Project description:Understanding cell diversification from a common genome in metazoans requires single-cell transcriptional analysis. We introduce scFLUENT-seq, a single-cell nascent RNA sequencing method using brief 10-minute metabolic labeling to capture genome-wide transcription. Surprisingly, individual cellsfrom splenic lymphocytes to pluripotent stem cellstranscribe only 0.02~3.1% of the genome, versus >80% in bulk, revealing limited genome engagement and profound cell-type and cell-to-cell heterogeneity. Intergenic transcription, especially from heterochromatin, is pervasive and stochastic. Promoter-associated antisense and genic transcription rarely co-occur in the same cell. Proximal intergenic transcription involves both gene readthrough and independent initiation, while distal intergenic transcription is largely independent of neighboring genes and correlates with increased transcriptional diversity, a hallmark of cellular plasticity. Although global RNA sysnthesis and turnover are coupled in bulk, individual mRNA transcription and decay are poorly coordinated in single cells, suggesting noise-buffering mechanisms. Overall, scFLUENT-seq uncovers complex coding and noncoding transcriptional dynamics that underlie single-cell heterogeneity and state transitions.
Project description:Understanding cell diversification from a common genome in metazoans requires single-cell transcriptional analysis. We introduce scFLUENT-seq, a single-cell nascent RNA sequencing method using brief 10-minute metabolic labeling to capture genome-wide transcription. Surprisingly, individual cellsfrom splenic lymphocytes to pluripotent stem cellstranscribe only 0.02~3.1% of the genome, versus >80% in bulk, revealing limited genome engagement and profound cell-type and cell-to-cell heterogeneity. Intergenic transcription, especially from heterochromatin, is pervasive and stochastic. Promoter-associated antisense and genic transcription rarely co-occur in the same cell. Proximal intergenic transcription involves both gene readthrough and independent initiation, while distal intergenic transcription is largely independent of neighboring genes and correlates with increased transcriptional diversity, a hallmark of cellular plasticity. Although global RNA sysnthesis and turnover are coupled in bulk, individual mRNA transcription and decay are poorly coordinated in single cells, suggesting noise-buffering mechanisms. Overall, scFLUENT-seq uncovers complex coding and noncoding transcriptional dynamics that underlie single-cell heterogeneity and state transitions.
Project description:Understanding cell diversification from a common genome in metazoans requires single-cell transcriptional analysis. We introduce scFLUENT-seq, a single-cell nascent RNA sequencing method using brief 10-minute metabolic labeling to capture genome-wide transcription. Surprisingly, individual cellsfrom splenic lymphocytes to pluripotent stem cellstranscribe only 0.02~3.1% of the genome, versus >80% in bulk, revealing limited genome engagement and profound cell-type and cell-to-cell heterogeneity. Intergenic transcription, especially from heterochromatin, is pervasive and stochastic. Promoter-associated antisense and genic transcription rarely co-occur in the same cell. Proximal intergenic transcription involves both gene readthrough and independent initiation, while distal intergenic transcription is largely independent of neighboring genes and correlates with increased transcriptional diversity, a hallmark of cellular plasticity. Although global RNA sysnthesis and turnover are coupled in bulk, individual mRNA transcription and decay are poorly coordinated in single cells, suggesting noise-buffering mechanisms. Overall, scFLUENT-seq uncovers complex coding and noncoding transcriptional dynamics that underlie single-cell heterogeneity and state transitions.
Project description:Experience-dependent synaptic plasticity refines brain circuits during development. To uncover protein synthesis-dependent mechanisms contributing to experience-dependent plasticity, we performed quantitative proteomic analysis of the nascent proteome using improved bio-orthogonal metabolic labeling (BONCAT) to identify candidate plasticity proteins (CPPs) that undergo differential protein synthesis in response to visual conditioning (VC) in Xenopus optic tectum. We identified 83 CPPs that formed strongly connected networks and were annotated to a variety of biological functions, including RNA splicing, protein translation, and chromatin remodeling. Functional analysis of select CPPs using translation blocking morpholinos revealed the requirement of eukaryotic initiation factor 3 subunit A (eIF3A), fused in sarcoma (FUS), and ribosomal protein s17 (RPS17) in experience-dependent structural plasticity of tectal neurons. These results demonstrate that the nascent proteome is dynamic in response to VC and that de novo synthesis of the machinery that regulates gene expression and protein translation is required for experience-dependent structural plasticity.
