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R.G. Gregg, M.A. McCall, N.S. Peachey; Bipolar Specific Expression of Nyctalopin Fusion Gene Rescues No–B Wave Phenotype in Nob Mice . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3554.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The nob mouse lacks the b–wave component of the ERG. This phenotype results from a molecular defect, a deletion in the nyx gene, thath encodes a protein called nyctalopin. The expression pattern of the nyctalopin protein in the retina is not unequivocally established, although the ERG phenotype suggests an ON bipolar localization. To test this hypothesis, we constructed transgenic mice and crossed them to nob mice and examined the ERGs in nob/Y transgenic male offspring. Methods: We expressed an enhanced yellow fluorescent protein (EYFP):nyctalopin fusion cDNA under the control of the GABAC rho1 promoter, which directs expression specifically to bipolar cells. Transgenic mice were generated by conventional methods. Twelve founders were identified and, to date, we have identified 2 lines that transmit and express the transgene. These mice then were crossed to nob mice. Genotypes were determined by PCR and mice that carried both nob and the transgene identified. ERGs were recorded from transgenic/nob and nob mice under ketamine and xylazine anesthesia. Retinas were immersion fixed and prepared for sectioning and immunohistochemistry using standard techniques. Cryostat sections were cut and sections reacted with a variety of markers to localize expression of EYFP:nyctalopin positive cells. Results: The expression of the EYFP:nyctalopin fusion protein in bipolar cells restores the ERG b–wave. Immunohistochemistry shows that the fusion protein is located in the OPL at the tips of the ON bipolar cells. A full light and dark adapted ERG series will be completed once additional mice have been generated by breeding. Conclusions: Expression of nyctalopin in bipolar cells can rescue the ERG in the nob mice. Thus, the absence of nyctalopin expression on bipolar cell dendrites in the OPL is the primary defect in nob retinal processing
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