Environmental light levels can be detected by systems other than the eye in non-mammalian vertebrates. These extra-retinal photoreceptors often are used by non-mammalian vertebrates to synchronize biological rhythms, and to control rapid changes in skin pigmentation for camouflage. The photopigment in the retina of the eye in vertebrates includes proteins called opsins, but the photopigments for this extra-retinal light sensitivity are unknown. Recently a new opsin protein molecule in the brain, skin and eye of frogs has been found, and is named melanopsin because it was isolated from the pigment cells in the skin called melanophores. This collaborative research project uses techniques of gene expression and molecular biology along with microscopy and immunochemistry to see how light interacts with the expression of the melanopsin in frogs. Tests will show whether melanopsin expression is required for the camouflage response of pigment dispersion in the melanophores, and whether melanopsin expression is required for light to suppress the output of the hormone melatonin from the pineal gland of the brain, which is important for photic control of biological rhythms. Transgenic tissues will be tested to see whether those that over-express melanopsin are hypersensitive to light while those with under-expression are insensitive to light. Results will be important for understanding how animals respond to light without relying only upon the eyes, and will have a broad impact not only on neuroendocrinology and sensory biology, but on cell phyisiology and behavioral biology, and comparisons of molecular structure could be important to evolutionary biology.
