Figure 5.

Model of role of JDP2 in cellular aging and cell differentiation. Self-renewing cells undergo repeated divisions, and p16^Ink4aor C/EBPδ expression increases with age, oxygen, and hormone, as a consequence of undefined stimuli. (a) Commitment model: p16^Ink4a or C/EBPδ expression occurs stochastically in a subpopulation of cells resulting in their senescence. In this model, the capacity for self-renewal of the noncommitted cells is not affected. (b) Threshold model: expression of p16^Ink4a or C/EBPδ increases or decreases, respectively, uniformly in the tissue specific. Self-renewing cells compartment is compromised over time. Self-renewal is indicated by curved arrows; committed cells are colored blue.