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Lee Ling Yang, Tami Bogea, Beatrice M. Tam, Orson L. Moritz; Investigation Of Protocadherin-21 Trafficking And Function In Transgenic Xenopus laevis Rod Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2011;52(14):906.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies in mice suggest that protocadherin-21 (PCDH-21) is involved in photoreceptor disk synthesis. Using X. laevis as a model organism, we aimed to investigate the role of PCDH-21 in regulating rod photoreceptor disk morphogenesis.
We expressed epitope-tagged X. laevis and untagged murine forms of PCDH-21 in X.laevis rod photoreceptors. We also attempted to generate dominant negative PCDH-21 mutants by deleting the C-terminal (xPCDH-21 ΔC) and N-terminal (xPCDH-21 ΔN) domains. Transgenic X. laevis expressing wild type and mutant PCDH-21 in rod photoreceptors were generated using restriction enzyme mediated integration and sperm nuclei transplantation. Retinal degeneration was assessed quantitatively by measuring total rhodopsin and qualitatively using confocal microscopy. Protein localization of PCDH-21 was determined by confocal microscopy. Effects on disk morphogenesis and photoreceptor ultrastructure were investigated by transmission electron microscopy.
xPCDH-21, xPCDH-21 ΔN and mPCDH-21were localized to the base of the outer segments, while xPCDH-21 ΔC was found only in inner segments. mPCDH-21 was expressed at higher levels than xPCDH-21 and high-level expression resulted in localization to the ER and ER abnormalities. High level expression of mPCDH-21 and mPCDH-21 ΔN were associated with retinal degeneration and abnormal outer segment morphology.
Our results confirm a role for PCDH-21 in synthesis of rod photoreceptor disks, possibly by regulating the size of nascent disks. In addition, our results indicate that the PCDH-21 C-terminal domain is required for targeting to basal disks. Overexpression of PCDH-21 may result in defects in intracellular trafficking.
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