Immortalization of neural precursors when telomerase is overexpressed in embryonal carcinomas and stem cells

• Published in: Molecular biology of the cell Vol. 19; no. 4; pp. 1548 - 1560
• Main Authors: Schwob, Anneke E, Nguyen, Lilly J, Meiri, Karina F
• Format: Journal Article
• Language: English
• Published: United States The American Society for Cell Biology 01-04-2008
• Subjects: Animals; Apoptosis; Base Sequence; Cell Aggregation - drug effects; Cell Differentiation - drug effects; Cell Differentiation - genetics; Cell Differentiation - physiology; Cell Line; Cell Proliferation; Embryonal Carcinoma Stem Cells - enzymology; Embryonal Carcinoma Stem Cells - pathology; Embryonic Stem Cells - cytology; Embryonic Stem Cells - enzymology; Fibroblast Growth Factor 2 - pharmacology; Gene Expression; Mice; Neurons - cytology; Neurons - enzymology; Pluripotent Stem Cells - cytology; Pluripotent Stem Cells - enzymology; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Telomerase - genetics; Telomerase - metabolism; Telomere - genetics
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.E06-11-1013

The DNA repair enzyme telomerase maintains chromosome stability by ensuring that telomeres regenerate each time the cell divides, protecting chromosome ends. During onset of neuroectodermal differentiation in P19 embryonal carcinoma (EC) cells three independent techniques (Southern blotting, Q-FISH, and Q-PCR) revealed a catastrophic reduction in telomere length in nestin-expressing neuronal precursors even though telomerase activity remained high. Overexpressing telomerase protein (mTERT) prevented telomere collapse and the neuroepithelial precursors produced continued to divide, but deaggregated and died. Addition of FGF-2 prevented deaggregation, protected the precursors from the apoptotic event that normally accompanies onset of terminal neuronal differentiation, allowed them to evade senescence, and enabled completion of morphological differentiation. Similarly, primary embryonic stem (ES) cells overexpressing mTERT also initiated neuroectodermal differentiation efficiently, acquiring markers of neuronal precursors and mature neurons. ES precursors are normally cultured with FGF-2, and overexpression of mTERT alone was sufficient to allow them to evade senescence. However, when FGF-2 was removed in order for differentiation to be completed most neural precursors underwent apoptosis indicating that in ES cells mTERT is not sufficient allow terminal differentiation of ES neural precursors in vitro. The results demonstrate that telomerase can potentiate the transition between pluripotent stem cell and committed neuron in both EC and ES cells.