Fig. 2. Cytoplasmic ninein speckles are prominent in cultured epithelial cells. (A) PtK2 cell showing ninein at the centrosome (arrow) and throughout the cytoplasm as numerous speckles. (B) Merged image, with ninein (red) and microtubules (green). (C,D) Control (C) and siRNA-ninein-treated ARPE-19 cells labelled for ninein showing lack of cytoplasmic speckles and centrosomal staining in depleted cells (D) (images acquired using the same microscope exposure settings). (E) UE1 cell showing numerous ninein speckles (arrowhead; see also inset), which appear to be associated with microtubules. A few ninein speckles appear not to be associated with microtubules (arrow; see also inset). (F-H) Ninein speckle at the end of a free microtubule in a PtK2 (F) and a FHL124 (G) cell and along microtubules in an ARPE-19 cell (H). (I,J) Immuno-gold localisation of ninein cytoplasmic speckles in PtK2 cells. Gold particles (highlighted in yellow) are evident close to the wall of microtubules either singly or in groups of 3-4. Bars, 5 µm (A,B), 10 µm (C,D), 2 µm (E), 50 nm (I,J).