Abstract 15441: Differential Sequestration of mRNA in Ribonucleoprotein Granules in the Heart
Posttranscriptional regulation of gene expression is fundamental to organogenesis and pathogenesis. One of the modes of regulation that has been observed, particularly during stress conditions, is the formation of stress granules. These granules have been shown to sequester mRNA in a microscopically visible complex with RNA-binding proteins that mainly include cytotoxic granule-associated RNA binding protein 1 (TIA-1 and TIAR). The proposed functions of these granules range from RNA storage to mRNA decay, depending on the cell and its environment. Until now we don’t know if these granules exist in the myocardium under any condition. Accordingly, we hypothesized that RNA granules assemble in the heart in association with selective mRNAs as a mechanism to differentially regulate protein translation during myocyte growth or stress conditions. To address this, we applied immunocytochemistry and immunoprecipitation (IP)-qPCR approaches in cardiac myocytes exposed to growth, hypoxia, and hypoglycemic conditions, using a TIA-1/TIAR antibody. For the first time, our results show an abundant formation of RNA granules in cardiac myocytes maintained in complete growth medium. However, these structures rapidly disappear (>90%) upon serum, glucose, or oxygen deprivation, suggesting a possible role in releasing stored mRNA that may be required under stress conditions. Similarly, we detected abundant TIA-1-positive granules in the adult mouse heart that appeared to increase after transverse aortic constriction for 7 days (more samples needed to determine significance). IP-qPCR established that the granules harbor selective mRNA molecules that included myosin heavy chain beta, sprouty2, AKT, and hypoxia-inducible factor-1 alpha, but excluded Cdk7, EIF4E, transcription factor IIB, and TATA-binding protein. Presently, a more comprehensive quantitative analysis of the RNA associated with the granules in control vs. hypertrophied hearts is underway using extensive deep RNA sequencing technology. Thus, our results uncover the assembly of unique ribonucleoprotein granules in the heart that harbor selective RNA molecules that may play a role in posttranscriptional regulation of gene expression in the heart during health and disease.
- © 2011 by American Heart Association, Inc.