Systemic AAV vectors for widespread and targeted gene delivery in rodents

Psychedelic control of neuroimmune interactions governing fear

Neuroimmune interactions-signals transmitted between immune and brain cells-regulate many aspects of tissue physiology1, including responses to psychological stress2-5, which can predispose individuals to develop neuropsychiatric diseases6-9. Still, the interactions between haematopoietic and brain-resident cells that influence complex behaviours are poorly understood. Here, we use a combination of genomic and behavioural screens to show that astrocytes in the amygdala limit stress-induced fear behaviour through epidermal growth factor receptor (EGFR). Mechanistically, EGFR expression in amygdala astrocytes inhibits a stress-induced, pro-inflammatory signal-transduction cascade that facilitates neuron-glial crosstalk and stress-induced fear behaviour through the orphan nuclear receptor NR2F2 in amygdala neurons. In turn, decreased EGFR signalling and fear behaviour are associated with the recruitment of meningeal monocytes during chronic stress. This set of neuroimmune interactions is therapeutically targetable through the administration of psychedelic compounds, which reversed the accumulation of monocytes in the brain meninges along with fear behaviour. Together with validation in clinical samples, these data suggest that psychedelics can be used to target neuroimmune interactions relevant to neuropsychiatric disorders and potentially other inflammatory diseases.

Activity-dependent synthesis of Emerin gates neuronal plasticity by regulating proteostasis

Neurons dynamically regulate their proteome in response to sensory input, a key process underlying experience-dependent plasticity. We characterized the visual experience-dependent nascent proteome in mice within a brief, defined time window after stimulation using an optimized metabolic labeling approach. Visual experience induced cell-type-specific and age-dependent alterations in the nascent proteome, including proteostasis-related proteins. Emerin is the top activity-induced candidate plasticity protein. Activity-induced neuronal Emerin synthesis is rapid and transcription independent. Emerin broadly inhibits protein synthesis, decreasing translation regulators and synaptic proteins. Decreasing Emerin shifted the dendritic spine population from a predominantly mushroom morphology to filopodia and decreased network connectivity. Blocking visual experience-induced Emerin reduced visually evoked electrophysiological responses and impaired behaviorally assessed visual information processing. Our findings support a proteostatic model in which visual experience-induced Emerin provides a feedforward block on further protein synthesis, refining temporal control of activity-induced plasticity proteins and optimizing visual system function.

An enhancer-AAV toolbox to target and manipulate distinct interneuron subtypes

In recent years, we and others have identified a number of enhancers that, when incorporated into rAAV vectors, can restrict the transgene expression to particular neuronal populations. Yet, viral tools to access and manipulate specific neuronal subtypes are still limited. Here, we performed systematic analysis of single cell genomic data to identify enhancer candidates for each of the telencephalic interneuron subtypes. We established a set of enhancer-AAV tools that are highly specific for distinct cortical interneuron populations and striatal cholinergic interneurons. These enhancers, when used in the context of different effectors, can target (fluorescent proteins), observe activity (GCaMP) and manipulate (opto-genetics) specific neuronal subtypes. We also validated our enhancer-AAV tools across species. Thus, we provide the field with a powerful set of tools to study neural circuits and functions and to develop precise and targeted therapy.

Dnmt3a overexpression disrupts skeletal muscle homeostasis, promotes an aging-like phenotype, and reduces metabolic elasticity

Mammalian aging is reportedly driven by the loss of epigenetic information; however, its impact on skeletal muscle aging remains unclear. This study shows that aging mouse skeletal muscle exhibits increased DNA methylation, and overexpression of DNA methyltransferase 3a (Dnmt3a) induces an aging-like phenotype. Muscle-specific Dnmt3a overexpression leads to an increase in central nucleus-positive myofibers, predominantly in fast-twitch fibers, a shift toward slow-twitch fibers, elevated inflammatory and senescence markers, mitochondrial OXPHOS complex I reduction, and decreased basal autophagy. Dnmt3a overexpression resulted in reduced muscle mass and strength and impaired endurance exercise capacity with age, accompanied by an enhanced inflammatory signature. In addition, Dnmt3a overexpression reduced not only sensitivity to starvation-induced muscle atrophy but also the restorability from muscle atrophy. These findings suggest that increased DNA methylation disrupts skeletal muscle homeostasis, promotes an aging-like phenotype, and reduces muscle metabolic elasticity.

Krüppel-like factor 5 remodels lipid metabolism in exercised skeletal muscle

Regular physical activity induces a variety of health benefits, preventing and counteracting diseases caused by a sedentary lifestyle. However, the molecular underpinnings of skeletal muscle plasticity in exercise remain poorly understood. We identified a role of the Krüppel-Like Factor 5 (Klf5) in this process, in particular in the regulation of lipid homeostasis. Surprisingly, gain- and loss-of-function studies in muscle in vivo revealed seemingly opposite functions of Klf5 in the response to an acute exercise bout and chronic training, modulating lipid oxidation and synthesis, respectively. Thus, even though only transiently induced, the function of Klf5 is complex and fundamental for a normal long-term training response. These findings highlight the importance of this mediator of external stress response to adaptive remodeling of skeletal muscle tissue.

Adeno-associated viruses escort nanomaterials to specific cells and tissues

The delivery of nanotherapeutics to specific tissues relies on bespoke targeting strategies or invasive surgeries. Conversely, adeno-associated viruses (AAVs) can target specific tissues following intravenous injections. Here we show that cell-targeting properties of AAVs could be broadly conferred to nanomaterials. We develop a strategy to couple AAV capsids to nanoparticles that is invariant of viral serotype or nanomaterial chemistry and permits control over stoichiometry of the AAV-nanoparticle chimeras. The chimeras selectively escort nanoparticles into cell classes governed by AAV serotypes. When applied to magnetic nanoparticles, the AAV-nanoparticle chimeras enable magnetically localized gene delivery. In vivo, we show that leveraging the brain-targeting AAV serotype CAP-B10 achieves nanoparticle delivery to the parenchyma with ∼10% efficiency (% injected dose/g [brain] ) while avoiding accumulation in the liver. The enhanced delivery efficiency and tissue specificity highlight the potential of AAV-chimeras as a versatile strategy to escort broad classes of nanotherapeutics to the brain and beyond.

A key role of PIEZO2 mechanosensitive ion channel in adipose sensory innervation

Compared with the well-established functions of sympathetic innervation, the role of sensory afferents in adipose tissues remains less understood. Recent work has revealed the anatomical and physiological significance of adipose sensory innervation; however, its molecular underpinning remains unclear. Here, using organ-targeted single-cell RNA sequencing, we identified the mechanoreceptor PIEZO2 as one of the most prevalent receptors in fat-innervating dorsal root ganglia (DRG) neurons. PIEZO2 deletion in fat-innervating neurons induced transcriptional programs in adipose tissue resembling sympathetic activation, mirroring DRG ablation. Conversely, a gain-of-function PIEZO2 mutant shifted the adipose phenotypes in the opposite direction. These results indicate that PIEZO2 plays a major role in the sensory regulation of adipose tissues. This discovery opens new avenues for exploring mechanosensation in organs not traditionally considered mechanically active, such as adipose tissues, and therefore sheds light on the broader significance of mechanosensation in regulating organ function and homeostasis.

