Microarray validation of an alternative splicing database
Ontology highlight
ABSTRACT: Alternative splicing generates functional diversity in higher organisms through alternative first and last exons, skipped and included exons, intron retentions and alternative donor and acceptor sites. In large-scale microarray studies in human and mouse, emphasis so far has been placed on exon-skip events, leaving the prevalence and importance of other splice types largely unexplored. Using a new human splice variant database and a genome-wide microarray to probes thousands of splice events of each type, we measured differential expression of splice types across 6 pairs of diverse cell lines and validated the database annotation process. Results suggest that splicing in human is more complex than simple exon skip events, which account for a minority of splicing differences. The relative frequency of differential expression of the splice types correlates with what is found by our annotation efforts. In conclusion, alternative splicing in human cells is considerably more complex than the canonical example of the exon-skip. The complementary approaches of genome-wide annotation of alternative splicing in human and design of genome-wide splicing microarrays to measure differential splicing in biological samples provide a powerful high-throughput tool to study the role of alternative splicing in human biology. Keywords: alternative splicing
Project description:We explored alternative splicing events upon hsa-miR-139-5p/HNRNPF axis regulation in our cell system using the Multivariate Analysis of Transcript Splicing (rMATS) computational tool (https://doi.org/10.1073/pnas.1419161111). Differential analysis of major splicing outcomes (skipped exon, alternative 5’/3’ splice, mutually exclusive exons and retained intron) revealed a total of 174 events significantly activated or repressed (FDR<0.05) upon HNRNPF regulation.
Project description:A better understanding of the mechanisms for plant in response to abiotic stresses is key for the improvement of plant to resistant to the stresses. Much has been known for the regulation of gene expression in response to salt stress at transcriptional level, however, little is known at posttranscriptional level for this response. Recently, we identified that SKIP is a component of spliceosome and is necessary for the regulation of alternative splicing and mRNA maturation of clock genes. In this study, we observed that skip-1 is hypersensitive to salt stress. SKIP is necessary for the alternative splicing and mRNA maturation of several salt tolerance genes, e.g. NHX1, CBL1, P5CS1, RCI2A, and PAT10. Genome-wide analysis reveals that SKIP mediates the alternative splicing of many genes under salt stress condition, most of the new alternative splicing events in skip-1 is intron retention, which leads to the premature termination codon in their mRNA. SKIP also controls the alternative splicing by modulating the recognition or cleavage of 5' and 3' splice donor and acceptor sites under salt stress condition. Therefore, this study addresses a fundamental question on how the mRNA splicing machinery contributes to salt response at a posttranscriptional level. Totally six samples, two treatments and two genotypes, and each have two replicats.
Project description:Alternative splicing diversifies mRNA transcripts in human cells. While the spliceosome pairs exons with a high degree of accuracy, the rates of rare aberrant and non-canonical pre-mRNA splicing have not been evaluated at the nucleotide level to determine the quantity and identity of these events across splice junctions. Using ultra-deep sequencing the frequency of aberrant and non-canonical splicing events for three splice junctions flanking exon 7 of SMN1 were determined at single nucleotide resolution. After correction for background noise introduced by PCR amplification and sequencing steps, pre-mRNA splicing was shown to maintain a low overall rate of aberrant and non-canonically spliced events. Several previously unannotated splicing events across 3 exon|intron junctions in SMN1 were identified. Mutations within SMN exon 7 were shown to affect splicing fidelity by modulating RNA secondary structures, by altering the binding site of regulatory proteins and by changing the 5’ splice site strength. Mutations also create a truncated SMN1 exon 7 through the introduction of a de novo non-canonical 5’ splice site. The results from the ultra-deep sequencing approach highlight the impressive fidelity of pre-mRNA splicing and demonstrate that the immediate sequence context around splice sites is the main driving force behind non-canonical splice site pairing.
