Project description:Since the discovery of radial glia as the source of neurons, their heterogeneity in regard to neurogenesis has been described by clonal and time-lapse analysis in vitro. However, the molecular determinants specifying neurogenic radial glia differently from radial glia that mostly self-renew remain ill-defined. Here, we isolated two radial glial subsets that co-exist at mid-neurogenesis in the developing cerebral cortex and their immediate progeny. While one subset generates neurons directly, the other is largely non-neurogenic but also gives rise to Tbr2-positive basal precursors, thereby contributing indirectly to neurogenesis. Isolation of ; these distinct radial glia subtypes allowed determining interesting differences in their transcriptome. These transcriptomes were also strikingly different from the transcriptome of radial glia isolated at the end of neurogenesis. This analysis therefore identifies, for the first time, the lineage origin of basal progenitors and the molecular differences of this lineage in comparison to directly neurogenic and gliogenic radial glia. Experiment Overall Design: Comparison of radial glial subtypes
Project description:The mammalian central nervous system (CNS) is capable of tolerating chronic hypoxia, but cell type-specific responses to this stress have not been systematically characterized. In the Norrin-knockout (NdpKO) mouse, a model of familial exudative vitreoretinopathy (FEVR), developmental hypovascularization of the retina produces chronic hypoxia of inner nuclear layer (INL) neurons and Muller glia. We have used single-cell RNA sequencing, untargeted metabolomics, and metabolite labeling from 13C-glucose to compare wild type and NdpKO retinas. In NdpKO retinas, we observe gene expression responses consistent with hypoxia in Muller glia and retinal neurons, and we find a metabolic shift that combines reduced flux through the tricarboxylic acid cycle with increased synthesis of serine, glycine, and glutathione. We also used single-cell RNA sequencing to compare the responses of individual cell types in NdpKO retinas to those in the hypoxic cerebral cortex of mice that were housed for one week in a reduced oxygen environment (7.5% oxygen). In the hypoxic cerebral cortex, glial transcriptome responses most closely resemble the response of Muller glia in the NdpKO retina. In both retina and brain, vascular endothelial cells activate a previously dormant tip cell gene expression program, which likely underlies the adaptive neo-angiogenic response to chronic hypoxia. These analyses of retina and brain transcriptomes at single-cell resolution reveal both shared and cell-type-specific changes in gene expression in response to chronic hypoxia, implying both shared and distinct cell type-specific physiologic responses.
Project description:The development of the mammalian cerebral cortex depends on careful orchestration of proliferation, maturation, and migration events, ultimately giving rise to a wide variety of neuronal and non-neuronal cell types. To better understand cellular and molecular processes that unfold during late corticogenesis, we perform single-cell RNA-seq on the mouse cerebral cortex at a progenitor driven phase (embryonic day 14.5) and at birth—after neurons from all six cortical layers are born. We identify numerous classes of neurons, progenitors, and glia, their proliferative, migratory, and activation states, and their relatedness within and across age. Using the cell-type-specific expression patterns of genes mutated in neurological and psychiatric diseases, we identify putative disease subtypes that associate with clinical phenotypes. Our study reveals the cellular template of a complex neurodevelopmental process, and provides a window into the cellular origins of brain diseases.
Project description:Transcriptomic studies revealed that hundreds of mRNAs show differential expression in the brains of sleeping versus awake rats, mice, flies, and sparrows. Although these results have offered clues regarding the molecular consequences of sleep and sleep loss, their functional significance thus far has been limited. This is because the previous studies pooled transcripts from all brain cells, including neurons and glia. In the following experiment, we studied the specific effects of sleep and wake conditions on glia cells of mouse cerebral cortex using the genetically targeted translating ribosome affinity purification (TRAP) methodology. We used bacterial artificial chromosome (BAC) transgenic mice expressing EGFP tagged ribosomal protein L10a in astrocytes which constitute a defined cellular population of the mouse brain. Using this approach, we could extract only the astrocytic mRNAs, and only those already committed to be translated into proteins (L10a is part of the translational machinery). Six mice for each vigilant state group (sleep (S), waking (W), and sleep deprivation (SD)) were considered. For each animal, cerebral cortex was dissected and immediately processed. Samples were immunoprecipitated to isolate astrocytes. The precipitated portion formed the bound sample (IP) containing astrocytes and the remaining part formed the unbound sample (UB) containing all the remaining cell types (neurons and other glia cells). Then, both IP and UB samples were processed and RNA was extracted. All the IP samples (n=18) were then hybridized to Affymetrix GeneChip Mouse Genome 430 2.0 arrays, while UB samples were pooled together in two biological replicates (UB1+UB2+UB3 and UB4+UB5+UB6) for each group (n=6 in total) and then hybridized to Affymetrix GeneChip Mouse Genome 430 2.0 arrays.
