Therapeutic manipulation of IKBKAP mis-splicing with a small molecule to cure familial dysautonomia

Approximately half of genetic disease-associated mutations cause aberrant splicing. However, a widely applicable therapeutic strategy to splicing diseases is yet to be developed. Here, we analyze the mechanism whereby IKBKAP-familial dysautonomia (FD) exon 20 inclusion is specifically promoted by a small molecule splice modulator, RECTAS, even though IKBKAP-FD exon 20 has a suboptimal 5 splice site due to the IVS20+6T>C mutation. Knockdown experiments reveal that exon 20 inclusion is suppressed in the absence of serine/arginine-rich splicing factor 6 (SRSF6) binding to an intronic splicing enhancer in intron 20. We show that RECTAS directly interacts with CDC-like kinases (CLKs) and enhances SRSF6 phosphorylation. Consistently, exon 20 splicing is bidirectionally manipulated by targeting cellular CLK activity with RECTAS versus CLK inhibitors. The therapeutic potential of RECTAS is validated in multiple FD disease models. Our study indicates that small synthetic molecules affecting phosphorylation state of SRSFs is available as a new therapeutic modality for mechanism-oriented precision medicine of splicing diseases. Familial dysautonomia is caused by splicing mutation of IKBKAP gene, which induces skipping of exon 20 and subsequent functional loss. Here, the authors report that a synthetic splice modulator RECTAS ameliorates pathogenic exon 20 skipping and shows therapeutic effects in cellular and animal models.

Automated summary

Research has shown that the small molecule splice modulator RECTAS can enhance the inclusion of exon 20 of the IKBKAP gene causing familial dysautonomia by promoting the binding of the splicing enhancer factor SRSF6. RECTAS interacts with CDC-like kinases (CLKs) and enhances SRSF6 phosphorylation to achieve its effects. By regulating cellular CLK activity, RECTAS can bidirectionally manipulate exon 20 splicing, which has been validated in multiple FD disease models.