Novel non-HAP class A HBV capsid assembly modulators have distinct in vitro and in vivo profiles

IMPORTANCE

Chronic hepatitis B is the most important cause of liver cancer worldwide and affects more than 290 million people. Current treatments are mostly suppressive and rarely lead to a cure. Therefore, there is a need for novel and curative drugs that target the host or the causative agent, hepatitis B virus itself. Capsid assembly modulators are an interesting class of antiviral molecules that may one day become part of curative treatment regimens for chronic hepatitis B. Here we explore the characteristics of a particularly interesting subclass of capsid assembly modulators. These so-called non-HAP CAM-As have intriguing properties in cell culture but also clear virus-infected cells from the mouse liver in a gradual and sustained way. We believe they represent a considerable improvement over previously reported molecules and may one day be part of curative treatment combinations for chronic hepatitis B.

Class A capsid assembly modulator RG7907 clears HBV-infected hepatocytes through core-dependent hepatocyte death and proliferation

BACKGROUND AND AIMS

Effective therapies leading to a functional cure for chronic hepatitis B are still lacking. Class A capsid assembly modulators (CAM-As) are an attractive modality to address this unmet medical need. CAM-As induce aggregation of the HBV core protein (HBc) and lead to sustained HBsAg reductions in a chronic hepatitis B mouse model. Here, we investigate the underlying mechanism of action for CAM-A compound RG7907.

APPROACH AND RESULTS

RG7907 induced extensive HBc aggregation in vitro , in hepatoma cells, and in primary hepatocytes. In the adeno-associated virus (AAV)-HBV mouse model, the RG7907 treatment led to a pronounced reduction in serum HBsAg and HBeAg, concomitant with clearance of HBsAg, HBc, and AAV-HBV episome from the liver. Transient increases in alanine transaminase, hepatocyte apoptosis, and proliferation markers were observed. These processes were confirmed by RNA sequencing, which also uncovered a role for interferon alpha and gamma signaling, including the interferon-stimulated gene 15 (ISG15) pathway. Finally, the in vitro observation of CAM-A-induced HBc-dependent cell death through apoptosis established the link of HBc aggregation to in vivo loss of infected hepatocytes.

CONCLUSIONS

Our study unravels a previously unknown mechanism of action for CAM-As such as RG7907 in which HBc aggregation induces cell death, resulting in hepatocyte proliferation and loss of covalently closed circular DNA or its equivalent, possibly assisted by an induced innate immune response. This represents a promising approach to attain a functional cure for chronic hepatitis B.

Mitochondria metabolism sets the species-specific tempo of neuronal development

Neuronal development in the human cerebral cortex is considerably prolonged compared with that of other mammals. We explored whether mitochondria influence the species-specific timing of cortical neuron maturation. By comparing human and mouse cortical neuronal maturation at high temporal and cell resolution, we found a slower mitochondria development in human cortical neurons compared with that in the mouse, together with lower mitochondria metabolic activity, particularly that of oxidative phosphorylation. Stimulation of mitochondria metabolism in human neurons resulted in accelerated development in vitro and in vivo, leading to maturation of cells weeks ahead of time, whereas its inhibition in mouse neurons led to decreased rates of maturation. Mitochondria are thus important regulators of the pace of neuronal development underlying human-specific brain neoteny.

Parkinsonism mutations in DNAJC6 cause lipid defects and neurodegeneration that are rescued by Synj1

Recent evidence links dysfunctional lipid metabolism to the pathogenesis of Parkinson's disease, but the mechanisms are not resolved. Here, we generated a new Drosophila knock-in model of DNAJC6/Auxilin and find that the pathogenic mutation causes synaptic dysfunction, neurological defects and neurodegeneration, as well as specific lipid metabolism alterations. In these mutants, membrane lipids containing long-chain polyunsaturated fatty acids, including phosphatidylinositol lipid species that are key for synaptic vesicle recycling and organelle function, are reduced. Overexpression of another protein mutated in Parkinson's disease, Synaptojanin-1, known to bind and metabolize specific phosphoinositides, rescues the DNAJC6/Auxilin lipid alterations, the neuronal function defects and neurodegeneration. Our work reveals a functional relation between two proteins mutated in Parkinsonism and implicates deregulated phosphoinositide metabolism in the maintenance of neuronal integrity and neuronal survival.

