Unknown,Transcriptomics,Genomics,Proteomics

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Single-molecule, full-length transcript isoform sequencing reveals disease-associated RNA isoforms

ABSTRACT: Alternative splicing generates differing RNA isoforms that govern phenotypic complexity of eukaryotes. Its malfunction underlies many diseases, including cancer and cardiovascular diseases. Comparative analysis of RNA isoforms at the genome-wide scale has been difficult. Here, we established an experimental and computational pipeline that accurately quantifies transcript isoforms in their entire length from cDNA sequences with a full-length isoform detection accuracy of 97.6%. We generated a searchable, quantitative human transcriptome annotation with 31,025 known and 5,740 novel transcript isoforms (http://steinmetzlab.embl.de/iBrowser/). By analyzing the isoforms in the presence of RNA Binding Motif Protein 20 (RBM20) mutations associated with aggressive dilated cardiomyopathy (DCM), we identified 121 differentially expressed transcript isoforms in 107 cardiac genes. By establishing an isoform-differential expression test, our approach revealed that 11 of these genes displayed no detectable change in overall RNA expression. However, significant differences in the expression of specific isoforms in these genes was observed. These isoform specific effects demonstrate the need of analyzing RNA isoform expression levels rather than total gene expression levels.

INSTRUMENT(S): MinION

ORGANISM(S): Homo sapiens

SUBMITTER: Chenchen Zhu

PROVIDER: E-MTAB-7334 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Pancreatic ductal adenocarcinoma is one of the most lethal cancers, with a 5 year-survival rate below 5%. Lack of curative treatment and failure of targeted therapies urge the need to identify novel efficient therapeutic strategy. Achievement of this goal will be obtained through the identification of diagnosis and prognosis biomarkers, identification of novel therapeutic targets and the knowledge of resistance mechanisms induced by these targeted therapies. PI3K/Akt/mTOR signalling, one of the most altered in cancers, is overactivated in pancreatic cancer and correlated with poor prognosis. In the Vertebrates, the family of class I phosphoinoitide-3-kinase (PI3K) includes four isoforms: p110α, p110β, p110δ and p110γ. Although they all perform the same biochemical reaction (phosphorylation of PIP2 in PIP3, a membrane lipid messenger), each isoform were demonstrated to have specific physiological roles. Global PI3K inhibitors are currently being tested in phase I/II clinical trials in advanced solid cancers, but show at maximal doses tolerated a limited therapeutic benefit. Isoform-selective PI3K inhibitors are currently the most promising agents because, at low doses, they are more efficient to inhibit one PI3K isoform, and thus, less toxic than pan-PI3K inhibitors. The objectives of this thesis are to determine isoform-specific PI3K roles and the therapeutic interest to target one or more isoforms in pancreatitis and PDAC, by the identification of isoform-specific pathways and the study of adaptive responses induced by targeting of one or all isoforms of PI3K. In a first part, my work has highlighted, validated and completed results obtained in the team, to demonstrate the significance of PI3K/Akt signalling in two physiological processes: chronic pancreatitis and initiation of pancreatic carcinogenesis. Precisely, the overactivation of PI3K/Akt pathway measured on human and murine chronic pancreatitis samples is correlated with a specific p110α activation gene expression signature. Moreover, genetic and pharmacologic inactivation of p110α during pancreatic chronic inflammation or cancerogenesis (by oncogenic Kras) prevents the formation of acino-ductal metaplasia, structures at the origin of pancreatic carcinogenesis initiation. Development of in vitro acino-ductal transdifferentiation protocol allowed me to demonstrate that only p110α is necessary at this initial step of pancreatic carcinogenesis by the regulation of Rho small GTPases, further regulating actin remodelling. In the second part, by a phosphoproteomic-based approach, I quantified PI3K downstream phosphorylation-regulated targets in a pancreatic cancer cell line treated or not by a pan- or selective PI3K inhibitor at different times. I demonstrated for the first time existence of targets, signalling pathways and adaptive responses regulated by each PI3K isoform. To conclude, all these results demonstrate the rational of combinatorial use of isoform-specific PI3K inhibitors in patients with pancreatic cancer for better clinical response

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Single-molecule, full-length transcript isoform sequencing reveals disease-associated RNA isoforms

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