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E. R. Ritchey, R. E. Bongini, K. A. Code, C. Zelinka, S. M. Petersen-Jones, A. J. Fischer; Conservation of Retinal GNB3 Expression in Vertebrate Species. Invest. Ophthalmol. Vis. Sci. 2010;51(13):897.
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Guanine nucleotide-binding protein β3 (GNB3) is an isoform of the β subunit of the heterotrimeric G protein second messenger complex. In the retina, GNB3 has been shown to play a critical role in photoreceptor signal transduction. In Retinopathy, Globe Enlarged (RGE) chickens, a spontaneous 3 base pair mutation in the GNB3 gene has been shown to cause vision loss with a progressive retinopathy and globe enlargement. Despite the apparent importance of GNB3 for normal retinal function, the patterns of expression of GNB3 in the retina remain relatively unknown. We examine the expression patterns of GNB3 in the retinas of representative vertebrate species and the presence of GNB3 mRNA and protein in wild-type and RGE chickens.
Retinal tissue from chickens, mice, guinea pigs, dogs and macaques were fixed, sectioned and immunolabeled with antibodies for photoreceptors (Red/Green Opsin, Human Cone Arrestin), bipolar cells (PKC, Islet1) and GNB3. Reverse-transcription PCR and Western blotting were performed on postnatal day 7 wild-type and RGE chickens retinas per standard protocols.
We find that the pattern of expression of GNB3 in the retina is highly conserved across vertebrate species, including wild-type chickens, mice, guinea pigs, dogs and macaques. We find that chickens homozygous for the RGE allele maintain mRNA transcription yet completely lack GNB3 protein in the retina. Regardless of the species, we find that GNB3 is expressed by Islet1-positive ON-bipolar cells and by cone photoreceptors.
GNB3 is expressed by cone photoreceptors and ON-bipolar cells across multiple species. Given that analogous types of retinal neurons express GNB3 in different species, we propose that the function of GNB3 and the mechanisms that regulate its expression are highly conserved across species.
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