Machine learning-assisted fluoroscopy of bladder function in awake mice

Understanding the lower urinary tract (LUT) and development of highly needed novel therapies to treat LUT disorders depends on accurate techniques to monitor LUT (dys)function in preclinical models. We recently developed videocystometry in rodents, which combines intravesical pressure measurements with X-ray-based fluoroscopy of the LUT, allowing the in vivo analysis of the process of urine storage and voiding with unprecedented detail. Videocystometry relies on the precise contrast-based determination of the bladder volume at high temporal resolution, which can readily be achieved in anesthetized or otherwise motion-restricted mice but not in awake and freely moving animals. To overcome this limitation, we developed a machine-learning method, in which we trained a neural network to automatically detect the bladder in fluoroscopic images, allowing the automatic analysis of bladder filling and voiding cycles based on large sets of time-lapse fluoroscopic images (>3 hr at 30 images/s) from behaving mice and in a noninvasive manner. With this approach, we found that urethane, an injectable anesthetic that is commonly used in preclinical urological research, has a profound, dose-dependent effect on urethral relaxation and voiding duration. Moreover, both in awake and in anesthetized mice, the bladder capacity was decreased ~fourfold when cystometry was performed acutely after surgical implantation of a suprapubic catheter. Our findings provide a paradigm for the noninvasive, in vivo monitoring of a hollow organ in behaving animals and pinpoint important limitations of the current gold standard techniques to study the LUT in mice.

Healthy adults empty their bladder many times a day with little thought. This seemingly simple process requires communication between the lower urinary tract and the central nervous system. About one in five adults experience conditions like urinary incontinence, urgency, or bladder pain caused by impairments in their lower urinary tract. Despite the harmful effects these conditions have on people’s health and well-being, few good treatments are available.

Mice are often used to study lower urinary tract conditions and treatments. One common technique is to fill a mouse’s bladder using a catheter and measure changes in pressure as the bladder empties and refills. But these procedures and the anesthesia used during them may affect bladder function and skew results.

Here, De Bruyn et al. have developed a new technique that allows scientists to measure bladder function in awake, freely moving mice. The mice’s bladders were photographed using a specialized X-ray based fluoroscope that captured 30 images per second over the course of three hours. A machine learning algorithm was then applied which can automatically detect the circumference of the bladder in each captured image (over 30,000 in total) and quantify its volume. This makes it is possible to measure the bladder as it empties and fills even if the mice move between time frames.

The new approach showed that ‘gold standard’ commonly used methods have a profound effect on the bladder. Surgical implantation of a catheter reduced the bladder to a quarter of its capacity. In addition, one of the most widely used anesthetic drugs in urinary tract research was found to affect the bladder’s ability to drain.

The technique created by De Bruyn et al. provides a new way to study lower urinary tract function and disease in awake, moving animals. This tool would be easy for other academic and pharmaceutical laboratories to implement, and may help scientists discover new therapies for lower urinary tract conditions.

Human iPSC-derived astrocytes transplanted into the mouse brain undergo morphological changes in response to amyloid-β plaques

BACKGROUND

Increasing evidence for a direct contribution of astrocytes to neuroinflammatory and neurodegenerative processes causing Alzheimer's disease comes from molecular and functional studies in rodent models. However, these models may not fully recapitulate human disease as human and rodent astrocytes differ considerably in morphology, functionality, and gene expression.

RESULTS

To address these challenges, we established an approach to study human astrocytes within the mouse brain by transplanting human induced pluripotent stem cell (hiPSC)-derived astrocyte progenitors into neonatal brains. Xenografted hiPSC-derived astrocyte progenitors differentiated into astrocytes that integrated functionally within the mouse host brain and matured in a cell-autonomous way retaining human-specific morphologies, unique features, and physiological properties. In Alzheimer´s chimeric brains, transplanted hiPSC-derived astrocytes responded to the presence of amyloid plaques undergoing morphological changes that seemed independent of the APOE allelic background.

