Induced skipping of human dystrophin exon 20 with PMOs. Primary human myogenic cultures were transfected with PMOs at the concentrations indicated and incubated for 24 hours before total RNA was extracted. Nested RT-PCR amplified between exons 18 and 26. The full-length and exon 20 deleted transcripts are represented by products of 1336 and 1094 bp, respectively. (a) Individual PMOs directed to exon 20. (b) PMO cocktail directed to exon 20. Note that the total concentration of PMOs is shown, ie, 5 μM indicates 2.5 μM of each PMO.