Axially decoupled photo-stimulation and two photon readout (ADePT) for mapping functional connectivity of neural circuits

All optical physiology in vivo provides a conduit for investigating the function of neural circuits in 3-D. Here, we report a new strategy for flexible, axially-decoupled photo-stimulation and two photon readout (ADePT) of neuronal activity. To achieve axially-contained widefield optogenetic patterned stimulation, we couple a digital micro-mirror device illuminated by a solid-state laser with a motorized holographic diffuser. In parallel, we use multiphoton imaging of neural activity across different z-planes. We use ADePT to analyze the excitatory and inhibitory functional connectivity of the mouse early olfactory system. Specifically, we control the activity of individual input glomeruli on the olfactory bulb surface, and map the ensuing responses of output mitral and tufted cell bodies in deeper layers. This approach identifies cohorts of sister mitral and tufted cells, whose firing is driven by the same parent glomerulus, and also reveals their differential inhibition by other glomeruli. In addition, selective optogenetic activation of glomerular GABAergic/dopaminergic (DAT+) interneurons triggers dense, but spatially heterogeneous suppression of mitral and tufted cell baseline activity and odor responses, further demonstrating specificity in the inhibitory olfactory bulb connectivity. In summary, ADePT enables high-throughput functional connectivity mapping in optically accessible brain regions.

Targeted gene silencing in mouse testicular Sertoli and Leydig cells using adeno-associated virus vectors

ABSTRACT

Researchers commonly use cyclization recombination enzyme/locus of X-over P1 (Cre/loxP) technology-based conditional gene knockouts of model mice to investigate the functional roles of genes of interest in Sertoli and Leydig cells within the testis. However, the shortcomings of these genetic tools include high costs, lengthy experimental periods, and limited accessibility for researchers. Therefore, exploring alternative gene silencing techniques is of great practical value. In this study, we employed adeno-associated virus (AAV) as a vector for gene silencing in Sertoli and Leydig cells. Our findings demonstrated that AAV serotypes 1, 8, and 9 exhibited high infection efficiency in both types of testis cells. Importantly, we discovered that all three AAV serotypes exhibited exquisite specificity in targeting Sertoli cells via tubular injection while demonstrating remarkable selectivity in targeting Leydig cells via interstitial injection. We achieved cell-specific knockouts of the steroidogenic acute regulatory (Star) and luteinizing hormone/human chorionic gonadotropin receptor (Lhcgr) genes in Leydig cells, but not in Sertoli cells, using AAV9-single guide RNA (sgRNA)-mediated gene editing in Rosa26-LSL-Cas9 mice. Knockdown of androgen receptor (Ar) gene expression in Sertoli cells of wild-type mice was achieved via tubular injection of AAV9-short hairpin RNA (shRNA)-mediated targeting. Our findings offer technical approaches for investigating gene function in Sertoli and Leydig cells through AAV9-mediated gene silencing.

Spatial genomics of AAV vectors reveals mechanism of transcriptional crosstalk that enables targeted delivery of large genetic cargo

Cell-type-specific regulatory elements such as enhancers can direct expression of recombinant adeno-associated viruses (AAVs) to specific cell types, but this approach is limited by the relatively small packaging capacity of AAVs. In this study, we used spatial genomics to show that transcriptional crosstalk between individual AAV genomes provides a general method for cell-type-specific expression of large cargo by separating distally acting regulatory elements into a second AAV genome. We identified and profiled transcriptional crosstalk in AAV genomes carrying 11 different enhancers active in mouse brain. We developed spatial genomics methods to identify and localize AAV genomes and their concatemeric forms in cultured cells and in tissue, and we demonstrate here that transcriptional crosstalk is dependent upon concatemer formation. Finally, we leveraged transcriptional crosstalk to drive expression of a 3.2-kb Cas9 cargo in a cell-type-specific manner with systemically administered engineered AAVs, and we demonstrate AAV-delivered, minimally invasive, cell-type-specific gene editing in wild-type mice that recapitulates known disease phenotypes.

Loss of endothelial CD2AP causes sex-dependent cerebrovascular dysfunction

Polymorphisms in CD2-associated protein (CD2AP) predispose to Alzheimer's disease (AD), but the underlying mechanisms remain unknown. Here, we show that loss of CD2AP in cerebral blood vessels is associated with cognitive decline in AD subjects and that genetic downregulation of CD2AP in brain vascular endothelial cells impairs memory function in male mice. Animals with reduced brain endothelial CD2AP display altered blood flow regulation at rest and during neurovascular coupling, defects in mural cell activity, and an abnormal vascular sex-dependent response to Aβ. Antagonizing endothelin-1 receptor A signaling partly rescues the vascular impairments, but only in male mice. Treatment of CD2AP mutant mice with reelin glycoprotein that mitigates the effects of CD2AP loss function via ApoER2 increases resting cerebral blood flow and even protects male mice against the noxious effect of Aβ. Thus, endothelial CD2AP plays critical roles in cerebrovascular functions and represents a novel target for sex-specific treatment in AD.

Meningeal lymphatics-microglia axis regulates synaptic physiology

Meningeal lymphatics serve as an outlet for cerebrospinal fluid, and their dysfunction is associated with various neurodegenerative conditions. Previous studies have demonstrated that dysfunctional meningeal lymphatics evoke behavioral changes, but the neural mechanisms underlying these changes have remained elusive. Here, we show that prolonged impairment of meningeal lymphatics alters the balance of cortical excitatory and inhibitory synaptic inputs, accompanied by deficits in memory tasks. These synaptic and behavioral alterations induced by lymphatic dysfunction are mediated by microglia, leading to increased expression of the interleukin 6 gene (Il6). IL-6 drives inhibitory synapse phenotypes via a combination of trans- and classical IL-6 signaling. Restoring meningeal lymphatic function in aged mice reverses age-associated synaptic and behavioral alterations. Our findings suggest that dysfunctional meningeal lymphatics adversely impact cortical circuitry through an IL-6-dependent mechanism and identify a potential target for treating aging-associated cognitive decline.

Glycocalyx dysregulation impairs blood-brain barrier in ageing and disease

The blood-brain barrier (BBB) is highly specialized to protect the brain from harmful circulating factors in the blood and maintain brain homeostasis1,2. The brain endothelial glycocalyx layer, a carbohydrate-rich meshwork composed primarily of proteoglycans, glycoproteins and glycolipids that coats the BBB lumen, is a key structural component of the BBB3,4. This layer forms the first interface between the blood and brain vasculature, yet little is known about its composition and roles in supporting BBB function in homeostatic and diseased states. Here we find that the brain endothelial glycocalyx is highly dysregulated during ageing and neurodegenerative disease. We identify significant perturbation in an underexplored class of densely O-glycosylated proteins known as mucin-domain glycoproteins. We demonstrate that ageing- and disease-associated aberrations in brain endothelial mucin-domain glycoproteins lead to dysregulated BBB function and, in severe cases, brain haemorrhaging in mice. Finally, we demonstrate that we can improve BBB function and reduce neuroinflammation and cognitive deficits in aged mice by restoring core 1 mucin-type O-glycans to the brain endothelium using adeno-associated viruses. Cumulatively, our findings provide a detailed compositional and structural mapping of the ageing brain endothelial glycocalyx layer and reveal important consequences of ageing- and disease-associated glycocalyx dysregulation on BBB integrity and brain health.

Staufen2 dysregulation in neurodegenerative disease

Staufen2 (STAU2) is an RNA-binding protein that controls mRNA trafficking and expression. Previously, we showed that its paralog, Staufen1 (STAU1), was overabundant in cellular and mouse models of neurodegenerative diseases and amyotrophic lateral sclerosis (ALS) patient spinal cord. Here, we investigated features of STAU2 that might parallel STAU1. STAU2 protein, but not mRNA, was overabundant in spinocerebellar ataxia type 2 (SCA2), ALS/frontotemporal dementia patient fibroblasts, ALS patient spinal cord tissues, and in central nervous system tissues from SCA2 and ALS animal models. Exogenous expression of STAU2 in human embryonic kidney 293 cells activated mechanistic target of rapamycin (mTOR) and stress granule formation. Targeting STAU2 by RNAi normalized mTOR in SCA2 and C9ORF72 cellular models. The microRNA miR-217, previously identified as downregulated in SCA2 mice, targets the STAU2 3'-UTR. We now demonstrate that exogenous expression of miR-217 significantly reduced STAU2 and mTOR levels in cellular models of neurodegenerative disease. These results suggest a functional link between STAU2 and mTOR signaling and identify a major role for miR-217 that could be exploited in therapeutic development.

