Project description:<p>Elucidating the cellular architecture of the human neocortex is central to understanding our cognitive abilities and susceptibility to disease. In this study, we applied single nucleus RNA sequencing to perform a comprehensive analysis of cell types in the middle temporal gyrus of human cerebral cortex. We identify a highly diverse set of excitatory and inhibitory neuronal types, many of which are relatively sparse. Additionally, we found that excitatory types are less layer-restricted than expected based prior knowledge from cell morphologies and from mouse studies. Comparison to a similar mouse cortex single cell RNA-sequencing dataset revealed a surprisingly well-conserved cellular architecture that enables matching of homologous types and predictions of human cell type properties. Despite this general conservation, we also find extensive differences between homologous cell types in human and mouse, including dramatic alterations in proportions, laminar distributions, gene expression, and morphology. These species-specific features emphasize the importance of directly studying human brain.</p> <p>This study conducted by the Allen Institute for Brain Science was supported by the Allen Institute for Brain Science and by US National Institutes of Health grant U01 MH114812-02 to E.S.L. Collaborators request that publications resulting from these data cite their original publication: Hodge RD, Bakken TE, et al. Conserved cell types with divergent features between human and mouse cortex. bioRxiv. 2018 doi: <a href="https://www.biorxiv.org/content/10.1101/384826v1" target="_blank">10.1101/384826</a>.</p>
Project description:To explore how brains change upon species evolution, we generated the first whole central brain comparative single-cell transcriptomic atlases of three closely-related but ecologically-distinct drosophilids: D. melanogaster, D. simulans and D. sechellia. D. melanogaster and D. simulans are cosmopolitan generalists, while the island endemic D. sechellia exhibits extreme niche specialism on the ripe noni fruit of the Morinda citrifolia shrub. The global cellular composition of central brains is well-conserved in the three Drosophila species, but we predicted a few cell types (perineurial glia, sNPF and Dh44 neurons) with divergent frequencies. Gene expression analysis revealed that distinct cell types within the central brain evolve at different rates and patterns; notably, several glial cell types exhibit the greatest divergence between species. Compared to D. melanogaster, the cellular composition and gene expression patterns of the central brain in D. sechellia displays greater deviation than those of D. simulans, indicating that the distinctive ecological specialization of D. sechellia is reflected in the structure and function of its brain. Gene expression changes in D. sechellia encompass metabolic and ecdysone signaling genes, indicative of adaptations to its novel ecological demands. Additional single-cell transcriptomic analysis on D. sechellia revealed genes and cell types responsive to noni juice supplementation, showing glial cells as key sites for both physiological and genetic adaptation to novel conditions. Our comparative transcriptomic atlases of drosophilid brains will provide an entry point to more broadly study the evolvability of nervous systems across and beyond the Drosophila genus.
Project description:Genome-wide Analysis Reveals Conserved and Divergent Features of Notch1/RBPJ Binding in Human and Murine T Lymphoblastic Leukemia Cells
Project description:Notch1 regulates gene expression by associating with the DNA-binding factor RBPJ and is oncogenic in murine and human T cell progenitors. Using ChIP-Seq, we find that in human and murine T-LL genomes Notch1 binds preferentially to promoters, to RBPJ binding sites, and near imputed ZNF143, Ets and Runx sites. ChIP-Seq confirmed that ZNF143 binds to ~40% of Notch1 sites. Notch1/ZNF143 sites are characterized by high Notch1 and ZNF143 signals, frequent co-binding of RBPJ (generally through sites embedded within ZNF143 motifs), strong promoter bias, and relatively low mean levels of activating chromatin marks. RBPJ and ZNF143 binding to DNA is mutually exclusive in vitro, suggesting RBPJ/Notch1 and ZNF143 complexes exchange on these sites in cells. K-means clustering of Notch1 binding sites and associated motifs identified conserved Notch1-Runx, Notch1-Ets, Notch1-RBPJ, Notch1-ZNF143, and Notch1-ZNF143-Ets clusters with different genomic distributions and levels of chromatin marks. Although Notch1 binds mainly to gene promoters, ~75% of direct target genes lack promoter binding and are presumably regulated by enhancers, which were identified near MYC, DTX1, IGF1R, IL7R and the GIMAP cluster. Human and murine T-LL genomes also have many sites that bind only RBPJ. Murine RBPJ M-CM-"M-BM-^@M-BM-^\onlyM-CM-"M-BM-^@M-BM-^] sites are highly enriched for imputed REST sites, whereas human RPBJ M-CM-"M-BM-^@M-BM-^\onlyM-CM-"M-BM-^@M-BM-^] sites lack REST motifs and are more highly enriched for imputed CREB sites. Thus, there is a conserved network of cis-regulatory factors that interacts with Notch1 to regulate gene expression in T-LL cells, as well as novel classes of divergent RBPJ M-CM-"M-BM-^@M-BM-^\onlyM-CM-"M-BM-^@M-BM-^] sites that also likely regulate transcription. Notch1, RBPJ, histone methylation ChIP-seq in human and mouse T-LL cell lines
Project description:Cortical neurons exhibit astounding diversity in gene expression as well as in morphological and electrophysiological properties. Most existing neural taxonomies are based on either transcriptomic or morpho-electric criteria, as it has been technically challenging to study both aspects of neuronal diversity in the same set of cells. Here we used Patch-seq to combine patch-clamp recording, biocytin staining, and single-cell RNA sequencing of over 1300 neurons in adult mouse motor cortex, providing a comprehensive morpho-electric annotation of almost all transcriptomically defined neural cell types. We found that, although broad families of transcriptomic types (Vip, Pvalb, Sst, etc.) had distinct and essentially non-overlapping morpho-electric phenotypes, individual transcriptomic types within the same family were not well-separated in the morpho-electric space. Instead, there was a continuum of variability in morphology and electrophysiology, with neighbouring transcriptomic cell types showing similar morpho-electric features, often without clear boundaries between them. Our results suggest that neural types in the neocortex do not always form discrete entities. Instead, neurons follow a hierarchy consisting of distinct non-overlapping branches at the level of families, but can form continuous and correlated transcriptomic and morpho-electrical landscapes within families.