Emerging roles for telomerase in neuronal development and apoptosis

Telomerase is an enzyme consisting of a reverse transcriptase called TERT a nd an RNA component that adds repeats of a DNA sequence (TTAGGG) to the end s of chromosomes, thereby preventing their shortening and cell cycle arrest . Telomerase levels are high in neural progenitor cells and neurons during early development, and decrease in association with cell differentiation. A role for TERT in regulation of developmental death of neurons is suggested by a decrease in TERT expression that coincides with the period of neurona l death and by data showing that TERT promotes survival of developing brain neurons. Suppression of telomerase activity and TERT expression promotes a poptosis, whereas overexpression of TERT prevents apoptosis by suppressing cell death at a premitochondrial step in the death cascade Moreover, neurot rophic factors known to play important roles in brain development can regul ate telomerase activity and TERT expression in cultured neural cells. A bet ter understanding of the functions of telomerase and TERT in neuronal diffe rentiation and survival may lead to novel approaches for preventing neurona l death and promoting recovery in various neurodegenerative conditions. Pub lished 2001 Wiley-Liss, Inc.