Non-epithelial stem cells and cortical interneuron production in the human ganglionic eminences
TL;DR: It is concluded that the vast majority of human cortical interneurons are produced in the ganglionic eminences, including an enormous contribution from non-epithelial SVZ stem cells.
Abstract: GABAergic cortical interneurons have important roles in the computations of neural circuits, but their developmental origin in primates is controversial. Here the authors characterize neural stem cell and progenitor cell organization in the developing human ganglionic eminences and reveal that, just as in rodents, they give rise to a majority of cortical GABAergic neurons.
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TL;DR: An anatomically comprehensive atlas of the mid-gestational human brain is described, including de novo reference atlases, in situ hybridization, ultra-high-resolution magnetic resonance imaging (MRI) and microarray analysis on highly discrete laser-microdissected brain regions.
Abstract: The anatomical and functional architecture of the human brain is mainly determined by prenatal transcriptional processes. We describe an anatomically comprehensive atlas of the mid-gestational human brain, including de novo reference atlases, in situ hybridization, ultra-high-resolution magnetic resonance imaging (MRI) and microarray analysis on highly discrete laser-microdissected brain regions. In developing cerebral cortex, transcriptional differences are found between different proliferative and post-mitotic layers, wherein laminar signatures reflect cellular composition and developmental processes. Cytoarchitectural differences between human and mouse have molecular correlates, including species differences in gene expression in subplate, although surprisingly we find minimal differences between the inner and outer subventricular zones even though the outer zone is expanded in humans. Both germinal and post-mitotic cortical layers exhibit fronto-temporal gradients, with particular enrichment in the frontal lobe. Finally, many neurodevelopmental disorder and human-evolution-related genes show patterned expression, potentially underlying unique features of human cortical formation. These data provide a rich, freely-accessible resource for understanding human brain development.
1,114 citations
TL;DR: RNA-sequencing analysis of cells in the human cortex enabled identification of diverse cell types, revealing well-conserved architecture and homologous cell types as well as extensive differences when compared with datasets covering the analogous region of the mouse brain.
Abstract: Elucidating the cellular architecture of the human cerebral cortex is central to understanding our cognitive abilities and susceptibility to disease. Here we used single-nucleus RNA-sequencing analysis to perform a comprehensive study of cell types in the middle temporal gyrus of human cortex. We identified a highly diverse set of excitatory and inhibitory neuron types that are mostly sparse, with excitatory types being less layer-restricted than expected. Comparison to similar mouse cortex single-cell RNA-sequencing datasets revealed a surprisingly well-conserved cellular architecture that enables matching of homologous types and predictions of properties of human cell types. Despite this general conservation, we also found extensive differences between homologous human and mouse cell types, including marked alterations in proportions, laminar distributions, gene expression and morphology. These species-specific features emphasize the importance of directly studying human brain.
1,044 citations
TL;DR: A scalable approach to sequence and quantify RNA molecules in isolated neuronal nuclei from a postmortem brain, generating 3227 sets of single-neuron data from six distinct regions of the cerebral cortex demonstrates a robust and scalable method for identifying and categorizing single nuclear transcriptomes.
Abstract: The human brain has enormously complex cellular diversity and connectivities fundamental to our neural functions, yet difficulties in interrogating individual neurons has impeded understanding of the underlying transcriptional landscape. We developed a scalable approach to sequence and quantify RNA molecules in isolated neuronal nuclei from a postmortem brain, generating 3227 sets of single-neuron data from six distinct regions of the cerebral cortex. Using an iterative clustering and classification approach, we identified 16 neuronal subtypes that were further annotated on the basis of known markers and cortical cytoarchitecture. These data demonstrate a robust and scalable method for identifying and categorizing single nuclear transcriptomes, revealing shared genes sufficient to distinguish previously unknown and orthologous neuronal subtypes as well as regional identity and transcriptomic heterogeneity within the human brain.
785 citations
TL;DR: Improved high-throughput methods for single-nucleus droplet-based sequencing and single-cell transposome hypersensitive site sequencing are reported, which revealed regulatory elements and transcription factors that underlie cell-type distinctions and mapped disease-associated risk variants to specific cellular populations, which provided insights into normal and pathogenic cellular processes in the human brain.
Abstract: Detailed characterization of the cell types in the human brain requires scalable experimental approaches to examine multiple aspects of the molecular state of individual cells, as well as computational integration of the data to produce unified cell-state annotations. Here we report improved high-throughput methods for single-nucleus droplet-based sequencing (snDrop-seq) and single-cell transposome hypersensitive site sequencing (scTHS-seq). We used each method to acquire nuclear transcriptomic and DNA accessibility maps for >60,000 single cells from human adult visual cortex, frontal cortex, and cerebellum. Integration of these data revealed regulatory elements and transcription factors that underlie cell-type distinctions, providing a basis for the study of complex processes in the brain, such as genetic programs that coordinate adult remyelination. We also mapped disease-associated risk variants to specific cellular populations, which provided insights into normal and pathogenic cellular processes in the human brain. This integrative multi-omics approach permits more detailed single-cell interrogation of complex organs and tissues.
717 citations
TL;DR: An overview of the current state of the field of interneuron research, focusing largely on the hippocampus, discusses recent advances related to the various cell types, including their development and maturation, expression of subtype-specific voltage- and ligand-gated channels, and their roles in network oscillations.
