Fig. 3. Asymmetric Numb distribution is correlated with asymmetric cell divisions generating a cortical progenitor cell and a neuron. (A-C) An E10 cell pair consisting of a neuron and a progenitor cell that has asymmetric Numb expression. (A) Phase-contrast image; (B) ß-tubulin III staining is present in one daughter; (C) Numb is present only in the neuronal daughter (arrow). In other pairs, Numb was found in the progenitor and not the neuronal daughter (not shown). (D-F) An E10 cell pair consisting of two neurons that have symmetric Numb expression. (D) Phase-contrast image; (E) ß-tubulin III staining is present in both daughter cells; (F) symmetric Numb staining. Scale bars: 20 µm.