Stem Cells

Regenerating tissues are maintained by stem cells that have the capacity to self-renew and to give rise to all lineages within a tissue. Telomerase is expressed in stem cells and progenitor cells, but its role in these compartments remains poorly understood. To begin to understand telomerase function in stem cell populations, we conditionally expressed TERT in mouse skin in vivo. We found that TERT activated quiescent stem cells in the bulge region of hair follicles. TERT-mediated activation of hair follicle stem cells led to a developmental change in the hair follicle from the resting stage (telogen) to the active stage (anagen). By enabling this transition, TERT supported robust hair growth. By labeling bulge stem cells with the thymidine analogue BrdU, we showed that TERT caused proliferation in this normally quiescent population. To understand the mechanism of this potent effect on stem cells, we studied conditional TERT upregulation in a TERC-/- background. The effects of TERT in a TERC-/- background were identical, initiating a new anagen cycle. Therefore, this novel role for TERT occurs through a mechanism that does not require TERC and is therefore independent of TERT's telomere synthesis function. We are actively investigating the effects of TERT on other stem cell populations. Furthermore, we are dissecting TERT's mechanism of action in molecular detail.