Project description:We sequenced mRNA from mouse E14.5 embryonic cortex to compare gene expression level and alternative splicing events between 2 control (WT) and 2 Qk cKO. A set of tissue specific splicing factors are thought to govern alternative splicing events during neural progenitors (NPC) to neuron transition by regulating neuron specific exons. Here we proposed one such a factor, RNA-binding protein Qki5, which is specifically expressed in neural stem cells. We performed mRNAseq analysis by using mRNAs obtained from developing cerebral cortices in Qk conditional knockout (cKO) mice. Expectedly, we found huge numbers of alternative splicing changes between control and conditional knock-out relative to that of transcripts level changes. Furthermore, DAVID and Meta-scape analysis revealed that affected spliced genes are involved in axon-development and microtubule-based process. Among these, Ninein protein coding mRNA is listed as a Qk protein dependent alternative splicing targets. Interestingly, this exon encodes very long poly-peptides (2,121 nt) and is known as a previously defined dynamic RNA switch during NPC-to-neuron transition. In addition, we validated that the regulation of this large exon is consistent with Qki5 dependent alternative exon inclusion mode obtained from our previous Qki5 HITS-CLIP analysis. Together Qki5 will add to a list factor of alternative splicing in NPC-to-neuron transition.
Project description:RNA secondary structures have been increasingly reported to serve critical regulatory roles in post-transcriptional gene regulation. RNA G-quadruplex secondary structures can serve as cis-elements to recruit splicing factors and regulate alternative RNA splicing. We recently showed that RNA G-quadruplexes play a critical regulatory role in regulating alternative splicing during the epithelial mesenchymal transition. Due to the critical role alternative splicing plays in human health and disease, an unmet need exists to identify small molecule modulators of alternative splicing. In this study, we performed high-throughput screening using a dual-output splicing reporter to identify small molecules capable of regulating alternative splicing by interacting with RNA secondary structure G-quadruplexes. We identify emetine and its analog cephaeline as small molecules that denature RNA G-quadruplexes in a sequence and location independent manner to modify alternative splicing. Transcriptome analysis reveals that treatment with emetine globally regulates alternative splicing, including events associated with exon-proximal G-quadruplexes. These data suggest a critical role for emetine and cephealine as splicing regulators with the selective ability to disrupt RNA G-quadruplex-associated alternative splicing in vivo.
Project description:Alternative splicing produces multiple, distinct mRNA transcripts from the same gene locus. To explore tissue-type specific gene expression and alternative splicing, we generated mRNA-Seq data from pupal tissues dissected from Drosophila. This allowed us to compare expression between dissected, highly enriched brain and indirect flight muscle (IFM) samples as well as whole legs. Bioinformatic analysis allowed us to characterize tissue-specific differences in gene expression as well as alternative splicing among the three tissues, as well as to identify a multitude of novel splicing events that are not currently contained in the Drosophila annotation. This suggests that tissue or cell-type specific sequencing at multiple timepoints during the fly life cycle will help extend existing annotations, and novel splice junction discovery is an important consideration in mRNA-Seq data analysis.
Project description:We carried out the first analysis of alternative splicing complexity in human tissues using mRNA-Seq data. New splice junctions were detected in 20% of multiexon genes, many of which are tissue specific. By combining mRNA-Seq and EST-cDNA sequence data, we estimate that transcripts from 95% of multiexon genes undergo alternative splicing and that there are 100,000 intermediate- to high-abundance alternative splicing events in major human tissues. From a comparison with quantitative alternative splicing microarray profiling data, we also show that mRNA-Seq data provide reliable measurements for exon inclusion levels. Keywords: mRNA expression 32-nucleotide sequence reads from six human tissues including brain, cerebral cortex, heart, liver, lung and skeletal muscle.
