Fig. 6.

Reduction of immobile SMN by FGF-2²³ leads to accumulation of U4 snRNPs at CBs. Fluorescence in situ hybridization (FISH, a3–d3) with probes for U4, U5 and U6 snRNAs and immunostainings with anti-coilin (a2–d2) were performed in HEK293T cells transfected with pFGF-2²³-ECFP (d1) or, as controls, pFGF-2¹⁸-ECFP (c1) or pECFP (a1, b1) 24 h before fixation. Arrows point to the CBs in the merged images (a4–d4) that were enlarged in the inserted PDM images. Here, intensity correlation analyses are demonstrated (LUT: orange, positive PDM; blue, negative PDM). Colocalized pixels (both channels vary synchronically from the mean pixel intensity) are represented by positive PDM (yellow). A significant increase in colocalization of coilin and U4 snRNP in CBs after overexpression of pFGF-2²³-ECFP was detected (E means ± SEM; ***p < 0.001; Mann-Whitney test; CFP: n = 45, FGF-2¹⁸: n = 45, FGF-2²³: n = 45, pooled from 3 independent experiments). Scale bar, 2 μm (a1–d4), 0.2 μm (insets). Stainings of U5 and U6 snRNPs and additional stainings of U4 snRNPs are shown in Supplemental Fig. 2