RESUMO
The neocortex varies in size and complexity among mammals due to the tremendous variability in the number and diversity of neuronal subtypes across species. The increased cellular diversity is paralleled by the expansion of the pool of neocortical progenitors and the emergence of indirect neurogenesis during brain evolution. The molecular pathways that control these biological processes and are disrupted in neurological disorders remain largely unknown. Here we show that the transcription factors BRN1 and BRN2 have an evolutionary conserved function in neocortical progenitors to control their proliferative capacity and the switch from direct to indirect neurogenesis. Functional studies in mice and ferrets show that BRN1/2 act in concert with NOTCH and primary microcephaly genes to regulate progenitor behavior. Analysis of transcriptomics data from genetically modified macaques provides evidence that these molecular pathways are conserved in non-human primates. Our findings thus demonstrate that BRN1/2 are central regulators of gene expression programs in neocortical progenitors critical to determine brain size during evolution.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Neocórtex , Células-Tronco Neurais , Neurogênese , Fatores do Domínio POU , Animais , Feminino , Masculino , Camundongos , Proliferação de Células , Furões , Proteínas de Homeodomínio/metabolismo , Proteínas de Homeodomínio/genética , Macaca , Neocórtex/metabolismo , Neocórtex/embriologia , Neocórtex/citologia , Proteínas do Tecido Nervoso/metabolismo , Proteínas do Tecido Nervoso/genética , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologia , Neurogênese/genética , Fatores do Domínio POU/metabolismo , Fatores do Domínio POU/genética , Receptores Notch/metabolismo , Receptores Notch/genéticaRESUMO
Large-scale analysis of single-cell gene expression has revealed transcriptomically defined cell subclasses present throughout the primate neocortex with gene expression profiles that differ depending upon neocortical region. Here, we test whether the interareal differences in gene expression translate to regional specializations in the physiology and morphology of infragranular glutamatergic neurons by performing Patch-seq experiments in brain slices from the temporal cortex (TCx) and motor cortex (MCx) of the macaque. We confirm that transcriptomically defined extratelencephalically projecting neurons of layer 5 (L5 ET neurons) include retrogradely labeled corticospinal neurons in the MCx and find multiple physiological properties and ion channel genes that distinguish L5 ET from non-ET neurons in both areas. Additionally, while infragranular ET and non-ET neurons retain distinct neuronal properties across multiple regions, there are regional morpho-electric and gene expression specializations in the L5 ET subclass, providing mechanistic insights into the specialized functional architecture of the primate neocortex.
Assuntos
Neurônios , Transcriptoma , Animais , Neurônios/metabolismo , Neurônios/citologia , Transcriptoma/genética , Neocórtex/citologia , Neocórtex/metabolismo , Córtex Motor/citologia , Córtex Motor/metabolismo , Masculino , Lobo Temporal/citologia , Lobo Temporal/metabolismo , Macaca mulattaRESUMO
Murine organotypic brain slice cultures have been widely used in neuroscientific research and are offering the opportunity to study neuronal function under normal and disease conditions. Despite the broad application, the mechanisms governing the maturation of immature cortical circuits in vitro are not well understood. In this study, we present a detailed investigation into the development of the neocortex in vitro. Using a holistic approach, we studied organotypic whole hemisphere brain slice cultures from postnatal mice and tracked the development of the somatosensory area over a 5-wk period. Our analysis revealed the maturation of passive and active intrinsic properties of pyramidal cells together with their morphology, closely resembling in vivo development. Detailed multielectrode array (MEA) electrophysiological assessments and RNA expression profiling demonstrated stable network properties by 2 wk in culture, followed by the transition of spontaneous activity toward more complex patterns including high-frequency oscillations. However, culturing weeks 4 and 5 exhibited increased variability and initial signs of neuronal loss, highlighting the importance of considering developmental stages in experimental design. This comprehensive characterization is vital for understanding the temporal dynamics of the neocortical development in vitro, with implications for neuroscientific research methodologies, particularly in the investigation of diseases such as epilepsy and other neurodevelopmental disorders.NEW & NOTEWORTHY The development of the mouse neocortex in vitro mimics the in vivo development. Mouse brain cultures can serve as a model system for cortical development for the first 2 wk in vitro and as a model system for the adult cortex from 2 to 4 wk in vitro. Mouse organotypic brain slice cultures develop high-frequency network oscillations at γ frequency after 2 wk in vitro. Mouse brain cultures exhibit increased heterogeneity and variability after 4 wk in culture.
