at the level of the endoplasmic reticulum. The endoplasmic reticulum is a critical organelle for myelin biosynthesis and maintenance as the site of myelin protein folding quality control, Ca2+ homeostasis, cholesterol biosynthesis, and modulation of cellular stress. This review paper highlights the role of the endoplasmic reticulum and its resident molecules as an upstream and dynamic contributor to myelin and myelin pathologies.

Prion Protein Prolines 102 and 105 and the Surrounding Lysine Cluster Impede Amyloid Formation

Human prion diseases can have acquired, sporadic, or genetic origins, each of which results in the conversion of prion protein (PrP) to transmissible, pathological forms. The genetic prion disease Gerstmann-Straussler-Scheinker syndrome can arise from point mutations of prolines 102 or 105. However, the structural effects of these two prolines, and mutations thereof, on PrP misfolding are not well understood. Here, we provide evidence that individual mutations of Pro-102 or Pro-105 to noncyclic aliphatic residues such as the Gerstmann-Straussler-Scheinker-linked leucines can promote the in vitro formation of PrP amyloid with extended protease-resistant cores reminiscent of infectious prions. This effect was enhanced by additional charge-neutralizing mutations of four nearby lysine residues comprising the so-called central lysine cluster. Substitution of these proline and lysine residues accelerated PrP conversion such that spontaneous amyloid formation was no longer slower than scrapie-seeded amyloid formation. Thus, Pro-102 and Pro-105, as well as the lysines in the central lysine cluster, impede amyloid formation by PrP, implicating these residues as key structural modulators in the conversion of PrP to disease-associated types of amyloid.

Large-scale discovery of novel genetic causes of developmental disorders

Despite three decades of successful, predominantly phenotype-driven discovery of the genetic causes of monogenic disorders, up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis. Particularly challenging are those disorders rare enough to have eluded recognition as a discrete clinical entity, those with highly variable clinical manifestations, and those that are difficult to distinguish from other, very similar, disorders. Here we demonstrate the power of using an unbiased genotype-driven approach to identify subsets of patients with similar disorders. By studying 1,133 children with severe, undiagnosed developmental disorders, and their parents, using a combination of exome sequencing and array-based detection of chromosomal rearrangements, we discovered 12 novel genes associated with developmental disorders. These newly implicated genes increase by 10% (from 28% to 31%) the proportion of children that could be diagnosed. Clustering of missense mutations in six of these newly implicated genes suggests that normal development is being perturbed by an activating or dominant-negative mechanism. Our findings demonstrate the value of adopting a comprehensive strategy, both genome-wide and nationwide, to elucidate the underlying causes of rare genetic disorders.

UBC9-dependent association between calnexin and protein tyrosine phosphatase 1B (PTP1B) at the endoplasmic reticulum

Calnexin is a type I integral endoplasmic reticulum (ER) membrane protein, molecular chaperone, and a component of the translocon. We discovered a novel interaction between the calnexin cytoplasmic domain and UBC9, a SUMOylation E2 ligase, which modified the calnexin cytoplasmic domain by the addition of SUMO. We demonstrated that calnexin interaction with the SUMOylation machinery modulates an interaction with protein tyrosine phosphatase 1B (PTP1B), an ER-associated protein tyrosine phosphatase involved in the negative regulation of insulin and leptin signaling. We showed that calnexin and PTP1B form UBC9-dependent complexes, revealing a previously unrecognized contribution of calnexin to the retention of PTP1B at the ER membrane. This work shows that the SUMOylation machinery links two ER proteins from divergent pathways to potentially affect cellular protein quality control and energy metabolism.

Charge neutralization of the central lysine cluster in prion protein (PrP) promotes PrP(Sc)-like folding of recombinant PrP amyloids

The structure of the infectious form of prion protein, PrP(Sc), remains unclear. Most pure recombinant prion protein (PrP) amyloids generated in vitro are not infectious and lack the extent of the protease-resistant core and solvent exclusion of infectious PrP(Sc), especially within residues ∼90-160. Polyanionic cofactors can enhance infectivity and PrP(Sc)-like characteristics of such fibrils, but the mechanism of this enhancement is unknown. In considering structural models of PrP(Sc) multimers, we identified an obstacle to tight packing that might be overcome with polyanionic cofactors, namely, electrostatic repulsion between four closely spaced cationic lysines within a central lysine cluster of residues 101-110. For example, in our parallel in-register intermolecular β-sheet model of PrP(Sc), not only would these lysines be clustered within the 101-110 region of the primary sequence, but they would have intermolecular spacings of only ∼4.8 Å between stacked β-strands. We have now performed molecular dynamics simulations predicting that neutralization of the charges on these lysine residues would allow more stable parallel in-register packing in this region. We also show empirically that substitution of these clustered lysine residues with alanines or asparagines results in recombinant PrP amyloid fibrils with extended proteinase-K resistant β-sheet cores and infrared spectra that are more reminiscent of bona fide PrP(Sc). These findings indicate that charge neutralization at the central lysine cluster is critical for the folding and tight packing of N-proximal residues within PrP amyloid fibrils. This charge neutralization may be a key aspect of the mechanism by which anionic cofactors promote PrP(Sc) formation.