Project description:The latest version of microarrays released by Affymetrix, the GeneChip Gene 1.0 ST Arrays (gene arrays), are designed in a similar fashion as exon arrays, which enables to identify differentially expressed exons, rather than only the expression level of whole transcripts. Here, we propose an extension, Gene Array Analyzer (GAA), to our previously published Exon Array Analyzer (EAA). GAA enables to analyse gene arrays on exon level and therefore supports to identify alternative splicing with gene arrays. To show the applicability of GAA, we used gene arrays to profile alternative splice events during the development of the heart. Further re-analysis of published gene arrays could show, that some of these splice events reoccur under pathological conditions. The web interface of GAA is user friendly, functional without set up and freely available at http://GAA.mpi-bn.mpg.de. Alternative splicing and gene expression analysis during development of the heart and cardiomyoyte differentiation.
Project description:The latest version of microarrays released by Affymetrix, the GeneChip Gene 1.0 ST Arrays (gene arrays), are designed in a similar fashion as exon arrays, which enables to identify differentially expressed exons, rather than only the expression level of whole transcripts. Here, we propose an extension, Gene Array Analyzer (GAA), to our previously published Exon Array Analyzer (EAA). GAA enables to analyse gene arrays on exon level and therefore supports to identify alternative splicing with gene arrays. To show the applicability of GAA, we used gene arrays to profile alternative splice events during the development of the heart. Further re-analysis of published gene arrays could show, that some of these splice events reoccur under pathological conditions. The web interface of GAA is user friendly, functional without set up and freely available at http://GAA.mpi-bn.mpg.de. Alternative splicing and gene expression analysis during development of the heart and cardiomyoyte differentiation.
Project description:Alternative pre-messenger RNA splicing impacts development, physiology, and disease, but its regulation in humans is not well understood, partially due to the limited scale to which the expression of specific splicing events has been measured. We generated the first genome-scale expression compendium of human alternative splicing events using custom whole-transcript microarrays monitoring expression of 24,426 mutually exclusive alternative splicing event pairs in 48 diverse human samples. Over 11,700 genes and 9,500 splicing events were differentially expressed, providing a rich resource for studying splicing regulation. An unbiased, systematic screen of 21,760 4-mer to 7-mer words for cis-regulatory motifs identified 143 RNA 'words' enriched near regulated cassette exons, including six clusters of motifs represented by UCUCU, UGCAUG, UGCU, UGUGU, UUUU, and AGGG, which map to trans-acting regulators PTB, Fox, Muscleblind, CELF/CUG-BP, TIA-1, and hnRNP F/H, respectively. Each cluster showed a distinct pattern of genomic location and tissue specificity. For example, UCUCU occurs 110 to 35 nucleotides preceding cassette exons upregulated in brain and striated muscle but depleted in other tissues. UCUCU and UGCAUG appear to have similar function but independent action, occurring 5' and 3', respectively, of 33% of the cassette exons upregulated in skeletal muscle but co-occurring for only 2%. Keywords: multiple tissue comparison PolyA+ purified RNA pooled from multiple donors of a single human tissue type (e.g. cerebellum) were amplified with random primers and hybridized on a two-color ink-jet oligonucletodie microarray (17 array set) against a common reference pool, comprising ~20 normal adult tissue pools, on custom microarray patterns containing probes to monitor every exon and exon-exon junction in transcript databases, patent databases, and predicted from mouse transcripts. Data were analyzed for gene expression (the average of multiple probes), exon and junction expression, and splice form proportionality (see paper).
Project description:Thousands of human genes contain introns ending in NAGNAG motifs (N any nucleotide), where both NAGs can function as 3' splice sites, yielding isoforms differing by inclusion/exclusion of just three bases. However, the functional importance of NAGNAG alternative splicing is highly controversial. Using very deep RNA-Seq data from sixteen human and eight mouse tissues, we found that approximately half of alternatively spliced NAGNAGs undergo tissue-specific regulation and that regulated events have been selectively retained: alternative splicing of strongly tissue-specific NAGNAGs was ten times as likely to be conserved between species as for non-tissue-specific events. Further, alternative splicing of human NAGNAGs was associated with an order of magnitude increase in the frequency of exon length changes at orthologous mouse/rat exon boundaries, suggesting that NAGNAGs accelerate exon evolution. Together, our analyses show that NAGNAG alternative splicing constitutes a major generator of tissue-specific proteome diversity and accelerates evolution of proteins at exon-exon boundaries. mRNA-Seq of sixteen human and eight mouse tissues. Supplementary files: human.nagnag.junctions.gff and mouse.nagnag.junctions.gff are the annotation files (in GFF3 format) corresponding to the 'bwtout' mapped reads files linked to the Sample records. Raw data files provided for Samples GSM742937-GSM742952 only.
