Publications by authors named "Viviana Gradinaru"

Dopaminergic neurons modulate movement, motivation, and learning by dynamically regulating dopamine release across distributed neural circuits. However, existing genetically encoded dopamine sensors lack the sensitivity and resolution to capture the full amplitude and temporal complexity of in vivo dopamine signaling, limiting insight into its functions across behavioral contexts. Here, we present dLight3.

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Crossing the blood-brain barrier while minimizing liver transduction is a key challenge in developing safe adeno-associated virus (AAV) vectors for treating brain disorders. In mice, the engineered capsid PHP.eB shows enhanced brain transduction, while the further engineered CAP-B10 is also de-targeted from astrocytes and liver.

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Neurons and astrocytes are predominant brain cells that extensively interact, but the molecular basis of their interactions remains largely unexplored. We identified and mapped striatal astrocytic and neuronal cell-surface proteins (CSPs) and found that many were shared, representing the cell-surface shared proteome of astrocytes and neurons (CS SPAN) bridging striatal astrocyte-neuron interaction sites. CS SPAN was replete with extracellular matrix proteins, cell adhesion molecules, transporters, ion channels, and G protein-coupled receptors.

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All optical physiology 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 () 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.

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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.

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Single-cell proteomics is an emerging field with significant potential to characterize heterogeneity within biological tissues. It offers complementary insights to single-cell transcriptomics by revealing unbiased proteomic changes downstream of the transcriptome. Recent advancements have focused on enhancing proteome coverage and depth, mostly in cultured cell lines, and a few recent studies have explored the potential of analyzing tissue micro-samples but were limited to homogenous peripheral tissues.

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Article Synopsis
  • Adeno-associated viruses (AAVs) are important tools used for delivering genes in research and clinical settings, but understanding how these viruses interact with cells can be challenging, especially for those that have been modified through directed evolution.
  • This study uses a human cell microarray platform to uncover how both natural and engineered AAVs connect with human cell receptors, discovering that AAV9 specifically interacts with interleukin 3 (IL3) and that engineered AAVs can interact with the low-density lipoprotein receptor-related protein 6 (LRP6), which might enhance their ability to cross the blood-brain barrier.
  • The findings also highlight potential side effects from engineered AAVs due to off-target tissue binding, paving the
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Article Synopsis
  • Deep-learning methods for protein structure prediction are highly accurate, but there's a gap in predicting which proteins can effectively bind to targets, limiting their practical applications in protein engineering.
  • To address this gap, a new tool called APPRAISE has been developed, which scores the target-binding ability of engineered proteins after their structures are predicted using tools like AlphaFold or ESMFold, doing so in less than a second per model.
  • APPRAISE has been successfully tested for various engineered proteins, including those targeting the SARS-CoV-2 spike and certain viral vectors, and is available online through Google Colaboratory, enhancing protein structure prediction and aiding biomedical research.
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A longstanding challenge in gene therapy is expressing a dosage-sensitive gene within a tight therapeutic window. For example, loss of function causes Rett syndrome, while its duplication causes duplication syndrome. Viral gene delivery methods generate variable numbers of gene copies in individual cells, creating a need for gene dosage-invariant expression systems.

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The gastrointestinal (GI) tract is innervated by intrinsic neurons of the enteric nervous system (ENS) and extrinsic neurons of the central nervous system and peripheral ganglia. The GI tract also harbors a diverse microbiome, but interactions between the ENS and the microbiome remain poorly understood. Here, we activate choline acetyltransferase (ChAT)-expressing or tyrosine hydroxylase (TH)-expressing gut-associated neurons in mice to determine effects on intestinal microbial communities and their metabolites as well as on host physiology.

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Article Synopsis
  • Integrating cell type-specific enhancers with recombinant adeno-associated viruses (AAVs) allows targeted genetic access to specific cell types, but AAVs have a limited capacity for the size of genetic material they can deliver.
  • The concept of transcriptional crosstalk involves separating large regulatory elements into a second AAV genome, offering a new way to achieve specific gene expression within a certain cell type.
  • The study identifies transcriptional crosstalk in AAVs with 11 mouse brain enhancers, using advanced spatial genomics to examine AAV behavior, and successfully demonstrates cell type-specific gene editing in tissues with minimal invasiveness.
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Background: Copy number variations, and particularly duplications of genomic regions, have been strongly associated with various neurodegenerative conditions including autism spectrum disorder (ASD). These genetic variations have been found to have a significant impact on brain development and function, which can lead to the emergence of neurological and behavioral symptoms. Developing strategies to target these genomic duplications has been challenging, as the presence of endogenous copies of the duplicate genes often complicates the editing strategies.

