Abstract 431: ScaRNAs Regulate Cardiac Differentiation and Development by Fine Tuning the Spliceosome
Alternative splicing (AS) of mRNA adds diversity to the proteome and precise regulation of AS is essential for proper development. We recently showed that multiple genes critical for heart development are irregularly spliced in the right ventricle of babies with tetralogy of Fallot (TOF). We also observed reduced expression of several noncoding small cajal body associated RNAs (scaRNAs). scaRNAs direct the biochemical modification of spliceosomal RNAs and are essential for the stability and function of the spliceosome. Our results provide compelling evidence for a direct role of scaRNAs in regulating splicing of genes that are critical for heart development. To further explore this novel paradigm of developmental regulation, we analyzed the transcriptome of stem cells as they differentiated to beating cardiomyocytes. We observed significant alternative splicing with respect to timepoint (with Bonferroni correction and fdr of 5%) in 3,165 of 20,301 (15.6%) total genes. Importantly, there were 79 alternatively spliced genes among 213 genes (37.1%) known to be critical for heart development. This is a significant enrichment in the cardiac network genes (p<0.001). Most of the alternative isoforms are known protein coding variants. In addition, we saw changes in expression of several scaRNAs. scaRNA1 is reduced in the right ventricle of children with TOF and we targeted it for knockdown in the quail embryo model system. Preliminary results revealed dramatic alterations in cardiac morphogenesis and embryonic lethality. At higher levels of the antisense oligo, cells appeared to undergo apoptosis, aggregated inappropriately and failed to gastrulate. Lower concentrations resulted in initiation of gastrulation with some cells from the cardiac lineage traversing the embryonic milieu to contribute to the heart and other organs. Interestingly, these cells appeared to lack protrusive phenotypes, and may be passively moved by neighboring groups of non-electroporated motile cells. Taken together, our results suggest scaRNAs are necessary to maintain the fidelity of the spliceosome and thus play an important role in vertebrate heart development. These observations provide additional new insights into regulatory mechanisms underlying cardiac development.
Author Disclosures: D.C. Bittel: None. B. Rongish: None. N. Kibiryeva: None. M. Filla: None. J. Marshall: None. M. Artman: None. J.E. O’Brien: None. R. Johnson: None.
- © 2015 by American Heart Association, Inc.