Modeling growth and telomere dynamics in Saccharomyces cerevisiae

Abstract

A general branching process is proposed to model a population of cells of the yeast Saccharomyces cerevisiae following loss of telomerase. Previously published experimental data indicate that a population of telomerase-deficient cells regain exponential growth after a period of slowing due to critical telomere shortening. The explanation for this phenomenon is that some cells engage telomerase-independent pathways to maintain telomeres that allow them to become "survivors." Our model takes into account random variation in individual cell cycle times, telomere length, finite replicative lifespan of mother cells, and survivorship. We identify and estimate crucial parameters such as the probability of an individual cell becoming a survivor, and compare our model predictions to experimental data.

Figure 1

Cell counts of 7 yeast cultures for 13 days (logarithmic scale).

Figure 2

Data from Figure 1 rescaled, with mean.

Figure 3

Cell count data sets with mean (dashed red line) and model predictions for different values of p (blue lines) with uniform n.

Figure 4

Data, mean, and model prediction with binomial n.