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Frontiers in Immunology 2023The development of new autoantigen discovery techniques, like programmable phage immunoprecipitation sequencing (PhIP-Seq), has accelerated the discovery of...
INTRODUCTION
The development of new autoantigen discovery techniques, like programmable phage immunoprecipitation sequencing (PhIP-Seq), has accelerated the discovery of neural-specific autoantibodies. Herein, we report the identification of a novel biomarker for paraneoplastic neurologic syndrome (PNS), Sloan-Kettering-Virus-Family-Transcriptional-Corepressor-2 (SKOR2)-IgG, utilizing PhIP-Seq. We have also performed a thorough clinical validation using normal, healthy, and disease/cancer control samples.
METHODS
Stored samples with unclassified staining at the junction of the Purkinje cell and the granule cell layers were analyzed by PhIP-Seq for putative autoantigen identification. The autoantigen was confirmed by recombinant antigen-expressing cell-based assay (CBA), Western blotting, and tissue immunofluorescence assay colocalization.
RESULTS
PhIP-Seq data revealed SKOR2 as the candidate autoantigen. The target antigen was confirmed by a recombinant SKOR-2-expressing, and cell lysate Western blot. Furthermore, IgG from both patient samples colocalized with a commercial SKOR2-specific IgG on cryosections of the mouse brain. Both SKOR2 IgG-positive patients had central nervous system involvement, one presenting with encephalitis and seizures (Patient 1) and the other with cognitive dysfunction, spastic ataxia, dysarthria, dysphagia, and pseudobulbar affect (Patient 2). They had a refractory progressive course and were diagnosed with adenocarcinoma (Patient 1: lung, Patient 2: gallbladder). Sera from adenocarcinoma patients without PNS (n=30) tested for SKOR2-IgG were negative.
DISCUSSION
SKOR2 IgG represents a novel biomarker for PNS associated with adenocarcinoma. Identification of additional SKOR2 IgG-positive cases will help categorize the associated neurological phenotype and the risk of underlying malignancy.
Topics: Mice; Animals; Humans; Paraneoplastic Syndromes, Nervous System; Biomarkers; Adenocarcinoma; Autoantigens; Immunoglobulin G
PubMed: 37795104
DOI: 10.3389/fimmu.2023.1243946 -
International Journal of Molecular... Jan 2024An important part of the central nervous system (CNS), the cerebellum is involved in motor control, learning, reflex adaptation, and cognition. Diminished cerebellar... (Review)
Review
An important part of the central nervous system (CNS), the cerebellum is involved in motor control, learning, reflex adaptation, and cognition. Diminished cerebellar function results in the motor and cognitive impairment observed in patients with neurodegenerative disorders such as Alzheimer's disease (AD), vascular dementia (VD), Parkinson's disease (PD), Huntington's disease (HD), spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), Friedreich's ataxia (FRDA), and multiple sclerosis (MS), and even during the normal aging process. In most neurodegenerative disorders, impairment mainly occurs as a result of morphological changes over time, although during the early stages of some disorders such as AD, the cerebellum also serves a compensatory function. Biological aging is accompanied by changes in cerebellar circuits, which are predominantly involved in motor control. Despite decades of research, the functional contributions of the cerebellum and the underlying molecular mechanisms in aging and neurodegenerative disorders remain largely unknown. Therefore, this review will highlight the molecular and cellular events in the cerebellum that are disrupted during the process of aging and the development of neurodegenerative disorders. We believe that deeper insights into the pathophysiological mechanisms of the cerebellum during aging and the development of neurodegenerative disorders will be essential for the design of new effective strategies for neuroprotection and the alleviation of some neurodegenerative disorders.
Topics: Humans; Neurodegenerative Diseases; Cerebellum; Alzheimer Disease; Huntington Disease; Aging
PubMed: 38256091
DOI: 10.3390/ijms25021018 -
Nature Communications Sep 2023Social recognition memory (SRM) is a key determinant of social interactions. While the cerebellum emerges as an important region for social behavior, how cerebellar...
Social recognition memory (SRM) is a key determinant of social interactions. While the cerebellum emerges as an important region for social behavior, how cerebellar activity affects social functions remains unclear. We selectively increased the excitability of molecular layer interneurons (MLIs) to suppress Purkinje cell firing in the mouse cerebellar vermis. Chemogenetic perturbation of MLIs impaired SRM without affecting sociability, anxiety levels, motor coordination or object recognition. Optogenetic interference of MLIs during distinct phases of a social recognition test revealed the cerebellar engagement in the retrieval, but not encoding, of social information. c-Fos mapping after the social recognition test showed that cerebellar manipulation decreased brain-wide interregional correlations and altered network structure from medial prefrontal cortex and hippocampus-centered to amygdala-centered modules. Anatomical tracing demonstrated hierarchical projections from the central cerebellum to the social brain network integrating amygdalar connections. Our findings suggest that the cerebellum organizes the neural matrix necessary for SRM.
