Fig. 4.

Decreased SMN concentrations increase the error rate of splicing. (A) Western blot confirming SMN knockdown in HeLa cells. The quantitation shown below was normalized to tubulin levels. SMN knockdown is also confirmed by RT-PCR (Fig. S7). (B) Bar graph showing the relative increase in splicing errors when cells are treated with RNAi against SMN. (C) Model showing the effect of normal versus reduced SMN concentrations on the recognition and inclusion of exons. At normal concentrations the scale of recognition is shown (Upper). When SMN concentrations are reduced, some alternatively spliced exons are less frequently included (Lower). *, P < 0.05.