Fig. 4.

Synonymous substitutions affect the splicing efficiency according to the mammalian exonic context. (a) Sequences of CFTR exon 12 highlighting the artificial composition of synonymous substitutions introduced in hybrid minigenes by site-directed mutagenesis. The three synonymous changes that in the human context induce exon skipping (25A, 40C, and 52T) are boxed. Numbers on the right of each sequence indicate the percentage of exon inclusion as determined by minigene splicing assay. For clarity, these percentages are also reported under the image in b that shows corresponding RT-PCR products from splicing assay. The RNA splicing variants that correspond to exon 12 inclusion and exclusion are indicated. M is the 1-kb marker.