Branchpoint sequence is a key determinant of minor intron retention in the spinal cord of SMA mice. RT-PCR analysis of minor intron splicing in spinal cords of control (WT6, WT7) and SMA (KO6, KO9, KO10) mice. (A) Minor introns containing canonical branchpoint sequences. (B) Minor introns containing suboptimal branchpoint sequences. Nucleotides diverging from the consensus are underlined. The putative branch site adenosine is indicated in bold. The branchpoint sequence is aligned with the anti-branch site of the U12 snRNA (in italics). Gene names and size (in base pairs) of the amplified products are indicated on the left. The schematic structure of the amplified products is shown on the right. (C) Retention index of minor introns in spinal cords of control (WT, n = 2) and SMA (SMA, n = 3) mice determined as described in the Materials and Methods section. Mean and SEM are shown. Statistical significance was calculated using the Student t-test (ns: nonsignificant; (**) P < 0.01). Histograms for Ddx54 and Ppp2r2b are not shown because retained intron is not detectable.
