Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Nanopore sequencing reveals endogenous NMD-targeted isoforms in human cells

ABSTRACT: Nonsense-mediated mRNA decay (NMD) is a eukaryotic, translation-dependent degradation pathway that targets mRNAs with premature termination codons and also regulates the expression of some mRNAs that encode full-length proteins. Although many genes express NMD-sensitive transcripts, identifying them based on short-read sequencing data remains a challenge. To identify and analyze endogenous targets of NMD, we applied cDNA Nanopore sequencing and short-read sequencing to human cells with varying expression levels of NMD factors. Our approach detects full-length NMD substrates that are highly unstable and increase in levels or even only appear when NMD is inhibited. Among the many new NMD-targeted isoforms that our analysis identified, most derive from alternative exon usage. The isoform-aware analysis revealed many genes with significant changes in splicing but no significant changes in overall expression levels upon NMD knockdown. NMD-sensitive mRNAs have more exons in the 3΄UTR and for mRNAs with a termination codon in the last exon. The length of the 3΄UTR per se does not correlate with NMD sensitivity. Analysis of splicing signals reveals isoforms where NMD has been co-opted in the regulation of gene expression, but a main function is most likely to rid the transcriptome of isoforms resulting from spurious splicing events. Long-read sequencing enabled the identification of many novel NMD-sensitive mRNAs and revealed both known and unexpected features concerning their biogenesis and their biological role. Our data provide a highly valuable resource of human NMD transcript targets for future genomic and transcriptomic applications.

INSTRUMENT(S): GridION

SUBMITTER: Foivos Gypas

PROVIDER: E-MTAB-10452 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

ACCESS DATA

Similar Datasets

Project description:Genome-wide association studies (GWASs) have revealed thousands of associations in many complex traits and diseases. Previous studies suggest that a subset of associations are due to alterations in splicing; however, interpreting the effects of splicing on protein isoforms is hindered by limitations in defining full-length transcript isoforms using short-read RNA-seq data. Long-read RNA-seq represents a powerful approach to define and quantify transcript isoforms. In this study, we developed a novel approach that integrates information from GWAS, splicing QTL (sQTL), and PacBio long-read RNA-seq in a disease relevant model to infer the effects of sQTL on the ultimate protein isoform products they encode. Such information enables identification of genes potentially responsible for GWAS associations. As a proof-of-concept, we generated deep coverage (N=~22 million full-length reads) PacBio long-read RNAseq data on human fetal osteoblasts (hFOBs), a cell-line of relevance to the regulation of bone mineral density (BMD). We identified 68,326 protein-coding isoforms, including 17,375 (25%) which were novel. Next, we used Bayesian colocalization to identify 1,863 sQTLs from the Genotype-Tissue Expression (GTEx) project in 732 protein-coding genes which colocalized with BMD associations (H4PP > 0.75). A total of 836 junctions with colocalizing sQTLs in 459 (of the 732) genes were expressed in hFOB long-read RNA-seq data. With these data, we formulated hypotheses regarding the potential mechanism of action of each sQTL. For example, we identified 7 junctions with colocalizing sQTLs (maximum H4PP = 0.98-0.99) in TPM2 for splice junctions between two nearly mutually exclusive exons, and two different transcript termination sites, making it impossible to interpret without long-read RNA-seq data. siRNA mediated knockdown in hFOBs showed two TPM2 isoforms with opposing effects on mineralization. Our results suggest that splicing is a major mechanism underlying GWAS associations and long-read proteogenomics data is critical to precisely define the protein isoforms that are produced from splicing alterations.

Dataset Information

Nanopore sequencing reveals endogenous NMD-targeted isoforms in human cells

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure