Identification of the coding elements in the genome is a fundamental step to understanding the building blocks of living systems. Short peptides (< 100 aa) have emerged as important regulators of development and physiology, but their identification has been limited by their size. We have leveraged the periodicity of ribosome movement on the mRNA to define actively translated ORFs by ribosome footprinting. This approach identifies several hundred translated small ORFs in zebrafish and human. Computational prediction of small ORFs from codon conservation patterns corroborates and extends these findings and identifies conserved sequences in zebrafish and human, suggesting functional peptide products (micropeptides). These results identify micropeptide-encoding genes in vertebrates, providing an entry point to define their function in vivo. Overall design: Ribosome profiling experiments at five timepoints across zebrafish development in WT embryos
Upstream ORFs are prevalent translational repressors in vertebrates.
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View SamplesMicroRNAs regulate gene expression through deadenylation, repression and mRNA decay. However, the contribution of each mechanism in non-steady-state situations remains unclear. We monitored the impact of miR-430 on ribosome occupancy of endogenous mRNAs in wild type and dicer mutants lacking mature miR-430. Our results indicate that miR-430 reduces the number of ribosomes on target mRNAs before causing mRNA decay. Translational repression occurs before complete deadenylation, and disrupting deadenylation using an internal poly(A) tail did not block target repression. Finally, we observe that ribosome density along the length of the target mRNA remains constant, suggesting that translational repression occurs by reducing the initiation rate rather than reducing elongation or causing ribosomal drop-off. In summary, our results show that miR-430 regulates translation initiation before inducing mRNA decay. Overall design: Time course parallel ribosome profiling and input mRNA quantification in wildtype and MZdicer mutant embryos
Ribosome profiling shows that miR-430 reduces translation before causing mRNA decay in zebrafish.
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View SamplesmicroRNAs (miRNAs) are typically generated as ~22-nucleotide double-stranded RNAs via processing of precursor hairpins by the RNase III enzyme Dicer, after which they are loaded into Argonaute (Ago) proteins to form RNA-induced silencing complex (RISC). However, the biogenesis of miR-451, an erythropoietic miRNA conserved in vertebrates, does not require Dicer processing. Instead, the short pre-miR-451 precursor hairpin is directly loaded into Ago, followed by cleavage of the 3'' arm and trimming of the 3'' end to the mature length by PARN. Here we show the in vivo activity of miR-430 Ago2-hairpin, a canonical microRNA engineered to fit the structure of miR-451 and hence become Ago2-dependent. Moreover, we test a modified miR-430 Ago2-haipin with 3x phoshorothioate bonds that impairs trimmng. Surprisingly, our data show that trimming of Ago-cleaved pre-miRNAs is not essential for target silencing, indicating that RISC is functional with miRNAs longer than 22-nucleotides. Overall design: Rescue of MZdicer zebrafish mutant with the injection of trimmable and nontrimmable miR-430 Ago2 hairpins: Transcriptome of wild type, MZdicer mutant, and MZdicer mutant micoinjected with miR-430 duplex, miR-430 (Ago2-haripin), miR-430 (Ago2-haripin 3xPhosphorothioate)
Poly(A)-specific ribonuclease mediates 3'-end trimming of Argonaute2-cleaved precursor microRNAs.
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View SamplesExtracellular RNAs (exRNAs) in blood and other biofluids have attracted great interest as potential biomarkers in liquid biopsy applications, as well as for their potential biological functions. Whereas it is well-established that extracellular microRNAs are present in human blood circulation, the degree to which messenger RNAs (mRNA) and long noncoding RNAs (lncRNA) are represented in plasma is less clear. Here we report that mRNA and lncRNA species are present as small fragments in plasma that are not detected by standard small RNA-seq methods, because they lack 5'-phosphorylation or carry 3'-phosphorylation. We developed a modified sequencing protocol (termed "phospho-sRNA-seq") that incorporates upfront RNA treatment with T4 polynucleotide kinase (which also has 3' phosphatase activity) and compared it to a standard small RNA-seq protocol, using as input both a pool of synthetic RNAs with diverse 5' and 3' end chemistries, as well exRNA isolated from human blood plasma. Using a custom, high-stringency pipeline for data analysis we identified mRNA and lncRNA transcriptome fingerprints in plasma, including multiple tissue-specific gene sets. In a longitudinal study of hematopoietic stem cell transplant (HSCT) patients, we found different sets corresponding to bone marrow- and liver- enriched genes, which tracked with bone marrow recovery or liver injury, providing proof-of-concept validation of this method as a biomarker approach. By accessing a previously unexplored realm of mRNA and lncRNA fragments in blood plasma, phospho-sRNA-seq opens up a new space for plasma transcriptome-based biomarker development in diverse clinical settings. Overall design: ExRNA-seq libraries were prepared from platelet-poor plasma obtained from serial blood draws collected from two individuals undergoing bone marrow transplantation. A total of 11 samples were collected from each individual, starting prior to chemotherapy/ratiation treatment (approximately 7 days pre-HSCT) the day of transplant, and then weekly up to approximately Day 63.
