  How much information does a cell inherit from its ancestors beyond its
genetic sequence? What are the epigenetic mechanisms that allow this? Despite
the rise in available epigenetic data, how such information is inherited
through the cell cycle is still not fully understood. Here, we develop and
analyse a simple mathematical model for histone-based epigenetic information
that describes how daughter cells can recapitulate the gene expression profiles
of their parent. We consider the dynamics of histone modifications during the
cell cycle deterministically but also incorporate the largest stochastic
element: DNA replication, where histones are randomly distributed between the
two daughter DNA strands. This hybrid stochastic-deterministic approach enables
an analytic derivation of the switching rate, i.e., the frequency of
loss-of-memory events due to replication. While retaining great simplicity, the
model can recapitulate experimental switching rate data, establishing its
biological importance as a framework to quantitatively study epigenetic
inheritance.