Project description:Since the discovery of radial glia as the source of neurons, their heterogeneity in regard to neurogenesis has been described by clonal and time-lapse analysis in vitro. However, the molecular determinants specifying neurogenic radial glia differently from radial glia that mostly self-renew remain ill-defined. Here, we isolated two radial glial subsets that co-exist at mid-neurogenesis in the developing cerebral cortex and their immediate progeny. While one subset generates neurons directly, the other is largely non-neurogenic but also gives rise to Tbr2-positive basal precursors, thereby contributing indirectly to neurogenesis. Isolation of these distinct radial glia subtypes allowed determining interesting differences in their transcriptome. These transcriptomes were also strikingly different from the transcriptome of radial glia isolated at the end of neurogenesis. This analysis therefore identifies, for the first time, the lineage origin of basal progenitors and the molecular differences of this lineage in comparison to directly neurogenic and gliogenic radial glia.
Project description:<p>Non-coding regions comprise most of the human genome and harbor a significant fraction of risk alleles for neuropsychiatric diseases, yet their functions remain poorly defined. We created a high-resolution map of non-coding elements involved in human cortical neurogenesis by contrasting chromatin accessibility and gene expression in the germinal zone and cortical plate of the developing cerebral cortex. To obtain a high resolution depiction of chromatin structure and gene expression in developing human fetal cortex, we dissected the post-conception week (PCW) 15-17 human neocortex into two major anatomical divisions to distinguish between proliferating neural progenitors and post mitotic neurons: (1) GZ: the neural progenitor-enriched region encompassing the ventricular zone (VZ), subventricular zone (SVZ), and intermediate zone (IZ) and (2) CP: the neuron-enriched region containing the subplate (SP), cortical plate (CP), and marginal zone (MZ). Tissues were obtained from three independent donors and three to four technical replicates from each tissue were processed for ATAC-seq to define the landscape of accessible chromatin and RNA-seq for genome-wide gene expression profiling.</p>
Project description:To determine the impact of Brap loss of function on cellular senescence in cerebral cortex, we performed gene expression profiling analysis of mice with Brap conditional deletions in neural progenitors, postnatal neurons, and vascular endothelium cells, respectively. To understand the premature death caused by Brap conditional deletions in neural progenitors or neurons, we also analyzed mice at two different ages.
Project description:The cerebral cortex is a cellularly-complex structure comprised of a rich diversity of neuronal and glial cell types. Cortical neurons can be broadly categorized into two classes—glutamatergic excitatory neurons and GABAergic inhibitory interneurons. Previous developmental studies in rodents have led to the prevailing model that while excitatory neurons are born from progenitors located in the cortex, cortical interneurons are born from a separate population of progenitors located outside of the developing cortex in the ganglionic eminences1-5. However, the developmental potential of human cortical progenitors has not been thoroughly explored. Here we show that in addition to excitatory neurons and glia, human cortical progenitors are also capable of producing GABAergic neurons with the transcriptional characteristics and morphologies of cortical interneurons. By developing a cellular barcoding tool called “ScRNAseq-compatible Tracer for Identifying Clonal Relationships” (STICR), we were able to perform clonal lineage tracing of 1912 primary human cortical progenitors from six specimens and capture both the transcriptional identities and clonal relationships of their resulting progeny. A subpopulation of cortically-born GABAergic neurons were transcriptionally similar to cortical interneurons born from the caudal ganglionic eminence and these cells were frequently related to excitatory neurons and glia. Thus, our results demonstrate that individual human cortical progenitors can generate both excitatory neurons and cortical interneurons, providing a new framework for understanding the origins of neuronal diversity in the human cortex.