CONCLUSIONS

In sum, we describe here a promising approach that consist of transplanting patient-derived and genetically modified astrocytes into the mouse brain to study human astrocyte pathophysiology in the context of Alzheimer´s disease.

Fetal hematopoietic stem cell homing is controlled by VEGF regulating the integrity and oxidative status of the stromal-vascular bone marrow niches

Hematopoietic stem and progenitor cell (HSPC) engraftment after transplantation during anticancer treatment depends on support from the recipient bone marrow (BM) microenvironment. Here, by studying physiological homing of fetal HSPCs, we show the critical requirement of balanced local crosstalk within the skeletal niche for successful HSPC settlement in BM. Transgene-induced overproduction of vascular endothelial growth factor (VEGF) by osteoprogenitor cells elicits stromal and endothelial hyperactivation, profoundly impacting the stromal-vessel interface and vascular architecture. Concomitantly, HSPC homing and survival are drastically impaired. Transcriptome profiling, flow cytometry, and high-resolution imaging indicate alterations in perivascular and endothelial cell characteristics, vascular function and cellular metabolism, associated with increased oxidative stress within the VEGF-enriched BM environment. Thus, developmental HSPC homing to bone is controlled by local stromal-vascular integrity and the oxidative-metabolic status of the recipient milieu. Interestingly, irradiation of adult mice also induces stromal VEGF expression and similar osteo-angiogenic niche changes, underscoring that our findings may contribute targets for improving stem cell therapies.

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Establishment of BM hematopoiesis is coupled to development of the skeletal niches

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Primary HSPC seeding of bone depends on balanced molecular crosstalk in the niche

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Stromal VEGF triggers EC activation and controls stromal-vascular niche integrity

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Excessive skeletal VEGF deranges cell metabolism and induces oxidative stress in BM

Loss-of-Function Mutations in TRAF7 and KLF4 Cooperatively Activate RAS-Like GTPase Signaling and Promote Meningioma Development

Meningiomas are the most common benign brain tumors. Mutations of the E3 ubiquitin ligase TRAF7 occur in 25% of meningiomas and commonly cooccur with mutations in KLF4, yet the functional link between TRAF7 and KLF4 mutations remains unclear. By generating an in vitro meningioma model derived from primary meningeal cells, we elucidated the cooperative interactions that promote meningioma development. By integrating TRAF7-driven ubiquitinome and proteome alterations in meningeal cells and the TRAF7 interactome, we identified TRAF7 as a proteostatic regulator of RAS-related small GTPases. Meningioma-associated TRAF7 mutations disrupted either its catalytic activity or its interaction with RAS GTPases. TRAF7 loss in meningeal cells altered actin dynamics and promoted anchorage-independent growth by inducing CDC42 and RAS signaling. TRAF deficiency-driven activation of the RAS/MAPK pathway promoted KLF4-dependent transcription that led to upregulation of the tumor-suppressive Semaphorin pathway, a negative regulator of small GTPases. KLF4 loss of function disrupted this negative feedback loop and enhanced mutant TRAF7-mediated cell transformation. Overall, this study provides new mechanistic insights into meningioma development, which could lead to novel treatment strategies. SIGNIFICANCE: The intricate molecular cross-talk between the ubiquitin ligase TRAF7 and the transcription factor KLF4 provides a first step toward the identification of new therapies for patients with meningioma.

Rectal organoid morphology analysis (ROMA) as a promising diagnostic tool in cystic fibrosis

Diagnosing cystic fibrosis (CF) when sweat chloride is not in the CF range and less than 2 disease-causing CFTR mutations are found requires physiological CFTR assays, which are not always feasible or available. We developed a new physiological CFTR assay based on the morphological differences between rectal organoids from subjects with and without CF. In organoids from 167 subjects with and 22 without CF, two parameters derived from a semi-automated image analysis protocol (rectal organoid morphology analysis, ROMA) fully discriminated CF subjects with two disease-causing mutations from non-CF subjects (p<0.001). ROMA, feasible at all ages, can be centralised to improve standardisation.

