The eye of the blind mole rat, spalax ehrenbergi, a behavioural and molecular analysis
David-Gray ZK., Von Schantz M., Argamaso SM., Nevo E., Foster RG.
Purpose. To investigate arcadian responses to light and identify and characterise the photopigments within the atrophied non-image forming eye of the blind mole rat Methods. Using mouse specific green cone opsm pnmers, RT-PCR was used to isolate a green-like cone opsm cDNA clone from mole rat ocular RNA. Mole rat specific PCR primers were designed and 3′ and 5′ RACE PCR were earned out to isolate the full coding region of the gteen-like cone opsm By exposing mole rats to differing light/dark (L/D) cycles, and monitoring wheel running activity as an assay of circadian behaviour, the effects of light on photoentrainment were determined 18 adult mole rats were exposed to the following lighting regime, 42 days at 12L/12D cycle (lights on at 7am), 30 days in constant darkness (DD); 30 days at 12L, 12D (lights on at 7am), 45 days 12L/12D cycle with a phase advance of 6 hours (lights on at Ipin) Results. The deduced ammo acid sequence of the mole rat green-like cone opsm shows a high percentage identity with both mouse (86%) and human (85%) green cone opsms The opsm has seven transmembrane domains and all the known structural features required for a functional photopigment These include a putative Schiff base lysine, glutamine countenon, and a paii of cysteines required for disulphide bond formation. Under DD animals showed freerunning rhythms significantly different from 24 hours All animals showed stable entramment to the differing L/D cycles after 5-7 days Enucleated animals failed to entrain to a L/D cycle Conclusions. The subcutaneous location and degenerate nature of the mole rat eye preclude image formation However, blind mole rats with entrain and phase shift their arcadian locomotor rhythms to a L/D cycle. To date only a single green-like cone opsm has been isolated from the mole rat eye Our findings are consistant with previous studies which have implicated green cone and short wave sensitive opsins in rodent photoentrainment We are currently looking for additional opsins in the mole rat eye. Wellcome Trust to RGF none.