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Cell Nov 2023Neurons build synaptic contacts using different protein combinations that define the specificity, function, and plasticity potential of synapses; however, the diversity...
Neurons build synaptic contacts using different protein combinations that define the specificity, function, and plasticity potential of synapses; however, the diversity of synaptic proteomes remains largely unexplored. We prepared synaptosomes from 7 different transgenic mouse lines with fluorescently labeled presynaptic terminals. Combining microdissection of 5 different brain regions with fluorescent-activated synaptosome sorting (FASS), we isolated and analyzed the proteomes of 18 different synapse types. We discovered ∼1,800 unique synapse-type-enriched proteins and allocated thousands of proteins to different types of synapses (https://syndive.org/). We identify shared synaptic protein modules and highlight the proteomic hotspots for synapse specialization. We reveal unique and common features of the striatal dopaminergic proteome and discover the proteome signatures that relate to the functional properties of different interneuron classes. This study provides a molecular systems-biology analysis of synapses and a framework to integrate proteomic information for synapse subtypes of interest with cellular or circuit-level experiments.
Topics: Animals; Mice; Brain; Mice, Transgenic; Proteome; Proteomics; Synapses; Synaptosomes
PubMed: 37918396
DOI: 10.1016/j.cell.2023.09.028 -
Nature Mar 2024Astrocytes are heterogeneous glial cells of the central nervous system. However, the physiological relevance of astrocyte diversity for neural circuits and behaviour...
Astrocytes are heterogeneous glial cells of the central nervous system. However, the physiological relevance of astrocyte diversity for neural circuits and behaviour remains unclear. Here we show that a specific population of astrocytes in the central striatum expresses μ-crystallin (encoded by Crym in mice and CRYM in humans) that is associated with several human diseases, including neuropsychiatric disorders. In adult mice, reducing the levels of μ-crystallin in striatal astrocytes through CRISPR-Cas9-mediated knockout of Crym resulted in perseverative behaviours, increased fast synaptic excitation in medium spiny neurons and dysfunctional excitatory-inhibitory synaptic balance. Increased perseveration stemmed from the loss of astrocyte-gated control of neurotransmitter release from presynaptic terminals of orbitofrontal cortex-striatum projections. We found that perseveration could be remedied using presynaptic inhibitory chemogenetics, and that this treatment also corrected the synaptic deficits. Together, our findings reveal converging molecular, synaptic, circuit and behavioural mechanisms by which a molecularly defined and allocated population of striatal astrocytes gates perseveration phenotypes that accompany neuropsychiatric disorders. Our data show that Crym-positive striatal astrocytes have key biological functions within the central nervous system, and uncover astrocyte-neuron interaction mechanisms that could be targeted in treatments for perseveration.
Topics: Animals; Humans; Mice; Astrocytes; Corpus Striatum; Gene Editing; Gene Knockout Techniques; mu-Crystallins; Rumination, Cognitive; Synaptic Transmission; CRISPR-Cas Systems; Medium Spiny Neurons; Synapses; Prefrontal Cortex; Presynaptic Terminals; Neural Inhibition
PubMed: 38418885
DOI: 10.1038/s41586-024-07138-0 -
Neuron Jul 2023In Alzheimer's disease, fibrillar tau pathology accumulates and spreads through the brain and synapses are lost. Evidence from mouse models indicates that tau spreads...
In Alzheimer's disease, fibrillar tau pathology accumulates and spreads through the brain and synapses are lost. Evidence from mouse models indicates that tau spreads trans-synaptically from pre- to postsynapses and that oligomeric tau is synaptotoxic, but data on synaptic tau in human brain are scarce. Here we used sub-diffraction-limit microscopy to study synaptic tau accumulation in postmortem temporal and occipital cortices of human Alzheimer's and control donors. Oligomeric tau is present in pre- and postsynaptic terminals, even in areas without abundant fibrillar tau deposition. Furthermore, there is a higher proportion of oligomeric tau compared with phosphorylated or misfolded tau found at synaptic terminals. These data suggest that accumulation of oligomeric tau in synapses is an early event in pathogenesis and that tau pathology may progress through the brain via trans-synaptic spread in human disease. Thus, specifically reducing oligomeric tau at synapses may be a promising therapeutic strategy for Alzheimer's disease.
Topics: Animals; Humans; Mice; Alzheimer Disease; Amyloid beta-Peptides; Brain; Presynaptic Terminals; Synapses; tau Proteins
PubMed: 37192625
DOI: 10.1016/j.neuron.2023.04.020 -
Nature Aug 2023Fasting initiates a multitude of adaptations to allow survival. Activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent release of glucocorticoid...
