Comparison of QKI-5 effects on alternative splicing in vivo. Splicing reporters: MAGPY (lanes 1–6), GABA γ2 (lanes 7–12), NMDA E21 (lanes 13–18); and protein expression plasmids, pcDNA QKI-5 and pcDNA PTB, were transfected into the nonneural cell line C2C12, and alternative splicing products were assayed by RT-PCR with primers (arrows) specific for sequences in the first and last exons. Exon-included and exon-skipped products are shown at left of each panel. Wedge indicates a 1:4 or 1:6 ratio of splicing reporter substrate to protein expression plasmid, left and right lanes, respectively. Control lanes (−) were transfected with empty pcDNA vector backbone. Structures of splicing reporter substrates are indicated schematically with exon and intron lengths in nucleotides (bottom right).