Gene regulatory networks

The Special Feature on gene regulatory networks in this issue of PNAS highlights an emerging field in the biosciences: gene regulatory networks that control animal development. The complex control systems underlying development have probably been evolving for more than a billion years. They regulate the expression of thousands of genes in any given developmental process. They are essentially hardwired genomic regulatory codes, the role of which is to specify the sets of genes that must be expressed in specific spatial and temporal patterns. In physical terms, these control systems consist of many thousands of modular DNA sequences. Each such module receives and integrates multiple inputs, in the form of regulatory proteins (activators and repressors) that recognize specific sequences within them. The end result is the precise …