Abstract 13269: Reduced Expression of scaRNAs Disrupts Spliceosome Function and Heart Development in Zebrafish and Infants with Tetralogy of Fallot
The splicing of messenger RNA plays a fundamental role in regulating vertebrate development and differentiation. Although it is well established that alternative splicing (AS) plays an important role in regulating mammalian heart development, a clear link between misregulated splicing and congenital heart defects has not been shown. We recently reported that more than 50% of genes associated with heart development had significant changes in splice forms in the right ventricle of infants with tetralogy of Fallot (TOF; 14M/7F; all less than 1 yr old). Moreover, there was a significant decrease (30-50%, p<0.05) in the level of 12 scaRNAs. scaRNAs are members of the large family of noncoding small RNAs that are responsible for biochemical modification of specific nucleotides in spliceosomal and ribosomal RNAs. These 12 scaRNAs target two spliceosomal RNAs, U2 and U6. We used primary cells derived from the RV of infants with TOF to show a direct link between scaRNA levels and splice isoforms of several key genes regulating human heart development (e.g., GATA4, NOTCH2, DAAM1, DICER1, MBNL1 and 2). In addition, using available RNA-Seq data, we provide evidence that during zebrafish development, there are dynamic oscillations in scaRNAs and splice isoforms of genes that regulate heart development. We knocked down the expression of two scaRNAs; ACA35 (Scarna1) and U94 (Snord94), in zebrafish and saw a corresponding disruption of heart development. Importantly, there was an accompanying alteration in the ratios of splice isoforms of key cardiac regulatory genes. Based on these combined results, we propose that scaRNAs directly regulate the proficiency of the spliceosome by controlling spliceosomal RNA maturation. This in turn contributes to splice isoform dynamic equilibrium and ultimately heart development. These results are consistent with a failure of normal temporal and spatial splicing patterns during early embryonic development, leading to a breakdown in communication between the first and second heart fields, resulting in conotruncal misalignment and TOF. Our findings represent a new paradigm for understanding congenital cardiac malformations.
Author Disclosures: D.C. Bittel: None. P. Patil: None. T. Uechi: None. N. Kibiryeva: None. J. Marshall: None. M. Artman: None. J.E. O’Brien: None. N. Kenmochi: None.
- © 2014 by American Heart Association, Inc.