Topics: Mice; Animals; Cerebellar Vermis; Cerebellum; Purkinje Cells; Interneurons; Memory Disorders
PubMed: 37752149
DOI: 10.1038/s41467-023-41744-2 -
Nature Genetics Mar 2024Brain region-specific degeneration and somatic expansions of the mutant Huntingtin (mHTT) CAG tract are key features of Huntington's disease (HD). However, the...
Brain region-specific degeneration and somatic expansions of the mutant Huntingtin (mHTT) CAG tract are key features of Huntington's disease (HD). However, the relationships among CAG expansions, death of specific cell types and molecular events associated with these processes are not established. Here, we used fluorescence-activated nuclear sorting (FANS) and deep molecular profiling to gain insight into the properties of cell types of the human striatum and cerebellum in HD and control donors. CAG expansions arise at mHTT in striatal medium spiny neurons (MSNs), cholinergic interneurons and cerebellar Purkinje neurons, and at mutant ATXN3 in MSNs from SCA3 donors. CAG expansions in MSNs are associated with higher levels of MSH2 and MSH3 (forming MutSβ), which can inhibit nucleolytic excision of CAG slip-outs by FAN1. Our data support a model in which CAG expansions are necessary but may not be sufficient for cell death and identify transcriptional changes associated with somatic CAG expansions and striatal toxicity.
Topics: Humans; Animals; Corpus Striatum; Cerebellum; Huntington Disease; Disease Models, Animal
PubMed: 38291334
DOI: 10.1038/s41588-024-01653-6 -
Cell Reports Jan 2024While ATM loss of function has long been identified as the genetic cause of ataxia-telangiectasia (A-T), how it leads to selective and progressive degeneration of...
While ATM loss of function has long been identified as the genetic cause of ataxia-telangiectasia (A-T), how it leads to selective and progressive degeneration of cerebellar Purkinje and granule neurons remains unclear. ATM expression is enriched in microglia throughout cerebellar development and adulthood. Here, we find evidence of microglial inflammation in the cerebellum of patients with A-T using single-nucleus RNA sequencing. Pseudotime analysis revealed that activation of A-T microglia preceded upregulation of apoptosis-related genes in granule and Purkinje neurons and that microglia exhibited increased neurotoxic cytokine signaling to granule and Purkinje neurons in A-T. To confirm these findings experimentally, we performed transcriptomic profiling of A-T induced pluripotent stem cell (iPSC)-derived microglia, which revealed cell-intrinsic microglial activation of cytokine production and innate immune response pathways compared to controls. Furthermore, A-T microglia co-culture with either control or A-T iPSC-derived neurons was sufficient to induce cytotoxicity. Taken together, these studies reveal that cell-intrinsic microglial activation may promote neurodegeneration in A-T.
Topics: Humans; Ataxia Telangiectasia; Microglia; Ataxia Telangiectasia Mutated Proteins; Neurons; Cytokines
PubMed: 38159274
DOI: 10.1016/j.celrep.2023.113622 -
Nature Communications Aug 2023Synaptic adhesion molecules (SAMs) shape the structural and functional properties of synapses and thereby control the information processing power of neural circuits....
Synaptic adhesion molecules (SAMs) shape the structural and functional properties of synapses and thereby control the information processing power of neural circuits. SAMs are broadly expressed in the brain, suggesting that they may instruct synapse formation and specification via a combinatorial logic. Here, we generate sextuple conditional knockout mice targeting all members of the two major families of presynaptic SAMs, Neurexins and leukocyte common antigen-related-type receptor phospho-tyrosine phosphatases (LAR-PTPRs), which together account for the majority of known trans-synaptic complexes. Using synapses formed by cerebellar Purkinje cells onto deep cerebellar nuclei as a model system, we confirm that Neurexins and LAR-PTPRs themselves are not essential for synapse assembly. The combinatorial deletion of both neurexins and LAR-PTPRs, however, decreases Purkinje-cell synapses on deep cerebellar nuclei, the major output pathway of cerebellar circuits. Consistent with this finding, combined but not separate deletions of neurexins and LAR-PTPRs impair motor behaviors. Thus, Neurexins and LAR-PTPRs are together required for the assembly of a functional cerebellar circuit.
