Making choices-how stochastic decisions determine disease progression.

In this issue of Genes & Development, Ginart and colleagues (pp. 567-578) study a mouse model for Russell-Silver syndrome (RSS) and show that similar cells within one individual can display distinct gene expression patterns because of epigenetic marks that are established stochastically during early development. Their results provide an excellent explanation for phenotypes seen in RSS and other imprinting disorders and especially help us understand how patients with similar or even identical genetic mutations can display distinct disease profiles.