Melanopsin Lights the Way

Courtesy Samer Hattar

At top left, an X-gal stained retina from a mouse heterozygous for a LacZ knockin at the melanopsin locus reveals axons coursing toward the optic disc. At top right, a melanopsin antibody labels cell bodies, dendrites and initial axon segments of roughly 1% of ganglion cells in the rat retina. At bottom left, a coronal section from the brain of a heterozygous animal shows bilateral innervation of the suprachiasmatic nucleus (SCN). At bottom right, a stained whole brain cleared with a Benzene-based solution allows visualization of the optic nerve fibers and the optic chiasm with concomitant view of the two SCN nuclei visible in the background.

"I see," said the blind man. Outlandish as it seems, people lacking functional rods and cones can receive and process visual information. At least two decades ago, scientists began speculating that there may be another, "nonclassical" photoreceptor responsible for synchronizing the ...