Topics: Animals; Mice; Cerebellum; Purkinje Cells; Brain; Cognition; Mice, Knockout; Phosphotyrosine; Protein Tyrosine Phosphatases; Receptor-Like Protein Tyrosine Phosphatases, Class 2
PubMed: 37591863
DOI: 10.1038/s41467-023-40526-0 -
Brain : a Journal of Neurology Mar 2024AFG3L2 is a mitochondrial protease exerting protein quality control in the inner mitochondrial membrane. Heterozygous AFG3L2 mutations cause spinocerebellar ataxia type...
AFG3L2 is a mitochondrial protease exerting protein quality control in the inner mitochondrial membrane. Heterozygous AFG3L2 mutations cause spinocerebellar ataxia type 28 (SCA28) or dominant optic atrophy type 12 (DOA12), while biallelic AFG3L2 mutations result in the rare and severe spastic ataxia type 5 (SPAX5). The clinical spectrum of SPAX5 includes childhood-onset cerebellar ataxia, spasticity, dystonia and myoclonic epilepsy. We previously reported that the absence or mutation of AFG3L2 leads to the accumulation of mitochondria-encoded proteins, causing the overactivation of the stress-sensitive protease OMA1, which over-processes OPA1, leading to mitochondrial fragmentation. Recently, OMA1 has been identified as the pivotal player communicating mitochondrial stress to the cytosol via a pathway involving the inner mitochondrial membrane protein DELE1 and the cytosolic kinase HRI, thus eliciting the integrated stress response. In general, the integrated stress response reduces global protein synthesis and drives the expression of cytoprotective genes that allow cells to endure proteotoxic stress. However, the relevance of the OMA1-DELE1-HRI axis in vivo, and especially in a human CNS disease context, has been poorly documented thus far. In this work, we demonstrated that mitochondrial proteotoxicity in the absence/mutation of AFG3L2 activates the OMA1-DELE1-HRI pathway eliciting the integrated stress response. We found enhanced OMA1-dependent processing of DELE1 upon depletion of AFG3L2. Also, in both skin fibroblasts from SPAX5 patients (including a novel case) and in the cerebellum of Afg3l2-/- mice we detected increased phosphorylation of the α-subunit of the eukaryotic translation initiation factor 2 (eIF2α), increased levels of ATF4 and strong upregulation of its downstream targets (Chop, Chac1, Ppp1r15a and Ffg21). Silencing of DELE1 or HRI in SPAX5 fibroblasts (where OMA1 is overactivated at basal state) reduces eIF2α phosphorylation and affects cell growth. In agreement, pharmacological potentiation of integrated stress response via Sephin-1, a drug that selectively inhibits the stress-induced eIF2alpha phosphatase GADD34 (encoded by Ppp1r15a), improved cell growth of SPAX5 fibroblasts and cell survival and dendritic arborization ex vivo in primary Afg3l2-/- Purkinje neurons. Notably, Sephin-1 treatment in vivo extended the lifespan of Afg3l2-/- mice, improved Purkinje neuron morphology, mitochondrial ultrastructure and respiratory capacity. These data indicate that activation of the OMA1-DELE1-HRI pathway is protective in the context of SPAX5. Pharmacological tuning of the integrated stress response may represent a future therapeutic strategy for SPAX5 and other cerebellar ataxias caused by impaired mitochondrial proteostasis.
Topics: Humans; Animals; Mice; Child; Spinocerebellar Ataxias; Muscle Spasticity; Optic Atrophy; Peptide Hydrolases; ATPases Associated with Diverse Cellular Activities; ATP-Dependent Proteases; Mitochondrial Proteins; Metalloproteases; Intellectual Disability
PubMed: 37804316
DOI: 10.1093/brain/awad340 -
Nature Communications Jul 2023The classification of neuronal subpopulations has significantly advanced, yet its relevance for behavior remains unclear. The highly organized flocculus of the...
The classification of neuronal subpopulations has significantly advanced, yet its relevance for behavior remains unclear. The highly organized flocculus of the cerebellum, known to fine-tune multi-axial eye movements, is an ideal substrate for the study of potential functions of neuronal subpopulations. Here, we demonstrate that its recently identified subpopulations of 9+ and 9- Purkinje cells exhibit an intermediate Aldolase C expression and electrophysiological profile, providing evidence for a graded continuum of intrinsic properties among PC subpopulations. By identifying and utilizing two Cre-lines that genetically target these floccular domains, we show with high spatial specificity that these subpopulations of Purkinje cells participate in separate micromodules with topographically organized connections. Finally, optogenetic excitation of the respective subpopulations results in movements around the same axis in space, yet with distinct kinematic profiles. These results indicate that Purkinje cell subpopulations integrate in discrete circuits and mediate particular parameters of single movements.
Topics: Purkinje Cells; Biomechanical Phenomena; Eye Movements; Cerebellum; Movement
PubMed: 37468512
DOI: 10.1038/s41467-023-40111-5