Haya AlGrain

Poster Presentation

Cetacean sunglasses? Deactivation kinetics of melanopsin in cetacean rod monochromats

Haya Algrain¹, Jeffry Fasick², Phyllis Robinson,

¹University of Maryland Baltimore County, ²The University of Tampa

Melanopsin is a non-image forming retinal pigment that is critical for the photoentrainment of circadian rhythms and the pupillary light reflex. In vitro calcium imaging of mouse melanopsin suggests that the proximal phosphorylation sites (amino acid residues 372-439) on the carboxyl tail regulate signaling activation and deactivation. Sequence alignment of the melanopsin gene from both cetaceans and terrestrial mammals demonstrates variability in the carboxyl tail phosphorylation sites. Currently, it is not understood how cetacean melanopsins have evolved to adapt in an aquatic light environment. We hypothesize that the cetacean melanopsin C-terminus phosphorylation sites have evolved to produce slower deactivation kinetics. Cetacean melanopsin signaling kinetics were assayed by measuring intracellular calcium levels in light stimulated melanopsin-expressing HEK cells using a Fluo-4AM dye. Initial findings indicate slower melanopsin deactivation kinetics in cetacean rod monochromats when compared to mouse controls. These results suggest that cetacean rod monocromats maintain a constricted pupil for a longer period of time when compared to animals possessing a duplex retina, and may be a mechanism to prevent photoreceptor bleaching during daylight hours.