Variable gene expression in eukaryotes: a network perspective.

Changes in gene expression underlie phenotypic plasticity, variation within species, and phenotypic divergence between species. These expression differences arise from modulation of regulatory networks. To understand the source of expression differences, networks of interactions among genes and gene products that orchestrate gene expression must be considered. Here I review the basic structure of eukaryotic regulatory networks and discuss selected case studies that provide insight into how these networks are altered to create expression differences within and between species.