  What is aging? Mechanistic answers to this question remain elusive despite
decades of research. Here, we propose a mathematical model of cellular aging
based on a model gene interaction network. Our network model is made of only
non-aging components - the biological functions of gene interactions decrease
with a constant mortality rate. Death of a cell occurs in the model when an
essential gene loses all of its interactions to other genes, equivalent to the
deletion of an essential gene. Gene interactions are stochastic based on a
binomial distribution. We show that the defining characteristic of biological
aging, the exponential increase of mortality rate over time, can arise from
this gene network model during the early stage of aging. Hence, we demonstrate
that cellular aging is an emergent property of this model network. Our model
predicts that the rate of aging, defined by the Gompertz coefficient, is
approximately proportional to the average number of active interactions per
gene and that the stochastic heterogeneity of gene interactions is an important
factor in the dynamics of the aging process. This theoretic framework offers a
mechanistic foundation for the pleiotropic nature of aging and can provide
insights on cellular aging.
