Cardiac glycosides correct aberrant splicing of IKBKAP -encoded mRNA in familial dysautonomia derived cells by suppressing expression of SRSF3

Abstract

The ability to modulate the production of the wild-type transcript in cells bearing the splice-altering familial dysautonomia (FD) causing mutation in the IKBKAP gene prompted a study of the impact of a panel of pharmaceuticals on the splicing of this transcript, which revealed the ability of the cardiac glycoside digoxin to increase the production of the wild-type, exon-20-containing, IKBKAP-encoded transcript and the full-length IκB-kinase-complex- associated protein in FD-derived cells. Characterization of the cis elements and trans factors involved in the digoxin-mediated effect on splicing reveals that this response is dependent on an SRSF3 binding site(s) located in the intron 5′ of the alternatively spliced exon and that digoxin mediates its effect by suppressing the level of the SRSF3 protein. Characterization of the digoxin-mediated effect on the RNA splicing process was facilitated by the identification of several RNA splicing events in which digoxin treatment mediates the enhanced inclusion of exonic sequence. Moreover, we demonstrate the ability of digoxin to impact the splicing process in neuronal cells, a cell type profoundly impacted by FD. This study represents the first demonstration that digoxin possesses splice-altering capabilities that are capable of reversing the impact of the FD-causing mutation. These findings support the clinical evaluation of the impact of digoxin on the FD patient population. We report the ability of the cardiac glycoside digoxin to alter the splicing process and thereby increase production of the wild-type IKAP transcript in cells bearing the splice-altering familial dysautonomia (FD)-causing IKBKAP mutation. This digoxin-mediated effect is dependent on an SRSF3-binding site(s) located near the alternatively spliced exon and is the result of the digoxin-mediated suppression of the SRSF3 transcript and protein. © 2013 FEBS.