Assuntos
Neocórtex , Técnicas de Cultura de Órgãos , Animais , Neocórtex/crescimento & desenvolvimento , Neocórtex/citologia , Neocórtex/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Células Piramidais/fisiologiaRESUMO
The astrocyte-to-neuron lactate shuttle model entails that, upon glutamatergic neurotransmission, glycolytically derived pyruvate in astrocytes is mainly converted to lactate instead of being entirely catabolized in mitochondria. The mechanism of this metabolic rewiring and its occurrence in human brain are unclear. Here by using immunohistochemistry (4 brains) and imaging mass cytometry (8 brains) we show that astrocytes of the adult human neocortex and hippocampal formation express barely detectable amounts of mitochondrial proteins critical for performing oxidative phosphorylation (OXPHOS). These data are corroborated by queries of transcriptomes (107 brains) of neuronal versus non-neuronal cells fetched from the Allen Institute for Brain Science for genes coding for a much larger repertoire of entities contributing to OXPHOS, showing that human non-neuronal elements barely expressed mRNAs coding for such proteins. With less OXPHOS, human brain astrocytes are thus bound to produce more lactate to avoid interruption of glycolysis.
Assuntos
Astrócitos , Hipocampo , Mitocôndrias , Neocórtex , Fosforilação Oxidativa , Humanos , Astrócitos/metabolismo , Hipocampo/metabolismo , Hipocampo/citologia , Neocórtex/metabolismo , Neocórtex/citologia , Mitocôndrias/metabolismo , Adulto , Masculino , Feminino , Neurônios/metabolismoRESUMO
The role of developmental cell death in the formation of brain circuits is not well understood. Cajal-Retzius cells constitute a major transient neuronal population in the mammalian neocortex, which largely disappears at the time of postnatal somatosensory maturation. In this study, we used mouse genetics, anatomical, functional, and behavioral approaches to explore the impact of the early postnatal death of Cajal-Retzius cells in the maturation of the cortical circuit. We find that before their death, Cajal-Retzius cells mainly receive inputs from layer 1 neurons, which can only develop their mature connectivity onto layer 2/3 pyramidal cells after Cajal-Retzius cells disappear. This developmental connectivity progression from layer 1 GABAergic to layer 2/3 pyramidal cells regulates sensory-driven inhibition within, and more so, across cortical columns. Here we show that Cajal-Retzius cell death prevention leads to layer 2/3 hyper-excitability, delayed learning and reduced performance in a multi-whisker-dependent texture discrimination task.
