EpiTracer - an algorithm for identifying epicenters in condition-specific biological networks

Diseases in biological systems may result from small perturbations in a complex network of protein-protein interactions (PPIs). The perturbations typically affect a small set of proteins, which then go on to disturb a larger part of the network. Biological systems attempt to counteract these perturbations by launching a stress-response, resulting in a complex pattern of variations in the cell. We present an algorithm, EpiTracer which identifies the key proteins, termed epicenters, from which a large number of the changes in PPI networks ripple out. We propose a new centrality measure, ripple centrality, that measures how effectively a change at a particular protein can ripple across the network, by identifying condition specific highest activity paths obtained by mapping gene expression profiles to the PPI network.