Project description:Transcriptional regulation of gene expression is a major mechanism utilized by plants to confer phenotypic plasticity, yet compared to archaebacteria, eubacteria, and other eukaryotes, very little is known about the design principles of plant transcription. We generated an extensive catalog of nascent and steady state transcripts in Arabidopsis thaliana seedlings using global nuclear run-on sequencing (GRO-seq), 5'GRO-seq and RNA-seq and reanalyzed published maize data to capture the general characteristics of plant transcription. De novo annotation of nascent transcripts enabled accurate start site annotations and revealed novel unstable transcripts. Coding and non-coding transcripts exhibit comparable promoter chromatin configurations. Motif analysis revealed new regulatory DNA elements including a conserved 'TGT core promoter motif' and unreported transcription factor (TF) binding sites. Mapping of engaged RNA polymerases revealed a lack of enhancer RNAs, promoter proximal pausing, and divergent transcription in Arabidopsis and maize, which are commonly present in humans and yeast. In contrast, Arabidopsis and maize genes accumulate RNA polymerases adjacent to the polyadenylation site immediately downstream of genes, a trend that correlated with increasing gene length and coincided with hypomethylation of CpG residues. Lack of promoter proximal pausing and a higher correlation of nascent and steady state transcripts indicates Arabidopsis regulates transcription predominantly at the level of initiation. Together, these findings provide insight into plant transcriptional mechanisms, but also eukaryotic transcription in general.
Project description:miRNAs are key post-transcriptional regulators of gene expression. However, it is still poorly understood how miRNAs themselves are regulated, mainly due to the sparse annotation of miRNA transcription start sites (TSSs). Here, we developed a novel method for identifying active miRNA TSSs from nascent transcriptomes generated by nuclear run-on sequencing. With the least data requirement, our method demonstrated better performance than existing methods. Moreover, it provided ways not only to recognize miRNA TSSs but also to quantify primary miRNA expression in one experiment, which is very useful for revealing miRNAs directly regulated by the regulator(s) of interest.
Project description:Over the past decade, genome-wide assays have underscored the broad sweep of circadian gene expression. A substantial fraction of the transcriptome undergoes oscillations in many organisms and tissues, which governs the many biochemical, physiological and behavioral functions under circadian control. Based predominantly on the transcription feedback loops important for core circadian timekeeping, it is commonly assumed that this widespread mRNA cycling reflects circadian transcriptional cycling. To address this issue, we directly measured dynamic changes in mouse liver transcription using Nascent-Seq. Many genes are rhythmically transcribed over the 24h day, which include precursors of several non-coding RNAs as well as the expected set of core clock genes. Surprisingly however, nascent RNA rhythms overlap poorly with mRNA abundance rhythms assayed by RNA-seq. This is because most mouse liver genes with rhythmic mRNA expression manifest poor transcriptional rhythms, indicating a prominent role of post-transcriptional regulation in setting mRNA cycling amplitude. To gain further insight into circadian transcriptional regulation, we also characterized the rhythmic transcription of liver genes targeted by the transcription factors CLOCK and BMAL1; they directly target other core clock genes and sit at the top of the molecular circadian clock hierarchy in mammals. CLK:BMAL1 rhythmically bind at the same discrete phase of the circadian cycle to all target genes, which not surprisingly have a much higher percentage of rhythmic transcription than the genome as a whole. However, there is a surprisingly heterogeneous set of cycling transcription phases of direct target genes, which even include core clock genes. This indicates a disconnect between rhythmic DNA binding and the peak of transcription, which is likely due to other transcription factors that collaborate with CLK:BMAL1. In summary, the application of Nascent-Seq to a mammalian tissue provides surprising insights into the rhythmic control of gene expression and should have broad applications beyond the analysis of circadian rhythms. Mouse liver nascent RNA profile over 6 time points of the 24h light:dark cycle, in duplicate, sequenced using Ilumina GAII (Nascent-Seq); Mouse liver mRNA profile over 6 time points of the 24h light:dark cycle, in duplicate, sequenced using Ilumina HiSeq2000 (RNA-Seq); CLK and BMAL1 DNA binding profile in the mouse liver at ZT8, sequenced along an Input sample using GAII (ChIP-Seq); Mouse liver strand-specific nascent RNA profile over 6 time points of the 24h light:dark cycle, in duplicate, sequenced using Ilumina HiSeq2000 (Strand-specific Nascent-Seq); Supplementary file NascentSeq_Mouse_Liver_NormalizedGeneSignal.txt represents Nascent RNA abundance (reads per base pair) for each sample.
Project description:This SuperSeries is composed of the following subset Series: GSE36871: Nascent-Seq Reveals Novel Features of Mouse Circadian Transcriptional Regulation [RNA-Seq] GSE36872: Nascent-Seq Reveals Novel Features of Mouse Circadian Transcriptional Regulation [Nascent-Seq] GSE36873: Nascent-Seq Reveals Novel Features of Mouse Circadian Transcriptional Regulation [StrandSpe_NascentSeq] GSE36874: Nascent-Seq Reveals Novel Features of Mouse Circadian Transcriptional Regulation [ChIP-seq] Refer to individual Series