Project description:Abstract: Alternative splicing (AS) plays a major role in the generation of proteomic diversity and in gene regulation. However, the role of the basal splicing machinery in regulating AS remains poorly understood. Here we show that the core snRNP protein SmB/B’ self-regulates its expression by promoting the inclusion of a highly-conserved alternative exon in its own pre-mRNA that targets the spliced transcript for nonsense-mediated mRNA decay (NMD). Depletion of SmB/B’ in human cells results in reduced levels of snRNPs and in a striking reduction in the inclusion levels of hundreds of alternative exons, with comparatively few effects on constitutive exon splicing levels. The affected alternative exons are enriched in genes encoding RNA processing and other RNA binding factors, and a subset of these exons also regulate gene expression by activating NMD. Our results thus demonstrate a role for the core spliceosomal machinery in controlling an exon network that appears to modulate the levels of many RNA processing factors. HeLa cells were transfected with a control non-targeting siRNA pool (siNT), or with siRNA pools designed to knockdown SmB/B' or SRSF1 (also known as SF2/ASF/SFRS1). Sequence reads were aligned to exon-exon junction sequences in a database of EST/cDNA-mined cassette-type alternative splicing events. Processed data files (.bed and .txt) provided as supplementary files on the Series record. Processed data file build information: hg18.
Project description:A better understanding of the mechanisms for plant in response to abiotic stresses is key for the improvement of plant to resistant to the stresses. Much has been known for the regulation of gene expression in response to salt stress at transcriptional level, however, little is known at posttranscriptional level for this response. Recently, we identified that SKIP is a component of spliceosome and is necessary for the regulation of alternative splicing and mRNA maturation of clock genes. In this study, we observed that skip-1 is hypersensitive to salt stress. SKIP is necessary for the alternative splicing and mRNA maturation of several salt tolerance genes, e.g. NHX1, CBL1, P5CS1, RCI2A, and PAT10. Genome-wide analysis reveals that SKIP mediates the alternative splicing of many genes under salt stress condition, most of the new alternative splicing events in skip-1 is intron retention, which leads to the premature termination codon in their mRNA. SKIP also controls the alternative splicing by modulating the recognition or cleavage of 5' and 3' splice donor and acceptor sites under salt stress condition. Therefore, this study addresses a fundamental question on how the mRNA splicing machinery contributes to salt response at a posttranscriptional level.
Project description:Alternative splicing of mRNA diversifies the function of human proteins, with tissue- and cell-specific protein isoforms being the most difficult to validate. While transcriptomic experiments enable the detection of many alternatively spliced transcripts, it is not known if these transcripts have protein-coding potential. We recently published the PG Nexus pipeline, which facilitates high confidence validation of exons and exon-exon junctions of spliced transcripts by integrating transcriptomics and proteomics data. Using the PG Nexus, we analyzed undifferentiated human mesenchymal stem cells and compared the number of protein isoforms validated using different protein sequence database, including public online databases and RNA-seq derived databases. With significant overlaps with other databases, we identified 8,011 exons and 3,824 splice junctions with the Ensembl database. Both exonic and junction peptides were important for protein isoform validation. The Ensembl database consistently outperformed the other data sources, but predicted open reading frames from RNA-seq derived transcripts were comparable, with only 6 less splice junctions validated. Using proteotypic and isoform-specific peptides, we validated 462 protein isoforms. This number increases to 1,083 if multiple proteotypic peptides per protein are included. Multiplexing proteotypic peptides in SRM assays or similar experiments will increase the confidence and coverage of protein isoform validation experiments.