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Article Synopsis
  • Multi-wavelength analytical ultracentrifugation (MW-AUC) offers enhanced accuracy for characterizing and quantifying adeno-associated viruses compared to traditional methods.
  • Guidelines for experimental design in sedimentation velocity and buoyant density equilibrium AUC are provided.
  • MW-AUC effectively identifies capsid ratios and contaminants, detects partially filled capsids, and delivers more reliable results than dual-wavelength AUC, transmission electron microscopy, and mass photometry, reinforcing its status as the gold standard for analyzing viral vectors.
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The circadian rhythm pacemaker, the suprachiasmatic nucleus (SCN), mediates light entrainment via vasoactive intestinal peptide (VIP) neurons (SCN). Yet, how these neurons uniquely respond and connect to intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing melanopsin (Opn4) has not been determined functionally in freely behaving animals. To address this, we first used monosynaptic tracing from SCN neurons in mice and identified two SCN subpopulations.

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Crossing the blood-brain barrier in primates is a major obstacle for gene delivery to the brain. Adeno-associated viruses (AAVs) promise robust, non-invasive gene delivery from the bloodstream to the brain. However, unlike in rodents, few neurotropic AAVs efficiently cross the blood-brain barrier in non-human primates.

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Article Synopsis
  • Modern neuroscience tools, like optogenetics and calcium imaging, help researchers study specific brain circuits in rodents to understand neurological diseases.
  • Using viral vectors, scientists can deliver genetic material to target specific cells in engineered rodents, but applying these methods to nonhuman primates poses challenges due to limited viral vectors.
  • Recent advancements in adeno-associated viral vectors for nonhuman primates could enhance research capabilities, leading to better insights and potential treatments for neurological and neurodegenerative conditions.
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Delivering genes to and across the brain vasculature efficiently and specifically across species remains a critical challenge for addressing neurological diseases. We have evolved adeno-associated virus (AAV9) capsids into vectors that transduce brain endothelial cells specifically and efficiently following systemic administration in wild-type mice with diverse genetic backgrounds, and in rats. These AAVs also exhibit superior transduction of the CNS across non-human primates (marmosets and rhesus macaques), and in ex vivo human brain slices, although the endothelial tropism is not conserved across species.

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Copy number variations, and particularly duplications of genomic regions, have been strongly associated with various neurodegenerative conditions including autism spectrum disorder (ASD). These genetic variations have been found to have a significant impact on brain development and function, which can lead to the emergence of neurological and behavioral symptoms. Developing strategies to target these genomic duplications has been challenging, as the presence of endogenous copies of the duplicate genes often complicates the editing strategies.

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The blood-brain barrier (BBB) presents a major challenge for delivering large molecules to study and treat the central nervous system. This is due in part to the scarcity of targets known to mediate BBB crossing. To identify novel targets, we leverage a panel of adeno-associated viruses (AAVs) previously identified through mechanism-agnostic directed evolution for improved BBB transcytosis.

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Tissue clearing combined with deep imaging has emerged as a powerful technology to expand classical histological techniques. Current techniques have been optimized for imaging sparsely pigmented organs such as the mammalian brain. In contrast, melanin-rich pigmented tissue, of great interest in the investigation of melanomas, remains challenging.

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Adeno-associated viruses (AAVs) promise robust gene delivery to the brain through non-invasive, intravenous delivery. However, unlike in rodents, few neurotropic AAVs efficiently cross the blood-brain barrier in non-human primates (NHPs). Here we describe AAV.

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Article Synopsis
  • Efficient delivery of genes across the brain's blood vessels is crucial for treating neurological diseases, and modified adeno-associated viruses (AAV9) have been developed to target brain endothelial cells effectively in various animal models.
  • These modified AAVs show enhanced ability to transduce cells in non-human primates and human brain tissue, although their targeting efficiency varies across species.
  • The research indicates that these mouse-specific capsids can be utilized to alter the blood-brain barrier, turning it into a functional biofactory that produces beneficial proteins, like Hevin, to improve synaptic function in mice with synaptic deficits.
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Article Synopsis
  • - The study addresses the challenges of using engineered adeno-associated viral vectors (AAVs) for targeting specific cell types by developing a new method called USeqFISH, which allows for high-resolution spatial profiling of RNA in tissues.
  • - USeqFISH was used to analyze the transduction patterns of six different systemic AAVs in mouse brain regions, revealing unique preferences for certain cell subtypes, such as AAV-PHP.N favoring excitatory neurons.
  • - The method also facilitates the profiling of regulatory elements within AAV genomes and shows promise for applications in studying gene delivery in non-human primates.
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