FIGURE 4.

Dyrk1A inhibits the role of ASF in tau exon 10 inclusion. a, overexpression of Dyrk1A inhibited the role of ASF in tau exon 10 inclusion. Mini-tau gene pCI-SI9/LI10 was co-transfected with ASF or Dyrk1A into COS7 cells for 48 h, and the total RNA was extracted and subjected for measurement of tau exon 10 splicing by using RT-PCR. Con, control. b, knock down of Dyrk1A by its siRNA elevated exon 10 inclusion induced by ASF. Mini-tau gene was co-transfected into HEK-293T cells with ASF and siRNA of Dyrk1A or its scrambled form, and then tau exon 10 splicing was analyzed by RT-PCR after a 48-h transfection. Expression of endogenous Dyrk1A was decreased by siRNA of Dyrk1A dose-dependently (inset panel). Transfection of Dyrk1A siRNA significantly increased the 4R-tau expression when compared with the scrambled form. c, inhibition of Dyrk1A increased 4R-tau expression in differentiated human neuronal progenitor cells. Human neuronal progenitor cells were differentiated with retinoid acid for 6 days and then treated with 12.5 μm EGCG or 10 μm Harmine for 24 h to inhibit Dyrk1A. The cell lysates were objected to Western blots with anti-3R-tau and anti-4R-tau antibodies. The ratio of 4R-tau and 3R-tau was calculated. The data are presented as mean ± S.D. d, Dyrk1A drove ASF into speckles. HA-ASF and/or Dyrk1A or Dyrk1A_K188R were co-transfected into HeLa cells. After a 48-h transfection, the cells were fixed and immunostained by anti-HA and anti-Dyrk1A and followed by TRITC-anti-rabbit IgG or FITC-anti-mouse IgG, respectively. Hoechst was used for nucleus staining. ^**, p < 0.01 versus control group, ^#, p < 0.05 versus ASF group.