Pigment dispersing factor (pdf) is a gene that encodes the protein PDF, which is part of a large family of neuropeptides.[1] Its hormonal product, pigment dispersing hormone (PDH), was named for the diurnal pigment movement effect it has in crustacean retinal cells upon its initial discovery in the central nervous system of arthropods.[1] The movement and aggregation of pigments in retina cells and extra-retinal cells is hypothesized to be under a split hormonal control mechanism.[1] One hormonal set is responsible for concentrating chromatophoral pigment by responding to changes in the organism's exposure time to darkness. Another hormonal set is responsible for dispersion and responds to the light cycle.[1] However, insect pdf genes do not function in such pigment migration since they lack the chromatophore.[2]
The gene was first isolated and studied in Drosophila by Jeffrey C. Hall's laboratory at Brandeis University in 1998, and has been found to function as a neuromodulator and coupling factor in controlling circadian rhythms.[3][4] A neuromodulator is a neuroregulator that can act on other neurons in close proximity or far away, altering the effect of neurotransmitters without itself initiating depolarization.[5]