Although TA/TA mice do not seem to be cancer prone, at least in the present study, our experimental results suggest that Fbw7-mediated c-Myb degradation is required for the quantitative regulation of c-Myb in early erythroid progenitors at the stage when c-Kit disappears, and failure of c-Myb downregulation causes attenuated erythroid differentiation and induces anemia in TA/TA mice. The gene discussed is MYB; the disease is cancer.