RGS9-1 is required for normal inactivation of mouse cone phototransduction.
OBJECTIVE
To test the hypothesis that Regulator of G-protein Signaling 9 (RGS9-1) is necessary for the normal inactivation of retinal cones.


METHODS
Mice having the gene RGS9-1 inactivated in both alleles (RGS9-1 -/-) were tested between the ages 8-10 weeks with electroretinographic (ERG) protocols that isolate cone-driven responses. Immunohistochemistry was performed with a primary antibody against RGS9-1 (anti-RGS9-1c), with the secondary conjugated to fluorescein isothiocyanate, and with rhodamine-conjugated peanut agglutinin.


RESULTS
(1) Immunohistochemistry showed RGS9-1 to be strongly expressed in the cones of wildtype (WT is C57BL/6) mice, but absent from the cones of RGS9-1 mice. (2) Cone-driven b-wave responses of dark-adapted RGS9-1 -/- mice had saturating amplitudes and sensitivities in the midwave and UV regions of the spectrum equal to or slightly greater than those of WT (C57BL/6) mice. (3) Cone-driven b-wave and a-wave responses of RGS9-1 -/- mice recovered much more slowly than those of WT after a strong conditioning flash: for a flash estimated to isomerize 1.2% of the M-cone pigment and 0.9% of the UV-cone pigment, recovery of 50% saturating amplitude was approximately 60-fold slower than in WT.


CONCLUSIONS
(1) The amplitudes and sensitivities of the cone-driven responses indicate that cones and cone-driven neurons in RGS9-1 -/- mice have normal generator currents. (2) The greatly retarded recovery of cone-driven responses of RGS9-1 -/- mice relative to those of WT mice establishes that RGS9-1 is required for normal inactivation of the cone phototransduction cascades of both UV- and M-cones.
Lyubarsky
A L
AL
F. M. Kirby Center and Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA 19104-6069, USA.
Naarendorp
F
F
Zhang
X
X
Wensel
T
T
Simon
M I
MI
Pugh
E N
EN
D000818:Animals; D004596:Electroretinography; D019793:Fluorescein; D019084:Fluorescent Antibody Technique, Indirect; D051379:Mice; D008810:Mice, Inbred C57BL; D010775:Photic Stimulation; D020710:RGS Proteins / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012235:Rhodamines; D014785:Vision, Ocular / Q000502:physiology*
D020710:RGS Proteins; D012235:Rhodamines; C116925:regulator of g-protein signaling 9; D019793:Fluorescein