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G.P. Lewis, K.E. Betts, P.T. Johnson, C.S. Sethi, D.G. Charteris, S.K. Fisher; Synaptic Ribbon and Vesicle Recycling Proteins Following Retinal Detachment and Reattachment in Feline and Human Retinas . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2444.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To examine the subcellular distribution and mRNA levels of the synaptic ribbon protein CtBP2 and the vesicle recycling protein clathrin following retinal detachment (RD) and reattachment (RR). Methods: Experimental RDs were created in feline eyes and the retinas harvested 1, 3, 7 or 28 days later. Two RR groups were used: 3–day RD followed by 28 days of RR and 1 day RD followed by 2 days of RR. Human tissue was obtained as retinectomy specimens from complex detachments taken as part of RR surgery. Anti–CtBP2 and anti–clathrin were used in combination with markers for the synaptic terminals of rod and cone photoreceptors (e.g. synaptophysin, vesicular glutamate transporter, rod opsin, and PDEgamma) and their distribution determined using an Olympus Fluoview confocal microscope. QPCR analysis was used to quantify the levels of CtBP2 and clathrin. Results: The feline and human retinas responded similarly and are described collectively. Synaptic ribbons were present at all RD and RR time–points in photoreceptor terminals although ribbons assumed a "clumped" appearance after RD compared to their normal arcuate morphology. Ribbons were present in the rod terminals that had retracted towards their cell body as a result of RD but they were absent from the terminals of rod axons that extended into the inner retina following RR. Anti–clathrin labeling decreased dramatically at one day and remained at low levels after both RR intervals. The QPCR analysis showed a rapid decline in clathrin mRNA whereas a decline in CtBP2 was not detected until day 28. Conclusions: Following RD, these 2 important presynaptic proteins within the terminals of both rod and cone photoreceptors undergo changes in their localization and changes in the levels of mRNA, although with different time courses. The change in morphology of the ribbons may adversely affect their ability to guide vesicles to the presynaptic release site. The loss of clathrin, and its failure to return to normal, suggests that vesicle, and hence neurotransmitter, recycling may be severely compromised after RD and remain so after a month of RR. The delayed decline in CtBP2 mRNA and immunocytochemical labeling may be in part due to the accumulated effects of cell death as a result of RD whereas the rapid decline in clathrin may be the result of decreased gene transcription. Disruption of the normal synaptic vesicle aggregation and recycling mechanisms may be still another variable in the return of vision after successful RR surgery.
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