Retinal ganglion cells induce stem cell-derived neuroprotection via IL-12 to SCGF-β crosstalk

BACKGROUND

Stem cell-derived secreted factors could protect neurons in neurodegenerative disease or after injury. The exact neuroprotective components in the secretome remain challenging to discover. Here we developed a cell-to-cell interaction model to identify a retinal ganglion cell (RGC)-protective factor derived from induced pluripotent stem cells (iPSCs).

METHODS

Primary RGCs were co-cultured with iPSCs or treated with iPSC-conditioned media in vitro. Cell viability were assayed using live-cell staining, and culture supernatant were analyzed via multiplexed antibody-based assays and ELISA. In vivo tests were carried out under mouse optic nerve crush model and RGC transplantation study in rats. Paired t-tests were used for data analysis between two groups.

RESULTS

RGC viability was significantly enhanced when iPSCs were first stimulated with RGC-derived supernatant before iPSC-conditioned medium was collected and added into RGC culture. A significant increase of stem cell growth factor-beta (SCGF-β) concentration was detected in the latter conditioned medium. SCGF-β enhanced RGC survival in vitro and in vivo, and RGC-derived interleukin-12(p70) (IL-12[p70]) promotes secretion of iPSC-derived SCGF-β. Downstream of this IL-12(p70)-to-SCGF-β axis, ngn2 was significantly upregulated, and was found both necessary and sufficient for RGC survival.

CONCLUSION

This study addresses a longstanding question of how neurons and stem cells interact to promote neuroprotection, and define a novel molecular interaction pathway whereby RGC's secretion of IL-12(p70) enhances iPSCs' secretion of SCGF-β, and SCGF-β protects RGCs via upregulating ngn2, suggesting that neurons may call on stem cells for their own protection.

AIF3 splicing variant elicits mitochondrial malfunction via the concurrent dysregulation of electron transport chain and glutathione-redox homeostasis

Genetic mutations in apoptosis-inducing factor (AIF) have a strong association with mitochondrial disorders; however, little is known about the aberrant splicing variants in affected patients and how these variants contribute to mitochondrial dysfunction and brain development defects. We identified pathologic AIF3/AIF3-like splicing variants in postmortem brain tissues of pediatric individuals with mitochondrial disorders. Mutations in AIFM1 exon-2/3 increase splicing risks. AIF3-splicing disrupts mitochondrial complexes, membrane potential, and respiration, causing brain development defects. Mechanistically, AIF is a mammalian NAD(P)H dehydrogenase and possesses glutathione reductase activity controlling respiratory chain functions and glutathione regeneration. Conversely, AIF3, lacking these activities, disassembles mitochondrial complexes, increases ROS generation, and simultaneously hinders antioxidant defense. Expression of NADH dehydrogenase NDI1 restores mitochondrial functions partially and protects neurons in AIF3-splicing mice. Our findings unveil an underrated role of AIF as a mammalian mitochondrial complex-I alternative NAD(P)H dehydrogenase and provide insights into pathologic AIF-variants in mitochondrial disorders and brain development.

Massively parallel in vivo Perturb-seq screening

Advances in genomics have identified thousands of risk genes impacting human health and diseases, but the functions of these genes and their mechanistic contribution to disease are often unclear. Moving beyond identification to actionable biological pathways requires dissecting risk gene function and cell type-specific action in intact tissues. This gap can in part be addressed by in vivo Perturb-seq, a method that combines state-of-the-art gene editing tools for programmable perturbation of genes with high-content, high-resolution single-cell genomic assays as phenotypic readouts. Here we describe a detailed protocol to perform massively parallel in vivo Perturb-seq using several versatile adeno-associated virus (AAV) vectors and provide guidance for conducting successful downstream analyses. Expertise in mouse work, AAV production and single-cell genomics is required. We discuss key parameters for designing in vivo Perturb-seq experiments across diverse biological questions and contexts. We further detail the step-by-step procedure, from designing a perturbation library to producing and administering AAV, highlighting where quality control checks can offer critical go-no-go points for this time- and cost-expensive method. Finally, we discuss data analysis options and available software. In vivo Perturb-seq has the potential to greatly accelerate functional genomics studies in mammalian systems, and this protocol will help others adopt it to answer a broad array of biological questions. From guide RNA design to tissue collection and data collection, this protocol is expected to take 9-15 weeks to complete, followed by data analysis.

Molecular and cellular characteristics of cerebrovascular cell types and their contribution to neurodegenerative diseases

Many diseases and disorders of the nervous system suffer from a lack of adequate therapeutics to halt or slow disease progression, and to this day, no cure exists for any of the fatal neurodegenerative diseases. In part this is due to the incredible diversity of cell types that comprise the brain, knowledge gaps in understanding basic mechanisms of disease, as well as a lack of reliable strategies for delivering new therapeutic modalities to affected areas. With the advent of single cell genomics, it is now possible to interrogate the molecular characteristics of diverse cell populations and their alterations in diseased states. More recently, much attention has been devoted to cell populations that have historically been difficult to profile with bulk single cell technologies. In particular, cell types that comprise the cerebrovasculature have become increasingly better characterized in normal and neurodegenerative disease contexts. In this review, we describe the current understanding of cerebrovasculature structure, function, and cell type diversity and its role in the mechanisms underlying various neurodegenerative diseases. We focus on human and mouse cerebrovasculature studies and discuss both origins and consequences of cerebrovascular dysfunction, emphasizing known cell type-specific vulnerabilities in neuronal and cerebrovascular cell populations. Lastly, we highlight how novel insights into cerebrovascular biology have impacted the development of modern therapeutic approaches and discuss outstanding questions in the field.

Decoding Codon Bias: The Role of tRNA Modifications in Tissue-Specific Translation

The tRNA epitranscriptome has been recognized as an important player in mRNA translation regulation. Our knowledge of the role of the tRNA epitranscriptome in fine-tuning translation via codon decoding at tissue or cell levels remains incomplete. We analyzed tRNA expression and modifications as well as codon optimality across seven mouse tissues. Our analysis revealed distinct enrichment patterns of tRNA modifications in different tissues. Queuosine (Q) tRNA modification was most enriched in the brain compared to other tissues, while mitochondrial tRNA modifications and tRNA expression were highest in the heart. Using this observation, we synthesized, and delivered in vivo, codon-mutated EGFP for Q-codons, where the C-ending Q-codons were replaced with U-ending codons. The protein levels of mutant EGFP were downregulated in liver, which is poor in Q, while in brain EGFP, levels did not change. These data show that understanding tRNA modification enrichments across tissues is not only essential for understanding codon decoding and bias but can also be utilized for optimizing gene and mRNA therapeutics to be more tissue-, cell-, or condition-specific.

An RNA editing strategy rescues gene duplication in a mouse model of MECP2 duplication syndrome and nonhuman primates

Duplication of methyl-CpG-binding protein 2 (MECP2) gene causes MECP2 duplication syndrome (MDS). To normalize the duplicated MECP2 in MDS, we developed a high-fidelity Cas13Y (hfCas13Y) system capable of targeting the MECP2 (hfCas13Y-gMECP2) messenger RNA for degradation and reducing protein levels in the brain of humanized MECP2 transgenic mice. Moreover, the intracerebroventricular adeno-associated virus (AAV) delivery of hfCas13Y-gMECP2 in newborn or adult MDS mice restored dysregulated gene expression and improved behavior deficits. Notably, treatment with AAV9-hfCas13Y-gMECP2 extended the median survival of MECP2 transgenic mice from 156.5 to 226 d. Furthermore, studies with monkeys showed a single injection of AAV9-hfCas13Y-gMECP2 was sufficient to drive robust expression of hfCas13Y in widespread brain regions, with MECP2 knockdown efficiency reaching 52.19 ± 0.03% and significantly decreased expression of biomarker gene GDF11. Our results demonstrate that the RNA-targeting hfCas13Y-gMECP2 system is an effective intervention for MDS, providing a potential strategy for treating other dosage-sensitive diseases.

