Stabilization of microtubules promotes their cortical reorganization. (A) Mouse keratinocytes grown in 1.2 mM Ca2+-containing media for 24 h have Lis1 at cell junctions. Microtubules, however, remain cytoplasmic (B). (C) Immunofluorescence analysis of Tau (red) in E17.5 mouse embryo epidermis. Hoechst labels DNA (blue) and the dotted line marks the basement membrane. (D) Tau levels in lysates prepared from basal and suprabasal (differentiated) cells of the epidermis. (E–G) Organization of microtubules in wild-type keratinocytes that were transfected with GFP-tagged Map2b (E), Map4 (F), or Tau-24 (G). Transfected cells were identified by GFP fluorescence and are marked with an asterisk. (H–J) Organization of microtubules in DP-null cells that were transfected with Map2b (H), Map4 (I), or Tau-24 (J). Microtubule organization in WT control cells (K) and in cells treated with 10 µM taxol for 1 h (L). (M) Microtubule organization in a small colony of WT keratinocytes. Note that microtubules accumulate at cell–cell junctions, but not free leading edges (arrows). Microtubule organization in α-catenin–null (N), p120-catenin–null (O), and DP-null cells (P). (Q) Transmission electron micrograph of a taxol-treated keratinocyte. Some of the microtubules are highlighted in red adjacent to the electron-dense desmosomes. All bars are 10 µm except Q, which is 0.5 µm.