Phospho-RNA-seq: a modified small RNA-seq method that reveals circulating mRNA and lncRNA fragments as potential biomarkers in human plasma.
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View SamplesWe report the RNAseq analysis of human dermal fibroblasts which have been treated by protocols to stimulate their differentiation towards the otic lineage. This was achieved by transfection with different transcription factors with the aim to induce an initial reprogramming of the cells and was followed by growth factor treatments known to promote otic differentiation. The results show that a partial differentiation towards the otic lineage is achieved by these protocols. Overall design: RNAseq profiles were obtained from human dermal fibroblasts with two different protocols. Prior to treatment with growth factors stimulating differentiation, the samples were either transfected with the transcription factors OCT4 or a combination of ATOH1, POU4F3 and GFI1.
Transcription factor induced conversion of human fibroblasts towards the hair cell lineage.
Specimen part, Subject
View SamplesMicroRNAs comprise 1-3% of all vertebrate genes, but their in vivo functions and mechanisms of action remain largely unknown. Zebrafish miR-430 is expressed at the onset of zygotic transcription and regulates morphogenesis during early development. Using a microarray approach and in vivo target validation, we find that miR-430 directly regulates several hundred target mRNAs. Targets are highly enriched for maternal mRNAs that accumulate in the absence of miR-430. We also show that miR-430 accelerates the deadenylation of target mRNAs. These results suggest that miR-430 facilitates the deadenylation and clearance of maternal mRNAs during early embryogenesis.
Zebrafish MiR-430 promotes deadenylation and clearance of maternal mRNAs.
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View SamplesThese experiments were designed as a benchmark tool for deconvolution methods. 5 immune cell populations were sorted from 3 healthy donors' peripheral bloods. Peripheral Blood Mononuclear Cells (PBCMs) and PolymorphoNuclear Cells (PMN) were separated using gradient centrifugation. T cells (DAPI-/CD3+/CD14-/CD19-/CD56-), monocytes (DAPI-/CD3-/CD14+/CD19-/CD56-), B cells (DAPI-/CD3-/CD14-/CD19+/CD56-) and NK cells (DAPI-/CD3-/CD14-/CD19-/CD56+) were FACS-sorted from PBMCs and neutrophils (DAPI-/CD66b+/CD19-/CD3-/CD56-/CD14-) were sorted from PMNs. RNA was extracted from the purified cell population, as well as from the HCT116 colon cancer cell line. RNAs from pure populations were then mixed in various proportions.
Estimating the population abundance of tissue-infiltrating immune and stromal cell populations using gene expression.
Cell line
View SamplesHere we identify a Dicer-independent miRNA biogenesis pathway that employs the slicer catalytic activity of Argonaute2 (Ago2). To uncover Dicer-independent miRNAs, we sequenced small RNAs in wild type, maternal-zygotic dicer (MZdicer) and MZago2 mutants, using zebrafish as a model system. We find that, in contrast to other miRNAs, miR-451 levels were increased in MZdicer but drastically reduced in the MZago2 mutants. We show that pre-miR-451 processing requires Ago2 catalytic activity in vivo. MZago2 mutant embryos display delayed erythrocyte maturation that can be rescued by wild type Ago2 or miR-451 duplex but not catalytically dead Ago2. We propose that Ago2-mediated cleavage of a subset of pre-miRNAs, followed by uridylation and trimming, generates functional miRNAs in a Dicer-independent manner. Overall design: Examination of small RNAs (18 to 35 nucleotides) in 3 different zebrafish genotypes (wild type, MZago2, MZdicer) at 48 hours post-fertilization.
A novel miRNA processing pathway independent of Dicer requires Argonaute2 catalytic activity.
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View SamplesRepA-WH1 is a synthetic bacterial prionoid, i.e., a protein that aggregates as amyloid in bacteria leading to cell death
Outlining Core Pathways of Amyloid Toxicity in Bacteria with the RepA-WH1 Prionoid.
Disease, Time
View SamplesProper functioning of tissues requires cells to behave in uniform, well-organized ways. Conversely, many diseases involve increased cellular heterogeneity due to genetic and epigenetic alterations. Defining the mechanisms that counteract phenotypic variability is therefore critical to understand how tissues sustain homeostasis. Here, we carried out a single-cell resolution screen of zebrafish embryonic blood vessels upon mutagenesis of single microRNA (miRNA) genes and multi-gene miRNA families. We found that miRNA mutants exhibit a profound increase in cellular phenotypic variability of specific vascular traits. Genome-wide analysis of endothelial miRNA target genes identified antagonistic regulatory nodes of vascular growth and morphogenesis signaling that allow variable cell behaviors when derepressed. Remarkably, lack of such miRNA activity greatly sensitized the vascular system to microenvironmental changes induced by pharmacological stress. We uncover a previously unrecognized role of miRNAs as a widespread protective mechanism that limits variability in cellular phenotypes. This discovery marks an important advance in our comprehension of how miRNAs function in the physiology of higher organisms. Overall design: Analysis of differential genes expression in Zebrafish endothelial cells for 4 different developmental stages
MicroRNAs Establish Uniform Traits during the Architecture of Vertebrate Embryos.
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