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Gesine B. Jaissle, C. Albrecht May, Jens Reinhard, Konrad Kohler, Sascha Fauser, Elke Lütjen–Drecoll, Eberhart Zrenner, Mathias W. Seeliger; Evaluation of the Rhodopsin Knockout Mouse as a Model of Pure Cone Function. Invest. Ophthalmol. Vis. Sci. 2001;42(2):506-513.
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purpose. To determine a time window in the rhodopsin knockout
(Rho−/−) mouse during which retinal function is already
sufficiently developed but cone degeneration is not yet substantial,
thus representing an all-cone retina.
methods. Electroretinograms (ERGs) were obtained from 14 homozygous
Rho−/− mice and eight C57Bl/6 control mice. The same
individuals were tested every 7 days, beginning as early as postnatal
day (P)14. The ERG protocols included flash and flicker stimuli, both
under photopic and scotopic conditions. Retinal and choroidal
morphology was observed in animals of comparable age.
results. Functionally, the developmental phase lasted until postnatal week (PW)3
in both the Rho−/− mice and the control animals. During
PW4 to 6, the Rho−/− mice showed a plateau in ERG
parameters with normal or even supernormal cone responses and complete
absence of rod contributions. At PW7, there was a marked onset of
degeneration, which progressed so that no ERG signals were left at
PW13, when the control eyes still had normal ERG responses.
Microscopically, cone degeneration paralleled the functional changes,
beginning at approximately PW6 and almost complete at PW13, whereas
retinal pigment epithelium (RPE) and choroid did not show any
conclusions. From PW4 to 6, Rho−/− mice appear to have normal cone and
no rod function. Despite the missing rod outer segment (OS), the
structure of retina, RPE, and choroid remained unchanged. Therefore,
the Rho−/− mice can serve during this age period as a
model for pure cone function. Such a model is particularly useful to
evaluate rod–cone interaction and to dissect rod- from cone-mediated
signaling pathways in vivo.
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