The majority of transcripts in the squid nervous system are extensively recoded by A-to-I RNA editing
- Tel Aviv University, Israel
- University of Connecticut Health Center, United States
- Bar-Ilan University, Israel
- University of Puerto Rico Medical Sciences Campus, Puerto Rico
Abstract
RNA editing by adenosine deamination alters genetic information from the genomic blueprint. When it recodes mRNAs, it gives organisms the option to express diverse, functionally distinct, protein isoforms. All eumetazoans, from cnidarians to humans, express RNA editing enzymes. However, transcriptome-wide screens have only uncovered about 25 transcripts harboring conserved recoding RNA editing sites in mammals and several hundred recoding sites in Drosophila. These studies on few established models have led to the general assumption that recoding by RNA editing is extremely rare. Here we employ a novel bioinformatic approach with extensive validation to show that the squid Doryteuthis pealeii recodes proteins by RNA editing to an unprecedented extent. We identify 57,108 recoding sites in the nervous system, affecting the majority of the proteins studied. Recoding is tissue-dependent, and enriched in genes with neuronal and cytoskeletal functions, suggesting it plays an important role in brain physiology.
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Author details
Ethics
Animal experimentation: Animal experimentation was conducted in accordance to the guidelines of the Marine Biological Laboratory in Woods Hole, Massachusetts.
Reviewing Editor
- Roderic Guigó, Center for Genomic Regulation, Spain
Publication history
- Received: October 15, 2014
- Accepted: January 8, 2015
- Accepted Manuscript published: January 8, 2015 (version 1)
- Version of Record published: February 4, 2015 (version 2)
Copyright
© 2015, Alon et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The majority of transcripts in the squid nervous system are extensively recoded by A-to-I RNA editing
eLife 4:e05198.
https://doi.org/10.7554/eLife.05198
Further reading
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- Epidemiology and Global Health
- Genetics and Genomics
Background:
Many genes associated with asthma explain only a fraction of its heritability. Most genome-wide association studies (GWASs) used a broad definition of 'doctor-diagnosed asthma', thereby diluting genetic signals by not considering asthma heterogeneity. The objective of our study was to identify genetic associates of childhood wheezing phenotypes.
Methods:
We conducted a novel multivariate GWAS meta-analysis of wheezing phenotypes jointly derived using unbiased analysis of data collected from birth to 18 years in 9,568 individuals from five UK birth-cohorts.
Results:
44 independent SNPs were associated with early-onset persistent, 25 with preschool remitting, 33 with mid-childhood remitting and 32 with late-onset wheeze. We identified a novel locus on chr9q21.13 (close to annexin 1 (ANXA1), p<6.7×10-9), associated exclusively with early-onset persistent wheeze. We identified rs75260654 as the most likely causative single nucleotide polymorphism (SNP) using Promoter Capture Hi-C loops, and then showed that the risk allele (T) confers a reduction in ANXA1 expression. Finally, in a murine model of house dust mite (HDM)-induced allergic airway disease, we demonstrated that anxa1 protein expression increased and anxa1 mRNA was significantly induced in lung tissue following HDM exposure. Using anxa1-/- deficient mice, we showed that loss of anxa1 results in heightened airway hyperreactivity and Th2 inflammation upon allergen challenge.
Conclusions:
Targeting this pathway in persistent disease may represent an exciting therapeutic prospect.
Funding:
UK Medical Research Council Programme Grant MR/S025340/1 and the Wellcome Trust Strategic Award (108,818/15/Z) provided most of the funding for this study.
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- Evolutionary Biology
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Functionally indispensable genes are likely to be retained and otherwise to be lost during evolution. This evolutionary fate of a gene can also be affected by factors independent of gene dispensability, including the mutability of genomic positions, but such features have not been examined well. To uncover the genomic features associated with gene loss, we investigated the characteristics of genomic regions where genes have been independently lost in multiple lineages. With a comprehensive scan of gene phylogenies of vertebrates with a careful inspection of evolutionary gene losses, we identified 813 human genes whose orthologs were lost in multiple mammalian lineages: designated ‘elusive genes.’ These elusive genes were located in genomic regions with rapid nucleotide substitution, high GC content, and high gene density. A comparison of the orthologous regions of such elusive genes across vertebrates revealed that these features had been established before the radiation of the extant vertebrates approximately 500 million years ago. The association of human elusive genes with transcriptomic and epigenomic characteristics illuminated that the genomic regions containing such genes were subject to repressive transcriptional regulation. Thus, the heterogeneous genomic features driving gene fates toward loss have been in place and may sometimes have relaxed the functional indispensability of such genes. This study sheds light on the complex interplay between gene function and local genomic properties in shaping gene evolution that has persisted since the vertebrate ancestor.
