Genome-wide analysis of the transcriptional and alternative splicing landscape in intestinal organoids undergoing nutrient starvation or ER stress
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ABSTRACT: Our study represents the first detailed analysis of the transcriptional and alternative splicing landscape of intestinal organoids undergoing stress, with biologic replicates, generated by RNA-seq technology. We report significant changes in the expression of genes involved in inflammation, proliferation and transcription, among others. Splicing events commonly regulated by both stresses affected genes regulating splicing and were associated with nonsense-mediated decay (NMD), suggesting that splicing is modulated by an auto-regulatory feedback loop during stress. Murine intestinal organoids were stimulated in triplicate with conditions for either ER stress or nutrient starvation and RNA-seq was conducted to analyze global changes in both gene expression at the transcriptional level and alternative splicing
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:Autism spectrum disorder (ASD) is a common, highly heritable neurodevelopmental condition characterized by marked genetic heterogeneity. Thus, a fundamental question is whether autism represents an aetiologically heterogeneous disorder in which the myriad genetic or environmental risk factors perturb common underlying molecular pathways in the brain. Here, we demonstrate consistent differences in transcriptome organization between autistic and normal brain by gene co-expression network analysis. Remarkably, regional patterns of gene expression that typically distinguish frontal and temporal cortex are significantly attenuated in the ASD brain, suggesting abnormalities in cortical patterning. We further identify discrete modules of co-expressed genes associated with autism: a neuronal module enriched for known autism susceptibility genes, including the neuronal specific splicing factor A2BP1 (also known as FOX1), and a module enriched for immune genes and glial markers. Using high-throughput RNA sequencing we demonstrate dysregulated splicing of A2BP1-dependent alternative exons in the ASD brain. Moreover, using a published autism genome-wide association study (GWAS) data set, we show that the neuronal module is enriched for genetically associated variants, providing independent support for the causal involvement of these genes in autism. In contrast, the immune-glial module showed no enrichment for autism GWAS signals, indicating a non-genetic aetiology for this process. Collectively, our results provide strong evidence for convergent molecular abnormalities in ASD, and implicate transcriptional and splicing dysregulation as underlying mechanisms of neuronal dysfunction in this disorder. To identify potential A2BP1-dependent differential splicing events in ASD brain, we performed high-throughput RNA sequencing (RNA-Seq) on three autism samples with significant downregulation of A2BP1 (average fold change by quantitative RT-PCR = 5.9) and three control samples with average A2BP1 levels. The list of potential A2BP1-depending differential splicing events in ASD is given in the Supplementary file linked at the foot of this record.
Project description:Alternative splicing (AS) generates extensive transcriptomic and proteomic complexity. However, the functions of species- and lineage-specific splice variants are largely unknown. Here, we show that mammalian-specific skipping of exon 9 of PTBP1 alters its splicing regulatory activities and affects the inclusion levels of numerous exons. During neurogenesis, skipping of exon 9 reduces PTBP1 repressive activity so as to facilitate activation of a brain-specific AS program. Engineered skipping of the orthologous exon in chicken cells induces a large number of mammalian-like AS changes in PTBP1 target exons. These results thus reveal that a single exon skipping event in an RNA binding regulator directs numerous AS changes between species. The results further suggest that these changes contributed to evolutionary differences in the formation of vertebrate nervous systems. This study contains two sets of samples: (Set 1) mRNA profiling of human 293 cells subjected to four different conditions in two biological replicates: non-targetting control siRNA, PTBP1 and PTBP2 siRNA, PTBP1 and PTBP2 siRNA with overexpression of full-length human PTBP1, PTBP1 and PTBP2 siRNA with overexpression of exon-excluded human PTBP1. (Set 2) mRNA profiling of chicken DT40 cells with 3 genotypes in two bioligcal replicates: wildtype cells, cells with PTBP1 exon 8 (orthologous to human PTBP1 exon 9) deleted in one allele, and cells with PTBP1 exon 8 deleted in both alleles.
Project description:Pre-mRNA splicing relies on the still poorly understood dynamic interplay between more than 150 protein components of the Spliceosome, and the steps at which splicing can be regulated remain largely unknown. Here we systematically analyze the effect of knocking down the components of the splicing machinery on alternative splicing events relevant for cell proliferation and apoptosis and use this information to reconstruct a network of functional interactions. The network accurately captures well-established physical and functional associations and identifies new, revealing remarkable regulatory potential of core spliceosomal components, related to the order and duration of their recruitment during Spliceosome assembly. In contrast with standard models of regulation at early events of splice site recognition, factors involved in catalytic activation of the Spliceosome display regulatory properties. The network also sheds light on the antagonism between hnRNP C and U2AF and on targets of anti-tumor drugs, and can be widely used to identify mechanisms of splicing regulation. RNA from 3 biological replicates of 72 hours knockdowns of human IK or SMU1 and a control set were used. Changes between the control and knockdowns were measured based on using a splice-junction array (Affymetrix HJAY).
Project description:The apolipoprotein A-I (apoA-I) mimetic peptide 4F displays prominent anti-inflammatory properties, including the ability to reduce vascular macrophage content. Macrophages are a heterogenous group of cells, represented by two principal phenotypes, the classically activated M1 macrophage and an alternatively activated M2 phenotype. We recently reported that 4F favors the differentiation of human monocytes to an anti-inflammatory phenotype similar to that displayed by M2 macrophages. In the current study, microarray analysis of gene expression in monocyte-derived macrophages (MDMs) was carried out to identify inflammatory pathways modulated by 4F treatment. ApoA-I treatment of MDMs served as a control. Transcriptional profiling revealed that 4F and apoA-I modulated expression of 113 and 135 genes that regulate inflammatory responses, respectively. Cluster heat maps revealed that 4F and apoA-I induced similar changes in expression for 69 common genes. Modulation of other gene products, including STAT1 and PPARG, were unique for 4F treatment. Besides modulating inflammatory responses, 4F was found to alter gene expression in cell-to-cell signaling, cell growth/proliferation, lipid metabolism and cardiovascular system development. These data suggest that the protective effects of 4F in a number of disease states may be due to underlying changes in monocyte/macrophage gene expression. 16 samples analyzed (four 4F+LPS, four 4F, four Controls+LPS, four Controls).
Project description:Xylella fastidiosa is the etiologic agent of a wide range of plant diseases including citrus variegated chlorosis (CVC), a major threat to the Brazilian citrus industry. Genome sequences of several strains of this phytopathogen are accessible, enabling large-scale functional studies. Transcript levels in different iron availabilities were assessed with DNA microarrays representing 2608 (91.6%) coding sequences (CDS) of X. fastidiosa CVC strain 9a5c. When treated with the iron chelator 2,2-dipyridyl, 193 CDS were considered as up-regulated and 216 as down-regulated. In the presence of 100uM of ferric pyrophosphate, 218 and 256 CDS were considered as up- and down-regulated, respectively. Differential expression for a subset of 44 CDS was further evaluated by reverse transcription - quantitative PCR that showed a Pearson correlation of 0.77 with array results. The CDS differentially expressed upon the iron concentration shift participate in diverse cellular functions. Many CDS involved with regulatory functions, pathogenicity and cell structure, were modulated in both conditions tested suggesting that major changes in cell architecture and metabolism occur when X. fastidiosa cells are exposed to extreme variations in iron concentration. Interestingly, the modulated CDS include those related to colicin V-like bacteriocin synthesis and secretion and to pili/fimbriae functions. We also investigated the contribution of the ferric uptake regulator Fur to the iron regulon of X. fastidiosa. The promoter regions of strain 9a5c genome were screened for putative Fur boxes and candidates were analyzed by electrophoretic mobility shift assays. Taken together, our data support the hypothesis that Fur is not solely responsible for the modulation of the iron regulon of X. fastidiosa and present novel evidence for iron regulation of pathogenicity determinants. Keywords: stress response; response to iron-depleted condition Direct comparison between low iron content (200uM 2,2-dipyridyl) and control condition. Hybridizations are dye-swaped. There are 2 biological replicates (independent harvest) and 2 technical replicates of each array (L - left and R - right).
Project description:Xylella fastidiosa is the etiologic agent of a wide range of plant diseases including citrus variegated chlorosis (CVC), a major threat to the Brazilian citrus industry. Genome sequences of several strains of this phytopathogen are accessible, enabling large-scale functional studies. Transcript levels in different iron availabilities were assessed with DNA microarrays representing 2608 (91.6%) coding sequences (CDS) of X. fastidiosa CVC strain 9a5c. When treated with the iron chelator 2,2-dipyridyl, 193 CDS were considered as up-regulated and 216 as down-regulated. In the presence of 100uM of ferric pyrophosphate, 218 and 256 CDS were considered as up- and down-regulated, respectively. Differential expression for a subset of 44 CDS was further evaluated by reverse transcription - quantitative PCR that showed a Pearson correlation of 0.77 with array results. The CDS differentially expressed upon the iron concentration shift participate in diverse cellular functions. Many CDS involved with regulatory functions, pathogenicity and cell structure, were modulated in both conditions tested suggesting that major changes in cell architecture and metabolism occur when X. fastidiosa cells are exposed to extreme variations in iron concentration. Interestingly, the modulated CDS include those related to colicin V-like bacteriocin synthesis and secretion and to pili/fimbriae functions. We also investigated the contribution of the ferric uptake regulator Fur to the iron regulon of X. fastidiosa. The promoter regions of strain 9a5c genome were screened for putative Fur boxes and candidates were analyzed by electrophoretic mobility shift assays. Taken together, our data support the hypothesis that Fur is not solely responsible for the modulation of the iron regulon of X. fastidiosa and present novel evidence for iron regulation of pathogenicity determinants. Direct comparison between high iron content (100uM ferric pyrophosphate) and control condition. Hybridizations are dye-swaped. There are 2 biological replicates (independent harvest) and 2 technical replicates of each array (L - left and R - right).