Intravital Imaging of Disease Mechanisms in a Mouse Model of CCM Skin Lesions-Brief Report

BACKGROUND

Cerebral cavernous malformation (CCM) is a disease characterized by vascular malformations that primarily develop in the brain. These malformations are prone to leak, and their rupture or thrombotic closure can cause life-threatening hemorrhages and strokes. Mouse models have been instrumental to study the disease, but most cause premature lethality, precluding the investigation of disease mechanisms through intravital microscopy. Current mouse models also do not recapitulate human CCM skin lesions.

METHODS

Endothelial-specific deletion of Ccm3 via systemic tamoxifen application at postnatal day 4 or 5 prolongs survival and induces vascular malformations in the mouse brain and ear skin. CCM skin lesions can also be induced by topical tamoxifen administration directly to the ear. The thin, flat morphology of the ear skin is ideal for intravital microscopy. Dextran dyes and platelet markers allow to study blood flow and blood clot formation in living animals, in real time.

RESULTS

We report that human CCM skin lesions can be recapitulated in a mouse model and that skin lesions share hallmarks of CCM brain lesions. Intravital imaging reveals that CCM skin lesions are slow-flow malformations prone to thrombus formation.

CONCLUSIONS

Intravital imaging of CCM skin lesions expands the toolkit of CCM research and allows longitudinal studies of lesion growth.

Retro-Orbital Delivery of AAVs for CNS Wide Astrocyte Targeting

Viral vector-mediated astrocyte targeting in live mice is a popular and valuable method to investigate astrocyte function in the context of intact neural circuits and complex brain physiology. Targeted genetic manipulation and functional investigation of this cell population can be accomplished by utilizing cell type-specific promoters to drive adeno-associated virus (AAV)-mediated transgene expression specifically in astrocytes. Here, we provide a comprehensive protocol for non-invasive retro-orbital (RO) administration of blood-brain barrier (BBB)-crossing AAVs in neonatal and adult mice, such as AAV-PHP.B, AAV-PHP.eB, and AAV.CAP-B22, which results in central nervous system (CNS)-wide transduction. Key procedures outlined include the preparation of AAV solutions for injection, a modified two-handed injection technique for precise and consistent RO injections, and a training strategy to practice mock RO injections using non-toxic dyes. This protocol serves as a valuable resource for researchers interested in exploring the roles of astrocytes in brain functions and neurological disorders.

CRISPR screening by AAV episome-sequencing (CrAAVe-seq) is a highly scalable cell type-specific in vivo screening platform

There is a significant need for scalable CRISPR-based genetic screening methods that can be applied directly in mammalian tissues in vivo while enabling cell type-specific analysis. To address this, we developed an adeno-associated virus (AAV)-based CRISPR screening platform, CrAAVe-seq, that incorporates a Cre-sensitive sgRNA construct for pooled screening within targeted cell populations in mouse tissues. We demonstrate the utility of this approach by screening two distinct large sgRNA libraries, together targeting over 5,000 genes, in mouse brains to create a robust profile of neuron-essential genes. We validate two genes as strongly neuron-essential in both primary mouse neurons and in vivo, confirming the predictive power of our platform. By comparing results from individual mice and across different cell populations, we highlight the reproducibility and scalability of the platform and show that it is highly sensitive even for screening smaller neuronal subpopulations. We systematically characterize the impact of sgRNA library size, mouse cohort size, the size of the targeted cell population, viral titer, and multiplicity of infection on screen performance to establish general guidelines for large-scale in vivo screens.

Optimal different adeno-associated virus capsid/promoter combinations to target specific cell types in the common marmoset cerebral cortex

To achieve cell-type-specific gene expression, using target cell-type-tropic different adeno-associated virus (AAV) capsids is advantageous. However, their tropism across brain cell types in nonhuman primates has not been fully elucidated. We assessed the tropism of nine AAV serotype capsids (AAV1, 2, 5, 6, 7, 8, 9, rh10, and DJ) expressing EGFP by chicken β-actin hybrid (CBh) promoter in marmoset cerebral cortical cells. All nine AAV capsid vectors, especially AAV9 and AAVrh10, caused highly neuron-selective EGFP expression. Some AAV capsids, including AAV5, induced EGFP expression to a lesser extent in oligodendrocytes. Different ubiquitous cytomegalovirus (CMV) and CMV early enhancer/chicken β-actin (CAG) promoters exhibited similar neuron-predominant transgene expression. Conversely, all nine AAV capsid vectors with the astrocyte-specific hGFA(ABC1D) promoter selectively expressed EGFP in astrocytes, except AAV5, which modestly expressed EGFP in oligodendrocytes. Oligodendrocyte-specific mouse myelin basic protein (mMBP) promoter in AAV5 vectors expressed EGFP in oligodendrocytes specifically and efficiently. The following are optimal combinations of capsids and promoters for cell-type-specific expression: AAV9 or AAVrh10 and ubiquitous CBh or CMV promoter for neuron-specific transgene expression, AAV2 or AAV7 and hGFA(ABC1D) promoters for astrocyte-specific transgene expression, and AAV5 and mMBP promoters for oligodendrocyte-specific transgene expression.

Another-regulin regulates cardiomyocyte calcium handling via integration of neuroendocrine signaling with SERCA2a activity

Calcium (Ca2+) dysregulation is a hallmark feature of cardiovascular disease. Intracellular Ca2+ regulation is essential for proper heart function and is controlled by the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA2a). Another-regulin (ALN) is a newly discovered cardiomyocyte-expressed SERCA2a inhibitor, suggesting cardiomyocyte Ca2+-handling is more complex than previously appreciated. To study the role of ALN in cardiomyocytes, we generated ALN null mice (knockout, KO) and found that cardiomyocytes from these animals displayed enhanced Ca2+ cycling and contractility compared to wildtype (WT) mice, indicating enhanced SERCA2a activity. In vitro and in vivo studies show that ALN is post-translationally modified via phosphorylation on Serine 19 (S19), suggesting this contributes to its ability to regulate SERCA2a. Immunoprecipitation and FRET analysis of ALN-WT, phospho-deficient ALN (S19A), or phosphomimetic ALN (S19D) revealed that S19 phosphorylation alters the SERCA2a-ALN interaction, leading to relief of its inhibitory effects. Adeno-associated virus mediated delivery of ALN-WT or phospho-mutant ALN-S19A/D in ALN KO mice showed that cardiomyocyte-specific expression of phospho-deficient ALN-S19A resulted in increased SERCA2a inhibition characterized by reduced rates of cytoplasmic Ca2+ clearance compared to ALN-WT and ALN-S19D expressing cells, further supporting a role for this phosphorylation event in controlling SERCA2a-regulation by ALN. Levels of ALN phosphorylation were markedly increased in cardiomyocytes in response to Gαq agonists (angiotensin II, endothelin-1, phenylephrine) and Gαq-mediated phosphorylation of ALN translated to increased Ca2+ cycling in cardiomyocytes from WT but not ALN KO mice. Collectively, these results indicate that ALN uniquely regulates Ca2+ handling in cardiomyocytes via integration of neuroendocrine signaling with SERCA2a activity.

