Figure 2

Differential outcomes of loss of Notch activity during regeneration and tissue turnover. During regeneration (left) both wild type and Rbpj null myoblasts proliferate and form new muscle fibres. In the absence of Notch signalling, the size of the amplified population is smaller since the cells fail to self-renew. During tissue homeostasis (right) a small fraction of satellites cells exit quiescence and divide (red chromosomes, BrdU⁺) to give rise to new satellite cells and fusion-competent myoblasts. Satellite cell specific deletion of Rbpj results in an increase in the number of cells that exit quiescence; these cells differentiate spontaneously. In sharp contrast to wild type cells the majority of Rbpj null satellite cells become Myogenin-positive without going through S-phase (black chromosomes).