Upregulation of TRPM3 in nociceptors innervating inflamed tissue

Genetic ablation or pharmacological inhibition of the heat-activated cation channel TRPM3 alleviates inflammatory heat hyperalgesia, but the underlying mechanisms are unknown. We induced unilateral inflammation of the hind paw in mice, and directly compared expression and function of TRPM3 and two other heat-activated TRP channels (TRPV1 and TRPA1) in sensory neurons innervating the ipsilateral and contralateral paw. We detected increased Trpm3 mRNA levels in dorsal root ganglion neurons innervating the inflamed paw, and augmented TRP channel-mediated calcium responses, both in the cell bodies and the intact peripheral endings of nociceptors. In particular, inflammation provoked a pronounced increase in nociceptors with functional co-expression of TRPM3, TRPV1 and TRPA1. Finally, pharmacological inhibition of TRPM3 dampened TRPV1- and TRPA1-mediated responses in nociceptors innervating the inflamed paw, but not in those innervating healthy tissue. These insights into the mechanisms underlying inflammatory heat hypersensitivity provide a rationale for developing TRPM3 antagonists to treat pathological pain.

Imaging axon regeneration within synthetic nerve conduits

While axons within the central nervous system (CNS) do not regenerate following injury, those in the peripheral nervous system (PNS) do, although not in a clinically satisfactory manner as only a small proportion of axons exhibit long-distance regeneration. Moreover, functional recovery is hampered by excessive axonal sprouting and aberrant reinnervation of target tissue. In order to investigate the mechanisms governing the regrowth of axons following injury, previous studies have used lesion paradigms of peripheral nerves in rat or mouse models, and reagents or cells have been administered to the lesion site through nerve conduits, aiming to improve early-stage regeneration. Morphological analysis of such in vivo experiments has however been limited by the incompatibility of synthetic nerve conduits with existing tissue-clearing and imaging techniques. We present herein a novel experimental approach that allows high-resolution imaging of individual axons within nerve conduits, together with quantitative assessment of fiber growth. We used a GFP-expressing mouse strain in a lesion model of the sciatic nerve to describe a strategy that combines nerve clearing, chemical treatment of chitosan nerve conduits, and long working distance confocal microscopy with image processing and analysis. This novel experimental setup provides a means of documenting axon growth within the actual conduit during the critical initial stage of regeneration. This will greatly facilitate the development and evaluation of treatment regimens to improve axonal regeneration following nerve damage.

A Label-free Multicolor Optical Surface Tomography (ALMOST) imaging method for nontransparent 3D samples

Background

Current mesoscale 3D imaging techniques are limited to transparent or cleared samples or require the use of X-rays. This is a severe limitation for many research areas, as the 3D color surface morphology of opaque samples—for example, intact adult Drosophila, Xenopus embryos, and other non-transparent samples—cannot be assessed. We have developed “ALMOST,” a novel optical method for 3D surface imaging of reflective opaque objects utilizing an optical projection tomography device in combination with oblique illumination and optical filters.

Results

As well as demonstrating image formation, we provide background information and explain the reconstruction—and consequent rendering—using a standard filtered back projection algorithm and 3D software. We expanded our approach to fluorescence and multi-channel spectral imaging, validating our results with micro-computed tomography. Different biological and inorganic test samples were used to highlight the versatility of our approach. To further demonstrate the applicability of ALMOST, we explored the muscle-induced form change of the Drosophila larva, imaged adult Drosophila, dynamically visualized the closure of neural folds during neurulation of live Xenopus embryos, and showed the complementarity of our approach by comparison with transmitted light and fluorescence OPT imaging of a Xenopus tadpole.

Conclusion

Thus, our new modality for spectral/color, macro/mesoscopic 3D imaging can be applied to a variety of model organisms and enables the longitudinal surface dynamics during development to be revealed.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0614-4) contains supplementary material, which is available to authorized users.

