The evolution of the nuclear receptor superfamily

Nuclear receptors form a superfamily of ligand-activated transcription factors implicated in various physiological functions from development to homoeostasis. Nuclear receptors share a common evolutionary history revealed by their conserved structure and by their high degree of sequence conservation. Here we review the latest advances on the evolution of nuclear receptors by addressing the following questions. What is known about the appearance and diversification of nuclear hormone receptors? How did their different functional characteristics evolve? What can we infer from the analysis of complete genomes? In summary, the study of the evolution of nuclear receptors will be very important not only for understanding their functions in vivo but also for obtaining insights into the evolution of animal genomes as a whole.