Assuntos
Morte Celular , Células Piramidais , Córtex Somatossensorial , Animais , Córtex Somatossensorial/fisiologia , Córtex Somatossensorial/citologia , Camundongos , Células Piramidais/fisiologia , Células Piramidais/metabolismo , Neocórtex/citologia , Neocórtex/fisiologia , Neurônios GABAérgicos/fisiologia , Neurônios GABAérgicos/metabolismo , Masculino , Vibrissas/fisiologia , Feminino , Camundongos Endogâmicos C57BL , Inibição Neural/fisiologia , Neurônios/fisiologia , Neurônios/metabolismoRESUMO
Although the mammalian cerebral cortex is most often described as a hexalaminar structure, there are cortical areas (primary motor cortex) and species (elephants, cetaceans, and hippopotami), where a cytoarchitecturally indistinct, or absent, layer 4 is noted. Thalamocortical projections from the core, or first order, thalamic system terminate primarily in layers 4/inner 3. We explored the termination sites of core thalamocortical projections in cortical areas and in species where there is no cytoarchitecturally distinct layer 4 using the immunolocalization of vesicular glutamate transporter 2, a known marker of core thalamocortical axon terminals, in 31 mammal species spanning the eutherian radiation. Several variations from the canonical cortical column outline of layer 4 and core thalamocortical inputs were noted. In shrews/microchiropterans, layer 4 was present, but many core thalamocortical projections terminated in layer 1 in addition to layers 4 and inner 3. In primate primary visual cortex, the sublaminated layer 4 was associated with a specialized core thalamocortical projection pattern. In primate primary motor cortex, no cytoarchitecturally distinct layer 4 was evident and the core thalamocortical projections terminated throughout layer 3. In the African elephant, cetaceans, and river hippopotamus, no cytoarchitecturally distinct layer 4 was observed and core thalamocortical projections terminated primarily in inner layer 3 and less densely in outer layer 3. These findings are contextualized in terms of cortical processing, perception, and the evolutionary trajectory leading to an indistinct or absent cortical layer 4.
Assuntos
Axônios , Neocórtex , Vias Neurais , Tálamo , Animais , Tálamo/citologia , Tálamo/anatomia & histologia , Neocórtex/citologia , Neocórtex/anatomia & histologia , Vias Neurais/citologia , Vias Neurais/anatomia & histologia , Axônios/fisiologia , Mamíferos/anatomia & histologia , Proteína Vesicular 2 de Transporte de Glutamato/metabolismo , Especificidade da EspécieRESUMO
Neuronal anatomy is central to the organization and function of brain cell types. However, anatomical variability within apparently homogeneous populations of cells can obscure such insights. Here, we report large-scale automation of neuronal morphology reconstruction and analysis on a dataset of 813 inhibitory neurons characterized using the Patch-seq method, which enables measurement of multiple properties from individual neurons, including local morphology and transcriptional signature. We demonstrate that these automated reconstructions can be used in the same manner as manual reconstructions to understand the relationship between some, but not all, cellular properties used to define cell types. We uncover gene expression correlates of laminar innervation on multiple transcriptomically defined neuronal subclasses and types. In particular, our results reveal correlates of the variability in Layer 1 (L1) axonal innervation in a transcriptomically defined subpopulation of Martinotti cells in the adult mouse neocortex.
Assuntos
Axônios , Dendritos , Neocórtex , Transcriptoma , Animais , Axônios/metabolismo , Camundongos , Dendritos/metabolismo , Neocórtex/citologia , Neocórtex/metabolismo , Neuroanatomia/métodos , Neurônios/metabolismo , Neurônios/citologia , Masculino , Perfilação da Expressão Gênica/métodos , Camundongos Endogâmicos C57BLRESUMO
Rhythmic brain activity is critical to many brain functions and is sensitive to neuromodulation, but so far very few studies have investigated this activity on the cellular level in vitro in human brain tissue samples. This study reveals and characterizes a novel rhythmic network activity in the human neocortex. Using intracellular patch-clamp recordings of human cortical neurons, we identify large rhythmic depolarizations (LRDs) driven by glutamate release but not by GABA. These LRDs are intricate events made up of multiple depolarizing phases, occurring at ~0.3 Hz, have large amplitudes and long decay times. Unlike human tissue, rat neocortex layers 2/3 exhibit no such activity under identical conditions. LRDs are mainly observed in a subset of L2/3 interneurons that receive substantial excitatory inputs and are likely large basket cells based on their morphology. LRDs are highly sensitive to norepinephrine (NE) and acetylcholine (ACh), two neuromodulators that affect network dynamics. NE increases LRD frequency through ß-adrenergic receptor activity while ACh decreases it via M4 muscarinic receptor activation. Multi-electrode array recordings show that NE enhances and synchronizes oscillatory network activity, whereas ACh causes desynchronization. Thus, NE and ACh distinctly modulate LRDs, exerting specific control over human neocortical activity.