SOX10 Single Transcription Factor-Based Fast and Efficient Generation of Oligodendrocytes from Human Pluripotent Stem Cells

Scarce access to primary samples and lack of efficient protocols to generate oligodendrocytes (OLs) from human pluripotent stem cells (hPSCs) are hampering our understanding of OL biology and the development of novel therapies. Here, we demonstrate that overexpression of the transcription factor SOX10 is sufficient to generate surface antigen O4-positive (O4⁺) and myelin basic protein-positive OLs from hPSCs in only 22 days, including from patients with multiple sclerosis or amyotrophic lateral sclerosis. The SOX10-induced O4⁺ population resembles primary human OLs at the transcriptome level and can myelinate neurons in vivo. Using in vitro OL-neuron co-cultures, myelination of neurons by OLs can also be demonstrated, which can be adapted to a high-throughput screening format to test the response of pro-myelinating drugs. In conclusion, we provide an approach to generate OLs in a very rapid and efficient manner, which can be used for disease modeling, drug discovery efforts, and potentially for therapeutic OL transplantation.

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SOX10 is sufficient to generate myelinating human OLs from hPSCs in only 22 days

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SOX10-induced OLs resemble primary human OLs at the transcriptome level

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The methodology allows efficient generation of OLs from MS and ALS patients

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OL-neuron co-cultures respond to myelinating drugs in a high-throughput setting

Tetraspanin 6: a pivotal protein of the multiple vesicular body determining exosome release and lysosomal degradation of amyloid precursor protein fragments

Background

The mechanisms behind Aβ-peptide accumulation in non-familial Alzheimer’s disease (AD) remain elusive. Proteins of the tetraspanin family modulate Aβ production by interacting to γ-secretase.

Methods

We searched for tetraspanins with altered expression in AD brains. The function of the selected tetraspanin was studied in vitro and the physiological relevance of our findings was confirmed in vivo.

Results

Tetraspanin-6 (TSPAN6) is increased in AD brains and overexpression in cells exerts paradoxical effects on Amyloid Precursor Protein (APP) metabolism, increasing APP-C-terminal fragments (APP-CTF) and Aβ levels at the same time. TSPAN6 affects autophagosome-lysosomal fusion slowing down the degradation of APP-CTF. TSPAN6 recruits also the cytosolic, exosome-forming adaptor syntenin which increases secretion of exosomes that contain APP-CTF.

Conclusions

TSPAN6 is a key player in the bifurcation between lysosomal-dependent degradation and exosome mediated secretion of APP-CTF. This corroborates the central role of the autophagosomal/lysosomal pathway in APP metabolism and shows that TSPAN6 is a crucial player in APP-CTF turnover.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-017-0165-0) contains supplementary material, which is available to authorized users.

Inhomogeneity Based Characterization of Distribution Patterns on the Plasma Membrane

Cell surface protein and lipid molecules are organized in various patterns: randomly, along gradients, or clustered when segregated into discrete micro- and nano-domains. Their distribution is tightly coupled to events such as polarization, endocytosis, and intracellular signaling, but challenging to quantify using traditional techniques. Here we present a novel approach to quantify the distribution of plasma membrane proteins and lipids. This approach describes spatial patterns in degrees of inhomogeneity and incorporates an intensity-based correction to analyze images with a wide range of resolutions; we have termed it Quantitative Analysis of the Spatial distributions in Images using Mosaic segmentation and Dual parameter Optimization in Histograms (QuASIMoDOH). We tested its applicability using simulated microscopy images and images acquired by widefield microscopy, total internal reflection microscopy, structured illumination microscopy, and photoactivated localization microscopy. We validated QuASIMoDOH, successfully quantifying the distribution of protein and lipid molecules detected with several labeling techniques, in different cell model systems. We also used this method to characterize the reorganization of cell surface lipids in response to disrupted endosomal trafficking and to detect dynamic changes in the global and local organization of epidermal growth factor receptors across the cell surface. Our findings demonstrate that QuASIMoDOH can be used to assess protein and lipid patterns, quantifying distribution changes and spatial reorganization at the cell surface. An ImageJ/Fiji plugin of this analysis tool is provided.

