Project description:Alternative splicing (AS) is a key mechanism of gene expression diversity, and dysregulation of AS is implicated in many human diseases. Identifying variants that disrupt splicing and characterizing their impact on isoform abundance across different cell types remains challenging. Here, we perform massively parallel reporter assays (MPRAs) to measure splicing phenotypes of over 87,000 sequence variants in five cell lines of different tissue origin. The MPRA encompasses 2,096 short human exons from 1,733 genes and tens of thousands of single and double variants. Our measurements identify variants that strongly modulate splicing but are currently classified as variants of unknown significance or have not yet been described. We systematically identify putative RNA-binding protein (RBP) binding motifs and quantify effect sizes associated with the disruption of these motifs, suggesting possible mechanisms for variant impact. A comparison across cell lines enables the identification of variants that differentially modulate splicing.
Project description:How species with similar repertoires of protein coding genes differ so dramatically at the phenotypic level is poorly understood. From comparing the transcriptomes of multiple organs from vertebrate species spanning ~350 million years of evolution, we observe significant differences in alternative splicing complexity between the main vertebrate lineages, with the highest complexity in the primate lineage. Moreover, within as little as six million years, the splicing profiles of physiologically-equivalent organs have diverged to the extent that they are more strongly related to the identity of a species than they are to organ type. Most vertebrate species-specific splicing patterns are governed by the highly variable use of a largely conserved cis-regulatory code. However, a smaller number of pronounced species-dependent splicing changes are predicted to remodel interactions involving factors acting at multiple steps in gene regulation. These events are expected to further contribute to the dramatic diversification of alternative splicing as well as to other gene regulatory changes that contribute to phenotypic differences among vertebrate species.
Project description:Alternative splicing is primarily controlled by the activity of splicing factors and by the elongation of the RNA polymerase II (RNAPII). Recent experiments have suggested a new complex network of splicing regulation involving chromatin, transcription and multiple protein factors. In particular, the CCCTC-binding factor (CTCF), the Argonaute protein AGO1, and members of heterochromatin protein 1 (HP1) family have been implicated in the regulation of splicing associated to chromatin and the elongation of RNAPII. These results raise the question of whether these proteins may associate at the chromatin level to modulate alternative splicing. RNA extraction from MCF-7 and MCF-10A cell lines. Splicing changes between these two cell lines were measured using a splice junction array (Affymetrix HJAY).
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:Alternative splicing (AS) plays key roles in plant development and responses to environmental changes. However, the mechanisms underlying AS divergence (differential expression of transcript isoforms resulting from alternative splicing) in plant accessions and its contributions to responses to environmental stimuli remain unclear. In this study, we investigated genome-wide variation of AS in Arabidopsis thaliana accessions Col-0, Bur-0, C24, Kro-0, and Ler-1, as well as their F1 hybrids, and characterized the regulatory mechanisms for AS divergence by RNA sequencing (RNA-seq). We found that most of the divergent AS events in Arabidopsis accessions were cis-regulated by sequence variation, including those in core splice site and splicing motifs. Many genes that differed in AS between Col-0 and Bur-0 were involved in stimulus responses. Further genome-wide association analyses of 22 environmental variables showed that SNPs influencing known splice site strength were also associated with environmental stress responses. These results demonstrate that cis-variation in genomic sequences among Arabidopsis accessions was the dominant contributor to AS divergence, and it may contribute to differences in environmental responses among Arabidopsis accessions.
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
Project description:Alternative splicing is primarily controlled by the activity of splicing factors and by the elongation of the RNA polymerase II (RNAPII). Recent experiments have suggested a new complex network of splicing regulation involving chromatin, transcription and multiple protein factors. In particular, the CCCTC-binding factor (CTCF), the Argonaute protein AGO1, and members of heterochromatin protein 1 (HP1) family have been implicated in the regulation of splicing associated to chromatin and the elongation of RNAPII. These results raise the question of whether these proteins may associate at the chromatin level to modulate alternative splicing.
Project description:Regulation and functionality of species-specific alternative splicing has remained enigmatic for many years. Calcium/calmodulin-dependent protein kinase IIβ (CaMKIIβ) is expressed in several splice variants and plays a key role in learning and memory. Here, we identify and characterize several primate-specific CAMK2B splice isoforms, which show altered kinetic properties and changes in substrate specificity. Furthermore, we demonstrate that primate-specific Camk2β alternative splicing is achieved through branch point weakening during evolution. We show that reducing branch point and splice site strength during evolution globally renders constitutive exons alternative, thus providing a paradigm for cis-directed species-specific alternative splicing regulation. Using CRISPR/Cas9 we introduced the weaker human branch point into the mouse genome, resulting in human-like CAMK2B splicing in the brain of mutant mice. We observe a strong impairment of long-term potentiation in CA3-CA1 synapses of mutant mice, thus connecting branch point-controlled, species-specific alternative splicing with a fundamental function in learning and memory.