Evidence for transcriptome-wide RNA editing among Sus scrofa PRE-1 SINE elements.

BACKGROUND: RNA editing by ADAR (adenosine deaminase acting on RNA) proteins is a form of transcriptional regulation that is widespread among humans and other primates. Based on high-throughput scans used to identify putative RNA editing sites, ADAR appears to catalyze a substantial number of adenosine to inosine transitions within repetitive regions of the primate transcriptome, thereby dramatically enhancing genetic variation beyond what is encoded in the genome. RESULTS: Here, we demonstrate the editing potential of the pig transcriptome by utilizing DNA and RNA sequence data from the same pig. We identified a total of 8550 mismatches between DNA and RNA sequences across three tissues, with 75% of these exhibiting an A-to-G (DNA to RNA) discrepancy, indicative of a canonical ADAR-catalyzed RNA editing event. When we consider only mismatches within repetitive regions of the genome, the A-to-G percentage increases to 94%, with the majority of these located within the swine specific SINE retrotransposon PRE-1. We also observe evidence of A-to-G editing within coding regions that were previously verified in primates. CONCLUSIONS: Thus, our high-throughput evidence suggests that pervasive RNA editing by ADAR can exist outside of the primate lineage to dramatically enhance genetic variation in pigs.

Endothelial Notch1 signaling in white adipose tissue promotes cancer cachexia.

Cachexia is a major cause of morbidity and mortality in individuals with cancer and is characterized by weight loss due to adipose and muscle tissue wasting. Hallmarks of white adipose tissue (WAT) remodeling, which often precedes weight loss, are impaired lipid storage, inflammation and eventually fibrosis. Tissue wasting occurs in response to tumor-secreted factors. Considering that the continuous endothelium in WAT is the first line of contact with circulating factors, we postulated whether the endothelium itself may orchestrate tissue remodeling. Here, we show using human and mouse cancer models that during precachexia, tumors overactivate Notch1 signaling in distant WAT endothelium. Sustained endothelial Notch1 signaling induces a WAT wasting phenotype in male mice through excessive retinoic acid production. Pharmacological blockade of retinoic acid signaling was sufficient to inhibit WAT wasting in a mouse cancer cachexia model. This demonstrates that cancer manipulates the endothelium at distant sites to mediate WAT wasting by altering angiocrine signals.