-
Annual Review of Neuroscience Jul 2022The cerebellar cortex is an important system for relating neural circuits and learning. Its promise reflects the longstanding idea that it contains simple, repeated... (Review)
Review
The cerebellar cortex is an important system for relating neural circuits and learning. Its promise reflects the longstanding idea that it contains simple, repeated circuit modules with only a few cell types and a single plasticity mechanism that mediates learning according to classical Marr-Albus models. However, emerging data have revealed surprising diversity in neuron types, synaptic connections, and plasticity mechanisms, both locally and regionally within the cerebellar cortex. In light of these findings, it is not surprising that attempts to generate a holistic model of cerebellar learning across different behaviors have not been successful. While the cerebellum remains an ideal system for linking neuronal function with behavior, it is necessary to update the cerebellar circuit framework to achieve its great promise. In this review, we highlight recent advances in our understanding of cerebellar-cortical cell types, synaptic connections, signaling mechanisms, and forms of plasticity that enrich cerebellar processing.
Topics: Cerebellar Cortex; Cerebellum; Learning; Neuronal Plasticity; Purkinje Cells
PubMed: 35803588
DOI: 10.1146/annurev-neuro-091421-125115 -
Cell Stem Cell Jan 2024Research on human cerebellar development and disease has been hampered by the need for a human cell-based system that recapitulates the human cerebellum's cellular...
Research on human cerebellar development and disease has been hampered by the need for a human cell-based system that recapitulates the human cerebellum's cellular diversity and functional features. Here, we report a human organoid model (human cerebellar organoids [hCerOs]) capable of developing the complex cellular diversity of the fetal cerebellum, including a human-specific rhombic lip progenitor population that have never been generated in vitro prior to this study. 2-month-old hCerOs form distinct cytoarchitectural features, including laminar organized layering, and create functional connections between inhibitory and excitatory neurons that display coordinated network activity. Long-term culture of hCerOs allows healthy survival and maturation of Purkinje cells that display molecular and electrophysiological hallmarks of their in vivo counterparts, addressing a long-standing challenge in the field. This study therefore provides a physiologically relevant, all-human model system to elucidate the cell-type-specific mechanisms governing cerebellar development and disease.
Topics: Humans; Infant; Purkinje Cells; Cerebellum; Metencephalon; Organoids
PubMed: 38181749
DOI: 10.1016/j.stem.2023.11.013 -
Neuron Oct 2022Dysregulation of long interspersed nuclear element 1 (LINE-1, L1), a dominant class of transposable elements in the human genome, has been linked to neurodegenerative...
Dysregulation of long interspersed nuclear element 1 (LINE-1, L1), a dominant class of transposable elements in the human genome, has been linked to neurodegenerative diseases, but whether elevated L1 expression is sufficient to cause neurodegeneration has not been directly tested. Here, we show that the cerebellar expression of L1 is significantly elevated in ataxia telangiectasia patients and strongly anti-correlated with the expression of epigenetic silencers. To examine the role of L1 in the disease etiology, we developed an approach for direct targeting of the L1 promoter for overexpression in mice. We demonstrated that L1 activation in the cerebellum led to Purkinje cell dysfunctions and degeneration and was sufficient to cause ataxia. Treatment with a nucleoside reverse transcriptase inhibitor blunted ataxia progression by reducing DNA damage, attenuating gliosis, and reversing deficits of molecular regulators for calcium homeostasis in Purkinje cells. Our study provides the first direct evidence that L1 activation can drive neurodegeneration.
Topics: Animals; Humans; Mice; Ataxia; Calcium; Cerebellum; DNA Transposable Elements; Nucleosides; Purkinje Cells; Reverse Transcriptase Inhibitors; Long Interspersed Nucleotide Elements
PubMed: 36070749
DOI: 10.1016/j.neuron.2022.08.011 -
Nature May 2022Cellular diversification is critical for specialized functions of the brain including learning and memory. Single-cell RNA sequencing facilitates transcriptomic...
Cellular diversification is critical for specialized functions of the brain including learning and memory. Single-cell RNA sequencing facilitates transcriptomic profiling of distinct major types of neuron, but the divergence of transcriptomic profiles within a neuronal population and their link to function remain poorly understood. Here we isolate nuclei tagged in specific cell types followed by single-nucleus RNA sequencing to profile Purkinje neurons and map their responses to motor activity and learning. We find that two major subpopulations of Purkinje neurons, identified by expression of the genes Aldoc and Plcb4, bear distinct transcriptomic features. Plcb4, but not Aldoc, Purkinje neurons exhibit robust plasticity of gene expression in mice subjected to sensorimotor and learning experience. In vivo calcium imaging and optogenetic perturbation reveal that Plcb4 Purkinje neurons have a crucial role in associative learning. Integrating single-nucleus RNA sequencing datasets with weighted gene co-expression network analysis uncovers a learning gene module that includes components of FGFR2 signalling in Plcb4 Purkinje neurons. Knockout of Fgfr2 in Plcb4 Purkinje neurons in mice using CRISPR disrupts motor learning. Our findings define how diversification of Purkinje neurons is linked to their responses in motor learning and provide a foundation for understanding their differential vulnerability to neurological disorders.
Topics: Animals; Cerebellum; Learning; Mice; Mice, Knockout; Neuronal Plasticity; Neurons; Purkinje Cells; Transcriptome
PubMed: 35545673
DOI: 10.1038/s41586-022-04711-3 -
Human Molecular Genetics Sep 2023Neurons within the cerebellum form temporal-spatial connections through the cerebellum, and the entire brain. Organoid models provide an opportunity to model the early...
Neurons within the cerebellum form temporal-spatial connections through the cerebellum, and the entire brain. Organoid models provide an opportunity to model the early differentiation of the developing human cerebellum, which is difficult to study in vivo, and affords the opportunity to study neurodegenerative and neurodevelopmental diseases of the cerebellum. Previous cerebellar organoid models focused on early neuron generation and single cell activity. Here, we modify previous protocols to generate more mature cerebellar organoids that allow for the establishment of several classes of mature neurons during cerebellar differentiation and development, including the establishment of neural networks during whole-organoid maturation. This will provide a means to study the generation of several more mature cerebellar cell types, including Purkinje cells, granule cells and interneurons expression as well as neuronal communication for biomedical, clinical and pharmaceutical applications.
Topics: Humans; Cerebellum; Neurons; Purkinje Cells; Neurogenesis; Organoids
PubMed: 37387247
DOI: 10.1093/hmg/ddad110 -
Neuron Feb 2024Neurodegeneration is a protracted process involving progressive changes in myriad cell types that ultimately results in the death of vulnerable neuronal populations. To...
Neurodegeneration is a protracted process involving progressive changes in myriad cell types that ultimately results in the death of vulnerable neuronal populations. To dissect how individual cell types within a heterogeneous tissue contribute to the pathogenesis and progression of a neurodegenerative disorder, we performed longitudinal single-nucleus RNA sequencing of mouse and human spinocerebellar ataxia type 1 (SCA1) cerebellar tissue, establishing continuous dynamic trajectories of each cell population. Importantly, we defined the precise transcriptional changes that precede loss of Purkinje cells and, for the first time, identified robust early transcriptional dysregulation in unipolar brush cells and oligodendroglia. Finally, we applied a deep learning method to predict disease state accurately and identified specific features that enable accurate distinction of wild-type and SCA1 cells. Together, this work reveals new roles for diverse cerebellar cell types in SCA1 and provides a generalizable analysis framework for studying neurodegeneration.
Topics: Animals; Mice; Humans; Ataxin-1; Mice, Transgenic; Spinocerebellar Ataxias; Cerebellum; Purkinje Cells; Disease Models, Animal
PubMed: 38016472
DOI: 10.1016/j.neuron.2023.10.039 -
Science Translational Medicine Nov 2023Inflammation early in life is a clinically established risk factor for autism spectrum disorders and schizophrenia, yet the impact of inflammation on human brain...
Inflammation early in life is a clinically established risk factor for autism spectrum disorders and schizophrenia, yet the impact of inflammation on human brain development is poorly understood. The cerebellum undergoes protracted postnatal maturation, making it especially susceptible to perturbations contributing to the risk of developing neurodevelopmental disorders. Here, using single-cell genomics of postmortem cerebellar brain samples, we characterized the postnatal development of cerebellar neurons and glia in 1- to 5-year-old children, comparing individuals who had died while experiencing inflammation with those who had died as a result of an accident. Our analyses revealed that inflammation and postnatal cerebellar maturation are associated with extensive, overlapping transcriptional changes primarily in two subtypes of inhibitory neurons: Purkinje neurons and Golgi neurons. Immunohistochemical analysis of a subset of these postmortem cerebellar samples revealed no change to Purkinje neuron soma size but evidence for increased activation of microglia in those children who had experienced inflammation. Maturation-associated and inflammation-associated gene expression changes included genes implicated in neurodevelopmental disorders. A gene regulatory network model integrating cell type-specific gene expression and chromatin accessibility identified seven temporally specific gene networks in Purkinje neurons and suggested that inflammation may be associated with the premature down-regulation of developmental gene expression programs.