Project description:Alternative mRNA splicing is a major mechanism for gene regulation and transcriptome diversity. Despite the extent of the phenomenon, the regulation and specificity of the splicing machinery are only partially understood. Adenosine-to-inosine (A-to-I) RNA editing of pre-mRNA by ADAR enzymes has been linked to splicing regulation in several cases. Here we used bioinformatics approaches, RNA-seq and exon-specific microarray of ADAR knockdown cells to globally examine how ADAR and its A-to-I RNA editing activity influence alternative mRNA splicing. Although A-to-I RNA editing only rarely targets canonical splicing acceptor, donor, and branch sites, it was found to affect splicing regulatory elements (SREs) within exons. Cassette exons were found to be significantly enriched with A-to-I RNA editing sites compared with constitutive exons. RNA-seq and exon-specific microarray revealed that ADAR knockdown in hepatocarcinoma and myelogenous leukemia cell lines leads to global changes in gene expression, with hundreds of genes changing their splicing patterns in both cell lines. This global change in splicing pattern cannot be explained by putative editing sites alone. Genes showing significant changes in their splicing pattern are frequently involved in RNA processing and splicing activity. Analysis of recently published RNA-seq data from glioblastoma cell lines showed similar results. Our global analysis reveals that ADAR plays a major role in splicing regulation. Although direct editing of the splicing motifs does occur, we suggest it is not likely to be the primary mechanism for ADAR-mediated regulation of alternative splicing. Rather, this regulation is achieved by modulating trans-acting factors involved in the splicing machinery. HepG2 and K562 cell lines were stably transfected with plasmids containing siRNA designed to specifically knock down ADAR expression (ADAR KD). This in order to examine how ADAR affects alternative splicing globally.
Project description:Although majority of the genes linked to pediatric cataract exhibit lens fiber cell-enriched expression, our understanding of gene regulation in these cells is limited to function of just eight transcription factors and largely in the context of crystallins. Here, we identify small Maf transcription factors MafG and MafK as regulators of several non-crystallin human cataract genes in fiber cells and establish their significance to cataract. We applied a bioinformatics tool for cataract gene discovery iSyTE to identify MafG and its co-regulators in the lens, and generated various null-allelic combinations of MafG:MafK mouse mutants for phenotypic and molecular analysis. By age 4-months, MafG-/-:MafK+/- mutants exhibit lens defects that progressively develop into cataract. High-resolution phenotypic characterization of MafG-/-:MafK+/- lens reveals severe defects in fiber cells, while microarrays-based expression profiling identifies 97 differentially regulated genes (DRGs). Integrative analysis of MafG-/-:MafK+/- lens-DRGs with 1) binding-motifs and genomic targets of small Mafs and their regulatory partners, 2) iSyTE lens-expression data, and 3) interactions between DRGs in the String database, unravels a detailed small Maf regulatory network in the lens, several nodes of which are linked to human cataract. This analysis prioritizes 36 highly promising candidates from the original 97 DRGs. Significantly, 8/36 (22%) DRGs are associated with cataracts in human (GSTO1, MGST1, SC4MOL, UCHL1) or mouse (Aldh3a1, Crygf, Hspb1, Pcbd1), suggesting a multifactorial etiology that includes elevation of oxidative stress. These data identify MafG and MafK as new cataract-associated candidates and define their function in regulating largely non-crystallin genes linked to mouse and human cataract. Microarray comparision of lenses from mixed background (129Sv/J, C57BL/6J, and ICR) control (MafG+/-:MafK+/-; no-cataract) and compound (MafG-/-:MafK+/-; cataract) mouse mutants
Project description:The aim of this study was to identify target genes of the SR protein kinase SPK-1. spk-1(RNAi) leads to defects in cell polarity. We were therefore primarily interested in genes who exhibit changes in splicing regulation upon depletion of SPK-1 and could underlie the polarity phenotype of spk-1(RNAi). Transcriptome profiling of control and spk-1(RNAi) worms by RNAseq