SIRT6 knockout cells resist apoptosis initiation but not progression: a computational method to evaluate the progression of apoptosis
Apoptosis is essential for numerous processes, such as development, resistance to infections, and suppression of tumorigenesis. Here, we investigate the influence of the nutrient sensing and longevity-assuring enzyme SIRT6 on the dynamics of apoptosis triggered by serum starvation. Specifically, we characterize the progression of apoptosis in wild type and SIRT6 deficient mouse embryonic fibroblasts using time-lapse flow cytometry and computational modelling based on rate-equations and cell distribution analysis. We find that SIRT6 deficient cells resist apoptosis by delaying its initiation. Interestingly, once apoptosis is initiated, the rate of its progression is higher in SIRT6 null cells compared to identically cultured wild type cells. However, SIRT6 null cells succumb to apoptosis more slowly, not only in response to nutrient deprivation but also in response to other stresses. Our data suggest that SIRT6 plays a role in several distinct steps of apoptosis. Overall, we demonstrate the utility of our computational model to describe stages of apoptosis progression and the integrity of the cellular membrane. Such measurements will be useful in a broad range of biological applications.
KeywordsApoptosis SIRT6 Cellular dynamics Plasma membrane
S.L. and J.N. were in part supported by a grant from American Federation for Aging Research (AFAR, Grant # 2015-030). S.L. received seed grant funding from the Cornell University Center for Vertebrate Genomics. J.N. was supported by a Glenn/AFAR Scholarship for Research in the Biology of Aging.
SD performed computational modelling and wrote the initial draft of the manuscript; JN performed cell culture experiments; JES assisted in optimizing the computational model; VP nucleated the method of modelling, supervised modelling efforts, designed the study; SL designed the study, supervised biological cell culture experiments, supervised computational modelling, edited the manuscript.
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Conflict of interest
All authors declare no conflicts of interest.
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