Project description:RNA-seq of amiloride-treated cell culture was conducted in order to understand the characteristics that make certain exons susceptible to splicing perturbations. Amiloride is a diuretic that acts by inhibiting epithelial sodium channels in the kidney. It also behaves as a non-specific kinase inhibitor, and has been shown to affect splicing in a handful of genes, presumably by altering phosphorylation of splicing factors. Two samples were sequenced (one untreated, one treated). Differential splicing was done using rMATS version 3.2.5.
Project description:High-throughput splicing assays have demonstrated that many exonic variants can disrupt splicing; however, splice-disrupting variants distribute non-uniformly across genes. We propose the existence of exons that are particularly susceptible to splice-disrupting variants, which we refer to as hotspot exons. Hotspot exons are also more susceptible to splicing perturbation through drug treatment and knock-down of RNA-binding proteins. We develop a classifier for exonic splice-disrupting variants and use it to infer hotspot exons. We estimate that 1400 exons in the human genome are hotspots. Using panels of splicing reporters, we demonstrate how the ability of an exon to tolerate a mutation is inversely proportional to the strength of its neighboring splice sites.
Project description:Disruptions in core cellular processes elicit stress responses that drive cell state changes leading to organismal phenotypes. Perturbations in the splicing machinery cause widespread mis-splicing, resulting in p53-dependent cell-state changes that give rise to cell-type specific phenotypes and disease. However, a unified framework for how cells respond to splicing perturbations, and how this response manifests itself in nuanced disease phenotypes, has yet to be established. Here, we show that a p53-stabilizing Mdm2 alternative splicing event and widespread downregulation of metabolic transcripts are common events that arise under various splicing perturbations in both cellular and organismal models. Together, our results classify a common cellular response to splicing perturbations, put forth a new mechanism behind the cell-type specific phenotypes that arise when splicing is broadly disrupted, and lend insight into the pleiotropic nature of the effects of p53 stabilization in disease.
Project description:The human transcriptome is so large, diverse and dynamic that, even after a decade of investigation by RNA sequencing (RNA-Seq), we are yet to resolve its true dimensions. RNA-Seq suffers from an expression-dependent bias that impedes discovery of low-abundance transcripts and has prevented a complete census of gene expression. Here we performed targeted single-molecule and short-read RNA-Seq to survey the transcriptional landscape of a single human chromosome (Hsa21) at unprecedented resolution. Our analysis reaches the lower limits of the transcriptome and identifies a fundamental distinction between the architecture of protein-coding and noncoding gene content. Unlike their coding counterparts, noncoding exons undergo universal alternative splicing to produce a seemingly limitless variety of isoforms. Targeted RNA-Seq analysis of syntenic regions of the mouse genome shows that few noncoding exons are shared between human and mouse. Despite this divergence, human alternative splicing profiles are recapitulated on Hsa21 in mouse cells, indicative of regulation by a local splicing code that is more strongly conserved than the noncoding isoforms themselves. We propose that noncoding exons are functionally modular, with combinatorial alternative splicing generating an enormous repertoire of potential regulatory RNAs and a rich transcriptional reservoir for gene evolution.
Project description:Systematic mutagenesis has revealed that synonymous, non-synonymous and intronic mutations frequently alter the inclusion levels of alternatively spliced exons, suggesting that altered splicing might be a common mechanism by which mutations cause disease. However, most exons expressed in any cell are highly-included in mature mRNAs. Here, by performing deep mutagenesis of highly-included exons and by analysing the association between sequence variation and exon inclusion across the genome, we report that mutations only very rarely alter the inclusion of highly-included exons. This is true for both exonic and intronic mutations as well as for perturbations in trans. Therefore, mutations that affect splicing are not evenly distributed across the genome but are focussed in and around alternatively spliced exons with intermediate inclusion levels. These results provide a resource for prioritising synonymous and other variants as disease-causing mutations.
Project description:ost characterized tumor antigens are ‘genomic’, i.e. encoded by canonical, non-canonical or somatically mutated genomic sequences. We investigate here the presentation and immunogenicity of tumor antigens derived from non-canonical mRNA splicing events between coding exons and transposable elements (TEs). Comparing non-small cell lung cancer (NSCLC), an immunogenic tumor type, and diverse non-tumor tissues, we identify several thousand splicing junctions between exons and diverse TE classes. A subset of these junctions is both tumor-specific and shared across patients. HLA-I peptidomic identifies peptides encoded by tumor-specific junctions in primary NSCLC samples and lung tumor cell lines. Recurrent junction-encoded peptides are immunogenic in vitro and CD8+ T cells specific for junction-encoded epitopes are present in tumors and tumor-draining lymph nodes from NSCLC patients. We conclude that non-canonical splicing junctions between exons and TEs represent a source of recurrent, immunogenic tumor-specific antigens in NSCLC cancer patients.
Project description:Pre-mRNA splicing is important for gene expression in most eukaryotic organisms. Regulation occurs during pre-mRNA splicing greatly expanded the transcriptome complexity. Recent studies from Mammals, Drosophila and Yeast showed that the majority of introns are spliced co-transcriptionally. However, in plant the nature of co-transcriptionally splicing (CTS) and its regulation is still largely unknown. Here, through sequencing the chromatin-bound RNA (CB-RNA-seq), we studied the feature of CTS in Arabidopsis. We found CTS is widespread in Arabidopsis seedlings and a large proportion of alternative splicing events are determined co-transcriptionally. We found the CTS efficiency correlate with gene expression level, chromatin landscape and most surprisingly, the number of intron/exon of individual genes, whilst independent of gene length. In combination with iCLIP analysis, we found splicing regulator RZ-1B/1C promotes efficient CTS of thousands genes involving direct binding mainly to the exonic sequences. Interestingly, for many cases, the splicing promotion activity of RZ-1C does not associate with its binding to the regions immediately adjacent to the regulated intron. We propose a model of plant gene splicing, where multiple exon of individual gene is in favour of efficient CTS likely involving RZ-1C cooperative interactions with many exons and splicing factors. Our work uncovers the robustness of plant CTS and highlighted the role of RZ-1C in this process.
Project description:Hotspot mutations in the spliceosomal component gene SF3B1 underpin a number of cancers and have a neomorphic function leading to global disruption of canonical splicing and aberrant splicing of hundreds of transcripts. However, the functional consequences of this misplicing and resultant genetic vulnerabilities imposed by these events are poorly understood. Through a synthetic-lethal approach we identify that SF3B1 mutant cells are selectively sensitive to PARP inhibitors. This vulnerability is preserved across multiple cell line and patent derived tumour models, independent of SF3B1 hotspot mutation and is manifested both in vitro and in vivo. These data provide the pre-clinical and mechanistic rationale for assessing SF3B1 mutations as a biomarker of single-agent PARP inhibitor response in a new patient population and may extend the clinical utility of these agents beyond BRCA mutated cancers.