Postsynaptic competition between calcineurin and PKA regulates mammalian sleep-wake cycles

The phosphorylation of synaptic proteins is a significant biochemical reaction that controls the sleep-wake cycle in mammals1-3. Protein phosphorylation in vivo is reversibly regulated by kinases and phosphatases. In this study, we investigate a pair of kinases and phosphatases that reciprocally regulate sleep duration. First, we perform a comprehensive screen of protein kinase A (PKA) and phosphoprotein phosphatase (PPP) family genes by generating 40 gene knockout mouse lines using prenatal and postnatal CRISPR targeting. We identify a regulatory subunit of PKA (Prkar2b), a regulatory subunit of protein phosphatase 1 (PP1; Pppr1r9b) and catalytic and regulatory subunits of calcineurin (also known as PP2B) (Ppp3ca and Ppp3r1) as sleep control genes. Using adeno-associated virus (AAV)-mediated stimulation of PKA and PP1-calcineurin activities, we show that PKA is a wake-promoting kinase, whereas PP1 and calcineurin function as sleep-promoting phosphatases. The importance of these phosphatases in sleep regulation is supported by the marked changes in sleep duration associated with their increased and decreased activities, ranging from approximately 17.3 h per day (PP1 expression) to 4.3 h per day (postnatal CRISPR targeting of calcineurin). Localization signals to the excitatory post-synapse are necessary for these phosphatases to exert their sleep-promoting effects. Furthermore, the wake-promoting effect of PKA localized to the excitatory post-synapse negated the sleep-promoting effect of PP1-calcineurin. These findings indicate that PKA and PP1-calcineurin have competing functions in sleep regulation at excitatory post-synapses.

Tropism of adeno-associated virus serotypes in mouse lungs via intratracheal instillation

BACKGROUND

Gene therapy holds great potential for treating various acquired and inherited pulmonary diseases. Adeno-associated viral (AAV) vectors have been thought to be primary candidates for gene delivery in patients with pulmonary diseases. However, the tropism of AAVs in the lungs remains largely unknown.

RESULTS

Here, we investigate the tropism of twenty serotypes of AAVs by examining AAV-packed vector expression of the enhanced green fluorescent protein (eGFP) in mice. AAV1, AAV4, AAV5, AAV6, AAV6.2, AAV-PHP.B, and AAV-PHP.S exhibit high transduction rates in the airway epithelium. AAV1, AAV4, AAV5, AAV6, and AAV6.2 highly infect club cells. AAV1, AAV4, AAV5, AAV6, AAV6.2, and AAV-PHP.B efficiently infect ciliated cells. AAV8 and AAVrh10 can infect a few alveolar type I cells. AAV1, AAV5, AAV6, AAV6.2, AAV9, and AAVie can infect alveolar type II cells. AAV1, AAV5, AAVie, AAV-PHP.B, AAV-PHP.eB, and AAV-PHP.S can infect a few endothelial cells. However, none of these AAVs can efficiently infect neuroendocrine or smooth muscle cells.

CONCLUSIONS

Our findings provide comprehensive information about the tropism of AAVs in pulmonary epithelium in mice, which might be helpful in developing efficient AAV-mediated gene therapy strategies for pulmonary disease treatment.

A key role of PIEZO2 mechanosensitive ion channel in adipose sensory innervation

Compared to the well-established functions of sympathetic innervation, the role of sensory afferents in adipose tissues remains less understood. Recent work revealed the anatomical and physiological significance of adipose sensory innervation; however, its molecular underpinning remains unclear. Here, using organ-targeted single-cell RNA sequencing, we identified the mechanoreceptor PIEZO2 as one of the most prevalent receptors in fat-innervating dorsal root ganglia (DRG) neurons. We found that selective PIEZO2 deletion in fat-innervating neurons phenocopied the molecular alternations in adipose tissue caused by DRG ablation. Conversely, a gain-of-function PIEZO2 mutant shifted the adipose phenotypes in the opposite direction. These results indicate that PIEZO2 plays a major role in the sensory regulation of adipose tissues. This discovery opens new avenues for exploring mechanosensation in organs not traditionally considered mechanically active, such as the adipose tissues, and therefore sheds light on the broader significance of mechanosensation in regulating organ function and homeostasis.

NMDA Receptors in Neurodevelopmental Disorders: Pathophysiology and Disease Models

N-methyl-D-aspartate receptors (NMDARs) are critical components of the mammalian central nervous system, involved in synaptic transmission, plasticity, and neurodevelopment. This review focuses on the structural and functional characteristics of NMDARs, with a particular emphasis on the GRIN2 subunits (GluN2A-D). The diversity of GRIN2 subunits, driven by alternative splicing and genetic variants, significantly impacts receptor function, synaptic localization, and disease manifestation. The temporal and spatial expression of these subunits is essential for typical neural development, with each subunit supporting distinct phases of synaptic formation and plasticity. Disruptions in their developmental regulation are linked to neurodevelopmental disorders, underscoring the importance of understanding these dynamics in NDD pathophysiology. We explore the physiological properties and developmental regulation of these subunits, highlighting their roles in the pathophysiology of various NDDs, including ASD, epilepsy, and schizophrenia. By reviewing current knowledge and experimental models, including mouse models and human-induced pluripotent stem cells (hiPSCs), this article aims to elucidate different approaches through which the intricacies of NMDAR dysfunction in NDDs are currently being explored. The comprehensive understanding of NMDAR subunit composition and their mutations provides a foundation for developing targeted therapeutic strategies to address these complex disorders.

Engineered serum markers for non-invasive monitoring of gene expression in the brain

Measurement of gene expression in the brain requires invasive analysis of brain tissue or non-invasive methods that are limited by low sensitivity. Here we introduce a method for non-invasive, multiplexed, site-specific monitoring of endogenous gene or transgene expression in the brain through engineered reporters called released markers of activity (RMAs). RMAs consist of an easily detectable reporter and a receptor-binding domain that enables transcytosis across the brain endothelium. RMAs are expressed in the brain but exit into the blood, where they can be easily measured. We show that expressing RMAs at a single mouse brain site representing approximately 1% of the brain volume provides up to a 100,000-fold signal increase over the baseline. Expression of RMAs in tens to hundreds of neurons is sufficient for their reliable detection. We demonstrate that chemogenetic activation of cells expressing Fos-responsive RMA increases serum RMA levels >6-fold compared to non-activated controls. RMAs provide a non-invasive method for repeatable, multiplexed monitoring of gene expression in the intact animal brain.

Bidirectional Control of Emotional Behaviors by Excitatory and Inhibitory Neurons in the Orbitofrontal Cortex

The orbitofrontal cortex (OFC) plays a crucial role in mood disorders; however, its specific role in the emotional behaviors of mice remains unclear. This study investigates the bidirectional control of emotional behaviors using population calcium dynamics and optogenetic manipulation of OFC neurons. Fiber photometry of OFC neurons revealed that OFC excitatory neurons consistently responded to the onset and offset of aversive conditions, showing decreased activation in response to anxiogenic and stressful stimuli, including tail suspension, restraint stress, and exposure to the center of the open field. The selective activation of excitatory neurons in the OFC reduced the time spent in the center of the open field, whereas optogenetic activation of inhibitory neurons in the OFC induced the opposite behavioral changes. We also provided a brain-wide activation map for OFC excitatory and inhibitory neuron activation. Our findings demonstrate that excitatory and inhibitory neurons in the OFC play opposing roles in the regulation of emotional behaviors. These results provide new insights into the neural mechanisms underlying emotional control and suggest that targeting these specific neuronal populations may offer novel therapeutic strategies for emotional disorders.