Abstract: In the hippocampus GABAergic local circuit inhibitory interneurons represent only ~10–15% of the total neuronal population; however, their remarkable anatomical and physiological diversity allows them to regulate virtually all aspects of cellular and circuit function. Here we provide an overview of the current state of the field of interneuron research, focusing largely on the hippocampus. We discuss recent advances related to the various cell types, including their development and maturation, expression of subtype-specific voltage- and ligand-gated channels, and their roles in network oscillations. We also discuss recent technological advances and approaches that have permitted high-resolution, subtype-specific examination of their roles in numerous neural circuit disorders and the emerging therapeutic strategies to ameliorate such pathophysiological conditions. The ultimate goal of this review is not only to provide a touchstone for the current state of the field, but to help pave the way for future research by highlighting where gaps in our knowledge exist and how a complete appreciation of their roles will aid in future therapeutic strategies.
545 citations
References
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TL;DR: In this paper, the number of GABA-expressing cells in neocortical slices is reduced by separating the neocortex from the subcortical telencephalon, and mice lacking the homeodomain proteins DLX-1/DLX-2 show no detectable cell migration from the cell to the brain.
Abstract: Although previous analyses indicate that neocortical neurons originate from the cortical proliferative zone, evidence suggests that a subpopulation of neocortical interneurons originates within the subcortical telencephalon. For example, gamma-aminobutyric acid (GABA)-expressing cells migrate in vitro from the subcortical telencephalon into the neocortex. The number of GABA-expressing cells in neocortical slices is reduced by separating the neocortex from the subcortical telencephalon. Finally, mice lacking the homeodomain proteins DLX-1 and DLX-2 show no detectable cell migration from the subcortical telencephalon to the neocortex and also have few GABA-expressing cells in the neocortex.
1,438 citations
TL;DR: This work finds that OSVZ radial glia-like cells have a long basal process but, surprisingly, are non-epithelial as they lack contact with the ventricular surface, and demonstrates that these cells can undergo proliferative divisions and self-renewing asymmetric divisions to generate neuronal progenitor cells that can proliferate further.
Abstract: Neurons in the developing rodent cortex are generated from radial glial cells that function as neural stem cells. These epithelial cells line the cerebral ventricles and generate intermediate progenitor cells that migrate into the subventricular zone (SVZ) and proliferate to increase neuronal number. The developing human SVZ has a massively expanded outer region (OSVZ) thought to contribute to cortical size and complexity. However, OSVZ progenitor cell types and their contribution to neurogenesis are not well understood. Here we show that large numbers of radial glia-like cells and intermediate progenitor cells populate the human OSVZ. We find that OSVZ radial glia-like cells have a long basal process but, surprisingly, are non-epithelial as they lack contact with the ventricular surface. Using real-time imaging and clonal analysis, we demonstrate that these cells can undergo proliferative divisions and self-renewing asymmetric divisions to generate neuronal progenitor cells that can proliferate further. We also show that inhibition of Notch signalling in OSVZ progenitor cells induces their neuronal differentiation. The establishment of non-ventricular radial glia-like cells may have been a critical evolutionary advance underlying increased cortical size and complexity in the human brain.
1,104 citations
TL;DR: In this paper, the authors discussed how proliferation of cells within the outer subventricular zone expands the human neocortex by increasing neuron number and modifying the trajectory of migrating neurons, and compared these features to other mammalian species and known molecular regulators of the mouse neocortex.
1,065 citations
TL;DR: Evidence is presented that a mouse deficient in Nkx2.1 function does not form pallidal structures, lacks basal forebrain TrkA-positive neurons (probable cholinergic neurons) and has reduced numbers of cortical cells expressing GABA, DLX2 and calbindin that migrate from the pallidum through the striatum and into the cortex.
Abstract: The telencephalon is organized into distinct longitudinal domains: the cerebral cortex and the basal ganglia. The basal ganglia primarily consists of a dorsal region (striatum) and a ventral region (pallidum). Within the telencephalon, the anlage of the pallidum expresses the Nkx2.1 homeobox gene. A mouse deficient in Nkx2.1 function does not form pallidal structures, lacks basal forebrain TrkA-positive neurons (probable cholinergic neurons) and has reduced numbers of cortical cells expressing GABA, DLX2 and calbindin that migrate from the pallidum through the striatum and into the cortex. We present evidence that these phenotypes result from a ventral-to-dorsal transformation of the pallidal primordium into a striatal-like anlage.
887 citations
TL;DR: Recent data that are beginning to illuminate the origins and specification of distinct subgroups of cortical interneurons are discussed.
Abstract: GABA-containing interneurons are crucial to both the development and function of the cerebral cortex. Unlike cortical projection neurons, which have a relatively conserved set of characteristics, interneurons include multiple phenotypes that vary on morphological, physiological and neurochemical axes. This diversity, and the relatively late, context-dependent maturation of defining features, has challenged efforts to uncover the transcriptional control of cortical interneuron development. Here, we discuss recent data that are beginning to illuminate the origins and specification of distinct subgroups of cortical interneurons.
887 citations
"Non-epithelial stem cells and corti..." refers background in this paper
...In the LGE OSVZ, only ~25% of cells expressed COUP-TFII, almost none of which were proliferating....
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...Along the CGE-LGE axis, OSVZ characteristics shifted gradually from CGE-like to LGE-like, suggesting that the CGE and LGE OSVZ is a continuum (Fig....
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...Probes for LHX6 mRNA further revealed MGE-derived cells throughout the entire LGE OSVZ and continuing into the cortex (Fig....
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...Boxed regions of the globus pallidus (1) and striatum (2) are magnified and shown below....
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...Magnified images of the LGE OSVZ (1), dLGE OSVZ (2), lateral cortical stream (3), lateral cortex (4), dorsal cortex intermediate zone near dLGE (5) and more distal dorsal cortex OSVZ (6) are shown....
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