The 3' coding region of mouse Tgif2 is required for alternate splicing. COS-1 cells were transfected with expression constructs and expression of human, mouse and chimeric TGIF2 RNAs was analyzed by RT-PCR. The positions of primers are indicated (arrows). Alternate splicing: + splicing, - no splicing, -/+ just detectable, +/- slightly reduced. Constructs are shown schematically: Gray = mouse, black = retained intron. Stripes = human, crosshatch = retained intron. A) Comparison of constructs in which regions 5' and 3' of the retained intron are swapped between human and mouse TGIF2. B) Comparison of splicing of 3' deletion constructs for human and mouse TGIF2. C) Analysis of a series of 3' deletions of mouse TGIF2.