Plasma membrane organization is fundamental to cellular signaling, transport of molecules, and cell adhesion. To achieve this, plasma membrane proteins and lipids are spatially organized: they form clusters, aggregate in signaling platforms, distribute into gradients on polarized cells, or randomly distribute across the membrane. It is also clear that these organizations can be affected in various contexts. For example, in aging or neurodegenerative diseases, the composition of the plasma membrane is altered and, consequently, the protein and lipid distributions in the membrane fluctuate. In addition, cancer progression is characterized by changes in cellular polarity, lipid content, and the redistribution of cell surface receptors and adhesion molecules. Here we have developed a method to quantify such alterations that, unlike current tools, is compatible with diverse types of cellular organization, including polarity. Our tool can be employed to screen for changes in a straightforward manner and to elucidate distributions of cell surface components in different disciplines, ranging from neurobiology to cancer research.

Loss of GPR3 reduces the amyloid plaque burden and improves memory in Alzheimer's disease mouse models

The orphan G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor (GPCR) GPR3 regulates activity of the γ-secretase complex in the absence of an effect on Notch proteolysis, providing a potential therapeutic target for Alzheimer's disease (AD). However, given the vast resources required to develop and evaluate any new therapy for AD and the multiple failures involved in translational research, demonstration of the pathophysiological relevance of research findings in multiple disease-relevant models is necessary before initiating costly drug development programs. We evaluated the physiological consequences of loss of Gpr3 in four AD transgenic mouse models, including two that contain the humanized murine Aβ sequence and express similar amyloid precursor protein (APP) levels as wild-type mice, thereby reducing potential artificial phenotypes. Our findings reveal that genetic deletion of Gpr3 reduced amyloid pathology in all of the AD mouse models and alleviated cognitive deficits in APP/PS1 mice. Additional three-dimensional visualization and analysis of the amyloid plaque burden provided accurate information on the amyloid load, distribution, and volume in the structurally intact adult mouse brain. Analysis of 10 different regions in healthy human postmortem brain tissue indicated that GPR3 expression was stable during aging. However, two cohorts of human AD postmortem brain tissue samples showed a correlation between elevated GPR3 and AD progression. Collectively, these studies provide evidence that GPR3 mediates the amyloidogenic proteolysis of APP in four AD transgenic mouse models as well as the physiological processing of APP in wild-type mice, suggesting that GPR3 may be a potential therapeutic target for AD drug development.

Hsc70-4 Deforms Membranes to Promote Synaptic Protein Turnover by Endosomal Microautophagy

Synapses are often far from their cell bodies and must largely independently cope with dysfunctional proteins resulting from synaptic activity and stress. To identify membrane-associated machines that can engulf synaptic targets destined for degradation, we performed a large-scale in vitro liposome-based screen followed by functional studies. We identified a presynaptically enriched chaperone Hsc70-4 that bends membranes based on its ability to oligomerize. This activity promotes endosomal microautophagy and the turnover of specific synaptic proteins. Loss of microautophagy slows down neurotransmission while gain of microautophagy increases neurotransmission. Interestingly, Sgt, a cochaperone of Hsc70-4, is able to switch the activity of Hsc70-4 from synaptic endosomal microautophagy toward chaperone activity. Hence, Hsc70-4 controls rejuvenation of the synaptic protein pool in a dual way: either by refolding proteins together with Sgt, or by targeting them for degradation by facilitating endosomal microautophagy based on its membrane deforming activity.

High-content imaging and gene expression analysis to study cell-nanomaterial interactions: the effect of surface hydrophobicity

The effects of nanoparticle (NP)-related parameters on cellular interactions are currently uncertain as analysis is complicated by the combinatorial diversity arising from the array of size, shape and surface properties. Here, we present a validated multiparametric high-content imaging method, with the utility of this approach demonstrated by in-depth analysis of the role of hydrophobicity on the interaction of Au NPs with cultured cells. In this methodology, we evaluate cell viability, membrane damage, induction of reactive oxygen species, mitochondrial health, cell area, skewness and induction of autophagy. High-content cell cycle phase studies and in-depth gene expression studies then serve to elucidate the underlying mechanisms. The data reveal a clear influence of the degree of NP surface hydrophobicity with membrane damage and autophagy induction, which is stronger than the effect of surface charge, for charges ranging between -50 and +20 mV. All labeling experiments occur in the same format, and can be further supplemented with additional parameters providing a broadly accessible format for studying cell-NP interactions under highly reproducible conditions.