Parallel in-register intermolecular β-sheet architectures for prion-seeded prion protein (PrP) amyloids

Structures of the infectious form of prion protein (e.g. PrP(Sc) or PrP-Scrapie) remain poorly defined. The prevalent structural models of PrP(Sc) retain most of the native α-helices of the normal, noninfectious prion protein, cellular prion protein (PrP(C)), but evidence is accumulating that these helices are absent in PrP(Sc) amyloid. Moreover, recombinant PrP(C) can form amyloid fibrils in vitro that have parallel in-register intermolecular β-sheet architectures in the domains originally occupied by helices 2 and 3. Here, we provide solid-state NMR evidence that the latter is also true of initially prion-seeded recombinant PrP amyloids formed in the absence of denaturants. These results, in the context of a primarily β-sheet structure, led us to build detailed models of PrP amyloid based on parallel in-register architectures, fibrillar shapes and dimensions, and other available experimentally derived conformational constraints. Molecular dynamics simulations of PrP(90-231) octameric segments suggested that such linear fibrils, which are consistent with many features of PrP(Sc) fibrils, can have stable parallel in-register β-sheet cores. These simulations revealed that the C-terminal residues ∼124-227 more readily adopt stable tightly packed structures than the N-terminal residues ∼90-123 in the absence of cofactors. Variations in the placement of turns and loops that link the β-sheets could give rise to distinct prion strains capable of faithful template-driven propagation. Moreover, our modeling suggests that single PrP monomers can comprise the entire cross-section of fibrils that have previously been assumed to be pairs of laterally associated protofilaments. Together, these insights provide a new basis for deciphering mammalian prion structures.

Treatment of intraarticular middle phalanx fractures using the Ligamentotaxor®

BACKGROUND

We evaluated the outcome of intraarticular middle phalanx fractures after dynamic treatment with the Ligamentotaxor® system.

MATERIALS AND METHODS

Ten consecutive patients (seven male, three female; mean age 52 years) with intraarticular middle phalanx fractures were treated with the Ligamentotaxor® between 2009 and 2011. Proximal interphalangeal joint mobility, grip strength and 'Disabilities of the Arm, Shoulder and Hand' (DASH) score were evaluated in a 15-month follow-up. The reconstitution of the intraarticular space was measured immediately after trauma, at 6 weeks and at 15 months by radiograph control. The severity of the trauma was classified according to AO.

RESULTS

We found B1 30 %, C1 (Seno I + II) 50 % and C3 (Seno III-V) 20 %. In 60 % of the cases, fractures were localized on the middle base of the fifth digit, in 20 % on the third digit and in 20 % on the index finger. The dynamic treatment lasted 7 weeks; patients were exposed to full workload after 9 weeks. The mean flexion mobility after 15 months reached 73° (range 60-100°), and the extension deficit was 13° (range 0-20°) on average. Grip strength attained 71.3 % (range 60-87 %) of the contralateral side. Initial x-ray after trauma compared to the x-ray after 15 months showed an intraarticular space reconstitution average of 0.5 mm (range 0.1-0.9 mm) anterior-posterior and 0.6 mm (range 0.1-1 mm) lateral. Patients evaluated their outcome with an average of 14.6 points (range 3.3-26.7) using the DASH score.

CONCLUSION

Good results can be obtained with the Ligamentotaxor®. We recommend it for the dynamic treatment of intraarticular middle phalanx finger fractures. Larger series and long-term results are needed.

A strong magnetic field around the supermassive black hole at the centre of the Galaxy

Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way. Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei. X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed. The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown. Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed. Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole. If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission--from radio to X-ray wavelengths--from the black hole.

Prions and the potential transmissibility of protein misfolding diseases

Prions, or infectious proteins, represent a major frontier in the study of infectious agents. The prions responsible for mammalian transmissible spongiform encephalopathies (TSEs) are due primarily to infectious self-propagation of misfolded prion proteins. TSE prion structures remain ill-defined, other than being highly structured, self-propagating, and often fibrillar protein multimers with the capacity to seed, or template, the conversion of their normal monomeric precursors into a pathogenic form. Purified TSE prions usually take the form of amyloid fibrils, which are self-seeding ultrastructures common to many serious protein misfolding diseases such as Alzheimer's, Parkinson's, Huntington's and Lou Gehrig's (amytrophic lateral sclerosis). Indeed, recent reports have now provided evidence of prion-like propagation of several misfolded proteins from cell to cell, if not from tissue to tissue or individual to individual. These findings raise concerns that various protein misfolding diseases might have spreading, prion-like etiologies that contribute to pathogenesis or prevalence.