Dark skin gives seven to eightfold protection against DNA damage, but even the darkest skin colour cannot protect against all damage to DNA. Dark skin offers great protection against UVR because of its eumelanin content, the UVR-absorbing capabilities of large melanosomes, and because eumelanin can be mobilized faster and brought to the surface of the skin from the depths of the epidermis. For the same body region, light- and dark-skinned individuals have similar numbers of melanocytes (there is considerable variation between different body regions), but pigment-containing organelles, called melanosomes, are larger and more numerous in dark-skinned individuals. Keratocytes from dark skin cocultured
Pigment dispersing factor mRNA levels, while PDF knockouts show reduced protein. Similar behavioral and molecular phenotypes are observed in loss of PDF and VIP receptors. Pigment dispersing factor Pigment dispersing factor (pdf) is a gene that encodes the protein PDF, which is part of a large family of neuropeptides. 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. The movement and aggregation of pigments in retina cells and extra-retinal cells is hypothesized to be under a split hormonal control mechanism.