Assuntos
Acetilcolina , Neocórtex , Norepinefrina , Humanos , Acetilcolina/farmacologia , Norepinefrina/farmacologia , Neocórtex/fisiologia , Neocórtex/metabolismo , Neocórtex/citologia , Neocórtex/efeitos dos fármacos , Masculino , Feminino , Animais , Pessoa de Meia-Idade , Ratos , Idoso , Periodicidade , Neurônios/fisiologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Interneurônios/fisiologia , Interneurônios/efeitos dos fármacos , Interneurônios/metabolismo , AdultoRESUMO
Mitochondria play critical roles in neural stem/progenitor cell proliferation and fate decisions. The subcellular localization of mitochondria in neural stem/progenitor cells during mitosis potentially influences the distribution of mitochondria to the daughter cells and thus their fates. Therefore, understanding the spatial dynamics of mitochondria provides important knowledge about brain development. In this study, we analyzed the subcellular localization of mitochondria in the fetal human neocortex with a particular focus on the basal radial glial cells (bRGCs), a neural stem/progenitor cell subtype attributed to the evolutionary expansion of the human neocortex. During interphase, bRGCs exhibit a polarized localization of mitochondria that is localized at the base of the process or the proximal part of the process. Thereafter, mitochondria in bRGCs at metaphase show unpolarized distribution in which the mitochondria are randomly localized in the cytoplasm. During anaphase and telophase, mitochondria are still localized evenly, but mainly in the periphery of the cytoplasm. Mitochondria start to accumulate at the cleavage furrow during cytokinesis. These results suggest that the mitochondrial localization in bRGCs is tightly regulated during the cell cycle, which may ensure the proper distribution of mitochondria to the daughter cells and, thus in turn, influence their fates.
Assuntos
Ciclo Celular , Células Ependimogliais , Mitocôndrias , Neocórtex , Humanos , Neocórtex/citologia , Neocórtex/metabolismo , Mitocôndrias/metabolismo , Ciclo Celular/fisiologia , Células Ependimogliais/metabolismo , Células Ependimogliais/citologia , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/citologiaRESUMO
The mammalian neocortex comprises an enormous diversity regarding cell types, morphology, and connectivity. In this work, we discover a post-transcriptional mechanism of gene expression regulation, protein translation, as a determinant of cortical neuron identity. We find specific upregulation of protein synthesis in the progenitors of later-born neurons and show that translation rates and concomitantly protein half-lives are inherent features of cortical neuron subtypes. In a small molecule screening, we identify Ire1α as a regulator of Satb2 expression and neuronal polarity. In the developing brain, Ire1α regulates global translation rates, coordinates ribosome traffic, and the expression of eIF4A1. Furthermore, we demonstrate that the Satb2 mRNA translation requires eIF4A1 helicase activity towards its 5'-untranslated region. Altogether, we show that cortical neuron diversity is generated by mechanisms operating beyond gene transcription, with Ire1α-safeguarded proteostasis serving as an essential regulator of brain development.
