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C. M. Whitaker, N. G. F. Cooper; Characterization of Phosphodiesterase 4 Within the Adult Rat Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3047.
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© ARVO (1962-2015); The Authors (2016-present)
Phosphodiesterases (PDEs) are important regulators of signal transduction processes. While much is known about the function of cyclic GMP specific PDEs in the retina, much less is known about the closely related, cyclic AMP specific PDEs. The purpose of this study is to characterize and localize PDE4 genes in the retina.
Retinas from euthanized Long Evans Hooded rats were removed and either processed as fresh tissue or immediately perfusion / post-fixed. Fresh tissue was used to harvest RNA or protein for analysis in real time RT-PCR and western blotting, respectively. Aldehyde-fixed retina was cryostat sectioned, co-labeled for PDE4 proteins against various other retinal cell markers, and examined using confocal microscopy.
Real time RT-PCR data reveal that PDE4A mRNA is expressed at approximately 300 fold and 900 fold less than PDE4B and PDE4D, respectively. Likewise, western blot analyses show that there are numerous splice variants of each gene, with PDE4D having the largest number of isoforms, about 5-6. Lastly we used immunohistochemistry to determine the location of these genes within the retina and show that all three PDE4s are highly expressed in inner plexiform and inner nuclear layers. Moreover all genes are highly expressed in retinal ganglion cells and to a lesser degree in amacrine and horizontal cells. Interestingly, while all 3 genes appear to be expressed post-synaptically in both plexiform layers, PDE4B is highly expressed pre-synaptically in the outer plexiform layer.
Together these results provide evidence that PDE4 is abundantly expressed within the rat retina and provides the framework for further functional studies.
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