mFox-2 enhances 4.1R exon 16 and DUP exon E2 splicing in an UGCAUG-dependent manner. (A) mFox-2 isoforms exhibit differential enhancing activities on exon 16 splicing. MELCs or exon 16 WT or PNB minigene stably expressing MELCs were transfected with vector alone, mFox-2A, or mFox-2F. Exon 16 splicing products were analyzed by semiquantitative RT-PCR. endo indicates endogenous; WT, wild-type; and PNB, mutant minigene PNB. Western blot analysis confirmed the expression of transfected mFox-2A or mFox-2F isoforms from WT-minigene–expressing MELCs by anti-Flag antibody; β-actin was used as a loading control. +E16 indicates spliced products with exon 16; −E16, spliced products without exon 16; and +16 (%), percentage of spliced products with standard deviation that include exon 16. The results shown are from 3 independent transfections. (B) mFox-2 isoforms exhibit differential enhancing activities on exon E2 splicing in the DUP system. DUP-3WT or DUP-3MU minigenes stably expressing MELCs were transfected with vector alone, mFox-2A, or mFox-2F and analyzed for exon E2 expressions. Western blot analysis confirmed the expression of mFox-2A or mFox-2F isoforms. +E2 indicates spliced products with exon E2; −E2, spliced products without exon E2; and +E2 (%), percentage of spliced products that include exon E2.