Assuntos
Proteínas de Ligação à Região de Interação com a Matriz , Neocórtex , Neurônios , Biossíntese de Proteínas , Proteínas Serina-Treonina Quinases , Animais , Neocórtex/metabolismo , Neocórtex/citologia , Neocórtex/embriologia , Neurônios/metabolismo , Neurônios/citologia , Camundongos , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas de Ligação à Região de Interação com a Matriz/metabolismo , Proteínas de Ligação à Região de Interação com a Matriz/genética , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteostase , Neurogênese/genética , RNA Mensageiro/metabolismo , RNA Mensageiro/genética , Regiões 5' não Traduzidas/genética , Ribossomos/metabolismo , Ribossomos/genética , Humanos , Endorribonucleases/metabolismo , Endorribonucleases/genética , Diferenciação Celular/genéticaRESUMO
The mammalian neocortex is formed by sequential radial migration of newborn excitatory neurons. Migrating neurons undergo a multipolar-to-bipolar transition at the subplate (SP) layer, where extracellular matrix (ECM) components are abundantly expressed. Here, we investigate the role of the ECM at the SP layer. We show that TGF-ß signaling-related ECM proteins, and their downstream effector, p-smad2/3, are selectively expressed in the SP layer. We also find that migrating neurons express a disintegrin and metalloproteinase with thrombospondin motif 2 (ADAMTS2), an ECM metalloproteinase, just below the SP layer. Knockdown and knockout of Adamts2 suppresses the multipolar-to-bipolar transition of migrating neurons and disturbs radial migration. Time-lapse luminescence imaging of TGF-ß signaling indicates that ADAMTS2 activates this signaling pathway in migrating neurons during the multipolar-to-bipolar transition at the SP layer. Overexpression of TGF-ß2 in migrating neurons partially rescues migration defects in ADAMTS2 knockout mice. Our data suggest that ADAMTS2 secreted by the migrating multipolar neurons activates TGF-ß signaling by ECM remodeling of the SP layer, which might drive the multipolar to bipolar transition.
Assuntos
Proteínas ADAMTS , Movimento Celular , Camundongos Knockout , Neocórtex , Neurônios , Transdução de Sinais , Fator de Crescimento Transformador beta , Animais , Neocórtex/metabolismo , Neocórtex/citologia , Proteínas ADAMTS/metabolismo , Proteínas ADAMTS/genética , Camundongos , Fator de Crescimento Transformador beta/metabolismo , Neurônios/metabolismo , Matriz Extracelular/metabolismoRESUMO
Neocortex is a complex structure with different cortical sublayers and regions. However, the precise positioning of cortical regions can be challenging due to the absence of distinct landmarks without special preparation. To address this challenge, we developed a cytoarchitectonic landmark identification pipeline. The fluorescence micro-optical sectioning tomography method was employed to image the whole mouse brain stained by general fluorescent nucleotide dye. A fast 3D convolution network was subsequently utilized to segment neuronal somas in entire neocortex. By approach, the cortical cytoarchitectonic profile and the neuronal morphology were analyzed in 3D, eliminating the influence of section angle. And the distribution maps were generated that visualized the number of neurons across diverse morphological types, revealing the cytoarchitectonic landscape which characterizes the landmarks of cortical regions, especially the typical signal pattern of barrel cortex. Furthermore, the cortical regions of various ages were aligned using the generated cytoarchitectonic landmarks suggesting the structural changes of barrel cortex during the aging process. Moreover, we observed the spatiotemporally gradient distributions of spindly neurons, concentrated in the deep layer of primary visual area, with their proportion decreased over time. These findings could improve structural understanding of neocortex, paving the way for further exploration with this method.
Assuntos
Aprendizado Profundo , Neocórtex , Neurônios , Animais , Neocórtex/citologia , Camundongos , Camundongos Endogâmicos C57BL , Masculino , Imageamento Tridimensional/métodos , Tomografia Óptica/métodosRESUMO
In this novel large-scale multiplexed immunofluorescence study we comprehensively characterized and compared layer-specific proteomic features within regions of interest of the widely divergent dorsolateral prefrontal cortex (A46) and primary visual cortex (A17) of adult rhesus monkeys. Twenty-eight markers were imaged in rounds of sequential staining, and their spatial distribution precisely quantified within gray matter layers and superficial white matter. Cells were classified as neurons, astrocytes, oligodendrocytes, microglia, or endothelial cells. The distribution of fibers and blood vessels were assessed by quantification of staining intensity across regions of interest. This method revealed multivariate similarities and differences between layers and areas. Protein expression in neurons was the strongest determinant of both laminar and regional differences, whereas protein expression in glia was more important for intra-areal laminar distinctions. Among specific results, we observed a lower glia-to-neuron ratio in A17 than in A46 and the pan-neuronal markers HuD and NeuN were differentially distributed in both brain areas with a lower intensity of NeuN in layers 4 and 5 of A17 compared to A46 and other A17 layers. Astrocytes and oligodendrocytes exhibited distinct marker-specific laminar distributions that differed between regions; notably, there was a high proportion of ALDH1L1-expressing astrocytes and of oligodendrocyte markers in layer 4 of A17. The many nuanced differences in protein expression between layers and regions observed here highlight the need for direct assessment of proteins, in addition to RNA expression, and set the stage for future protein-focused studies of these and other brain regions in normal and pathological conditions.
