Emerging roles for telomerase in neuronal development and apoptosis

Telomerase is an enzyme consisting of a reverse transcriptase called TERT and an RNA component that adds repeats of a DNA sequence (TTAGGG) to the ends 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 neuronal death and by data showing that TERT promotes survival of developing brain neurons. Suppression of telomerase activity and TERT expression promotes apoptosis, whereas overexpression of TERT prevents apoptosis by suppressing cell death at a premitochondrial step in the death cascade Moreover, neurotrophic factors known to play important roles in brain development can regulate telomerase activity and TERT expression in cultured neural cells. A better understanding of the functions of telomerase and TERT in neuronal differentiation and survival may lead to novel approaches for preventing neuronal death and promoting recovery in various neurodegenerative conditions.