Astrocyte regional specialization is shaped by postnatal development

Astrocytes are an abundant class of glial cells with critical roles in neural circuit assembly and function. Though many studies have uncovered significant molecular distinctions between astrocytes from different brain regions, how this regionalization unfolds over development is not fully understood. We used single-nucleus RNA sequencing to characterize the molecular diversity of brain cells across six developmental stages and four brain regions in the mouse and marmoset brain. Our analysis of over 170,000 single astrocyte nuclei revealed striking regional heterogeneity among astrocytes, particularly between telencephalic and diencephalic regions, at all developmental time points surveyed in both species. At the stages sampled, most of the region patterning was private to astrocytes and not shared with neurons or other glial types. Though astrocytes were already regionally patterned in late embryonic stages, this region-specific astrocyte gene expression signature changed dramatically over postnatal development, and its composition suggests that regional astrocytes further specialize postnatally to support their local neuronal circuits. Comparing across species, we found divergence in the expression of astrocytic region- and age-differentially expressed genes and the timing of astrocyte maturation relative to birth between mouse and marmoset, as well as hundreds of species differentially expressed genes. Finally, we used expansion microscopy to show that astrocyte morphology is largely conserved across gray matter regions of prefrontal cortex, striatum, and thalamus in the mouse, despite substantial molecular divergence.

Size-reduced DREADD derivatives for AAV-assisted multimodal chemogenetic control of neuronal activity and behavior

Designer receptors exclusively activated by designer drugs (DREADDs) are engineered G-protein-coupled receptors that afford reversible manipulation of neuronal activity in vivo. Here, we introduce size-reduced DREADD derivatives miniDq and miniDi, which inherit the basic receptor properties from the Gq-coupled excitatory receptor hM3Dq and the Gi-coupled inhibitory receptor hM4Di, respectively, while being approximately 30% smaller in size. Taking advantage of the compact size of the receptors, we generated an adeno-associated virus (AAV) vector carrying both miniDq and the other DREADD family receptor (κ-opioid receptor-based inhibitory DREADD [KORD]) within the maximum AAV capacity (4.7 kb), allowing us to modulate neuronal activity and animal behavior in both excitatory and inhibitory directions using a single viral vector. We confirmed that expressing miniDq, but not miniDi, allowed activation of striatum activity in the cynomolgus monkey (Macaca fascicularis). The compact DREADDs may thus widen the opportunity for multiplexed interrogation and/or intervention in neuronal regulation in mice and non-human primates.

Heterogeneous Nuclear Ribonucleoprotein A1 Knockdown Alters Constituents of Nucleocytoplasmic Transport

BACKGROUND/OBJECTIVES

Changes in nuclear morphology, alterations to the nuclear pore complex (NPC), including loss, aggregation, and dysfunction of nucleoporins (Nups), and nucleocytoplasmic transport (NCT) abnormalities have become hallmarks of neurodegenerative diseases. Previous RNA sequencing data utilizing knockdown of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) identified enrichment for pathways and changes in RNAs related to nuclear morphology and showed differential expression of key nuclear targets. This suggests that dysfunction of hnRNP A1, which is observed in neurodegenerative diseases, may contribute to abnormalities in nuclear morphology, NPC, and NCT.

METHODS

We performed knockdown of hnRNP A1 in Neuro-2A cells, a neuronal cell line, to examine nuclear morphology, NPC, and NCT.

RESULTS

First, we examined nuclear morphology using Lamin B, wherein we observed increased nuclear envelope abnormalities in cells with hnRNP A1 knockdown as compared to control. To quantify changes in Lamin B, we designed and validated an automated computer-based model, which quantitatively confirmed our observations. Next, we investigated the impact of hnRNP A1 knockdown on components of the NPC and NCT. In line with the previous literature, we found changes in Nups, including altered distribution and reduced protein expression, as well as disrupted NCT. Finally, we validated our findings in multiple sclerosis (MS) brains, a disease with a significant neurodegenerative component caused by hnRNP A1 dysfunction, where neuronal nuclear envelope alterations were significantly increased as compared to controls.

CONCLUSIONS

Together, these data implicate hnRNP A1 as an important contributor to nuclear morphology, Nup expression and distribution, and NCT and suggest that hnRNP A1 dysfunction may lead to defects in these processes in neurodegenerative diseases.

Advanced deep-tissue imaging and manipulation enabled by biliverdin reductase knockout

We developed near-infrared (NIR) photoacoustic and fluorescence probes, as well as optogenetic tools from bacteriophytochromes, and enhanced their performance using biliverdin reductase-A knock-out model (Blvra-/-). Blvra-/- elevates endogenous heme-derived biliverdin chromophore for bacteriophytochrome-derived NIR constructs. Consequently, light-controlled transcription with IsPadC-based optogenetic tool improved up to 25-fold compared to wild-type cells, with 100-fold activation in Blvra-/- neurons. In vivo , light-induced insulin production in Blvra-/- reduced blood glucose in diabetes by ∼60%, indicating high potential for optogenetic therapy. Using 3D photoacoustic, ultrasound, and two-photon fluorescence imaging, we overcame depth limitations of recording NIR probes. We achieved simultaneous photoacoustic imaging of DrBphP in neurons and super-resolution ultrasound localization microscopy of blood vessels ∼7 mm deep in the brain, with intact scalp and skull. Two-photon microscopy provided cell-level resolution of miRFP720-expressing neurons ∼2.2 mm deep. Blvra-/- significantly enhances efficacy of biliverdin-dependent NIR systems, making it promising platform for interrogation and manipulation of biological processes.

The neuroscience of mental illness: Building toward the future

Mental illnesses arise from dysfunction in the brain. Although numerous extraneural factors influence these illnesses, ultimately, it is the science of the brain that will lead to novel therapies. Meanwhile, our understanding of this complex organ is incomplete, leading to the oft-repeated trope that neuroscience has yet to make significant contributions to the care of individuals with mental illnesses. This review seeks to counter this narrative, using specific examples of how neuroscientific advances have contributed to progress in mental health care in the past and how current achievements set the stage for further progress in the future.

An atlas of the aging mouse proteome reveals the features of age-related post-transcriptional dysregulation

To what extent and how post-transcriptional dysregulation affects aging proteome remains unclear. Here, we provide proteomic data of whole-tissue lysates (WTL) and low-solubility protein-enriched fractions (LSF) of major tissues collected from mice of 6, 15, 24, and 30 months of age. Low-solubility proteins are preferentially affected by age and the analysis of LSF doubles the number of proteins identified to be differentially expressed with age. Simultaneous analysis of proteome and transcriptome using the same tissue homogenates reveals the features of age-related post-transcriptional dysregulation. Post-transcriptional dysregulation becomes evident especially after 24 months of age and age-related post-transcriptional dysregulation leads to accumulation of core matrisome proteins and reduction of mitochondrial membrane proteins in multiple tissues. Based on our in-depth proteomic data and sample-matched transcriptome data of adult, middle-aged, old, and geriatric mice, we construct the Mouse aging proteomic atlas ( https://aging-proteomics.info/ ), which provides a thorough and integrative view of age-related gene expression changes.

In situ direct reprogramming of astrocytes to neurons via polypyrimidine tract-binding protein 1 knockdown in a mouse model of ischemic stroke

JOURNAL/nrgr/04.03/01300535-202410000-00025/figure1/v/2024-02-06T055622Z/r/image-tiff In situ direct reprogramming technology can directly convert endogenous glial cells into functional neurons in vivo for central nervous system repair. Polypyrimidine tract-binding protein 1 (PTB) knockdown has been shown to reprogram astrocytes to functional neurons in situ. In this study, we used AAV-PHP.eB-GFAP-shPTB to knockdown PTB in a mouse model of ischemic stroke induced by endothelin-1, and investigated the effects of GFAP-shPTB-mediated direct reprogramming to neurons. Our results showed that in the mouse model of ischemic stroke, PTB knockdown effectively reprogrammed GFAP-positive cells to neurons in ischemic foci, restored neural tissue structure, reduced inflammatory response, and improved behavioral function. These findings validate the effectiveness of in situ transdifferentiation of astrocytes, and suggest that the approach may be a promising strategy for stroke treatment.