Assuntos
Substância Cinzenta , Macaca mulatta , Córtex Pré-Frontal , Proteômica , Substância Branca , Animais , Substância Branca/metabolismo , Substância Cinzenta/metabolismo , Córtex Pré-Frontal/metabolismo , Neocórtex/metabolismo , Neocórtex/citologia , Masculino , Astrócitos/metabolismo , Neurônios/metabolismo , Oligodendroglia/metabolismo , Neuroglia/metabolismo , Feminino , Lobo Occipital/metabolismo , Córtex Visual/metabolismoRESUMO
Diverse types of inhibitory interneurons (INs) impart computational power and flexibility to neocortical circuits. Whereas markers for different IN types in cortical layers 2-6 (L2-L6) have been instrumental for generating a wealth of functional insights, only the recent identification of a selective marker (neuron-derived neurotrophic factor [NDNF]) has opened comparable opportunities for INs in L1 (L1INs). However, at present we know very little about the connectivity of NDNF L1INs with other IN types, their input-output conversion, and the existence of potential NDNF L1IN subtypes. Here, we report pervasive inhibition of L2/3 INs (including parvalbumin INs and vasoactive intestinal peptide INs) by NDNF L1INs. Intersectional genetics revealed similar physiology and connectivity in the NDNF L1IN subpopulation co-expressing neuropeptide Y. Finally, NDNF L1INs prominently and selectively engage in persistent firing, a physiological hallmark disconnecting their output from the current input. Collectively, our work therefore identifies NDNF L1INs as specialized master regulators of superficial neocortex according to their pervasive top-down afferents.
Assuntos
Interneurônios , Animais , Camundongos , Interneurônios/metabolismo , Neocórtex/metabolismo , Neocórtex/citologia , Neocórtex/fisiologia , Neuropeptídeo Y/metabolismo , Parvalbuminas/metabolismo , Peptídeo Intestinal Vasoativo/metabolismoRESUMO
Aging is associated with the slowdown of neuronal processing and cognitive performance in the brain; however, the exact cellular mechanisms behind this deterioration in humans are poorly elucidated. Recordings in human acute brain slices prepared from tissue resected during brain surgery enable the investigation of neuronal changes with age. Although neocortical fast-spiking cells are widely implicated in neuronal network activities underlying cognitive processes, they are vulnerable to neurodegeneration. Herein, we analyzed the electrical properties of 147 fast-spiking interneurons in neocortex samples resected in brain surgery from 106 patients aged 11-84 years. By studying the electrophysiological features of action potentials and passive membrane properties, we report that action potential overshoot significantly decreases and spike half-width increases with age. Moreover, the action potential maximum-rise speed (but not the repolarization speed or the afterhyperpolarization amplitude) significantly changed with age, suggesting a particular weakening of the sodium channel current generated in the soma. Cell passive membrane properties measured as the input resistance, membrane time constant, and cell capacitance remained unaffected by senescence. Thus, we conclude that the action potential in fast-spiking interneurons shows a significant weakening in the human neocortex with age. This may contribute to the deterioration of cortical functions by aging.
