Ignacio Provencio (born 29 June 1965) is an American neuroscientist and the discoverer of melanopsin,[1] an opsin found in specialized photosensitive ganglion cells of the mammalian retina.
However, when melanopsin was knocked out in blind mice without rods and cones, they exhibited “complete loss of photoentrainment of the circadian oscillator, pupillary light responses, photic suppression of arylalkylamine-N-acetyltransferase transcript, and acute suppression of locomotor activity by light.”[8] Provencio concluded that either melanopsin-containing retinal ganglion cells or outer-retinal photoreceptors (rods and cones) are sufficient to induce a response to light.
[8] To further investigate the role of melanopsin in light-induced phase shifting in mammals, the Provencio lab studied the locomotor activities of melanopsin-null mice (Opn4 -/-) in response to light.
[9] In 2008, the Provencio lab was able to specifically destroy melanopsin cells in the fully developed mouse retina using an immunotoxin made of an anti-melanopsin antibody conjugated to the protein saporin.
[10] Provencio's discovery of melanopsin and its function in photoentrainment supports earlier studies showing that some blind patients can entrain to a daily light cycle.
These studies also show that blind patients who cannot entrain and lack melanopsin cells have a significantly greater risk of suffering from circadian rhythm sleep disorders.
[13] In addition, there are now studies attempting to optimize light therapy for those with circadian rhythm sleep disorders that specifically try to stimulate melanopsin cells in blind patients.
[14] Provencio's research team has found that in albino mice, the amount of melanopsin protein in various retinal cells varies based on the environmental light conditions.
RPE65 is an important protein found in intrinsically photosensitive retinal ganglion cells (ipRGCs) that is necessary for regeneration of visual chromophore in rods and cones.