Staurosporine allows dystrophin expression by skipping of nonsense-encoding exon

Background: Antisense oligonucleotides that induce exon skipping have been nominated as the most plausible treatment method for dystrophin expression in dystrophin-deficient Duchenne muscular dystrophy. Considering this therapeutic efficiency, small chemical compounds that can enable exon skipping have been highly awaited. In our previous report, a small chemical kinase inhibitor, TG003, was shown to enhance dystrophin expression by enhancing exon skipping.

Purpose: Staurosporine (STS), a small chemical broad kinase inhibitor, was examined for enhanced skipping of a nonsense-encoding dystrophin exon.

Methods: STS was added to culture medium of HeLa cells transfected with minigenes expressing wild-type or mutated exon 31 with c.4303G>T (p.Glu1435X), and the resulting mRNAs were analyzed by RT-PCR amplification. Dystrophin mRNA and protein were analyzed in muscle cells treated with STS by RT-PCR and western blotting, respectively.

Results: STS did not alter splicing of the wild-type minigene. In the mutated minigene, STS increased the exon 31-skipped product. A combination of STS and TG003 did not significantly increase the exon 31-skipped product. STS enhanced skipping of exon 4 of the CDC-like kinase 1 gene, whereas TG003 suppressed it. Two STS analogs with selective kinase inhibitory activity did not enhance the mutated exon 31 skipping. When immortalized muscle cells with c.4303G>T in the dystrophin gene were treated with STS, skipping of the mutated exon 31 and dystrophin expression was enhanced.

Conclusions: STS, a broad kinase inhibitor, was shown to enhance skipping of the mutated exon 31 and dystrophin expression, but selective kinase inhibitors did not.