Topics: Child, Preschool; Humans; Cerebellum; Neurons; Purkinje Cells; Genomics; Inflammation
PubMed: 37824600
DOI: 10.1126/scitranslmed.ade1283 -
Experimental Neurology Dec 2021The dystonias are a group of disorders characterized by excessive muscle contractions leading to abnormal repetitive movements or postures. In blepharospasm, the face is...
BACKGROUND
The dystonias are a group of disorders characterized by excessive muscle contractions leading to abnormal repetitive movements or postures. In blepharospasm, the face is affected, leading to excessive eye blinking and spasms of muscles around the eyes. The pathogenesis of blepharospasm is not well understood, but several imaging studies have implied subtle structural defects in several brain regions, including the cerebellum.
OBJECTIVE
To delineate cerebellar pathology in brains collected at autopsy from 7 human subjects with blepharospasm and 9 matched controls.
METHODS
Sections from 3 cerebellar regions were sampled and processed using Nissl and silver impregnation stains. Purkinje neurons were the focus of the evaluation, along with as several other subtle pathological features of cerebellar dysfunction such as Purkinje neuron axonal swellings (torpedo bodies), proliferation of basket cell processes around Purkinje neurons (hairy baskets), empty baskets (missing Purkinje neurons), and displacement of cell soma from their usual location (ectopic Purkinje neurons).
RESULTS
The results revealed a significant reduction in Purkinje neuron and torpedo body density, but no changes in any of the other measures.
CONCLUSIONS
These findings demonstrate subtle neuropathological changes similar to those reported for subjects with cervical dystonia. These findings may underly some of the subtle imaging changes reported for blepharospasm.
Topics: Aged; Aged, 80 and over; Blepharospasm; Cerebellum; Female; Humans; Male; Middle Aged; Purkinje Cells
PubMed: 34464652
DOI: 10.1016/j.expneurol.2021.113855 -
Nature Jan 2024The expansion of the neocortex, a hallmark of mammalian evolution, was accompanied by an increase in cerebellar neuron numbers. However, little is known about the... (Comparative Study)
Comparative Study
The expansion of the neocortex, a hallmark of mammalian evolution, was accompanied by an increase in cerebellar neuron numbers. However, little is known about the evolution of the cellular programmes underlying the development of the cerebellum in mammals. In this study we generated single-nucleus RNA-sequencing data for around 400,000 cells to trace the development of the cerebellum from early neurogenesis to adulthood in human, mouse and the marsupial opossum. We established a consensus classification of the cellular diversity in the developing mammalian cerebellum and validated it by spatial mapping in the fetal human cerebellum. Our cross-species analyses revealed largely conserved developmental dynamics of cell-type generation, except for Purkinje cells, for which we observed an expansion of early-born subtypes in the human lineage. Global transcriptome profiles, conserved cell-state markers and gene-expression trajectories across neuronal differentiation show that cerebellar cell-type-defining programmes have been overall preserved for at least 160 million years. However, we also identified many orthologous genes that gained or lost expression in cerebellar neural cell types in one of the species or evolved new expression trajectories during neuronal differentiation, indicating widespread gene repurposing at the cell-type level. In sum, our study unveils shared and lineage-specific gene-expression programmes governing the development of cerebellar cells and expands our understanding of mammalian brain evolution.
Topics: Animals; Humans; Mice; Cell Lineage; Cerebellum; Evolution, Molecular; Fetus; Gene Expression Regulation, Developmental; Neurogenesis; Neurons; Opossums; Purkinje Cells; Single-Cell Gene Expression Analysis; Species Specificity; Transcriptome; Mammals
PubMed: 38029793
DOI: 10.1038/s41586-023-06884-x -
Cells Sep 2022Despite their homogeneous appearance, Purkinje cells are remarkably diverse with respect to their molecular phenotypes, physiological properties, afferent and efferent... (Review)
Review
Despite their homogeneous appearance, Purkinje cells are remarkably diverse with respect to their molecular phenotypes, physiological properties, afferent and efferent connectivity, as well as their vulnerability to insults. Heterogeneity in Purkinje cells arises early in development, with molecularly distinct embryonic cell clusters present soon after Purkinje cell specification. Traditional methods have characterized cerebellar development and cell types, including Purkinje cell subtypes, based on knowledge of selected markers. However, recent single-cell RNA sequencing studies provide vastly increased resolution of the whole cerebellar transcriptome. Here we draw together the results of multiple single-cell transcriptomic studies in developing and adult cerebellum in both mouse and human. We describe how this detailed transcriptomic data has increased our understanding of the intricate development and function of Purkinje cells and provides first clues into features specific to human cerebellar development.
Topics: Animals; Biomarkers; Cerebellum; Humans; Mice; Nerve Tissue Proteins; Phenotype; Purkinje Cells
PubMed: 36139493
DOI: 10.3390/cells11182918