Remaining rod activity mediates visual behavior in adult Rpe65-/- mice.
OBJECTIVE
C57/Bl6, Cpfl1(-/-) (cone photoreceptors function loss 1; pure rod function), Gnat1a(-/-) (rod α-transducin; pure cone function), and Rpe65(-/-);Rho(-/-) double-knockout mice were studied to distinguish the respective contributions of the different photoreceptor (PR) systems that enable light perception and mediate a visual reflex in adult Rpe65(-/-) mice, with a simple behavioral procedure.


METHODS
Visual function was estimated using a rotating automated optomotor drum covered with vertical black-and-white stripes at spatial frequencies of 0.025 to 0.5 cycles per degree (cyc/deg) in both photopic and scotopic conditions. Mouse strains with different luminances were tested to evaluate the contribution and the light-intensity threshold of each PR system.


RESULTS
Stripe rotation elicited head movements in the wild-type (WT) animals in photopic and scotopic conditions, depending on the spatial frequency, whereas the Cpfl1(-/-) mice show a reduced activity in the photopic condition and the Gnat1a(-/-) mice an almost absent response in the scotopic condition. A robust visual response was obtained with Rpe65(-/-) knockout mice at 0.075 and 0.1 cyc/deg in the photopic condition. The residual rod function in the Rpe65(-/-) animals was demonstrated by testing Rpe65(-/-);Rho(-/-) mice that present no response in photopic conditions.


CONCLUSIONS
The optomotor test is a simple method of estimating the visual function and evaluating the respective contributions of rod and cone systems. This test was used to demonstrate that in Rpe65(-/-) mice, devoid of functional cones and of detectable 11-cis-retinal protein, the rods mimic cone function in part, by mediating vision in photopic conditions.
Cachafeiro
Maité
M
Ophthalmology Department, University of Lausanne, Jules-Gonin Eye Hospital, Lausanne, Switzerland.
Bemelmans
Alexis-Pierre
AP
Canola
Kriss
K
Pignat
Vérène
V
Crippa
Sylvain Vincent
SV
Kostic
Corinne
C
Arsenijevic
Yvan
Y
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics*; D055253:Color Vision / Q000502:physiology; D005136:Eye Proteins / Q000235:genetics*; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics; D020868:Gene Silencing / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology; D055254:Night Vision / Q000502:physiology; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D015293:Transducin / Q000235:genetics; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D019745:cis-trans-Isomerases; D020741:rho GTP-Binding Proteins / Q000235:genetics; D000099178:Retinoid Isomerohydrolase
D002352:Carrier Proteins; D005136:Eye Proteins; D044385:GTP-Binding Protein alpha Subunits; D015293:Transducin; D019745:cis-trans-Isomerases; D020741:rho GTP-Binding Proteins; D000099178:Retinoid Isomerohydrolase; C488949:Gnat1 protein, mouse