Figure 2.

Heterogeneity at the level of single‐cell lineages. (a) Many telomerase‐negative cell lineages, defined here as consecutive cell divisions upon telomerase inactivation until irreversible cell cycle arrest, undergo senescence in a single switch from proliferative to arrested state. (b) In contrast, other cell lineages are likely subject to accidental damage at telomeres that triggers the DNA damage checkpoint and DNA repair mechanisms. The frequent failure of repair mechanisms, combined with the relative ease of bypassing checkpoints by adaptation, then leads to a cascade of genome instability and a multiplicity of cell fates. Modified from Coutelier et al., (2018)