Project description:The epithelial-mesenchymal transition (EMT) is a fundamental developmental process that is abnormally activated in cancer metastasis. Dynamic changes in alternative splicing occur during EMT. ESRP1 and hnRNPM are splicing regulators that promote an epithelial splicing program and a mesenchymal splicing program, respectively. The functional relationships between these splicing factors in the genome-scale remain elusive. Comparing alternative splicing targets of hnRNPM and ESRP1 revealed that they co-regulate a set of cassette exon events, with the majority showing discordant splicing regulation. hnRNPM discordantly regulated splicing events show a positive correlation with splicing during EMT while concordant splicing events do not, highlighting the antagonistic role of hnRNPM and ESRP1 during EMT. Motif enrichment analysis near co-regulated exons identifies guanine-uridine rich motifs downstream of hnRNPM-repressed and ESRP1-enhanced exons, supporting a model of competitive binding to these cis-elements to antagonize alternative splicing. The set of co-regulated exons are enriched in genes associated with cell-migration and cytoskeletal reorganization, which are pathways associated with EMT. Splicing levels of co-regulated exons are associated with breast cancer patient survival and correlate with gene sets involved in EMT and breast cancer subtypes. In conclusion, hnRNPM and ESRP1 co-regulate antagonistically a set of alternative splicing events that occur during EMT. This regulation is likely mediated through competition for the same intronic binding sites downstream of variable exons. hnRNPM and ESRP1 regulated splicing events are associated with breast cancer survival.
Project description:Background: There are significant sex differences in human physiology and disease; the genomic sources of these differences, however, are not well understood. During puberty, a drastic neuroendocrine shift signals physical changes resulting in robust sex differences in human physiology. Here, we explore how shifting patterns of DNA methylation may inform these pathways of biological plasticity during the pubertal transition. Methods: In this study we analyzed DNA methylation (DNAm) in saliva at two time points across the pubertal transition within the same individuals. We targeted two domains of DNAm patterns that may inform processes of sexual differentiation 1) sex related sites, which demonstrated differences between males from females and 2) time related sites in which DNAm shifted significantly between timepoints. We further explored the correlated network structure sex and time related DNAm networks and linked these patterns to pubertal stage, assays of salivary testosterone, a reliable diagnostic of free, unbound hormone that is available to act on target tissues, and overlap with androgen response elements. Results: Sites that differed by biological sex were largely independent of sites that underwent change across puberty. Time-related DNAm sites, but not sex-related sites, formed correlated networks that were associated with pubertal stage. Both time and sex DNAm networks reflected salivary testosterone levels that were enriched for androgen response elements, with sex-related DNAm networks being informative of testosterone levels above and beyond biological sex later in the pubertal transition. Conclusions: These results inform our understanding of the distinction between sex- and time-related differences in DNAm during the critical period of puberty and highlight a novel linkage between correlated patterns of sex-related DNAm and levels of salivary testosterone.
Project description:Regulation of cell-cell junction formation and regulation of cell migration were enriched among EMT (Epithelial-Mesenchymal Transition)-associated alternatively splicing events. Our analysis suggested that most EMT-associated alternative splicing events are regulated by one or more members of the RBFOX, MBNL, CELF, hnRNP or ESRP classes of splicing factors. The EMT alternative splicing signature was confirmed in human breast cancer cell lines, which could be classified into basal and luminal subtypes based exclusively on their EMTassociated splicing pattern. Expression of EMT-associated alternative mRNA transcripts was also observed in primary breast cancer samples, indicating that EMT-dependent splicing changes occur commonly in human tumors. The functional significance of EMT-associated alternative splicing was tested by expression of the epithelial-specific splicing factor ESRP1 or depletion of RBFOX2 in mesenchymal cells, both of which elicited significant changes in cell morphology and motility towards an epithelial phenotype, suggesting that splicing regulation alone can drive critical aspects of EMT-associated phenotypic changes. The molecular description obtained here may aid in the development of new diagnostic and prognostic markers for analysis of breast cancer progression. Examination of transcriptomes of HMLE/Twist-ER before and after induction of EMT by tamoxifen
Project description:Alternative splicing achieves coordinated changes in post-transcriptional gene expression programs through the activities of diverse RNA binding proteins. Epithelial Splicing Regulatory Proteins 1 and 2 (ESRP1 and ESRP2) are cell type-specific regulators of transcripts that switch splicing during the Epithelial Mesenchymal Transition (EMT). To define a comprehensive program of alternative splicing that is regulated during the EMT, we identified an extensive ESRP-regulated splicing network of hundreds of alternative splicing events within numerous genes with roles in cell-cell adhesion, polarity, and migration. Loss of this global ESRP-regulated epithelial splicing program induces the phenotypic changes in cell morphology that are observed during the EMT. Components of this splicing signature provide novel molecular markers that can be used to characterize the EMT. Bioinformatics and experimental approaches revealed a high affinity ESRP binding motif and a predictive RNA map that governs their activity. This work establishes the ESRPs as coordinators of a complex alternative splicing network that adds an important post-transcriptional layer to the changes in gene expression that underlie epithelial-mesenchymal transitions during development and disease. Keywords: control / knockdown comparison and control / ectopic expression comparison