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Expression of a pathogenic mutation of SOD1 sensitizes aprataxin-deficient cells and mice to oxidative stress and triggers hallmarks of premature ageing.

Authors: Jean J. Carroll, Tristan K W TK. Page, Shih-Chieh SC. Chiang, Bernadett B. Kalmar, David D. Bode, Linda L. Greensmith, Peter J PJ. Mckinnon, Julian R JR. Thorpe, Majid M. Hafezparast, Sherif F SF. El-Khamisy
Published: 09/30/2014, Human molecular genetics


Aprataxin (APTX) deficiency causes progressive cerebellar degeneration, ataxia and oculomotor apraxia in man. Cell free assays and crystal structure studies demonstrate a role for APTX in resolving 5'-adenylated nucleic acid breaks, however, APTX function in vertebrates remains unclear due to the lack of an appropriate model system. Here, we generated a murine model in which a pathogenic mutant of superoxide dismutase 1 (SOD1(G93A)) is expressed in an Aptx-/- mouse strain. We report a delayed population doubling and accelerated senescence in Aptx-/- primary mouse fibroblasts, which is not due to detectable telomere instability or cell cycle deregulation but is associated with a reduction in transcription recovery following oxidative stress. Expression of SOD1(G93A) uncovers a survival defect ex vivo in cultured cells and in vivo in tissues lacking Aptx. The surviving neurons feature numerous and deep nuclear envelope invaginations, a hallmark of cellular stress. Furthermore, they possess an elevated number of high-density nuclear regions and a concomitant increase in histone H3 K9 trimethylation, hallmarks of silenced chromatin. Finally, the accelerated cellular senescence was also observed at the organismal level as shown by down-regulation of insulin-like growth factor 1 (IGF-1), a hallmark of premature ageing. Together, this study demonstrates a protective role of Aptx in vivo and suggests that its loss results in progressive accumulation of DNA breaks in the nervous system, triggering hallmarks of premature ageing, systemically.

© The Author 2014. Published by Oxford University Press.
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