Assuntos
Potenciais de Ação , Envelhecimento , Interneurônios , Neocórtex , Humanos , Neocórtex/fisiologia , Neocórtex/citologia , Idoso , Interneurônios/fisiologia , Idoso de 80 Anos ou mais , Adulto , Envelhecimento/fisiologia , Adolescente , Criança , Pessoa de Meia-Idade , Potenciais de Ação/fisiologia , Masculino , Adulto Jovem , FemininoRESUMO
Metabolism has recently emerged as a major target of genes implicated in the evolutionary expansion of human neocortex. One such gene is the human-specific gene ARHGAP11B. During human neocortex development, ARHGAP11B increases the abundance of basal radial glia, key progenitors for neocortex expansion, by stimulating glutaminolysis (glutamine-to-glutamate-to-alpha-ketoglutarate) in mitochondria. Here we show that the ape-specific protein GLUD2 (glutamate dehydrogenase 2), which also operates in mitochondria and converts glutamate-to-αKG, enhances ARHGAP11B's ability to increase basal radial glia abundance. ARHGAP11B + GLUD2 double-transgenic bRG show increased production of aspartate, a metabolite essential for cell proliferation, from glutamate via alpha-ketoglutarate and the TCA cycle. Hence, during human evolution, a human-specific gene exploited the existence of another gene that emerged during ape evolution, to increase, via concerted changes in metabolism, progenitor abundance and neocortex size.
Assuntos
Proteínas Ativadoras de GTPase , Glutamato Desidrogenase , Neocórtex , Neocórtex/metabolismo , Neocórtex/embriologia , Neocórtex/crescimento & desenvolvimento , Neocórtex/citologia , Humanos , Animais , Glutamato Desidrogenase/metabolismo , Glutamato Desidrogenase/genética , Proteínas Ativadoras de GTPase/metabolismo , Proteínas Ativadoras de GTPase/genética , Ácidos Cetoglutáricos/metabolismo , Neuroglia/metabolismo , Ácido Glutâmico/metabolismo , Mitocôndrias/metabolismo , Mitocôndrias/genética , Camundongos , Ciclo do Ácido Cítrico/genética , FemininoRESUMO
Debate remains around the anatomical origins of specific brain cell subtypes and lineage relationships within the human forebrain1-7. Thus, direct observation in the mature human brain is critical for a complete understanding of its structural organization and cellular origins. Here we utilize brain mosaic variation within specific cell types as distinct indicators for clonal dynamics, denoted as cell-type-specific mosaic variant barcode analysis. From four hemispheres and two different human neurotypical donors, we identified 287 and 780 mosaic variants, respectively, that were used to deconvolve clonal dynamics. Clonal spread and allele fractions within the brain reveal that local hippocampal excitatory neurons are more lineage-restricted than resident neocortical excitatory neurons or resident basal ganglia GABAergic inhibitory neurons. Furthermore, simultaneous genome transcriptome analysis at both a cell-type-specific and a single-cell level suggests a dorsal neocortical origin for a subgroup of DLX1+ inhibitory neurons that disperse radially from an origin shared with excitatory neurons. Finally, the distribution of mosaic variants across 17 locations within one parietal lobe reveals that restriction of clonal spread in the anterior-posterior axis precedes restriction in the dorsal-ventral axis for both excitatory and inhibitory neurons. Thus, cell-type-resolved somatic mosaicism can uncover lineage relationships governing the development of the human forebrain.
Assuntos
Linhagem da Célula , Células Clonais , Mosaicismo , Neurônios , Prosencéfalo , Idoso , Feminino , Humanos , Alelos , Linhagem da Célula/genética , Células Clonais/citologia , Células Clonais/metabolismo , Neurônios GABAérgicos/citologia , Neurônios GABAérgicos/metabolismo , Hipocampo/citologia , Proteínas de Homeodomínio/metabolismo , Neocórtex/citologia , Inibição Neural , Neurônios/citologia , Neurônios/metabolismo , Lobo Parietal/citologia , Prosencéfalo/anatomia & histologia , Prosencéfalo/citologia , Prosencéfalo/metabolismo , Análise de Célula Única , Transcriptoma/genéticaRESUMO
Throughout life, neuronal networks in the mammalian neocortex maintain a balance of excitation and inhibition, which is essential for neuronal computation1,2. Deviations from a balanced state have been linked to neurodevelopmental disorders, and severe disruptions result in epilepsy3-5. To maintain balance, neuronal microcircuits composed of excitatory and inhibitory neurons sense alterations in neural activity and adjust neuronal connectivity and function. Here we identify a signalling pathway in the adult mouse neocortex that is activated in response to increased neuronal network activity. Overactivation of excitatory neurons is signalled to the network through an increase in the levels of BMP2, a growth factor that is well known for its role as a morphogen in embryonic development. BMP2 acts on parvalbumin-expressing (PV) interneurons through the transcription factor SMAD1, which controls an array of glutamatergic synapse proteins and components of perineuronal nets. PV-interneuron-specific disruption of BMP2-SMAD1 signalling is accompanied by a loss of glutamatergic innervation in PV cells, underdeveloped perineuronal nets and decreased excitability. Ultimately, this impairment of the functional recruitment of PV interneurons disrupts the cortical excitation-inhibition balance, with mice exhibiting spontaneous epileptic seizures. Our findings suggest that developmental morphogen signalling is repurposed to stabilize cortical networks in the adult mammalian brain.
