Fig. 3. β-Tubulin-positive cells are abnormal in differentiated Sox2 mutant cell cultures from adult mouse. (A) β-Tubulin immunofluorescence of normal (left) and mutant (right) day 9-differentiated cells. Bottom: DAPI. Many of the mutant poorly arborized, less intensely stained cells are barely visible in this low-magnification image. (B) Higher magnification of normal and mutant β-tubulin staining. In mutant, the arrowhead indicates a cell with well-developed neuronal morphology and long arborizations; arrows indicate abnormal cells with short processes and often weak β-tubulin staining typical of the mutant. (C) Time course of β-tubulin expression during differentiation. `Mut, well developed' indicates cells with long arborizations (B, wt or arrowhead in mutant); `mut, total': total β-tubulin-positive cells (including those indicated by arrows in B, mut). The abnormal phenotype is already observed at day 5, the earliest stage when significant numbers of β-tubulin-positive cells appear.