Daily light-induced transcription in visual cortex neurons drives downward firing rate homeostasis and stabilizes sensory processing

Balancing plasticity and stability in neural circuits is essential for an animal's ability to learn from its environment while preserving proper processing and perception of sensory information. However, unlike the mechanisms that drive plasticity in neural circuits, the activity-induced molecular mechanisms that convey functional stability remain poorly understood. Focusing on the visual cortex of adult mice and combining transcriptomics, electrophysiology, and in vivo calcium imaging, we find that the daily appearance of light induces, in excitatory neurons, a large gene program along with rapid and transient increases in the ratio of excitation and inhibition (E/I ratio) and neural activity. Furthermore, we find that the light-induced transcription factor NPAS4 drives these daily normalizations of the E/I ratio and neural activity rates and that it stabilizes the neurons' response properties. These findings indicate that daily sensory-induced transcription normalizes the E/I ratio and drives downward firing rate homeostasis to maintain proper sensory processing and perception.

Thyroid Hormone Clearance in the Paraventricular Nucleus of Male Mice Regulates Lean Mass and Physical Activity

INTRODUCTION

The actions of thyroid hormones (THs) in the central nervous system are relevant to food intake and energy expenditure. TH receptors exhibit high expression in brain areas modulating energy balance, including the arcuate, paraventricular (PVN), supraoptic, and ventromedial (VMH) hypothalamic nuclei.

METHODS

To examine the role of THs in the regulation of energy balance via action in specific hypothalamic nuclei of the adult mouse, we performed experiments of conditional inactivation of DIO3, the enzyme responsible for the clearance of THs, in the lateral hypothalamus (LH), and VMH and PVN hypothalamic nuclei. We accomplished DIO3 genetic inactivation via stereotaxic injection of the AAV-cre vector into adult mice homozygous for a "floxed" Dio3 allele.

RESULTS

Dio3 inactivation in the LH and VMH of males or females did not result in significant changes in body weight 8 weeks after injection. However, inactivation of Dio3 in the PVN resulted in increased body weight (both fat mass and lean mass) and locomotor activity, and decreased hypothalamic Mc4r expression in male, but not female mice. However, PNV-specific Dio3 KO did not cause hyperphagia.

CONCLUSION

These results suggest local TH action influences MC4R signaling and possibly other PVN-associated circuitries, with consequences for body composition and energy balance endpoints, but not for orexigenic pathways. They also support a regulatory role for PVN Dio3 in the central regulation of energy homeostasis in adult life.

Human cell surface-AAV interactomes identify LRP6 as blood-brain barrier transcytosis receptor and immune cytokine IL3 as AAV9 binder

Adeno-associated viruses (AAVs) are foundational gene delivery tools for basic science and clinical therapeutics. However, lack of mechanistic insight, especially for engineered vectors created by directed evolution, can hamper their application. Here, we adapt an unbiased human cell microarray platform to determine the extracellular and cell surface interactomes of natural and engineered AAVs. We identify a naturally-evolved and serotype-specific interaction between the AAV9 capsid and human interleukin 3 (IL3), with possible roles in host immune modulation, as well as lab-evolved low-density lipoprotein receptor-related protein 6 (LRP6) interactions specific to engineered capsids with enhanced blood-brain barrier crossing in non-human primates after intravenous administration. The unbiased cell microarray screening approach also allows us to identify off-target tissue binding interactions of engineered brain-enriched AAV capsids that may inform vectors' peripheral organ tropism and side effects. Our cryo-electron tomography and AlphaFold modeling of capsid-interactor complexes reveal LRP6 and IL3 binding sites. These results allow confident application of engineered AAVs in diverse organisms and unlock future target-informed engineering of improved viral and non-viral vectors for non-invasive therapeutic delivery to the brain.

Activation of Cell-Intrinsic Signaling in CAR-T Cells via a Chimeric IL7R Domain

Chimeric antigen receptor (CAR) T cells can effectively treat leukemias, but sustained antitumor responses can be hindered by a lack of CAR T-cell persistence. Cytotoxic effector T cells are short-lived, and establishment of CAR-T cells with memory to ensure immune surveillance is important. Memory T cells depend on cytokine support, with IL7 activation of the IL7 receptor (IL7R) being critical. However, IL7R surface expression is negatively regulated by exposure to IL7. We aimed to support CAR T-cell persistence by equipping CAR-T cells with a sustained IL7Rα signal. We engineered T cells to constitutively secrete IL7 or to express an anti-acute myeloid leukemia-targeted IL7Rα-chimeric cytokine receptor (CCR) and characterized the phenotype of these cell types. Canonical downstream signaling was activated in CCR-T cells with IL7R activation. When coexpressed with a cytotoxic CAR, functionality of both the CCR and CAR was maintained. We designed hybrid CAR-CCR and noted membrane proximity of the intracellular domains as vital for signaling. These data show cell-intrinsic cytokine support with canonical signaling, and functionality can be provided via expression of an IL7Rα domain whether independently expressed or incorporated into a cytotoxic CAR for use in anticancer therapy.

SIGNIFICANCE

To improve the phenotype of tumor-directed T-cell therapy, we show that provision of cell-intrinsic IL7R-mediated signaling is preferable to activation of cells with exogenous IL7. We engineer this signaling via independent receptor engineering and incorporation into a CAR and validate maintained antigen-specific cytotoxic activity.

Microglia contribute to polyG-dependent neurodegeneration in neuronal intranuclear inclusion disease

Neuronal intranuclear inclusion disease (NIID) is a neurodegenerative disorder caused by the expansion of GGC trinucleotide repeats in NOTCH2NLC gene. Despite identifying uN2CpolyG, a toxic polyglycine (polyG) protein translated by expanded GGC repeats, the exact pathogenic mechanisms of NIID remain unclear. In this study, we investigated the role of polyG by expressing various forms of NOTCH2NLC in mice: the wild-type, the expanded form with 100 GGC repeats (either translating or not translating into uN2CpolyG), and the mutated form that encodes a pure polyG without GGC-repeat RNA and the C-terminal stretch (uN2CpolyG-dCT). Both uN2CpolyG and uN2CpolyG-dCT induced the formation of inclusions composed by filamentous materials and resulted in neurodegenerative phenotypes in mice, including impaired motor and cognitive performance, shortened lifespan, and pathologic lesions such as white-matter lesions, microgliosis, and astrogliosis. In contrast, expressing GGC-repeat RNA alone was non-pathogenic. Through bulk and single-nuclei RNA sequencing, we identified common molecular signatures linked to the expression of uN2CpolyG and uN2CpolyG-dCT, particularly the upregulation of inflammation and microglia markers, and the downregulation of immediate early genes and splicing factors. Importantly, microglia-mediated inflammation was visualized in NIID patients using positron emission tomography, correlating with levels of white-matter atrophy. Furthermore, microglia ablation ameliorated neurodegenerative phenotypes and transcriptional alterations in uN2CpolyG-expressing mice but did not affect polyG inclusions. Together, these results demonstrate that polyG is crucial for the pathogenesis of NIID and highlight the significant role of microglia in polyG-induced neurodegeneration.

