Dueling orphans--interacting nuclear receptors coordinate Drosophila metamorphosis.

At least seven orphan members of the nuclear receptor superfamily are transcriptionally regulated by the steroid hormone ecdysone and expressed during the onset of Drosophila metamorphosis. A recent paper provides functions for two of these receptors, E75B and DHR3, through trans-regulation and heterodimerization. DHR3 appears to function as a switch that defines the transition from a late larva to a prepupa, and E75B functions as a timer that modulates this transition. This study provides a biological function for orphan receptor interactions during development.