Fig. 9. Model for Myc function in epidermis. In the presence of Myc, daughters of stem cells undergo clonal expansion (TAC). A blue square represents the stem cell decision to enter the (TAC) compartment before terminal differentiation; Myc would behave as an `amplifier'. In the absence of Myc, stem cells are able to divide, but their daughters cannot amplify and directly undergo terminal differentiation. Stem cells would be driven to divide and differentiate more frequently to replenish the epidermis and their compartment might be depleted over time. SC, stem cells; TD, terminal differentiation.