Figure 7.

Model for the Role of In Vivo Reprogramming in Tissue Repair and Cancer Initiation

Adult stem cells within a tissue show the longest telomeres, telomerase activity, and high levels of TRF1 protein. As they mobilize for tissue renewal, telomeres shorten, telomerase activity is lost, and TRF1 expression diminishes. In vivo reprogramming reverses these features generating dedifferentiated cells with longer telomeres, telomerase expression, and higher levels of TRF1. The similarities of the in vivo reprogrammed cells to the adult stem cells suggest the possibility that reprogrammed cells could have a role in tissue regeneration. Other cellular plastic processes, such as dedifferentiation associated with initiation of tumorigenesis, also show increased levels of TRF1 protein and elongation of telomeres, indicating a general role of these telomeric events in processes associated with cell fate change.