Fasting initiates a multitude of adaptations to allow survival. Activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent release of glucocorticoid hormones is a key response that mobilizes fuel stores to meet energy demands. Despite the importance of the HPA axis response, the neural mechanisms that drive its activation during energy deficit are unknown. Here, we show that fasting-activated hypothalamic agouti-related peptide (AgRP)-expressing neurons trigger and are essential for fasting-induced HPA axis activation. AgRP neurons do so through projections to the paraventricular hypothalamus (PVH), where, in a mechanism not previously described for AgRP neurons, they presynaptically inhibit the terminals of tonically active GABAergic afferents from the bed nucleus of the stria terminalis (BNST) that otherwise restrain activity of corticotrophin-releasing hormone (CRH)-expressing neurons. This disinhibition of PVH neurons requires γ-aminobutyric acid (GABA)/GABA-B receptor signalling and potently activates the HPA axis. Notably, stimulation of the HPA axis by AgRP neurons is independent of their induction of hunger, showing that these canonical 'hunger neurons' drive many distinctly different adaptations to the fasted state. Together, our findings identify the neural basis for fasting-induced HPA axis activation and uncover a unique means by which AgRP neurons activate downstream neurons: through presynaptic inhibition of GABAergic afferents. Given the potency of this disinhibition of tonically active BNST afferents, other activators of the HPA axis, such as psychological stress, may also work by reducing BNST inhibitory tone onto PVH neurons.
Topics: Agouti-Related Protein; Corticotropin-Releasing Hormone; Fasting; GABAergic Neurons; gamma-Aminobutyric Acid; Hypothalamo-Hypophyseal System; Neurons; Paraventricular Hypothalamic Nucleus; Pituitary-Adrenal System; Presynaptic Terminals; Septal Nuclei
PubMed: 37495689
DOI: 10.1038/s41586-023-06358-0 -
Molecular Psychiatry Sep 2023Accumulation of amyloid β-peptide (Aβ) is a driver of Alzheimer's disease (AD). Amyloid precursor protein (App) knock-in mouse models recapitulate AD-associated Aβ...
Accumulation of amyloid β-peptide (Aβ) is a driver of Alzheimer's disease (AD). Amyloid precursor protein (App) knock-in mouse models recapitulate AD-associated Aβ pathology, allowing elucidation of downstream effects of Aβ accumulation and their temporal appearance upon disease progression. Here we have investigated the sequential onset of AD-like pathologies in App and App knock-in mice by time-course transcriptome analysis of hippocampus, a region severely affected in AD. Strikingly, energy metabolism emerged as one of the most significantly altered pathways already at an early stage of pathology. Functional experiments in isolated mitochondria from hippocampus of both App and App mice confirmed an upregulation of oxidative phosphorylation driven by the activity of mitochondrial complexes I, IV and V, associated with higher susceptibility to oxidative damage and Ca-overload. Upon increasing pathologies, the brain shifts to a state of hypometabolism with reduced abundancy of mitochondria in presynaptic terminals. These late-stage mice also displayed enlarged presynaptic areas associated with abnormal accumulation of synaptic vesicles and autophagosomes, the latter ultimately leading to local autophagy impairment in the synapses. In summary, we report that Aβ-induced pathways in App knock-in mouse models recapitulate key pathologies observed in AD brain, and our data herein adds a comprehensive understanding of the pathologies including dysregulated metabolism and synapses and their timewise appearance to find new therapeutic approaches for AD.
Topics: Animals; Mice; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Autophagy; Disease Models, Animal; Mice, Transgenic; Mobile Applications
PubMed: 37907591
DOI: 10.1038/s41380-023-02289-4 -
Scientific Reports Nov 2023Acoustic overexposure can eliminate synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs), even if hair-cell function recovers. This synaptopathy has...
Acoustic overexposure can eliminate synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs), even if hair-cell function recovers. This synaptopathy has been extensively studied by confocal microscopy, however, understanding the nature and sequence of damage requires ultrastructural analysis. Here, we used focused ion-beam scanning electron microscopy to mill, image, segment and reconstruct ANF terminals in mice, 1 day and 1 week after synaptopathic exposure (8-16 kHz, 98 dB SPL). At both survivals, ANF terminals were normal in number, but 62% and 53%, respectively, lacked normal synaptic specializations. Most non-synapsing fibers (57% and 48% at 1 day and 1 week) remained in contact with an IHC and contained healthy-looking organelles. ANFs showed a transient increase in mitochondrial content (51%) and efferent innervation (34%) at 1 day. Fibers maintaining synaptic connections showed hypertrophy of pre-synaptic ribbons at both 1 day and 1 week. Non-synaptic fibers were lower in mitochondrial content and typically on the modiolar side of the IHC, where ANFs with high-thresholds and low spontaneous rates are normally found. Even 1 week post-exposure, many ANF terminals remained in IHC contact despite loss of synaptic specializations, thus, regeneration efforts at early post-exposure times should concentrate on synaptogenesis rather than neurite extension.
Topics: Mice; Animals; Cochlea; Noise; Hearing Loss, Noise-Induced; Hair Cells, Auditory; Hair Cells, Auditory, Inner; Synapses; Cochlear Nerve; Auditory Threshold
PubMed: 37945811
DOI: 10.1038/s41598-023-46859-6