Alzheimer's disease protective allele of Clusterin modulates neuronal excitability through lipid-droplet-mediated neuron-glia communication

Genome-wide association studies (GWAS) of Alzheimer's disease (AD) have identified a plethora of risk loci. However, the disease variants/genes and the underlying mechanisms remain largely unknown. For a strong AD-associated locus near Clusterin (CLU), we tied an AD protective allele to a role of neuronal CLU in promoting neuron excitability through lipid-mediated neuron-glia communication. We identified a putative causal SNP of CLU that impacts neuron-specific chromatin accessibility to transcription-factor(s), with the AD protective allele upregulating neuronal CLU and promoting neuron excitability. Transcriptomic analysis and functional studies in induced pluripotent stem cell (iPSC)-derived neurons co-cultured with mouse astrocytes show that neuronal CLU facilitates neuron-to-glia lipid transfer and astrocytic lipid droplet formation coupled with reactive oxygen species (ROS) accumulation. These changes cause astrocytes to uptake less glutamate thereby altering neuron excitability. Our study provides insights into how CLU confers resilience to AD through neuron-glia interactions.

Systematic multi-trait AAV capsid engineering for efficient gene delivery

Broadening gene therapy applications requires manufacturable vectors that efficiently transduce target cells in humans and preclinical models. Conventional selections of adeno-associated virus (AAV) capsid libraries are inefficient at searching the vast sequence space for the small fraction of vectors possessing multiple traits essential for clinical translation. Here, we present Fit4Function, a generalizable machine learning (ML) approach for systematically engineering multi-trait AAV capsids. By leveraging a capsid library that uniformly samples the manufacturable sequence space, reproducible screening data are generated to train accurate sequence-to-function models. Combining six models, we designed a multi-trait (liver-targeted, manufacturable) capsid library and validated 88% of library variants on all six predetermined criteria. Furthermore, the models, trained only on mouse in vivo and human in vitro Fit4Function data, accurately predicted AAV capsid variant biodistribution in macaque. Top candidates exhibited production yields comparable to AAV9, efficient murine liver transduction, up to 1000-fold greater human hepatocyte transduction, and increased enrichment relative to AAV9 in a screen for liver transduction in macaques. The Fit4Function strategy ultimately makes it possible to predict cross-species traits of peptide-modified AAV capsids and is a critical step toward assembling an ML atlas that predicts AAV capsid performance across dozens of traits.

The Impact of Inflammation on Thermal Hyperpnea: Relevance for Heat Stress and Febrile Seizures

Extreme heat caused by climate change is increasing the transmission of infectious diseases, resulting in a sharp rise in heat-related illness and mortality. Understanding the mechanistic link between heat, inflammation, and disease is thus important for public health. Thermal hyperpnea, and consequent respiratory alkalosis, is crucial in febrile seizures and convulsions induced by heat stress in humans. Here, we address what causes thermal hyperpnea in neonates and how it is affected by inflammation. Transient receptor potential cation channel subfamily V member 1 (TRPV1), a heat-activated channel, is sensitized by inflammation and modulates breathing and thus may play a key role. To investigate whether inflammatory sensitization of TRPV1 modifies neonatal ventilatory responses to heat stress, leading to respiratory alkalosis and an increased susceptibility to hyperthermic seizures, we treated neonatal rats with bacterial LPS, and breathing, arterial pH, in vitro vagus nerve activity, and seizure susceptibility were assessed during heat stress in the presence or absence of a TRPV1 antagonist (AMG-9810) or shRNA-mediated TRPV1 suppression. LPS-induced inflammatory preconditioning lowered the threshold temperature and latency of hyperthermic seizures. This was accompanied by increased tidal volume, minute ventilation, expired CO2, and arterial pH (alkalosis). LPS exposure also elevated vagal spiking and intracellular calcium concentrations in response to hyperthermia. TRPV1 inhibition with AMG-9810 or shRNA reduced the LPS-induced susceptibility to hyperthermic seizures and altered the breathing pattern to fast shallow breaths (tachypnea), making each breath less efficient and restoring arterial pH. These results indicate that inflammation exacerbates thermal hyperpnea-induced respiratory alkalosis associated with increased susceptibility to hyperthermic seizures, primarily mediated by TRPV1 localized to vagus neurons.

Adeno-associated virus vector delivery to the brain: Technology advancements and clinical applications

Adeno-associated virus (AAV) vectors have emerged as a promising tool in the development of gene therapies for various neurological diseases, including Alzheimer's disease and Parkinson's disease. However, the blood-brain barrier (BBB) poses a significant challenge to successfully delivering AAV vectors to the brain. Strategies that can overcome the BBB to improve the AAV delivery efficiency to the brain are essential to successful brain-targeted gene therapy. This review provides an overview of existing strategies employed for AAV delivery to the brain, including direct intraparenchymal injection, intra-cerebral spinal fluid injection, intranasal delivery, and intravenous injection of BBB-permeable AAVs. Focused ultrasound has emerged as a promising technology for the noninvasive and spatially targeted delivery of AAV administered by intravenous injection. This review also summarizes each strategy's current preclinical and clinical applications in treating neurological diseases. Moreover, this review includes a detailed discussion of the recent advances in the emerging focused ultrasound-mediated AAV delivery. Understanding the state-of-the-art of these gene delivery approaches is critical for future technology development to fulfill the great promise of AAV in neurological disease treatment.

Production of VP3-only virus-like particles of Adeno-associated virus 2 in E. coli cells

Adeno-associated Virus (AAV) is a promising vector for gene therapy. However, few studies have focused on producing virus-like particles (VLPs) of AAV in cells, especially in E. coli. In this study, we describe a method to produce empty VP3-only VLPs of AAV2 in E. coli by co-expressing VP3 and assembly-activating protein (AAP) of AAV2. Although the yields of VLPs produced with our method were low, the VLPs were able to self-assemble in E. coli without the need of in vitro capsid assembly. The produced VLPs were characterized by immunological detection and transmission electron microscopy (TEM). In conclusion, this study demonstrated that capsid assembly of AAV2 is possible in E. coli, and E. coli may be a candidate system for production of VLPs of AAV.

Cortical parvalbumin neurons are responsible for homeostatic sleep rebound through CaMKII activation

The homeostatic regulation of sleep is characterized by rebound sleep after prolonged wakefulness, but the molecular and cellular mechanisms underlying this regulation are still unknown. In this study, we show that Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent activity control of parvalbumin (PV)-expressing cortical neurons is involved in homeostatic regulation of sleep in male mice. Prolonged wakefulness enhances cortical PV-neuron activity. Chemogenetic suppression or activation of cortical PV neurons inhibits or induces rebound sleep, implying that rebound sleep is dependent on increased activity of cortical PV neurons. Furthermore, we discovered that CaMKII kinase activity boosts the activity of cortical PV neurons, and that kinase activity is important for homeostatic sleep rebound. Here, we propose that CaMKII-dependent PV-neuron activity represents negative feedback inhibition of cortical neural excitability, which serves as the distributive cortical circuits for sleep homeostatic regulation.

Phospholipase C beta 1 in the dentate gyrus gates fear memory formation through regulation of neuronal excitability

Memory processes rely on a molecular signaling system that balances the interplay between positive and negative modulators. Recent research has focused on identifying memory-regulating genes and their mechanisms. Phospholipase C beta 1 (PLCβ1), highly expressed in the hippocampus, reportedly serves as a convergence point for signal transduction through G protein-coupled receptors. However, the detailed role of PLCβ1 in memory function has not been elucidated. Here, we demonstrate that PLCβ1 in the dentate gyrus functions as a memory suppressor. We reveal that mice lacking PLCβ1 in the dentate gyrus exhibit a heightened fear response and impaired memory extinction, and this excessive fear response is repressed by upregulation of PLCβ1 through its overexpression or activation using a newly developed optogenetic system. Last, our results demonstrate that PLCβ1 overexpression partially inhibits exaggerated fear response caused by traumatic experience. Together, PLCβ1 is crucial in regulating contextual fear memory formation and potentially enhancing the resilience to trauma-related conditions.