Assuntos
Proteína Morfogenética Óssea 2 , Interneurônios , Neocórtex , Rede Nervosa , Inibição Neural , Neurônios , Transdução de Sinais , Proteína Smad1 , Animais , Feminino , Humanos , Masculino , Camundongos , Proteína Morfogenética Óssea 2/metabolismo , Epilepsia/metabolismo , Epilepsia/fisiopatologia , Interneurônios/metabolismo , Neocórtex/metabolismo , Neocórtex/citologia , Rede Nervosa/metabolismo , Neurônios/metabolismo , Parvalbuminas/metabolismo , Proteína Smad1/metabolismo , Sinapses/metabolismo , Ácido Glutâmico/metabolismoRESUMO
Neocortex expansion during evolution is linked to higher numbers of neurons, which are thought to result from increased proliferative capacity and neurogenic potential of basal progenitor cells during development. Here, we show that EREG, encoding the growth factor EPIREGULIN, is expressed in the human developing neocortex and in gorilla cerebral organoids, but not in the mouse neocortex. Addition of EPIREGULIN to the mouse neocortex increases proliferation of basal progenitor cells, whereas EREG ablation in human cortical organoids reduces proliferation in the subventricular zone. Treatment of cortical organoids with EPIREGULIN promotes a further increase in proliferation of gorilla but not of human basal progenitor cells. EPIREGULIN competes with the epidermal growth factor (EGF) to promote proliferation, and inhibition of the EGF receptor abrogates the EPIREGULIN-mediated increase in basal progenitor cells. Finally, we identify putative cis-regulatory elements that may contribute to the observed inter-species differences in EREG expression. Our findings suggest that species-specific regulation of EPIREGULIN expression may contribute to the increased neocortex size of primates by providing a tunable pro-proliferative signal to basal progenitor cells in the subventricular zone.
Assuntos
Epirregulina , Neocórtex , Animais , Humanos , Camundongos , Proliferação de Células , Epirregulina/genética , Epirregulina/metabolismo , Gorilla gorilla/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Neocórtex/citologia , Neocórtex/metabolismo , Primatas/fisiologiaRESUMO
The human neocortex has undergone strong evolutionary expansion, largely due to an increased progenitor population, the basal radial glial cells. These cells are responsible for the production of a diversity of cell types, but the successive cell fate decisions taken by individual progenitors remain unknown. Here we developed a semi-automated live/fixed correlative imaging method to map basal radial glial cell division modes in early fetal tissue and cerebral organoids. Through the live analysis of hundreds of dividing progenitors, we show that basal radial glial cells undergo abundant symmetric amplifying divisions, and frequent self-consuming direct neurogenic divisions, bypassing intermediate progenitors. These direct neurogenic divisions are more abundant in the upper part of the subventricular zone. We furthermore demonstrate asymmetric Notch activation in the self-renewing daughter cells, independently of basal fibre inheritance. Our results reveal a remarkable conservation of fate decisions in cerebral organoids, supporting their value as models of early human neurogenesis.